Age Owner Branch data TLA Line data Source code
1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * async.c
4 : : * Asynchronous notification: NOTIFY, LISTEN, UNLISTEN
5 : : *
6 : : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
7 : : * Portions Copyright (c) 1994, Regents of the University of California
8 : : *
9 : : * IDENTIFICATION
10 : : * src/backend/commands/async.c
11 : : *
12 : : *-------------------------------------------------------------------------
13 : : */
14 : :
15 : : /*-------------------------------------------------------------------------
16 : : * Async Notification Model as of v19:
17 : : *
18 : : * 1. Multiple backends on same machine. Multiple backends may be listening
19 : : * on each of several channels.
20 : : *
21 : : * 2. There is one central queue in disk-based storage (directory pg_notify/),
22 : : * with actively-used pages mapped into shared memory by the slru.c module.
23 : : * All notification messages are placed in the queue and later read out
24 : : * by listening backends. The single queue allows us to guarantee that
25 : : * notifications are received in commit order.
26 : : *
27 : : * Although there is only one queue, notifications are treated as being
28 : : * database-local; this is done by including the sender's database OID
29 : : * in each notification message. Listening backends ignore messages
30 : : * that don't match their database OID. This is important because it
31 : : * ensures senders and receivers have the same database encoding and won't
32 : : * misinterpret non-ASCII text in the channel name or payload string.
33 : : *
34 : : * Since notifications are not expected to survive database crashes,
35 : : * we can simply clean out the pg_notify data at any reboot, and there
36 : : * is no need for WAL support or fsync'ing.
37 : : *
38 : : * 3. Every backend that is listening on at least one channel registers by
39 : : * entering its PID into the array in AsyncQueueControl. It then scans all
40 : : * incoming notifications in the central queue and first compares the
41 : : * database OID of the notification with its own database OID and then
42 : : * compares the notified channel with the list of channels that it listens
43 : : * to. In case there is a match it delivers the notification event to its
44 : : * frontend. Non-matching events are simply skipped.
45 : : *
46 : : * 4. The NOTIFY statement (routine Async_Notify) stores the notification in
47 : : * a backend-local list which will not be processed until transaction end.
48 : : *
49 : : * Duplicate notifications from the same transaction are sent out as one
50 : : * notification only. This is done to save work when for example a trigger
51 : : * on a 2 million row table fires a notification for each row that has been
52 : : * changed. If the application needs to receive every single notification
53 : : * that has been sent, it can easily add some unique string into the extra
54 : : * payload parameter.
55 : : *
56 : : * When the transaction is ready to commit, PreCommit_Notify() adds the
57 : : * pending notifications to the head of the queue. The head pointer of the
58 : : * queue always points to the next free position and a position is just a
59 : : * page number and the offset in that page. This is done before marking the
60 : : * transaction as committed in clog. If we run into problems writing the
61 : : * notifications, we can still call elog(ERROR, ...) and the transaction
62 : : * will roll back safely.
63 : : *
64 : : * Once we have put all of the notifications into the queue, we return to
65 : : * CommitTransaction() which will then do the actual transaction commit.
66 : : *
67 : : * After commit we are called another time (AtCommit_Notify()). Here we
68 : : * make any required updates to the effective listen state (see below).
69 : : * Then we signal any backends that may be interested in our messages
70 : : * (including our own backend, if listening). This is done by
71 : : * SignalBackends(), which sends a PROCSIG_NOTIFY_INTERRUPT signal to
72 : : * each relevant backend, as described below.
73 : : *
74 : : * Finally, after we are out of the transaction altogether and about to go
75 : : * idle, we scan the queue for messages that need to be sent to our
76 : : * frontend (which might be notifies from other backends, or self-notifies
77 : : * from our own). This step is not part of the CommitTransaction sequence
78 : : * for two important reasons. First, we could get errors while sending
79 : : * data to our frontend, and it's really bad for errors to happen in
80 : : * post-commit cleanup. Second, in cases where a procedure issues commits
81 : : * within a single frontend command, we don't want to send notifies to our
82 : : * frontend until the command is done; but notifies to other backends
83 : : * should go out immediately after each commit.
84 : : *
85 : : * 5. Upon receipt of a PROCSIG_NOTIFY_INTERRUPT signal, the signal handler
86 : : * sets the process's latch, which triggers the event to be processed
87 : : * immediately if this backend is idle (i.e., it is waiting for a frontend
88 : : * command and is not within a transaction block. C.f.
89 : : * ProcessClientReadInterrupt()). Otherwise the handler may only set a
90 : : * flag, which will cause the processing to occur just before we next go
91 : : * idle.
92 : : *
93 : : * Inbound-notify processing consists of reading all of the notifications
94 : : * that have arrived since scanning last time. We read every notification
95 : : * until we reach either a notification from an uncommitted transaction or
96 : : * the head pointer's position.
97 : : *
98 : : * 6. To limit disk space consumption, the tail pointer needs to be advanced
99 : : * so that old pages can be truncated. This is relatively expensive
100 : : * (notably, it requires an exclusive lock), so we don't want to do it
101 : : * often. We make sending backends do this work if they advanced the queue
102 : : * head into a new page, but only once every QUEUE_CLEANUP_DELAY pages.
103 : : *
104 : : * 7. So far we have not discussed how backends change their listening state,
105 : : * nor how notification senders know which backends to awaken. To handle
106 : : * the latter, we maintain a global channel table (implemented as a dynamic
107 : : * shared hash table, or dshash) that maps channel names to the set of
108 : : * backends listening on each channel. This table is created lazily on the
109 : : * first LISTEN command and grows dynamically as needed. There is also a
110 : : * local channel table (a plain dynahash table) in each listening backend,
111 : : * tracking which channels that backend is listening to. The local table
112 : : * serves to reduce the number of accesses needed to the shared table.
113 : : *
114 : : * If the current transaction has executed any LISTEN/UNLISTEN actions,
115 : : * PreCommit_Notify() prepares to commit those. For LISTEN, it
116 : : * pre-allocates entries in both the per-backend localChannelTable and the
117 : : * shared globalChannelTable, marking new shared entries removeOnAbort.
118 : : * It also records the final per-channel intent in pendingListenActions,
119 : : * so post-commit/abort processing can apply that in a single step.
120 : : * Since all these allocations happen before committing to clog, we can
121 : : * safely abort the transaction on failure.
122 : : *
123 : : * After commit, AtCommit_Notify() runs through pendingListenActions and
124 : : * applies the final per-channel listen/unlisten state. This happens
125 : : * before sending signals.
126 : : *
127 : : * SignalBackends() consults the shared global channel table to identify
128 : : * listeners for the channels that the current transaction sent
129 : : * notification(s) to. Each selected backend is marked as having a wakeup
130 : : * pending to avoid duplicate signals, and a PROCSIG_NOTIFY_INTERRUPT
131 : : * signal is sent to it.
132 : : *
133 : : * 8. While writing notifications, PreCommit_Notify() records the queue head
134 : : * position both before and after the write. Because all writers serialize
135 : : * on a cluster-wide heavyweight lock, no other backend can insert entries
136 : : * between these two points. SignalBackends() uses this fact to directly
137 : : * advance the queue pointer for any backend that is still positioned at
138 : : * the old head, or within the range written, but is not interested in any
139 : : * of our notifications. This avoids unnecessary wakeups for idle
140 : : * listeners that have nothing to read. Backends that are not interested
141 : : * in our notifications, but cannot be directly advanced, are signaled only
142 : : * if they are far behind the current queue head; that is to ensure that
143 : : * we can advance the queue tail without undue delay.
144 : : *
145 : : * An application that listens on the same channel it notifies will get
146 : : * NOTIFY messages for its own NOTIFYs. These can be ignored, if not useful,
147 : : * by comparing be_pid in the NOTIFY message to the application's own backend's
148 : : * PID. (As of FE/BE protocol 2.0, the backend's PID is provided to the
149 : : * frontend during startup.) The above design guarantees that notifies from
150 : : * other backends will never be missed by ignoring self-notifies.
151 : : *
152 : : * The amount of shared memory used for notify management (notify_buffers)
153 : : * can be varied without affecting anything but performance. The maximum
154 : : * amount of notification data that can be queued at one time is determined
155 : : * by the max_notify_queue_pages GUC.
156 : : *-------------------------------------------------------------------------
157 : : */
158 : :
159 : : #include "postgres.h"
160 : :
161 : : #include <limits.h>
162 : : #include <unistd.h>
163 : : #include <signal.h>
164 : :
165 : : #include "access/parallel.h"
166 : : #include "access/slru.h"
167 : : #include "access/transam.h"
168 : : #include "access/xact.h"
169 : : #include "catalog/pg_database.h"
170 : : #include "commands/async.h"
171 : : #include "common/hashfn.h"
172 : : #include "funcapi.h"
173 : : #include "lib/dshash.h"
174 : : #include "libpq/libpq.h"
175 : : #include "libpq/pqformat.h"
176 : : #include "miscadmin.h"
177 : : #include "storage/dsm_registry.h"
178 : : #include "storage/ipc.h"
179 : : #include "storage/latch.h"
180 : : #include "storage/lmgr.h"
181 : : #include "storage/procsignal.h"
182 : : #include "storage/subsystems.h"
183 : : #include "tcop/tcopprot.h"
184 : : #include "utils/builtins.h"
185 : : #include "utils/dsa.h"
186 : : #include "utils/guc_hooks.h"
187 : : #include "utils/memutils.h"
188 : : #include "utils/ps_status.h"
189 : : #include "utils/snapmgr.h"
190 : : #include "utils/timestamp.h"
191 : :
192 : :
193 : : /*
194 : : * Maximum size of a NOTIFY payload, including terminating NULL. This
195 : : * must be kept small enough so that a notification message fits on one
196 : : * SLRU page. The magic fudge factor here is noncritical as long as it's
197 : : * more than AsyncQueueEntryEmptySize --- we make it significantly bigger
198 : : * than that, so changes in that data structure won't affect user-visible
199 : : * restrictions.
200 : : */
201 : : #define NOTIFY_PAYLOAD_MAX_LENGTH (BLCKSZ - NAMEDATALEN - 128)
202 : :
203 : : /*
204 : : * Struct representing an entry in the global notify queue
205 : : *
206 : : * This struct declaration has the maximal length, but in a real queue entry
207 : : * the data area is only big enough for the actual channel and payload strings
208 : : * (each null-terminated). AsyncQueueEntryEmptySize is the minimum possible
209 : : * entry size, if both channel and payload strings are empty (but note it
210 : : * doesn't include alignment padding).
211 : : *
212 : : * The "length" field should always be rounded up to the next QUEUEALIGN
213 : : * multiple so that all fields are properly aligned.
214 : : */
215 : : typedef struct AsyncQueueEntry
216 : : {
217 : : int length; /* total allocated length of entry */
218 : : Oid dboid; /* sender's database OID */
219 : : TransactionId xid; /* sender's XID */
220 : : int32 srcPid; /* sender's PID */
221 : : char data[NAMEDATALEN + NOTIFY_PAYLOAD_MAX_LENGTH];
222 : : } AsyncQueueEntry;
223 : :
224 : : /* Currently, no field of AsyncQueueEntry requires more than int alignment */
225 : : #define QUEUEALIGN(len) INTALIGN(len)
226 : :
227 : : #define AsyncQueueEntryEmptySize (offsetof(AsyncQueueEntry, data) + 2)
228 : :
229 : : /*
230 : : * Struct describing a queue position, and assorted macros for working with it
231 : : */
232 : : typedef struct QueuePosition
233 : : {
234 : : int64 page; /* SLRU page number */
235 : : int offset; /* byte offset within page */
236 : : } QueuePosition;
237 : :
238 : : #define QUEUE_POS_PAGE(x) ((x).page)
239 : : #define QUEUE_POS_OFFSET(x) ((x).offset)
240 : :
241 : : #define SET_QUEUE_POS(x,y,z) \
242 : : do { \
243 : : (x).page = (y); \
244 : : (x).offset = (z); \
245 : : } while (0)
246 : :
247 : : #define QUEUE_POS_EQUAL(x,y) \
248 : : ((x).page == (y).page && (x).offset == (y).offset)
249 : :
250 : : #define QUEUE_POS_IS_ZERO(x) \
251 : : ((x).page == 0 && (x).offset == 0)
252 : :
253 : : /* choose logically smaller QueuePosition */
254 : : #define QUEUE_POS_MIN(x,y) \
255 : : (asyncQueuePagePrecedes((x).page, (y).page) ? (x) : \
256 : : (x).page != (y).page ? (y) : \
257 : : (x).offset < (y).offset ? (x) : (y))
258 : :
259 : : /* choose logically larger QueuePosition */
260 : : #define QUEUE_POS_MAX(x,y) \
261 : : (asyncQueuePagePrecedes((x).page, (y).page) ? (y) : \
262 : : (x).page != (y).page ? (x) : \
263 : : (x).offset > (y).offset ? (x) : (y))
264 : :
265 : : /* returns true if x comes before y in queue order */
266 : : #define QUEUE_POS_PRECEDES(x,y) \
267 : : (asyncQueuePagePrecedes((x).page, (y).page) || \
268 : : ((x).page == (y).page && (x).offset < (y).offset))
269 : :
270 : : /*
271 : : * Parameter determining how often we try to advance the tail pointer:
272 : : * we do that after every QUEUE_CLEANUP_DELAY pages of NOTIFY data. This is
273 : : * also the distance by which a backend that's not interested in our
274 : : * notifications needs to be behind before we'll decide we need to wake it
275 : : * up so it can advance its pointer.
276 : : *
277 : : * Resist the temptation to make this really large. While that would save
278 : : * work in some places, it would add cost in others. In particular, this
279 : : * should likely be less than notify_buffers, to ensure that backends
280 : : * catch up before the pages they'll need to read fall out of SLRU cache.
281 : : */
282 : : #define QUEUE_CLEANUP_DELAY 4
283 : :
284 : : /*
285 : : * Struct describing a listening backend's status
286 : : */
287 : : typedef struct QueueBackendStatus
288 : : {
289 : : int32 pid; /* either a PID or InvalidPid */
290 : : Oid dboid; /* backend's database OID, or InvalidOid */
291 : : ProcNumber nextListener; /* id of next listener, or INVALID_PROC_NUMBER */
292 : : QueuePosition pos; /* backend has read queue up to here */
293 : : bool wakeupPending; /* signal sent to backend, not yet processed */
294 : : bool isAdvancing; /* backend is advancing its position */
295 : : } QueueBackendStatus;
296 : :
297 : : /*
298 : : * Shared memory state for LISTEN/NOTIFY (excluding its SLRU stuff)
299 : : *
300 : : * The AsyncQueueControl structure is protected by the NotifyQueueLock and
301 : : * NotifyQueueTailLock.
302 : : *
303 : : * When holding NotifyQueueLock in SHARED mode, backends may only inspect
304 : : * their own entries as well as the head and tail pointers. Consequently we
305 : : * can allow a backend to update its own record while holding only SHARED lock
306 : : * (since no other backend will inspect it).
307 : : *
308 : : * When holding NotifyQueueLock in EXCLUSIVE mode, backends can inspect the
309 : : * entries of other backends and also change the head pointer. They can
310 : : * also advance other backends' queue positions, unless the other backend
311 : : * has isAdvancing set (i.e., is in process of doing that itself).
312 : : *
313 : : * When holding both NotifyQueueLock and NotifyQueueTailLock in EXCLUSIVE
314 : : * mode, backends can change the tail pointers.
315 : : *
316 : : * SLRU buffer pool is divided in banks and bank wise SLRU lock is used as
317 : : * the control lock for the pg_notify SLRU buffers.
318 : : * In order to avoid deadlocks, whenever we need multiple locks, we first get
319 : : * NotifyQueueTailLock, then NotifyQueueLock, then SLRU bank lock, and lastly
320 : : * globalChannelTable partition locks.
321 : : *
322 : : * Each backend uses the backend[] array entry with index equal to its
323 : : * ProcNumber. We rely on this to make SendProcSignal fast.
324 : : *
325 : : * The backend[] array entries for actively-listening backends are threaded
326 : : * together using firstListener and the nextListener links, so that we can
327 : : * scan them without having to iterate over inactive entries. We keep this
328 : : * list in order by ProcNumber so that the scan is cache-friendly when there
329 : : * are many active entries.
330 : : */
331 : : typedef struct AsyncQueueControl
332 : : {
333 : : QueuePosition head; /* head points to the next free location */
334 : : QueuePosition tail; /* tail must be <= the queue position of every
335 : : * listening backend */
336 : : int64 stopPage; /* oldest unrecycled page; must be <=
337 : : * tail.page */
338 : : ProcNumber firstListener; /* id of first listener, or
339 : : * INVALID_PROC_NUMBER */
340 : : TimestampTz lastQueueFillWarn; /* time of last queue-full msg */
341 : : dsa_handle globalChannelTableDSA; /* global channel table's DSA handle */
342 : : dshash_table_handle globalChannelTableDSH; /* and its dshash handle */
343 : : /* Array with room for MaxBackends entries: */
344 : : QueueBackendStatus backend[FLEXIBLE_ARRAY_MEMBER];
345 : : } AsyncQueueControl;
346 : :
347 : : static AsyncQueueControl *asyncQueueControl;
348 : :
349 : : static void AsyncShmemRequest(void *arg);
350 : : static void AsyncShmemInit(void *arg);
351 : :
352 : : const ShmemCallbacks AsyncShmemCallbacks = {
353 : : .request_fn = AsyncShmemRequest,
354 : : .init_fn = AsyncShmemInit,
355 : : };
356 : :
357 : :
358 : : #define QUEUE_HEAD (asyncQueueControl->head)
359 : : #define QUEUE_TAIL (asyncQueueControl->tail)
360 : : #define QUEUE_STOP_PAGE (asyncQueueControl->stopPage)
361 : : #define QUEUE_FIRST_LISTENER (asyncQueueControl->firstListener)
362 : : #define QUEUE_BACKEND_PID(i) (asyncQueueControl->backend[i].pid)
363 : : #define QUEUE_BACKEND_DBOID(i) (asyncQueueControl->backend[i].dboid)
364 : : #define QUEUE_NEXT_LISTENER(i) (asyncQueueControl->backend[i].nextListener)
365 : : #define QUEUE_BACKEND_POS(i) (asyncQueueControl->backend[i].pos)
366 : : #define QUEUE_BACKEND_WAKEUP_PENDING(i) (asyncQueueControl->backend[i].wakeupPending)
367 : : #define QUEUE_BACKEND_IS_ADVANCING(i) (asyncQueueControl->backend[i].isAdvancing)
368 : :
369 : : /*
370 : : * The SLRU buffer area through which we access the notification queue
371 : : */
372 : : static inline bool asyncQueuePagePrecedes(int64 p, int64 q);
373 : : static int asyncQueueErrdetailForIoError(const void *opaque_data);
374 : :
375 : : static SlruDesc NotifySlruDesc;
376 : :
377 : :
378 : : #define NotifyCtl (&NotifySlruDesc)
379 : : #define QUEUE_PAGESIZE BLCKSZ
380 : :
381 : : #define QUEUE_FULL_WARN_INTERVAL 5000 /* warn at most once every 5s */
382 : :
383 : : /*
384 : : * Global channel table definitions
385 : : *
386 : : * This hash table maps (database OID, channel name) keys to arrays of
387 : : * ProcNumbers representing the backends listening or about to listen
388 : : * on each channel. The removeOnAbort flags allow us to create hash table
389 : : * entries pre-commit and not have to assume that creating them post-commit
390 : : * will succeed.
391 : : */
392 : : #define INITIAL_LISTENERS_ARRAY_SIZE 4
393 : :
394 : : typedef struct GlobalChannelKey
395 : : {
396 : : Oid dboid;
397 : : char channel[NAMEDATALEN];
398 : : } GlobalChannelKey;
399 : :
400 : : typedef struct ListenerEntry
401 : : {
402 : : ProcNumber procNo; /* listener's ProcNumber */
403 : : bool removeOnAbort; /* remove entry if current xact aborts */
404 : : } ListenerEntry;
405 : :
406 : : typedef struct GlobalChannelEntry
407 : : {
408 : : GlobalChannelKey key; /* hash key */
409 : : dsa_pointer listenersArray; /* DSA pointer to ListenerEntry array */
410 : : int numListeners; /* Number of listeners currently stored */
411 : : int allocatedListeners; /* Allocated size of array */
412 : : } GlobalChannelEntry;
413 : :
414 : : static dshash_table *globalChannelTable = NULL;
415 : : static dsa_area *globalChannelDSA = NULL;
416 : :
417 : : /*
418 : : * localChannelTable caches the channel names this backend is listening on
419 : : * (including those we have staged to be listened on, but not yet committed).
420 : : * Used by IsListeningOn() for fast lookups when reading notifications.
421 : : */
422 : : static HTAB *localChannelTable = NULL;
423 : :
424 : : /* We test this condition to detect that we're not listening at all */
425 : : #define LocalChannelTableIsEmpty() \
426 : : (localChannelTable == NULL || hash_get_num_entries(localChannelTable) == 0)
427 : :
428 : : /*
429 : : * State for pending LISTEN/UNLISTEN actions consists of an ordered list of
430 : : * all actions requested in the current transaction. As explained above,
431 : : * we don't actually change listen state until we reach transaction commit.
432 : : *
433 : : * The list is kept in CurTransactionContext. In subtransactions, each
434 : : * subtransaction has its own list in its own CurTransactionContext, but
435 : : * successful subtransactions attach their lists to their parent's list.
436 : : * Failed subtransactions simply discard their lists.
437 : : */
438 : : typedef enum
439 : : {
440 : : LISTEN_LISTEN,
441 : : LISTEN_UNLISTEN,
442 : : LISTEN_UNLISTEN_ALL,
443 : : } ListenActionKind;
444 : :
445 : : typedef struct
446 : : {
447 : : ListenActionKind action;
448 : : char channel[FLEXIBLE_ARRAY_MEMBER]; /* nul-terminated string */
449 : : } ListenAction;
450 : :
451 : : typedef struct ActionList
452 : : {
453 : : int nestingLevel; /* current transaction nesting depth */
454 : : List *actions; /* list of ListenAction structs */
455 : : struct ActionList *upper; /* details for upper transaction levels */
456 : : } ActionList;
457 : :
458 : : static ActionList *pendingActions = NULL;
459 : :
460 : : /*
461 : : * Hash table recording the final listen/unlisten intent per channel for
462 : : * the current transaction. Key is channel name, value is PENDING_LISTEN or
463 : : * PENDING_UNLISTEN. This keeps critical commit/abort processing to one step
464 : : * per channel instead of replaying every action. This is built from the
465 : : * pendingActions list by PreCommit_Notify, then used by AtCommit_Notify or
466 : : * AtAbort_Notify.
467 : : */
468 : : typedef enum
469 : : {
470 : : PENDING_LISTEN,
471 : : PENDING_UNLISTEN,
472 : : } PendingListenAction;
473 : :
474 : : typedef struct PendingListenEntry
475 : : {
476 : : char channel[NAMEDATALEN]; /* hash key */
477 : : PendingListenAction action; /* which action should we perform? */
478 : : } PendingListenEntry;
479 : :
480 : : static HTAB *pendingListenActions = NULL;
481 : :
482 : : /*
483 : : * State for outbound notifies consists of a list of all channels+payloads
484 : : * NOTIFYed in the current transaction. We do not actually perform a NOTIFY
485 : : * until and unless the transaction commits. pendingNotifies is NULL if no
486 : : * NOTIFYs have been done in the current (sub) transaction.
487 : : *
488 : : * We discard duplicate notify events issued in the same transaction.
489 : : * Hence, in addition to the list proper (which we need to track the order
490 : : * of the events, since we guarantee to deliver them in order), we build a
491 : : * hash table which we can probe to detect duplicates. Since building the
492 : : * hash table is somewhat expensive, we do so only once we have at least
493 : : * MIN_HASHABLE_NOTIFIES events queued in the current (sub) transaction;
494 : : * before that we just scan the events linearly.
495 : : *
496 : : * The list is kept in CurTransactionContext. In subtransactions, each
497 : : * subtransaction has its own list in its own CurTransactionContext, but
498 : : * successful subtransactions add their entries to their parent's list.
499 : : * Failed subtransactions simply discard their lists. Since these lists
500 : : * are independent, there may be notify events in a subtransaction's list
501 : : * that duplicate events in some ancestor (sub) transaction; we get rid of
502 : : * the dups when merging the subtransaction's list into its parent's.
503 : : *
504 : : * Note: the action and notify lists do not interact within a transaction.
505 : : * In particular, if a transaction does NOTIFY and then LISTEN on the same
506 : : * condition name, it will get a self-notify at commit. This is a bit odd
507 : : * but is consistent with our historical behavior.
508 : : */
509 : : typedef struct Notification
510 : : {
511 : : uint16 channel_len; /* length of channel-name string */
512 : : uint16 payload_len; /* length of payload string */
513 : : /* null-terminated channel name, then null-terminated payload follow */
514 : : char data[FLEXIBLE_ARRAY_MEMBER];
515 : : } Notification;
516 : :
517 : : typedef struct NotificationList
518 : : {
519 : : int nestingLevel; /* current transaction nesting depth */
520 : : List *events; /* list of Notification structs */
521 : : HTAB *hashtab; /* hash of NotificationHash structs, or NULL */
522 : : List *uniqueChannelNames; /* unique channel names being notified */
523 : : HTAB *uniqueChannelHash; /* hash of unique channel names, or NULL */
524 : : struct NotificationList *upper; /* details for upper transaction levels */
525 : : } NotificationList;
526 : :
527 : : #define MIN_HASHABLE_NOTIFIES 16 /* threshold to build hashtab */
528 : :
529 : : struct NotificationHash
530 : : {
531 : : Notification *event; /* => the actual Notification struct */
532 : : };
533 : :
534 : : static NotificationList *pendingNotifies = NULL;
535 : :
536 : : /*
537 : : * Hash entry in NotificationList.uniqueChannelHash or localChannelTable
538 : : * (both just carry the channel name, with no payload).
539 : : */
540 : : typedef struct ChannelName
541 : : {
542 : : char channel[NAMEDATALEN]; /* hash key */
543 : : } ChannelName;
544 : :
545 : : /*
546 : : * Inbound notifications are initially processed by HandleNotifyInterrupt(),
547 : : * called from inside a signal handler. That just sets the
548 : : * notifyInterruptPending flag and sets the process
549 : : * latch. ProcessNotifyInterrupt() will then be called whenever it's safe to
550 : : * actually deal with the interrupt.
551 : : */
552 : : volatile sig_atomic_t notifyInterruptPending = false;
553 : :
554 : : /* True if we've registered an on_shmem_exit cleanup */
555 : : static bool unlistenExitRegistered = false;
556 : :
557 : : /* True if we're currently registered as a listener in asyncQueueControl */
558 : : static bool amRegisteredListener = false;
559 : :
560 : : /*
561 : : * Queue head positions for direct advancement.
562 : : * These are captured during PreCommit_Notify while holding the heavyweight
563 : : * lock on database 0, ensuring no other backend can insert notifications
564 : : * between them. SignalBackends uses these to advance idle backends.
565 : : */
566 : : static QueuePosition queueHeadBeforeWrite;
567 : : static QueuePosition queueHeadAfterWrite;
568 : :
569 : : /*
570 : : * Workspace arrays for SignalBackends. These are preallocated in
571 : : * PreCommit_Notify to avoid needing memory allocation after committing to
572 : : * clog.
573 : : */
574 : : static int32 *signalPids = NULL;
575 : : static ProcNumber *signalProcnos = NULL;
576 : :
577 : : /* have we advanced to a page that's a multiple of QUEUE_CLEANUP_DELAY? */
578 : : static bool tryAdvanceTail = false;
579 : :
580 : : /* GUC parameters */
581 : : bool Trace_notify = false;
582 : :
583 : : /* For 8 KB pages this gives 8 GB of disk space */
584 : : int max_notify_queue_pages = 1048576;
585 : :
586 : : /* local function prototypes */
587 : : static inline int64 asyncQueuePageDiff(int64 p, int64 q);
588 : : static inline void GlobalChannelKeyInit(GlobalChannelKey *key, Oid dboid,
589 : : const char *channel);
590 : : static dshash_hash globalChannelTableHash(const void *key, size_t size,
591 : : void *arg);
592 : : static void initGlobalChannelTable(void);
593 : : static void initLocalChannelTable(void);
594 : : static void queue_listen(ListenActionKind action, const char *channel);
595 : : static void Async_UnlistenOnExit(int code, Datum arg);
596 : : static void BecomeRegisteredListener(void);
597 : : static void PrepareTableEntriesForListen(const char *channel);
598 : : static void PrepareTableEntriesForUnlisten(const char *channel);
599 : : static void PrepareTableEntriesForUnlistenAll(void);
600 : : static void RemoveListenerFromChannel(GlobalChannelEntry **entry_ptr,
601 : : ListenerEntry *listeners,
602 : : int idx);
603 : : static void ApplyPendingListenActions(bool isCommit);
604 : : static void CleanupListenersOnExit(void);
605 : : static bool IsListeningOn(const char *channel);
606 : : static void asyncQueueUnregister(void);
607 : : static bool asyncQueueIsFull(void);
608 : : static bool asyncQueueAdvance(volatile QueuePosition *position, int entryLength);
609 : : static void asyncQueueNotificationToEntry(Notification *n, AsyncQueueEntry *qe);
610 : : static ListCell *asyncQueueAddEntries(ListCell *nextNotify);
611 : : static double asyncQueueUsage(void);
612 : : static void asyncQueueFillWarning(void);
613 : : static void SignalBackends(void);
614 : : static void asyncQueueReadAllNotifications(void);
615 : : static bool asyncQueueProcessPageEntries(QueuePosition *current,
616 : : QueuePosition stop,
617 : : Snapshot snapshot);
618 : : static void asyncQueueAdvanceTail(void);
619 : : static void ProcessIncomingNotify(bool flush);
620 : : static bool AsyncExistsPendingNotify(Notification *n);
621 : : static void AddEventToPendingNotifies(Notification *n);
622 : : static uint32 notification_hash(const void *key, Size keysize);
623 : : static int notification_match(const void *key1, const void *key2, Size keysize);
624 : : static void ClearPendingActionsAndNotifies(void);
625 : :
626 : : static int
78 heikki.linnakangas@i 627 :UNC 0 : asyncQueueErrdetailForIoError(const void *opaque_data)
628 : : {
629 : 0 : const QueuePosition *position = opaque_data;
630 : :
631 : 0 : return errdetail("Could not access async queue at page %" PRId64 ", offset %d.",
632 : 0 : position->page, position->offset);
633 : : }
634 : :
635 : : /*
636 : : * Compute the difference between two queue page numbers.
637 : : * Previously this function accounted for a wraparound.
638 : : */
639 : : static inline int64
913 akorotkov@postgresql 640 :UBC 0 : asyncQueuePageDiff(int64 p, int64 q)
641 : : {
642 : 0 : return p - q;
643 : : }
644 : :
645 : : /*
646 : : * Determines whether p precedes q.
647 : : * Previously this function accounted for a wraparound.
648 : : */
649 : : static inline bool
913 akorotkov@postgresql 650 :CBC 116 : asyncQueuePagePrecedes(int64 p, int64 q)
651 : : {
652 : 116 : return p < q;
653 : : }
654 : :
655 : : /*
656 : : * GlobalChannelKeyInit
657 : : * Prepare a global channel table key for hashing.
658 : : */
659 : : static inline void
135 tgl@sss.pgh.pa.us 660 :GNC 193 : GlobalChannelKeyInit(GlobalChannelKey *key, Oid dboid, const char *channel)
661 : : {
662 : 193 : memset(key, 0, sizeof(GlobalChannelKey));
663 : 193 : key->dboid = dboid;
664 : 193 : strlcpy(key->channel, channel, NAMEDATALEN);
665 : 193 : }
666 : :
667 : : /*
668 : : * globalChannelTableHash
669 : : * Hash function for global channel table keys.
670 : : */
671 : : static dshash_hash
672 : 193 : globalChannelTableHash(const void *key, size_t size, void *arg)
673 : : {
674 : 193 : const GlobalChannelKey *k = (const GlobalChannelKey *) key;
675 : : dshash_hash h;
676 : :
677 : 193 : h = DatumGetUInt32(hash_uint32(k->dboid));
678 : 193 : h ^= DatumGetUInt32(hash_any((const unsigned char *) k->channel,
679 : 193 : strnlen(k->channel, NAMEDATALEN)));
680 : :
681 : 193 : return h;
682 : : }
683 : :
684 : : /* parameters for the global channel table */
685 : : static const dshash_parameters globalChannelTableDSHParams = {
686 : : sizeof(GlobalChannelKey),
687 : : sizeof(GlobalChannelEntry),
688 : : dshash_memcmp,
689 : : globalChannelTableHash,
690 : : dshash_memcpy,
691 : : LWTRANCHE_NOTIFY_CHANNEL_HASH
692 : : };
693 : :
694 : : /*
695 : : * initGlobalChannelTable
696 : : * Lazy initialization of the global channel table.
697 : : */
698 : : static void
699 : 141 : initGlobalChannelTable(void)
700 : : {
701 : : MemoryContext oldcontext;
702 : :
703 : : /* Quick exit if we already did this */
704 [ + + ]: 141 : if (asyncQueueControl->globalChannelTableDSH != DSHASH_HANDLE_INVALID &&
705 [ + + ]: 133 : globalChannelTable != NULL)
706 : 121 : return;
707 : :
708 : : /* Otherwise, use a lock to ensure only one process creates the table */
709 : 20 : LWLockAcquire(NotifyQueueLock, LW_EXCLUSIVE);
710 : :
711 : : /* Be sure any local memory allocated by DSA routines is persistent */
712 : 20 : oldcontext = MemoryContextSwitchTo(TopMemoryContext);
713 : :
714 [ + + ]: 20 : if (asyncQueueControl->globalChannelTableDSH == DSHASH_HANDLE_INVALID)
715 : : {
716 : : /* Initialize dynamic shared hash table for global channels */
717 : 8 : globalChannelDSA = dsa_create(LWTRANCHE_NOTIFY_CHANNEL_HASH);
718 : 8 : dsa_pin(globalChannelDSA);
719 : 8 : dsa_pin_mapping(globalChannelDSA);
720 : 8 : globalChannelTable = dshash_create(globalChannelDSA,
721 : : &globalChannelTableDSHParams,
722 : : NULL);
723 : :
724 : : /* Store handles in shared memory for other backends to use */
725 : 8 : asyncQueueControl->globalChannelTableDSA = dsa_get_handle(globalChannelDSA);
726 : 8 : asyncQueueControl->globalChannelTableDSH =
727 : 8 : dshash_get_hash_table_handle(globalChannelTable);
728 : : }
729 [ + - ]: 12 : else if (!globalChannelTable)
730 : : {
731 : : /* Attach to existing dynamic shared hash table */
732 : 12 : globalChannelDSA = dsa_attach(asyncQueueControl->globalChannelTableDSA);
733 : 12 : dsa_pin_mapping(globalChannelDSA);
734 : 12 : globalChannelTable = dshash_attach(globalChannelDSA,
735 : : &globalChannelTableDSHParams,
736 : 12 : asyncQueueControl->globalChannelTableDSH,
737 : : NULL);
738 : : }
739 : :
740 : 20 : MemoryContextSwitchTo(oldcontext);
741 : 20 : LWLockRelease(NotifyQueueLock);
742 : : }
743 : :
744 : : /*
745 : : * initLocalChannelTable
746 : : * Lazy initialization of the local channel table.
747 : : * Once created, this table lasts for the life of the session.
748 : : */
749 : : static void
750 : 82 : initLocalChannelTable(void)
751 : : {
752 : : HASHCTL hash_ctl;
753 : :
754 : : /* Quick exit if we already did this */
755 [ + + ]: 82 : if (localChannelTable != NULL)
756 : 64 : return;
757 : :
758 : : /* Initialize local hash table for this backend's listened channels */
759 : 18 : hash_ctl.keysize = NAMEDATALEN;
760 : 18 : hash_ctl.entrysize = sizeof(ChannelName);
761 : :
762 : 18 : localChannelTable =
763 : 18 : hash_create("Local Listen Channels",
764 : : 64,
765 : : &hash_ctl,
766 : : HASH_ELEM | HASH_STRINGS);
767 : : }
768 : :
769 : : /*
770 : : * initPendingListenActions
771 : : * Lazy initialization of the pending listen actions hash table.
772 : : * This is allocated in CurTransactionContext during PreCommit_Notify,
773 : : * and destroyed at transaction end.
774 : : */
775 : : static void
776 : 82 : initPendingListenActions(void)
777 : : {
778 : : HASHCTL hash_ctl;
779 : :
780 [ - + ]: 82 : if (pendingListenActions != NULL)
135 tgl@sss.pgh.pa.us 781 :UNC 0 : return;
782 : :
135 tgl@sss.pgh.pa.us 783 :GNC 82 : hash_ctl.keysize = NAMEDATALEN;
784 : 82 : hash_ctl.entrysize = sizeof(PendingListenEntry);
785 : 82 : hash_ctl.hcxt = CurTransactionContext;
786 : :
787 : 82 : pendingListenActions =
788 : 82 : hash_create("Pending Listen Actions",
789 : 82 : list_length(pendingActions->actions),
790 : : &hash_ctl,
791 : : HASH_ELEM | HASH_STRINGS | HASH_CONTEXT);
792 : : }
793 : :
794 : : /*
795 : : * Register our shared memory needs
796 : : */
797 : : static void
54 heikki.linnakangas@i 798 : 1251 : AsyncShmemRequest(void *arg)
799 : : {
800 : : Size size;
801 : :
818 heikki.linnakangas@i 802 :CBC 1251 : size = mul_size(MaxBackends, sizeof(QueueBackendStatus));
4116 tgl@sss.pgh.pa.us 803 : 1251 : size = add_size(size, offsetof(AsyncQueueControl, backend));
804 : :
54 heikki.linnakangas@i 805 :GNC 1251 : ShmemRequestStruct(.name = "Async Queue Control",
806 : : .size = size,
807 : : .ptr = (void **) &asyncQueueControl,
808 : : );
809 : :
810 : 1251 : SimpleLruRequest(.desc = &NotifySlruDesc,
811 : : .name = "notify",
812 : : .Dir = "pg_notify",
813 : :
814 : : /* long segment names are used in order to avoid wraparound */
815 : : .long_segment_names = true,
816 : :
817 : : .nslots = notify_buffers,
818 : :
819 : : .sync_handler = SYNC_HANDLER_NONE,
820 : : .PagePrecedes = asyncQueuePagePrecedes,
821 : : .errdetail_for_io_error = asyncQueueErrdetailForIoError,
822 : :
823 : : .buffer_tranche_id = LWTRANCHE_NOTIFY_BUFFER,
824 : : .bank_tranche_id = LWTRANCHE_NOTIFY_SLRU,
825 : : );
826 : 1251 : }
827 : :
828 : : static void
829 : 1248 : AsyncShmemInit(void *arg)
830 : : {
831 : 1248 : SET_QUEUE_POS(QUEUE_HEAD, 0, 0);
832 : 1248 : SET_QUEUE_POS(QUEUE_TAIL, 0, 0);
833 : 1248 : QUEUE_STOP_PAGE = 0;
834 : 1248 : QUEUE_FIRST_LISTENER = INVALID_PROC_NUMBER;
835 : 1248 : asyncQueueControl->lastQueueFillWarn = 0;
836 : 1248 : asyncQueueControl->globalChannelTableDSA = DSA_HANDLE_INVALID;
837 : 1248 : asyncQueueControl->globalChannelTableDSH = DSHASH_HANDLE_INVALID;
838 [ + + ]: 117284 : for (int i = 0; i < MaxBackends; i++)
839 : : {
840 : 116036 : QUEUE_BACKEND_PID(i) = InvalidPid;
841 : 116036 : QUEUE_BACKEND_DBOID(i) = InvalidOid;
842 : 116036 : QUEUE_NEXT_LISTENER(i) = INVALID_PROC_NUMBER;
843 : 116036 : SET_QUEUE_POS(QUEUE_BACKEND_POS(i), 0, 0);
844 : 116036 : QUEUE_BACKEND_WAKEUP_PENDING(i) = false;
845 : 116036 : QUEUE_BACKEND_IS_ADVANCING(i) = false;
846 : : }
847 : :
848 : : /*
849 : : * During start or reboot, clean out the pg_notify directory.
850 : : */
851 : 1248 : (void) SlruScanDirectory(NotifyCtl, SlruScanDirCbDeleteAll, NULL);
5947 tgl@sss.pgh.pa.us 852 :CBC 1248 : }
853 : :
854 : :
855 : : /*
856 : : * pg_notify -
857 : : * SQL function to send a notification event
858 : : */
859 : : Datum
860 : 1078 : pg_notify(PG_FUNCTION_ARGS)
861 : : {
862 : : const char *channel;
863 : : const char *payload;
864 : :
865 [ + + ]: 1078 : if (PG_ARGISNULL(0))
866 : 4 : channel = "";
867 : : else
868 : 1074 : channel = text_to_cstring(PG_GETARG_TEXT_PP(0));
869 : :
870 [ + + ]: 1078 : if (PG_ARGISNULL(1))
871 : 7 : payload = "";
872 : : else
873 : 1071 : payload = text_to_cstring(PG_GETARG_TEXT_PP(1));
874 : :
875 : : /* For NOTIFY as a statement, this is checked in ProcessUtility */
5943 876 : 1078 : PreventCommandDuringRecovery("NOTIFY");
877 : :
5947 878 : 1078 : Async_Notify(channel, payload);
879 : :
880 : 1066 : PG_RETURN_VOID();
881 : : }
882 : :
883 : :
884 : : /*
885 : : * Async_Notify
886 : : *
887 : : * This is executed by the SQL notify command.
888 : : *
889 : : * Adds the message to the list of pending notifies.
890 : : * Actual notification happens during transaction commit.
891 : : * ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
892 : : */
893 : : void
894 : 1135 : Async_Notify(const char *channel, const char *payload)
895 : : {
2430 rhaas@postgresql.org 896 : 1135 : int my_level = GetCurrentTransactionNestLevel();
897 : : size_t channel_len;
898 : : size_t payload_len;
899 : : Notification *n;
900 : : MemoryContext oldcontext;
901 : :
3873 902 [ - + ]: 1135 : if (IsParallelWorker())
3873 rhaas@postgresql.org 903 [ # # ]:UBC 0 : elog(ERROR, "cannot send notifications from a parallel worker");
904 : :
9495 peter_e@gmx.net 905 [ - + ]:CBC 1135 : if (Trace_notify)
5947 tgl@sss.pgh.pa.us 906 [ # # ]:UBC 0 : elog(DEBUG1, "Async_Notify(%s)", channel);
907 : :
2480 tgl@sss.pgh.pa.us 908 [ + - ]:CBC 1135 : channel_len = channel ? strlen(channel) : 0;
909 [ + + ]: 1135 : payload_len = payload ? strlen(payload) : 0;
910 : :
911 : : /* a channel name must be specified */
912 [ + + ]: 1135 : if (channel_len == 0)
5947 913 [ + - ]: 8 : ereport(ERROR,
914 : : (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
915 : : errmsg("channel name cannot be empty")));
916 : :
917 : : /* enforce length limits */
2480 918 [ + + ]: 1127 : if (channel_len >= NAMEDATALEN)
5947 919 [ + - ]: 4 : ereport(ERROR,
920 : : (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
921 : : errmsg("channel name too long")));
922 : :
2480 923 [ - + ]: 1123 : if (payload_len >= NOTIFY_PAYLOAD_MAX_LENGTH)
2480 tgl@sss.pgh.pa.us 924 [ # # ]:UBC 0 : ereport(ERROR,
925 : : (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
926 : : errmsg("payload string too long")));
927 : :
928 : : /*
929 : : * We must construct the Notification entry, even if we end up not using
930 : : * it, in order to compare it cheaply to existing list entries.
931 : : *
932 : : * The notification list needs to live until end of transaction, so store
933 : : * it in the transaction context.
934 : : */
5947 tgl@sss.pgh.pa.us 935 :CBC 1123 : oldcontext = MemoryContextSwitchTo(CurTransactionContext);
936 : :
2480 937 : 1123 : n = (Notification *) palloc(offsetof(Notification, data) +
938 : 1123 : channel_len + payload_len + 2);
939 : 1123 : n->channel_len = channel_len;
940 : 1123 : n->payload_len = payload_len;
941 : 1123 : strcpy(n->data, channel);
5947 942 [ + + ]: 1123 : if (payload)
2480 943 : 1108 : strcpy(n->data + channel_len + 1, payload);
944 : : else
945 : 15 : n->data[channel_len + 1] = '\0';
946 : :
2430 rhaas@postgresql.org 947 [ + + + + ]: 1123 : if (pendingNotifies == NULL || my_level > pendingNotifies->nestingLevel)
2480 tgl@sss.pgh.pa.us 948 : 61 : {
949 : : NotificationList *notifies;
950 : :
951 : : /*
952 : : * First notify event in current (sub)xact. Note that we allocate the
953 : : * NotificationList in TopTransactionContext; the nestingLevel might
954 : : * get changed later by AtSubCommit_Notify.
955 : : */
956 : : notifies = (NotificationList *)
2430 rhaas@postgresql.org 957 : 61 : MemoryContextAlloc(TopTransactionContext,
958 : : sizeof(NotificationList));
959 : 61 : notifies->nestingLevel = my_level;
960 : 61 : notifies->events = list_make1(n);
961 : : /* We certainly don't need a hashtable yet */
962 : 61 : notifies->hashtab = NULL;
963 : : /* We won't build uniqueChannelNames/Hash till later, either */
135 tgl@sss.pgh.pa.us 964 :GNC 61 : notifies->uniqueChannelNames = NIL;
965 : 61 : notifies->uniqueChannelHash = NULL;
2430 rhaas@postgresql.org 966 :CBC 61 : notifies->upper = pendingNotifies;
967 : 61 : pendingNotifies = notifies;
968 : : }
969 : : else
970 : : {
971 : : /* Now check for duplicates */
972 [ + + ]: 1062 : if (AsyncExistsPendingNotify(n))
973 : : {
974 : : /* It's a dup, so forget it */
975 : 13 : pfree(n);
976 : 13 : MemoryContextSwitchTo(oldcontext);
977 : 13 : return;
978 : : }
979 : :
980 : : /* Append more events to existing list */
2480 tgl@sss.pgh.pa.us 981 : 1049 : AddEventToPendingNotifies(n);
982 : : }
983 : :
5947 984 : 1110 : MemoryContextSwitchTo(oldcontext);
985 : : }
986 : :
987 : : /*
988 : : * queue_listen
989 : : * Common code for listen, unlisten, unlisten all commands.
990 : : *
991 : : * Adds the request to the list of pending actions.
992 : : * Actual update of localChannelTable and globalChannelTable happens during
993 : : * PreCommit_Notify, with staged changes committed in AtCommit_Notify.
994 : : */
995 : : static void
996 : 98 : queue_listen(ListenActionKind action, const char *channel)
997 : : {
998 : : MemoryContext oldcontext;
999 : : ListenAction *actrec;
2430 rhaas@postgresql.org 1000 : 98 : int my_level = GetCurrentTransactionNestLevel();
1001 : :
1002 : : /*
1003 : : * Unlike Async_Notify, we don't try to collapse out duplicates here. We
1004 : : * keep the ordered list to preserve interactions like UNLISTEN ALL; the
1005 : : * final per-channel intent is computed during PreCommit_Notify.
1006 : : */
6653 tgl@sss.pgh.pa.us 1007 : 98 : oldcontext = MemoryContextSwitchTo(CurTransactionContext);
1008 : :
1009 : : /* space for terminating null is included in sizeof(ListenAction) */
4116 1010 : 98 : actrec = (ListenAction *) palloc(offsetof(ListenAction, channel) +
1011 : 98 : strlen(channel) + 1);
6653 1012 : 98 : actrec->action = action;
5947 1013 : 98 : strcpy(actrec->channel, channel);
1014 : :
2430 rhaas@postgresql.org 1015 [ + + + + ]: 98 : if (pendingActions == NULL || my_level > pendingActions->nestingLevel)
1016 : 85 : {
1017 : : ActionList *actions;
1018 : :
1019 : : /*
1020 : : * First action in current sub(xact). Note that we allocate the
1021 : : * ActionList in TopTransactionContext; the nestingLevel might get
1022 : : * changed later by AtSubCommit_Notify.
1023 : : */
1024 : : actions = (ActionList *)
1025 : 85 : MemoryContextAlloc(TopTransactionContext, sizeof(ActionList));
1026 : 85 : actions->nestingLevel = my_level;
1027 : 85 : actions->actions = list_make1(actrec);
1028 : 85 : actions->upper = pendingActions;
1029 : 85 : pendingActions = actions;
1030 : : }
1031 : : else
1032 : 13 : pendingActions->actions = lappend(pendingActions->actions, actrec);
1033 : :
6653 tgl@sss.pgh.pa.us 1034 : 98 : MemoryContextSwitchTo(oldcontext);
1035 : 98 : }
1036 : :
1037 : : /*
1038 : : * Async_Listen
1039 : : *
1040 : : * This is executed by the SQL listen command.
1041 : : */
1042 : : void
5947 1043 : 52 : Async_Listen(const char *channel)
1044 : : {
6653 1045 [ - + ]: 52 : if (Trace_notify)
5947 tgl@sss.pgh.pa.us 1046 [ # # ]:UBC 0 : elog(DEBUG1, "Async_Listen(%s,%d)", channel, MyProcPid);
1047 : :
5947 tgl@sss.pgh.pa.us 1048 :CBC 52 : queue_listen(LISTEN_LISTEN, channel);
6653 1049 : 52 : }
1050 : :
1051 : : /*
1052 : : * Async_Unlisten
1053 : : *
1054 : : * This is executed by the SQL unlisten command.
1055 : : */
1056 : : void
5947 1057 : 4 : Async_Unlisten(const char *channel)
1058 : : {
6482 1059 [ - + ]: 4 : if (Trace_notify)
5947 tgl@sss.pgh.pa.us 1060 [ # # ]:UBC 0 : elog(DEBUG1, "Async_Unlisten(%s,%d)", channel, MyProcPid);
1061 : :
1062 : : /* If we couldn't possibly be listening, no need to queue anything */
2430 rhaas@postgresql.org 1063 [ + - - + ]:CBC 4 : if (pendingActions == NULL && !unlistenExitRegistered)
6315 tgl@sss.pgh.pa.us 1064 :UBC 0 : return;
1065 : :
5947 tgl@sss.pgh.pa.us 1066 :CBC 4 : queue_listen(LISTEN_UNLISTEN, channel);
1067 : : }
1068 : :
1069 : : /*
1070 : : * Async_UnlistenAll
1071 : : *
1072 : : * This is invoked by UNLISTEN * command, and also at backend exit.
1073 : : */
1074 : : void
6653 1075 : 62 : Async_UnlistenAll(void)
1076 : : {
1077 [ - + ]: 62 : if (Trace_notify)
6653 tgl@sss.pgh.pa.us 1078 [ # # ]:UBC 0 : elog(DEBUG1, "Async_UnlistenAll(%d)", MyProcPid);
1079 : :
1080 : : /* If we couldn't possibly be listening, no need to queue anything */
2430 rhaas@postgresql.org 1081 [ + + + + ]:CBC 62 : if (pendingActions == NULL && !unlistenExitRegistered)
6315 tgl@sss.pgh.pa.us 1082 : 20 : return;
1083 : :
6653 1084 : 42 : queue_listen(LISTEN_UNLISTEN_ALL, "");
1085 : : }
1086 : :
1087 : : /*
1088 : : * SQL function: return a set of the channel names this backend is actively
1089 : : * listening to.
1090 : : *
1091 : : * Note: this coding relies on the fact that the localChannelTable cannot
1092 : : * change within a transaction.
1093 : : */
1094 : : Datum
5947 1095 : 12 : pg_listening_channels(PG_FUNCTION_ARGS)
1096 : : {
1097 : : FuncCallContext *funcctx;
1098 : : HASH_SEQ_STATUS *status;
1099 : :
1100 : : /* stuff done only on the first call of the function */
1101 [ + + ]: 12 : if (SRF_IS_FIRSTCALL())
1102 : : {
1103 : : /* create a function context for cross-call persistence */
1104 : 8 : funcctx = SRF_FIRSTCALL_INIT();
1105 : :
1106 : : /* Initialize hash table iteration if we have any channels */
135 tgl@sss.pgh.pa.us 1107 [ + - ]:GNC 8 : if (localChannelTable != NULL)
1108 : : {
1109 : : MemoryContext oldcontext;
1110 : :
1111 : 8 : oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
1112 : 8 : status = (HASH_SEQ_STATUS *) palloc(sizeof(HASH_SEQ_STATUS));
1113 : 8 : hash_seq_init(status, localChannelTable);
1114 : 8 : funcctx->user_fctx = status;
1115 : 8 : MemoryContextSwitchTo(oldcontext);
1116 : : }
1117 : : else
1118 : : {
135 tgl@sss.pgh.pa.us 1119 :UNC 0 : funcctx->user_fctx = NULL;
1120 : : }
1121 : : }
1122 : :
1123 : : /* stuff done on every call of the function */
5947 tgl@sss.pgh.pa.us 1124 :CBC 12 : funcctx = SRF_PERCALL_SETUP();
135 tgl@sss.pgh.pa.us 1125 :GNC 12 : status = (HASH_SEQ_STATUS *) funcctx->user_fctx;
1126 : :
1127 [ + - ]: 12 : if (status != NULL)
1128 : : {
1129 : : ChannelName *entry;
1130 : :
1131 : 12 : entry = (ChannelName *) hash_seq_search(status);
1132 [ + + ]: 12 : if (entry != NULL)
1133 : 4 : SRF_RETURN_NEXT(funcctx, CStringGetTextDatum(entry->channel));
1134 : : }
1135 : :
5947 tgl@sss.pgh.pa.us 1136 :CBC 8 : SRF_RETURN_DONE(funcctx);
1137 : : }
1138 : :
1139 : : /*
1140 : : * Async_UnlistenOnExit
1141 : : *
1142 : : * This is executed at backend exit if we have done any LISTENs in this
1143 : : * backend. It might not be necessary anymore, if the user UNLISTENed
1144 : : * everything, but we don't try to detect that case.
1145 : : */
1146 : : static void
6653 1147 : 18 : Async_UnlistenOnExit(int code, Datum arg)
1148 : : {
135 tgl@sss.pgh.pa.us 1149 :GNC 18 : CleanupListenersOnExit();
4854 tgl@sss.pgh.pa.us 1150 :CBC 18 : asyncQueueUnregister();
6653 1151 : 18 : }
1152 : :
1153 : : /*
1154 : : * AtPrepare_Notify
1155 : : *
1156 : : * This is called at the prepare phase of a two-phase
1157 : : * transaction. Save the state for possible commit later.
1158 : : */
1159 : : void
1160 : 336 : AtPrepare_Notify(void)
1161 : : {
1162 : : /* It's not allowed to have any pending LISTEN/UNLISTEN/NOTIFY actions */
5947 1163 [ + - - + ]: 336 : if (pendingActions || pendingNotifies)
6653 tgl@sss.pgh.pa.us 1164 [ # # ]:UBC 0 : ereport(ERROR,
1165 : : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1166 : : errmsg("cannot PREPARE a transaction that has executed LISTEN, UNLISTEN, or NOTIFY")));
5947 tgl@sss.pgh.pa.us 1167 :CBC 336 : }
1168 : :
1169 : : /*
1170 : : * PreCommit_Notify
1171 : : *
1172 : : * This is called at transaction commit, before actually committing to
1173 : : * clog.
1174 : : *
1175 : : * If there are pending LISTEN actions, make sure we are listed in the
1176 : : * shared-memory listener array. This must happen before commit to
1177 : : * ensure we don't miss any notifies from transactions that commit
1178 : : * just after ours.
1179 : : *
1180 : : * If there are outbound notify requests in the pendingNotifies list,
1181 : : * add them to the global queue. We do that before commit so that
1182 : : * we can still throw error if we run out of queue space.
1183 : : */
1184 : : void
1185 : 388618 : PreCommit_Notify(void)
1186 : : {
1187 : : ListCell *p;
1188 : :
2480 1189 [ + + + + ]: 388618 : if (!pendingActions && !pendingNotifies)
5947 1190 : 388477 : return; /* no relevant statements in this xact */
1191 : :
1192 [ - + ]: 141 : if (Trace_notify)
5947 tgl@sss.pgh.pa.us 1193 [ # # ]:UBC 0 : elog(DEBUG1, "PreCommit_Notify");
1194 : :
1195 : : /* Preflight for any pending listen/unlisten actions */
135 tgl@sss.pgh.pa.us 1196 :GNC 141 : initGlobalChannelTable();
1197 : :
2430 rhaas@postgresql.org 1198 [ + + ]:CBC 141 : if (pendingActions != NULL)
1199 : : {
1200 : : /* Ensure we have a local channel table */
135 tgl@sss.pgh.pa.us 1201 :GNC 82 : initLocalChannelTable();
1202 : : /* Create pendingListenActions hash table for this transaction */
1203 : 82 : initPendingListenActions();
1204 : :
1205 : : /* Stage all the actions this transaction wants to perform */
2430 rhaas@postgresql.org 1206 [ + - + + :CBC 177 : foreach(p, pendingActions->actions)
+ + ]
1207 : : {
1208 : 95 : ListenAction *actrec = (ListenAction *) lfirst(p);
1209 : :
1210 [ + + + - ]: 95 : switch (actrec->action)
1211 : : {
1212 : 50 : case LISTEN_LISTEN:
135 tgl@sss.pgh.pa.us 1213 :GNC 50 : BecomeRegisteredListener();
1214 : 50 : PrepareTableEntriesForListen(actrec->channel);
2430 rhaas@postgresql.org 1215 :CBC 50 : break;
1216 : 4 : case LISTEN_UNLISTEN:
135 tgl@sss.pgh.pa.us 1217 :GNC 4 : PrepareTableEntriesForUnlisten(actrec->channel);
2430 rhaas@postgresql.org 1218 :CBC 4 : break;
1219 : 41 : case LISTEN_UNLISTEN_ALL:
135 tgl@sss.pgh.pa.us 1220 :GNC 41 : PrepareTableEntriesForUnlistenAll();
2430 rhaas@postgresql.org 1221 :CBC 41 : break;
1222 : : }
1223 : : }
1224 : : }
1225 : :
1226 : : /* Queue any pending notifies (must happen after the above) */
5947 tgl@sss.pgh.pa.us 1227 [ + + ]: 141 : if (pendingNotifies)
1228 : : {
1229 : : ListCell *nextNotify;
135 tgl@sss.pgh.pa.us 1230 :GNC 59 : bool firstIteration = true;
1231 : :
1232 : : /*
1233 : : * Build list of unique channel names being notified for use by
1234 : : * SignalBackends().
1235 : : *
1236 : : * If uniqueChannelHash is available, use it to efficiently get the
1237 : : * unique channels. Otherwise, fall back to the O(N^2) approach.
1238 : : */
1239 : 59 : pendingNotifies->uniqueChannelNames = NIL;
1240 [ + + ]: 59 : if (pendingNotifies->uniqueChannelHash != NULL)
1241 : : {
1242 : : HASH_SEQ_STATUS status;
1243 : : ChannelName *channelEntry;
1244 : :
1245 : 2 : hash_seq_init(&status, pendingNotifies->uniqueChannelHash);
1246 [ + + ]: 4 : while ((channelEntry = (ChannelName *) hash_seq_search(&status)) != NULL)
1247 : 2 : pendingNotifies->uniqueChannelNames =
1248 : 2 : lappend(pendingNotifies->uniqueChannelNames,
1249 : 2 : channelEntry->channel);
1250 : : }
1251 : : else
1252 : : {
1253 : : /* O(N^2) approach is better for small number of notifications */
1254 [ + - + + : 201 : foreach_ptr(Notification, n, pendingNotifies->events)
+ + ]
1255 : : {
1256 : 87 : char *channel = n->data;
1257 : 87 : bool found = false;
1258 : :
1259 : : /* Name present in list? */
1260 [ + + + + : 178 : foreach_ptr(char, oldchan, pendingNotifies->uniqueChannelNames)
+ + ]
1261 : : {
1262 [ + + ]: 31 : if (strcmp(oldchan, channel) == 0)
1263 : : {
1264 : 27 : found = true;
1265 : 27 : break;
1266 : : }
1267 : : }
1268 : : /* Add if not already in list */
1269 [ + + ]: 87 : if (!found)
1270 : 60 : pendingNotifies->uniqueChannelNames =
1271 : 60 : lappend(pendingNotifies->uniqueChannelNames,
1272 : : channel);
1273 : : }
1274 : : }
1275 : :
1276 : : /* Preallocate workspace that will be needed by SignalBackends() */
1277 [ + + ]: 59 : if (signalPids == NULL)
1278 : 13 : signalPids = MemoryContextAlloc(TopMemoryContext,
1279 : : MaxBackends * sizeof(int32));
1280 : :
1281 [ + + ]: 59 : if (signalProcnos == NULL)
1282 : 13 : signalProcnos = MemoryContextAlloc(TopMemoryContext,
1283 : : MaxBackends * sizeof(ProcNumber));
1284 : :
1285 : : /*
1286 : : * Make sure that we have an XID assigned to the current transaction.
1287 : : * GetCurrentTransactionId is cheap if we already have an XID, but not
1288 : : * so cheap if we don't, and we'd prefer not to do that work while
1289 : : * holding NotifyQueueLock.
1290 : : */
5947 tgl@sss.pgh.pa.us 1291 :CBC 59 : (void) GetCurrentTransactionId();
1292 : :
1293 : : /*
1294 : : * Serialize writers by acquiring a special lock that we hold till
1295 : : * after commit. This ensures that queue entries appear in commit
1296 : : * order, and in particular that there are never uncommitted queue
1297 : : * entries ahead of committed ones, so an uncommitted transaction
1298 : : * can't block delivery of deliverable notifications.
1299 : : *
1300 : : * We use a heavyweight lock so that it'll automatically be released
1301 : : * after either commit or abort. This also allows deadlocks to be
1302 : : * detected, though really a deadlock shouldn't be possible here.
1303 : : *
1304 : : * The lock is on "database 0", which is pretty ugly but it doesn't
1305 : : * seem worth inventing a special locktag category just for this.
1306 : : * (Historical note: before PG 9.0, a similar lock on "database 0" was
1307 : : * used by the flatfiles mechanism.)
1308 : : */
1309 : 59 : LockSharedObject(DatabaseRelationId, InvalidOid, 0,
1310 : : AccessExclusiveLock);
1311 : :
1312 : : /*
1313 : : * For the direct advancement optimization in SignalBackends(), we
1314 : : * need to ensure that no other backend can insert queue entries
1315 : : * between queueHeadBeforeWrite and queueHeadAfterWrite. The
1316 : : * heavyweight lock above provides this guarantee, since it serializes
1317 : : * all writers.
1318 : : *
1319 : : * Note: if the heavyweight lock were ever removed for scalability
1320 : : * reasons, we could achieve the same guarantee by holding
1321 : : * NotifyQueueLock in EXCLUSIVE mode across all our insertions, rather
1322 : : * than releasing and reacquiring it for each page as we do below.
1323 : : */
1324 : :
1325 : : /* Initialize values to a safe default in case list is empty */
135 tgl@sss.pgh.pa.us 1326 :GNC 59 : SET_QUEUE_POS(queueHeadBeforeWrite, 0, 0);
1327 : 59 : SET_QUEUE_POS(queueHeadAfterWrite, 0, 0);
1328 : :
1329 : : /* Now push the notifications into the queue */
2480 tgl@sss.pgh.pa.us 1330 :CBC 59 : nextNotify = list_head(pendingNotifies->events);
5947 1331 [ + + ]: 153 : while (nextNotify != NULL)
1332 : : {
1333 : : /*
1334 : : * Add the pending notifications to the queue. We acquire and
1335 : : * release NotifyQueueLock once per page, which might be overkill
1336 : : * but it does allow readers to get in while we're doing this.
1337 : : *
1338 : : * A full queue is very uncommon and should really not happen,
1339 : : * given that we have so much space available in the SLRU pages.
1340 : : * Nevertheless we need to deal with this possibility. Note that
1341 : : * when we get here we are in the process of committing our
1342 : : * transaction, but we have not yet committed to clog, so at this
1343 : : * point in time we can still roll the transaction back.
1344 : : */
2206 1345 : 94 : LWLockAcquire(NotifyQueueLock, LW_EXCLUSIVE);
135 tgl@sss.pgh.pa.us 1346 [ + + ]:GNC 94 : if (firstIteration)
1347 : : {
1348 : 59 : queueHeadBeforeWrite = QUEUE_HEAD;
1349 : 59 : firstIteration = false;
1350 : : }
5947 tgl@sss.pgh.pa.us 1351 :CBC 94 : asyncQueueFillWarning();
1352 [ - + ]: 94 : if (asyncQueueIsFull())
5947 tgl@sss.pgh.pa.us 1353 [ # # ]:UBC 0 : ereport(ERROR,
1354 : : (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
1355 : : errmsg("too many notifications in the NOTIFY queue")));
5947 tgl@sss.pgh.pa.us 1356 :CBC 94 : nextNotify = asyncQueueAddEntries(nextNotify);
135 tgl@sss.pgh.pa.us 1357 :GNC 94 : queueHeadAfterWrite = QUEUE_HEAD;
2206 tgl@sss.pgh.pa.us 1358 :CBC 94 : LWLockRelease(NotifyQueueLock);
1359 : : }
1360 : :
1361 : : /* Note that we don't clear pendingNotifies; AtCommit_Notify will. */
1362 : : }
1363 : : }
1364 : :
1365 : : /*
1366 : : * AtCommit_Notify
1367 : : *
1368 : : * This is called at transaction commit, after committing to clog.
1369 : : *
1370 : : * Apply pending listen/unlisten changes and clear transaction-local state.
1371 : : *
1372 : : * If we issued any notifications in the transaction, send signals to
1373 : : * listening backends (possibly including ourselves) to process them.
1374 : : * Also, if we filled enough queue pages with new notifies, try to
1375 : : * advance the queue tail pointer.
1376 : : */
1377 : : void
6653 1378 : 388463 : AtCommit_Notify(void)
1379 : : {
1380 : : /*
1381 : : * Allow transactions that have not executed LISTEN/UNLISTEN/NOTIFY to
1382 : : * return as soon as possible
1383 : : */
5947 1384 [ + + + + ]: 388463 : if (!pendingActions && !pendingNotifies)
6653 1385 : 388322 : return;
1386 : :
1387 [ - + ]: 141 : if (Trace_notify)
6653 tgl@sss.pgh.pa.us 1388 [ # # ]:UBC 0 : elog(DEBUG1, "AtCommit_Notify");
1389 : :
1390 : : /* Apply staged listen/unlisten changes */
135 tgl@sss.pgh.pa.us 1391 :GNC 141 : ApplyPendingListenActions(true);
1392 : :
1393 : : /* If no longer listening to anything, get out of listener array */
1394 [ + + + - : 141 : if (amRegisteredListener && LocalChannelTableIsEmpty())
+ + ]
4854 tgl@sss.pgh.pa.us 1395 :CBC 21 : asyncQueueUnregister();
1396 : :
1397 : : /*
1398 : : * Send signals to listening backends. We need do this only if there are
1399 : : * pending notifies, which were previously added to the shared queue by
1400 : : * PreCommit_Notify().
1401 : : */
1719 1402 [ + + ]: 141 : if (pendingNotifies != NULL)
1403 : 59 : SignalBackends();
1404 : :
1405 : : /*
1406 : : * If it's time to try to advance the global tail pointer, do that.
1407 : : *
1408 : : * (It might seem odd to do this in the sender, when more than likely the
1409 : : * listeners won't yet have read the messages we just sent. However,
1410 : : * there's less contention if only the sender does it, and there is little
1411 : : * need for urgency in advancing the global tail. So this typically will
1412 : : * be clearing out messages that were sent some time ago.)
1413 : : */
1414 [ + + ]: 141 : if (tryAdvanceTail)
1415 : : {
1416 : 8 : tryAdvanceTail = false;
1417 : 8 : asyncQueueAdvanceTail();
1418 : : }
1419 : :
1420 : : /* And clean up */
5947 1421 : 141 : ClearPendingActionsAndNotifies();
1422 : : }
1423 : :
1424 : : /*
1425 : : * BecomeRegisteredListener --- subroutine for PreCommit_Notify
1426 : : *
1427 : : * This function must make sure we are ready to catch any incoming messages.
1428 : : */
1429 : : static void
135 tgl@sss.pgh.pa.us 1430 :GNC 50 : BecomeRegisteredListener(void)
1431 : : {
1432 : : QueuePosition head;
1433 : : QueuePosition max;
1434 : : ProcNumber prevListener;
1435 : :
1436 : : /*
1437 : : * Nothing to do if we are already listening to something, nor if we
1438 : : * already ran this routine in this transaction.
1439 : : */
4854 tgl@sss.pgh.pa.us 1440 [ + + ]:CBC 50 : if (amRegisteredListener)
5947 1441 : 23 : return;
1442 : :
1443 [ - + ]: 27 : if (Trace_notify)
135 tgl@sss.pgh.pa.us 1444 [ # # ]:UNC 0 : elog(DEBUG1, "BecomeRegisteredListener(%d)", MyProcPid);
1445 : :
1446 : : /*
1447 : : * Before registering, make sure we will unlisten before dying. (Note:
1448 : : * this action does not get undone if we abort later.)
1449 : : */
5947 tgl@sss.pgh.pa.us 1450 [ + + ]:CBC 27 : if (!unlistenExitRegistered)
1451 : : {
4546 rhaas@postgresql.org 1452 : 18 : before_shmem_exit(Async_UnlistenOnExit, 0);
5947 tgl@sss.pgh.pa.us 1453 : 18 : unlistenExitRegistered = true;
1454 : : }
1455 : :
1456 : : /*
1457 : : * This is our first LISTEN, so establish our pointer.
1458 : : *
1459 : : * We set our pointer to the global tail pointer and then move it forward
1460 : : * over already-committed notifications. This ensures we cannot miss any
1461 : : * not-yet-committed notifications. We might get a few more but that
1462 : : * doesn't hurt.
1463 : : *
1464 : : * In some scenarios there might be a lot of committed notifications that
1465 : : * have not yet been pruned away (because some backend is being lazy about
1466 : : * reading them). To reduce our startup time, we can look at other
1467 : : * backends and adopt the maximum "pos" pointer of any backend that's in
1468 : : * our database; any notifications it's already advanced over are surely
1469 : : * committed and need not be re-examined by us. (We must consider only
1470 : : * backends connected to our DB, because others will not have bothered to
1471 : : * check committed-ness of notifications in our DB.)
1472 : : *
1473 : : * We need exclusive lock here so we can look at other backends' entries
1474 : : * and manipulate the list links.
1475 : : */
2206 1476 : 27 : LWLockAcquire(NotifyQueueLock, LW_EXCLUSIVE);
3895 1477 : 27 : head = QUEUE_HEAD;
1478 : 27 : max = QUEUE_TAIL;
818 heikki.linnakangas@i 1479 : 27 : prevListener = INVALID_PROC_NUMBER;
1480 [ + + ]: 29 : for (ProcNumber i = QUEUE_FIRST_LISTENER; i != INVALID_PROC_NUMBER; i = QUEUE_NEXT_LISTENER(i))
1481 : : {
2454 tgl@sss.pgh.pa.us 1482 [ + - ]: 2 : if (QUEUE_BACKEND_DBOID(i) == MyDatabaseId)
1483 [ - + + - : 2 : max = QUEUE_POS_MAX(max, QUEUE_BACKEND_POS(i));
+ - ]
1484 : : /* Also find last listening backend before this one */
818 heikki.linnakangas@i 1485 [ - + ]: 2 : if (i < MyProcNumber)
2454 tgl@sss.pgh.pa.us 1486 :LBC (1) : prevListener = i;
1487 : : }
818 heikki.linnakangas@i 1488 :CBC 27 : QUEUE_BACKEND_POS(MyProcNumber) = max;
1489 : 27 : QUEUE_BACKEND_PID(MyProcNumber) = MyProcPid;
1490 : 27 : QUEUE_BACKEND_DBOID(MyProcNumber) = MyDatabaseId;
135 tgl@sss.pgh.pa.us 1491 :GNC 27 : QUEUE_BACKEND_WAKEUP_PENDING(MyProcNumber) = false;
1492 : 27 : QUEUE_BACKEND_IS_ADVANCING(MyProcNumber) = false;
1493 : : /* Insert backend into list of listeners at correct position */
818 heikki.linnakangas@i 1494 [ - + ]:CBC 27 : if (prevListener != INVALID_PROC_NUMBER)
1495 : : {
818 heikki.linnakangas@i 1496 :LBC (1) : QUEUE_NEXT_LISTENER(MyProcNumber) = QUEUE_NEXT_LISTENER(prevListener);
1497 : (1) : QUEUE_NEXT_LISTENER(prevListener) = MyProcNumber;
1498 : : }
1499 : : else
1500 : : {
818 heikki.linnakangas@i 1501 :CBC 27 : QUEUE_NEXT_LISTENER(MyProcNumber) = QUEUE_FIRST_LISTENER;
1502 : 27 : QUEUE_FIRST_LISTENER = MyProcNumber;
1503 : : }
2206 tgl@sss.pgh.pa.us 1504 : 27 : LWLockRelease(NotifyQueueLock);
1505 : :
1506 : : /* Now we are listed in the global array, so remember we're listening */
4854 1507 : 27 : amRegisteredListener = true;
1508 : :
1509 : : /*
1510 : : * Try to move our pointer forward as far as possible. This will skip
1511 : : * over already-committed notifications, which we want to do because they
1512 : : * might be quite stale. Note that we are not yet listening on anything,
1513 : : * so we won't deliver such notifications to our frontend. Also, although
1514 : : * our transaction might have executed NOTIFY, those message(s) aren't
1515 : : * queued yet so we won't skip them here.
1516 : : */
3895 1517 [ + + + + ]: 27 : if (!QUEUE_POS_EQUAL(max, head))
1518 : 18 : asyncQueueReadAllNotifications();
1519 : : }
1520 : :
1521 : : /*
1522 : : * PrepareTableEntriesForListen --- subroutine for PreCommit_Notify
1523 : : *
1524 : : * Prepare a LISTEN by recording it in pendingListenActions, pre-allocating
1525 : : * an entry in localChannelTable, and pre-allocating an entry in the shared
1526 : : * globalChannelTable with removeOnAbort set. AtCommit_Notify will clear
1527 : : * removeOnAbort; abort processing will remove entries still marked so.
1528 : : */
1529 : : static void
135 tgl@sss.pgh.pa.us 1530 :GNC 50 : PrepareTableEntriesForListen(const char *channel)
1531 : : {
1532 : : GlobalChannelKey key;
1533 : : GlobalChannelEntry *entry;
1534 : : bool found;
1535 : : ListenerEntry *listeners;
1536 : : PendingListenEntry *pending;
1537 : :
1538 : : /*
1539 : : * Record in local pending hash that we want to LISTEN, overwriting any
1540 : : * earlier attempt to UNLISTEN.
1541 : : */
1542 : : pending = (PendingListenEntry *)
1543 : 50 : hash_search(pendingListenActions, channel, HASH_ENTER, NULL);
1544 : 50 : pending->action = PENDING_LISTEN;
1545 : :
1546 : : /*
1547 : : * Ensure that there is an entry for the channel in localChannelTable.
1548 : : * (Should this fail, we can just roll back.) If the transaction fails
1549 : : * after this point, we will remove the entry if appropriate during
1550 : : * ApplyPendingListenActions. Note that this entry allows IsListeningOn()
1551 : : * to return TRUE; we assume nothing is going to consult that before
1552 : : * AtCommit_Notify/AtAbort_Notify. However, if later actions attempt to
1553 : : * UNLISTEN this channel or UNLISTEN *, we need to have the local entry
1554 : : * present to ensure they do the right things; see
1555 : : * PrepareTableEntriesForUnlisten and PrepareTableEntriesForUnlistenAll.
1556 : : */
1557 : 50 : (void) hash_search(localChannelTable, channel, HASH_ENTER, NULL);
1558 : :
1559 : : /* Pre-allocate entry in shared globalChannelTable */
1560 : 50 : GlobalChannelKeyInit(&key, MyDatabaseId, channel);
1561 : 50 : entry = dshash_find_or_insert(globalChannelTable, &key, &found);
1562 : :
1563 [ + + ]: 50 : if (!found)
1564 : : {
1565 : : /* New channel entry, so initialize it to a safe state */
1566 : 37 : entry->listenersArray = InvalidDsaPointer;
1567 : 37 : entry->numListeners = 0;
1568 : 37 : entry->allocatedListeners = 0;
1569 : : }
1570 : :
1571 : : /*
1572 : : * Create listenersArray if entry doesn't have one. It's tempting to fold
1573 : : * this into the !found case, but this coding allows us to cope in case
1574 : : * dsa_allocate() failed in an earlier attempt.
1575 : : */
1576 [ + + ]: 50 : if (!DsaPointerIsValid(entry->listenersArray))
1577 : : {
1578 : 37 : entry->listenersArray = dsa_allocate(globalChannelDSA,
1579 : : sizeof(ListenerEntry) * INITIAL_LISTENERS_ARRAY_SIZE);
1580 : 37 : entry->allocatedListeners = INITIAL_LISTENERS_ARRAY_SIZE;
1581 : : }
1582 : :
1583 : : listeners = (ListenerEntry *)
1584 : 50 : dsa_get_address(globalChannelDSA, entry->listenersArray);
1585 : :
1586 : : /*
1587 : : * Check if we already have a ListenerEntry (possibly from earlier in this
1588 : : * transaction)
1589 : : */
1590 [ + + ]: 53 : for (int i = 0; i < entry->numListeners; i++)
1591 : : {
1592 [ + + ]: 13 : if (listeners[i].procNo == MyProcNumber)
1593 : : {
1594 : : /* Already have an entry; leave removeOnAbort as-is */
1595 : 10 : dshash_release_lock(globalChannelTable, entry);
1596 : 10 : return;
1597 : : }
1598 : : }
1599 : :
1600 : : /* Need to add a new entry; grow array if necessary */
1601 [ - + ]: 40 : if (entry->numListeners >= entry->allocatedListeners)
1602 : : {
135 tgl@sss.pgh.pa.us 1603 :UNC 0 : int new_size = entry->allocatedListeners * 2;
1604 : 0 : dsa_pointer old_array = entry->listenersArray;
1605 : 0 : dsa_pointer new_array = dsa_allocate(globalChannelDSA,
1606 : : sizeof(ListenerEntry) * new_size);
1607 : 0 : ListenerEntry *new_listeners = (ListenerEntry *) dsa_get_address(globalChannelDSA, new_array);
1608 : :
1609 : 0 : memcpy(new_listeners, listeners, sizeof(ListenerEntry) * entry->numListeners);
1610 : 0 : entry->listenersArray = new_array;
1611 : 0 : entry->allocatedListeners = new_size;
1612 : 0 : dsa_free(globalChannelDSA, old_array);
1613 : 0 : listeners = new_listeners;
1614 : : }
1615 : :
135 tgl@sss.pgh.pa.us 1616 :GNC 40 : listeners[entry->numListeners].procNo = MyProcNumber;
3 1617 : 40 : listeners[entry->numListeners].removeOnAbort = true;
135 1618 : 40 : entry->numListeners++;
1619 : :
1620 : 40 : dshash_release_lock(globalChannelTable, entry);
1621 : : }
1622 : :
1623 : : /*
1624 : : * PrepareTableEntriesForUnlisten --- subroutine for PreCommit_Notify
1625 : : *
1626 : : * Prepare an UNLISTEN by recording it in pendingListenActions, but only if
1627 : : * we're currently listening (committed or staged). We don't touch
1628 : : * globalChannelTable yet - the listener keeps receiving signals until
1629 : : * commit, when the entry is removed.
1630 : : */
1631 : : static void
1632 : 4 : PrepareTableEntriesForUnlisten(const char *channel)
1633 : : {
1634 : : PendingListenEntry *pending;
1635 : :
1636 : : /*
1637 : : * If the channel name is not in localChannelTable, then we are neither
1638 : : * listening on it nor preparing to listen on it, so we don't need to
1639 : : * record an UNLISTEN action.
1640 : : */
1641 [ - + ]: 4 : Assert(localChannelTable != NULL);
1642 [ - + ]: 4 : if (hash_search(localChannelTable, channel, HASH_FIND, NULL) == NULL)
5947 tgl@sss.pgh.pa.us 1643 :LBC (10) : return;
1644 : :
1645 : : /*
1646 : : * Record in local pending hash that we want to UNLISTEN, overwriting any
1647 : : * earlier attempt to LISTEN. Don't touch localChannelTable or
1648 : : * globalChannelTable yet - we keep receiving signals until commit.
1649 : : */
1650 : : pending = (PendingListenEntry *)
135 tgl@sss.pgh.pa.us 1651 :GNC 4 : hash_search(pendingListenActions, channel, HASH_ENTER, NULL);
1652 : 4 : pending->action = PENDING_UNLISTEN;
1653 : : }
1654 : :
1655 : : /*
1656 : : * PrepareTableEntriesForUnlistenAll --- subroutine for PreCommit_Notify
1657 : : *
1658 : : * Prepare UNLISTEN * by recording an UNLISTEN for all listened or
1659 : : * about-to-be-listened channels in pendingListenActions.
1660 : : */
1661 : : static void
1662 : 41 : PrepareTableEntriesForUnlistenAll(void)
1663 : : {
1664 : : HASH_SEQ_STATUS seq;
1665 : : ChannelName *channelEntry;
1666 : : PendingListenEntry *pending;
1667 : :
1668 : : /*
1669 : : * Scan localChannelTable, which will have the names of all channels that
1670 : : * we are listening on or have prepared to listen on. Record an UNLISTEN
1671 : : * action for each one, overwriting any earlier attempt to LISTEN.
1672 : : */
1673 : 41 : hash_seq_init(&seq, localChannelTable);
1674 [ + + ]: 69 : while ((channelEntry = (ChannelName *) hash_seq_search(&seq)) != NULL)
1675 : : {
1676 : : pending = (PendingListenEntry *)
1677 : 28 : hash_search(pendingListenActions, channelEntry->channel, HASH_ENTER, NULL);
1678 : 28 : pending->action = PENDING_UNLISTEN;
1679 : : }
1680 : 41 : }
1681 : :
1682 : : /*
1683 : : * RemoveListenerFromChannel --- remove idx'th listener from global channel entry
1684 : : *
1685 : : * Decrements numListeners, compacts the array, and frees the entry if empty.
1686 : : * Sets *entry_ptr to NULL if the entry was deleted.
1687 : : *
1688 : : * We could get the listeners pointer from the entry, but all callers
1689 : : * already have it at hand.
1690 : : */
1691 : : static void
1692 : 32 : RemoveListenerFromChannel(GlobalChannelEntry **entry_ptr,
1693 : : ListenerEntry *listeners,
1694 : : int idx)
1695 : : {
1696 : 32 : GlobalChannelEntry *entry = *entry_ptr;
1697 : :
1698 : 32 : entry->numListeners--;
1699 [ + + ]: 32 : if (idx < entry->numListeners)
1700 : 3 : memmove(&listeners[idx], &listeners[idx + 1],
1701 : 3 : sizeof(ListenerEntry) * (entry->numListeners - idx));
1702 : :
1703 [ + + ]: 32 : if (entry->numListeners == 0)
1704 : : {
1705 : 29 : dsa_free(globalChannelDSA, entry->listenersArray);
1706 : 29 : dshash_delete_entry(globalChannelTable, entry);
1707 : : /* tells caller not to release the entry's lock: */
1708 : 29 : *entry_ptr = NULL;
1709 : : }
1710 : 32 : }
1711 : :
1712 : : /*
1713 : : * ApplyPendingListenActions
1714 : : *
1715 : : * Apply, or revert, staged listen/unlisten changes to the local and global
1716 : : * hash tables.
1717 : : */
1718 : : static void
1719 : 35491 : ApplyPendingListenActions(bool isCommit)
1720 : : {
1721 : : HASH_SEQ_STATUS seq;
1722 : : PendingListenEntry *pending;
1723 : :
1724 : : /* Quick exit if nothing to do */
1725 [ + + ]: 35491 : if (pendingListenActions == NULL)
1726 : 35409 : return;
1727 : :
1728 : : /* We made a globalChannelTable before building pendingListenActions */
1729 [ - + ]: 82 : if (globalChannelTable == NULL)
135 tgl@sss.pgh.pa.us 1730 [ # # ]:UNC 0 : elog(PANIC, "global channel table missing post-commit/abort");
1731 : :
1732 : : /* For each staged action ... */
135 tgl@sss.pgh.pa.us 1733 :GNC 82 : hash_seq_init(&seq, pendingListenActions);
1734 [ + + ]: 163 : while ((pending = (PendingListenEntry *) hash_seq_search(&seq)) != NULL)
1735 : : {
1736 : : GlobalChannelKey key;
1737 : : GlobalChannelEntry *entry;
1738 : 81 : bool removeLocal = true;
1739 : 81 : bool foundListener = false;
1740 : :
1741 : : /*
1742 : : * Find the global entry for this channel. If isCommit, it had better
1743 : : * exist (it was created in PreCommit). In an abort, it might not
1744 : : * exist, in which case we are not listening and should discard any
1745 : : * local entry that PreCommit may have managed to create.
1746 : : */
1747 : 81 : GlobalChannelKeyInit(&key, MyDatabaseId, pending->channel);
1748 : 81 : entry = dshash_find(globalChannelTable, &key, true);
1749 [ + - ]: 81 : if (entry != NULL)
1750 : : {
1751 : : /* Scan entry to find the ListenerEntry for this backend */
1752 : : ListenerEntry *listeners;
1753 : :
1754 : : listeners = (ListenerEntry *)
1755 : 81 : dsa_get_address(globalChannelDSA, entry->listenersArray);
1756 : :
1757 [ + - ]: 84 : for (int i = 0; i < entry->numListeners; i++)
1758 : : {
1759 [ + + ]: 84 : if (listeners[i].procNo != MyProcNumber)
1760 : 3 : continue;
1761 : 81 : foundListener = true;
1762 [ + - ]: 81 : if (isCommit)
1763 : : {
1764 [ + + ]: 81 : if (pending->action == PENDING_LISTEN)
1765 : : {
1766 : : /*
1767 : : * LISTEN being committed: entry is now permanent.
1768 : : * localChannelTable entry was created during
1769 : : * PreCommit and should be kept.
1770 : : */
3 1771 : 49 : listeners[i].removeOnAbort = false;
135 1772 : 49 : removeLocal = false;
1773 : : }
1774 : : else
1775 : : {
1776 : : /*
1777 : : * UNLISTEN being committed: remove pre-allocated
1778 : : * entries from both tables.
1779 : : */
1780 : 32 : RemoveListenerFromChannel(&entry, listeners, i);
1781 : : }
1782 : : }
1783 : : else
1784 : : {
1785 : : /*
1786 : : * Note: this part is reachable only if the transaction
1787 : : * aborts after PreCommit_Notify() has made some
1788 : : * pendingListenActions entries, so it's pretty hard to
1789 : : * test.
1790 : : */
3 tgl@sss.pgh.pa.us 1791 [ # # ]:UNC 0 : if (listeners[i].removeOnAbort)
1792 : : {
1793 : : /*
1794 : : * Staged LISTEN (or LISTEN+UNLISTEN) being aborted,
1795 : : * so remove pre-allocated entries from both tables.
1796 : : */
135 1797 : 0 : RemoveListenerFromChannel(&entry, listeners, i);
1798 : : }
1799 : : else
1800 : : {
1801 : : /*
1802 : : * Entry predates this transaction, so keep the
1803 : : * localChannelTable entry.
1804 : : */
1805 : 0 : removeLocal = false;
1806 : : }
1807 : : }
135 tgl@sss.pgh.pa.us 1808 :GNC 81 : break; /* there shouldn't be another match */
1809 : : }
1810 : :
1811 : : /* We might have already released the entry by removing it */
1812 [ + + ]: 81 : if (entry != NULL)
1813 : 52 : dshash_release_lock(globalChannelTable, entry);
1814 : : }
1815 : :
1816 : : /*
1817 : : * If we're committing a LISTEN action, we should have found a
1818 : : * matching ListenerEntry, but otherwise it's okay if we didn't.
1819 : : */
1820 [ + - + + : 81 : if (isCommit && pending->action == PENDING_LISTEN && !foundListener)
- + ]
135 tgl@sss.pgh.pa.us 1821 [ # # ]:UNC 0 : elog(PANIC, "could not find listener entry for channel \"%s\" backend %d",
1822 : : pending->channel, MyProcNumber);
1823 : :
1824 : : /*
1825 : : * If we did not find a globalChannelTable entry for our backend, or
1826 : : * if we are unlistening, remove any localChannelTable entry that may
1827 : : * exist. (Note in particular that this cleans up if we created a
1828 : : * localChannelTable entry and then failed while trying to create a
1829 : : * globalChannelTable entry.)
1830 : : */
135 tgl@sss.pgh.pa.us 1831 [ + + + - ]:GNC 81 : if (removeLocal && localChannelTable != NULL)
1832 : 32 : (void) hash_search(localChannelTable, pending->channel,
1833 : : HASH_REMOVE, NULL);
1834 : : }
5947 tgl@sss.pgh.pa.us 1835 :ECB (3) : }
1836 : :
1837 : : /*
1838 : : * CleanupListenersOnExit --- called from Async_UnlistenOnExit
1839 : : *
1840 : : * Remove this backend from all channels in the shared global table.
1841 : : */
1842 : : static void
135 tgl@sss.pgh.pa.us 1843 :GNC 18 : CleanupListenersOnExit(void)
1844 : : {
1845 : : dshash_seq_status status;
1846 : : GlobalChannelEntry *entry;
1847 : :
5947 tgl@sss.pgh.pa.us 1848 [ - + ]:CBC 18 : if (Trace_notify)
135 tgl@sss.pgh.pa.us 1849 [ # # ]:UNC 0 : elog(DEBUG1, "CleanupListenersOnExit(%d)", MyProcPid);
1850 : :
1851 : : /* Clear our local cache (not really necessary, but be consistent) */
135 tgl@sss.pgh.pa.us 1852 [ + - ]:GNC 18 : if (localChannelTable != NULL)
1853 : : {
1854 : 18 : hash_destroy(localChannelTable);
1855 : 18 : localChannelTable = NULL;
1856 : : }
1857 : :
1858 : : /* Now remove our entries from the shared globalChannelTable */
1859 [ - + ]: 18 : if (globalChannelTable == NULL)
135 tgl@sss.pgh.pa.us 1860 :UNC 0 : return;
1861 : :
135 tgl@sss.pgh.pa.us 1862 :GNC 18 : dshash_seq_init(&status, globalChannelTable, true);
1863 [ + + ]: 32 : while ((entry = dshash_seq_next(&status)) != NULL)
1864 : : {
1865 : : ListenerEntry *listeners;
1866 : :
1867 [ - + ]: 14 : if (entry->key.dboid != MyDatabaseId)
135 tgl@sss.pgh.pa.us 1868 :UNC 0 : continue; /* not relevant */
1869 : :
1870 : : listeners = (ListenerEntry *)
135 tgl@sss.pgh.pa.us 1871 :GNC 14 : dsa_get_address(globalChannelDSA, entry->listenersArray);
1872 : :
1873 [ + + ]: 20 : for (int i = 0; i < entry->numListeners; i++)
1874 : : {
1875 [ + + ]: 14 : if (listeners[i].procNo == MyProcNumber)
1876 : : {
1877 : 8 : entry->numListeners--;
1878 [ - + ]: 8 : if (i < entry->numListeners)
135 tgl@sss.pgh.pa.us 1879 :UNC 0 : memmove(&listeners[i], &listeners[i + 1],
1880 : 0 : sizeof(ListenerEntry) * (entry->numListeners - i));
1881 : :
135 tgl@sss.pgh.pa.us 1882 [ + - ]:GNC 8 : if (entry->numListeners == 0)
1883 : : {
1884 : 8 : dsa_free(globalChannelDSA, entry->listenersArray);
1885 : 8 : dshash_delete_current(&status);
1886 : : }
1887 : 8 : break;
1888 : : }
1889 : : }
1890 : : }
1891 : 18 : dshash_seq_term(&status);
5947 tgl@sss.pgh.pa.us 1892 :ECB (30) : }
1893 : :
1894 : : /*
1895 : : * Test whether we are actively listening on the given channel name.
1896 : : *
1897 : : * Note: this function is executed for every notification found in the queue.
1898 : : */
1899 : : static bool
5947 tgl@sss.pgh.pa.us 1900 :CBC 55 : IsListeningOn(const char *channel)
1901 : : {
135 tgl@sss.pgh.pa.us 1902 [ - + ]:GNC 55 : if (localChannelTable == NULL)
135 tgl@sss.pgh.pa.us 1903 :UNC 0 : return false;
1904 : :
135 tgl@sss.pgh.pa.us 1905 :GNC 55 : return (hash_search(localChannelTable, channel, HASH_FIND, NULL) != NULL);
1906 : : }
1907 : :
1908 : : /*
1909 : : * Remove our entry from the listeners array when we are no longer listening
1910 : : * on any channel. NB: must not fail if we're already not listening.
1911 : : */
1912 : : static void
5947 tgl@sss.pgh.pa.us 1913 :CBC 39 : asyncQueueUnregister(void)
1914 : : {
135 tgl@sss.pgh.pa.us 1915 [ + + - + ]:GNC 39 : Assert(LocalChannelTableIsEmpty()); /* else caller error */
1916 : :
4749 bruce@momjian.us 1917 [ + + ]:CBC 39 : if (!amRegisteredListener) /* nothing to do */
4854 tgl@sss.pgh.pa.us 1918 : 12 : return;
1919 : :
1920 : : /*
1921 : : * Need exclusive lock here to manipulate list links.
1922 : : */
2206 1923 : 27 : LWLockAcquire(NotifyQueueLock, LW_EXCLUSIVE);
1924 : : /* Mark our entry as invalid */
818 heikki.linnakangas@i 1925 : 27 : QUEUE_BACKEND_PID(MyProcNumber) = InvalidPid;
1926 : 27 : QUEUE_BACKEND_DBOID(MyProcNumber) = InvalidOid;
135 tgl@sss.pgh.pa.us 1927 :GNC 27 : QUEUE_BACKEND_WAKEUP_PENDING(MyProcNumber) = false;
1928 : 27 : QUEUE_BACKEND_IS_ADVANCING(MyProcNumber) = false;
1929 : : /* and remove it from the list */
818 heikki.linnakangas@i 1930 [ + + ]:CBC 27 : if (QUEUE_FIRST_LISTENER == MyProcNumber)
1931 : 25 : QUEUE_FIRST_LISTENER = QUEUE_NEXT_LISTENER(MyProcNumber);
1932 : : else
1933 : : {
1934 [ + - ]: 2 : for (ProcNumber i = QUEUE_FIRST_LISTENER; i != INVALID_PROC_NUMBER; i = QUEUE_NEXT_LISTENER(i))
1935 : : {
1936 [ + - ]: 2 : if (QUEUE_NEXT_LISTENER(i) == MyProcNumber)
1937 : : {
1938 : 2 : QUEUE_NEXT_LISTENER(i) = QUEUE_NEXT_LISTENER(MyProcNumber);
2454 tgl@sss.pgh.pa.us 1939 : 2 : break;
1940 : : }
1941 : : }
1942 : : }
818 heikki.linnakangas@i 1943 : 27 : QUEUE_NEXT_LISTENER(MyProcNumber) = INVALID_PROC_NUMBER;
2206 tgl@sss.pgh.pa.us 1944 : 27 : LWLockRelease(NotifyQueueLock);
1945 : :
1946 : : /* mark ourselves as no longer listed in the global array */
4854 1947 : 27 : amRegisteredListener = false;
1948 : : }
1949 : :
1950 : : /*
1951 : : * Test whether there is room to insert more notification messages.
1952 : : *
1953 : : * Caller must hold at least shared NotifyQueueLock.
1954 : : */
1955 : : static bool
5947 1956 : 94 : asyncQueueIsFull(void)
1957 : : {
676 michael@paquier.xyz 1958 : 94 : int64 headPage = QUEUE_POS_PAGE(QUEUE_HEAD);
1959 : 94 : int64 tailPage = QUEUE_POS_PAGE(QUEUE_TAIL);
1960 : 94 : int64 occupied = headPage - tailPage;
1961 : :
913 akorotkov@postgresql 1962 : 94 : return occupied >= max_notify_queue_pages;
1963 : : }
1964 : :
1965 : : /*
1966 : : * Advance the QueuePosition to the next entry, assuming that the current
1967 : : * entry is of length entryLength. If we jump to a new page the function
1968 : : * returns true, else false.
1969 : : */
1970 : : static bool
4142 tgl@sss.pgh.pa.us 1971 : 2505 : asyncQueueAdvance(volatile QueuePosition *position, int entryLength)
1972 : : {
913 akorotkov@postgresql 1973 : 2505 : int64 pageno = QUEUE_POS_PAGE(*position);
5937 bruce@momjian.us 1974 : 2505 : int offset = QUEUE_POS_OFFSET(*position);
1975 : 2505 : bool pageJump = false;
1976 : :
1977 : : /*
1978 : : * Move to the next writing position: First jump over what we have just
1979 : : * written or read.
1980 : : */
5947 tgl@sss.pgh.pa.us 1981 : 2505 : offset += entryLength;
1982 [ - + ]: 2505 : Assert(offset <= QUEUE_PAGESIZE);
1983 : :
1984 : : /*
1985 : : * In a second step check if another entry can possibly be written to the
1986 : : * page. If so, stay here, we have reached the next position. If not, then
1987 : : * we need to move on to the next page.
1988 : : */
1989 [ + + ]: 2505 : if (offset + QUEUEALIGN(AsyncQueueEntryEmptySize) > QUEUE_PAGESIZE)
1990 : : {
1991 : 38 : pageno++;
1992 : 38 : offset = 0;
1993 : 38 : pageJump = true;
1994 : : }
1995 : :
1996 : 2505 : SET_QUEUE_POS(*position, pageno, offset);
1997 : 2505 : return pageJump;
1998 : : }
1999 : :
2000 : : /*
2001 : : * Fill the AsyncQueueEntry at *qe with an outbound notification message.
2002 : : */
2003 : : static void
2004 : 1136 : asyncQueueNotificationToEntry(Notification *n, AsyncQueueEntry *qe)
2005 : : {
2480 2006 : 1136 : size_t channellen = n->channel_len;
2007 : 1136 : size_t payloadlen = n->payload_len;
2008 : : int entryLength;
2009 : :
5947 2010 [ - + ]: 1136 : Assert(channellen < NAMEDATALEN);
2011 [ - + ]: 1136 : Assert(payloadlen < NOTIFY_PAYLOAD_MAX_LENGTH);
2012 : :
2013 : : /* The terminators are already included in AsyncQueueEntryEmptySize */
2014 : 1136 : entryLength = AsyncQueueEntryEmptySize + payloadlen + channellen;
2015 : 1136 : entryLength = QUEUEALIGN(entryLength);
2016 : 1136 : qe->length = entryLength;
2017 : 1136 : qe->dboid = MyDatabaseId;
2018 : 1136 : qe->xid = GetCurrentTransactionId();
2019 : 1136 : qe->srcPid = MyProcPid;
2480 2020 : 1136 : memcpy(qe->data, n->data, channellen + payloadlen + 2);
5947 2021 : 1136 : }
2022 : :
2023 : : /*
2024 : : * Add pending notifications to the queue.
2025 : : *
2026 : : * We go page by page here, i.e. we stop once we have to go to a new page but
2027 : : * we will be called again and then fill that next page. If an entry does not
2028 : : * fit into the current page, we write a dummy entry with an InvalidOid as the
2029 : : * database OID in order to fill the page. So every page is always used up to
2030 : : * the last byte which simplifies reading the page later.
2031 : : *
2032 : : * We are passed the list cell (in pendingNotifies->events) containing the next
2033 : : * notification to write and return the first still-unwritten cell back.
2034 : : * Eventually we will return NULL indicating all is done.
2035 : : *
2036 : : * We are holding NotifyQueueLock already from the caller and grab
2037 : : * page specific SLRU bank lock locally in this function.
2038 : : */
2039 : : static ListCell *
2040 : 94 : asyncQueueAddEntries(ListCell *nextNotify)
2041 : : {
2042 : : AsyncQueueEntry qe;
2043 : : QueuePosition queue_head;
2044 : : int64 pageno;
2045 : : int offset;
2046 : : int slotno;
2047 : : LWLock *prevlock;
2048 : :
2049 : : /*
2050 : : * We work with a local copy of QUEUE_HEAD, which we write back to shared
2051 : : * memory upon exiting. The reason for this is that if we have to advance
2052 : : * to a new page, SimpleLruZeroPage might fail (out of disk space, for
2053 : : * instance), and we must not advance QUEUE_HEAD if it does. (Otherwise,
2054 : : * subsequent insertions would try to put entries into a page that slru.c
2055 : : * thinks doesn't exist yet.) So, use a local position variable. Note
2056 : : * that if we do fail, any already-inserted queue entries are forgotten;
2057 : : * this is okay, since they'd be useless anyway after our transaction
2058 : : * rolls back.
2059 : : */
5083 2060 : 94 : queue_head = QUEUE_HEAD;
2061 : :
2062 : : /*
2063 : : * If this is the first write since the postmaster started, we need to
2064 : : * initialize the first page of the async SLRU. Otherwise, the current
2065 : : * page should be initialized already, so just fetch it.
2066 : : */
2067 : 94 : pageno = QUEUE_POS_PAGE(queue_head);
822 alvherre@alvh.no-ip. 2068 : 94 : prevlock = SimpleLruGetBankLock(NotifyCtl, pageno);
2069 : :
2070 : : /* We hold both NotifyQueueLock and SLRU bank lock during this operation */
2071 : 94 : LWLockAcquire(prevlock, LW_EXCLUSIVE);
2072 : :
2208 tgl@sss.pgh.pa.us 2073 [ + + + + ]: 94 : if (QUEUE_POS_IS_ZERO(queue_head))
2206 2074 : 8 : slotno = SimpleLruZeroPage(NotifyCtl, pageno);
2075 : : else
78 heikki.linnakangas@i 2076 :GNC 86 : slotno = SimpleLruReadPage(NotifyCtl, pageno, true, &queue_head);
2077 : :
2078 : : /* Note we mark the page dirty before writing in it */
2206 tgl@sss.pgh.pa.us 2079 :CBC 94 : NotifyCtl->shared->page_dirty[slotno] = true;
2080 : :
5947 2081 [ + + ]: 1195 : while (nextNotify != NULL)
2082 : : {
5937 bruce@momjian.us 2083 : 1136 : Notification *n = (Notification *) lfirst(nextNotify);
2084 : :
2085 : : /* Construct a valid queue entry in local variable qe */
5947 tgl@sss.pgh.pa.us 2086 : 1136 : asyncQueueNotificationToEntry(n, &qe);
2087 : :
5083 2088 : 1136 : offset = QUEUE_POS_OFFSET(queue_head);
2089 : :
2090 : : /* Check whether the entry really fits on the current page */
5947 2091 [ + + ]: 1136 : if (offset + qe.length <= QUEUE_PAGESIZE)
2092 : : {
2093 : : /* OK, so advance nextNotify past this item */
2480 2094 : 1104 : nextNotify = lnext(pendingNotifies->events, nextNotify);
2095 : : }
2096 : : else
2097 : : {
2098 : : /*
2099 : : * Write a dummy entry to fill up the page. Actually readers will
2100 : : * only check dboid and since it won't match any reader's database
2101 : : * OID, they will ignore this entry and move on.
2102 : : */
5947 2103 : 32 : qe.length = QUEUE_PAGESIZE - offset;
2104 : 32 : qe.dboid = InvalidOid;
199 heikki.linnakangas@i 2105 : 32 : qe.xid = InvalidTransactionId;
5937 bruce@momjian.us 2106 : 32 : qe.data[0] = '\0'; /* empty channel */
2107 : 32 : qe.data[1] = '\0'; /* empty payload */
2108 : : }
2109 : :
2110 : : /* Now copy qe into the shared buffer page */
2206 tgl@sss.pgh.pa.us 2111 : 1136 : memcpy(NotifyCtl->shared->page_buffer[slotno] + offset,
2112 : : &qe,
5947 2113 : 1136 : qe.length);
2114 : :
2115 : : /* Advance queue_head appropriately, and detect if page is full */
5083 2116 [ + + ]: 1136 : if (asyncQueueAdvance(&(queue_head), qe.length))
2117 : : {
2118 : : LWLock *lock;
2119 : :
822 alvherre@alvh.no-ip. 2120 : 35 : pageno = QUEUE_POS_PAGE(queue_head);
2121 : 35 : lock = SimpleLruGetBankLock(NotifyCtl, pageno);
2122 [ - + ]: 35 : if (lock != prevlock)
2123 : : {
822 alvherre@alvh.no-ip. 2124 :UBC 0 : LWLockRelease(prevlock);
2125 : 0 : LWLockAcquire(lock, LW_EXCLUSIVE);
2126 : 0 : prevlock = lock;
2127 : : }
2128 : :
2129 : : /*
2130 : : * Page is full, so we're done here, but first fill the next page
2131 : : * with zeroes. The reason to do this is to ensure that slru.c's
2132 : : * idea of the head page is always the same as ours, which avoids
2133 : : * boundary problems in SimpleLruTruncate. The test in
2134 : : * asyncQueueIsFull() ensured that there is room to create this
2135 : : * page without overrunning the queue.
2136 : : */
2206 tgl@sss.pgh.pa.us 2137 :CBC 35 : slotno = SimpleLruZeroPage(NotifyCtl, QUEUE_POS_PAGE(queue_head));
2138 : :
2139 : : /*
2140 : : * If the new page address is a multiple of QUEUE_CLEANUP_DELAY,
2141 : : * set flag to remember that we should try to advance the tail
2142 : : * pointer (we don't want to actually do that right here).
2143 : : */
2442 2144 [ + + ]: 35 : if (QUEUE_POS_PAGE(queue_head) % QUEUE_CLEANUP_DELAY == 0)
1719 2145 : 8 : tryAdvanceTail = true;
2146 : :
2147 : : /* And exit the loop */
9118 2148 : 35 : break;
2149 : : }
2150 : : }
2151 : :
2152 : : /* Success, so update the global QUEUE_HEAD */
5083 2153 : 94 : QUEUE_HEAD = queue_head;
2154 : :
822 alvherre@alvh.no-ip. 2155 : 94 : LWLockRelease(prevlock);
2156 : :
5947 tgl@sss.pgh.pa.us 2157 : 94 : return nextNotify;
2158 : : }
2159 : :
2160 : : /*
2161 : : * SQL function to return the fraction of the notification queue currently
2162 : : * occupied.
2163 : : */
2164 : : Datum
3970 rhaas@postgresql.org 2165 : 6 : pg_notification_queue_usage(PG_FUNCTION_ARGS)
2166 : : {
2167 : : double usage;
2168 : :
2169 : : /* Advance the queue tail so we don't report a too-large result */
2379 tgl@sss.pgh.pa.us 2170 : 6 : asyncQueueAdvanceTail();
2171 : :
2206 2172 : 6 : LWLockAcquire(NotifyQueueLock, LW_SHARED);
3970 rhaas@postgresql.org 2173 : 6 : usage = asyncQueueUsage();
2206 tgl@sss.pgh.pa.us 2174 : 6 : LWLockRelease(NotifyQueueLock);
2175 : :
3970 rhaas@postgresql.org 2176 : 6 : PG_RETURN_FLOAT8(usage);
2177 : : }
2178 : :
2179 : : /*
2180 : : * Return the fraction of the queue that is currently occupied.
2181 : : *
2182 : : * The caller must hold NotifyQueueLock in (at least) shared mode.
2183 : : *
2184 : : * Note: we measure the distance to the logical tail page, not the physical
2185 : : * tail page. In some sense that's wrong, but the relative position of the
2186 : : * physical tail is affected by details such as SLRU segment boundaries,
2187 : : * so that a result based on that is unpleasantly unstable.
2188 : : */
2189 : : static double
2190 : 100 : asyncQueueUsage(void)
2191 : : {
676 michael@paquier.xyz 2192 : 100 : int64 headPage = QUEUE_POS_PAGE(QUEUE_HEAD);
2193 : 100 : int64 tailPage = QUEUE_POS_PAGE(QUEUE_TAIL);
2194 : 100 : int64 occupied = headPage - tailPage;
2195 : :
5947 tgl@sss.pgh.pa.us 2196 [ + + ]: 100 : if (occupied == 0)
3970 rhaas@postgresql.org 2197 : 61 : return (double) 0; /* fast exit for common case */
2198 : :
913 akorotkov@postgresql 2199 : 39 : return (double) occupied / (double) max_notify_queue_pages;
2200 : : }
2201 : :
2202 : : /*
2203 : : * Check whether the queue is at least half full, and emit a warning if so.
2204 : : *
2205 : : * This is unlikely given the size of the queue, but possible.
2206 : : * The warnings show up at most once every QUEUE_FULL_WARN_INTERVAL.
2207 : : *
2208 : : * Caller must hold exclusive NotifyQueueLock.
2209 : : */
2210 : : static void
3970 rhaas@postgresql.org 2211 : 94 : asyncQueueFillWarning(void)
2212 : : {
2213 : : double fillDegree;
2214 : : TimestampTz t;
2215 : :
2216 : 94 : fillDegree = asyncQueueUsage();
5947 tgl@sss.pgh.pa.us 2217 [ + - ]: 94 : if (fillDegree < 0.5)
2218 : 94 : return;
2219 : :
5947 tgl@sss.pgh.pa.us 2220 :UBC 0 : t = GetCurrentTimestamp();
2221 : :
2222 [ # # ]: 0 : if (TimestampDifferenceExceeds(asyncQueueControl->lastQueueFillWarn,
2223 : : t, QUEUE_FULL_WARN_INTERVAL))
2224 : : {
5937 bruce@momjian.us 2225 : 0 : QueuePosition min = QUEUE_HEAD;
2226 : 0 : int32 minPid = InvalidPid;
2227 : :
818 heikki.linnakangas@i 2228 [ # # ]: 0 : for (ProcNumber i = QUEUE_FIRST_LISTENER; i != INVALID_PROC_NUMBER; i = QUEUE_NEXT_LISTENER(i))
2229 : : {
2454 tgl@sss.pgh.pa.us 2230 [ # # ]: 0 : Assert(QUEUE_BACKEND_PID(i) != InvalidPid);
2231 [ # # # # : 0 : min = QUEUE_POS_MIN(min, QUEUE_BACKEND_POS(i));
# # ]
2232 [ # # # # ]: 0 : if (QUEUE_POS_EQUAL(min, QUEUE_BACKEND_POS(i)))
2233 : 0 : minPid = QUEUE_BACKEND_PID(i);
2234 : : }
2235 : :
5947 2236 [ # # # # : 0 : ereport(WARNING,
# # ]
2237 : : (errmsg("NOTIFY queue is %.0f%% full", fillDegree * 100),
2238 : : (minPid != InvalidPid ?
2239 : : errdetail("The server process with PID %d is among those with the oldest transactions.", minPid)
2240 : : : 0),
2241 : : (minPid != InvalidPid ?
2242 : : errhint("The NOTIFY queue cannot be emptied until that process ends its current transaction.")
2243 : : : 0)));
2244 : :
2245 : 0 : asyncQueueControl->lastQueueFillWarn = t;
2246 : : }
2247 : : }
2248 : :
2249 : : /*
2250 : : * Send signals to listening backends.
2251 : : *
2252 : : * Normally we signal only backends that are interested in the notifies that
2253 : : * we just sent. However, that will leave idle listeners falling further and
2254 : : * further behind. Waken them anyway if they're far enough behind, so they'll
2255 : : * advance their queue position pointers, allowing the global tail to advance.
2256 : : *
2257 : : * Since we know the ProcNumber and the Pid the signaling is quite cheap.
2258 : : *
2259 : : * This is called during CommitTransaction(), so it's important for it
2260 : : * to have very low probability of failure.
2261 : : */
2262 : : static void
5947 tgl@sss.pgh.pa.us 2263 :CBC 59 : SignalBackends(void)
2264 : : {
2265 : : int count;
2266 : :
2267 : : /* Can't get here without PreCommit_Notify having made the global table */
135 tgl@sss.pgh.pa.us 2268 [ - + ]:GNC 59 : Assert(globalChannelTable != NULL);
2269 : :
2270 : : /* It should have set up these arrays, too */
2271 [ + - - + ]: 59 : Assert(signalPids != NULL && signalProcnos != NULL);
2272 : :
2273 : : /*
2274 : : * Identify backends that we need to signal. We don't want to send
2275 : : * signals while holding the NotifyQueueLock, so this part just builds a
2276 : : * list of target PIDs in signalPids[] and signalProcnos[].
2277 : : */
5947 tgl@sss.pgh.pa.us 2278 :CBC 59 : count = 0;
2279 : :
2206 2280 : 59 : LWLockAcquire(NotifyQueueLock, LW_EXCLUSIVE);
2281 : :
2282 : : /* Scan each channel name that we notified in this transaction */
135 tgl@sss.pgh.pa.us 2283 [ + - + + :GNC 180 : foreach_ptr(char, channel, pendingNotifies->uniqueChannelNames)
+ + ]
2284 : : {
2285 : : GlobalChannelKey key;
2286 : : GlobalChannelEntry *entry;
2287 : : ListenerEntry *listeners;
2288 : :
2289 : 62 : GlobalChannelKeyInit(&key, MyDatabaseId, channel);
2290 : 62 : entry = dshash_find(globalChannelTable, &key, false);
2291 [ + + ]: 62 : if (entry == NULL)
2292 : 32 : continue; /* nobody is listening */
2293 : :
2294 : 30 : listeners = (ListenerEntry *) dsa_get_address(globalChannelDSA,
2295 : : entry->listenersArray);
2296 : :
2297 : : /*
2298 : : * Identify listeners that now need waking, add them to arrays.
2299 : : *
2300 : : * Note that we signal listeners regardless of the state of their
2301 : : * removeOnAbort flags. Hence a new listener that reached PreCommit,
2302 : : * but then failed before AtCommit_Notify, can receive a signal even
2303 : : * though it was never really listening. This is okay because it will
2304 : : * not do anything in response to that signal. If we did not do it
2305 : : * like this then a new listener might miss some messages due to the
2306 : : * direct-advance logic below.
2307 : : */
2308 [ + + ]: 63 : for (int j = 0; j < entry->numListeners; j++)
2309 : : {
3 2310 : 33 : ProcNumber i = listeners[j].procNo;
2311 : : int32 pid;
2312 : : QueuePosition pos;
2313 : :
135 2314 [ + + ]: 33 : if (QUEUE_BACKEND_WAKEUP_PENDING(i))
2315 : 6 : continue; /* already signaled, no need to repeat */
2316 : :
2317 : 27 : pid = QUEUE_BACKEND_PID(i);
2318 : 27 : pos = QUEUE_BACKEND_POS(i);
2319 : :
2320 [ + + - + ]: 27 : if (QUEUE_POS_EQUAL(pos, QUEUE_HEAD))
135 tgl@sss.pgh.pa.us 2321 :UNC 0 : continue; /* it's fully caught up already */
2322 : :
135 tgl@sss.pgh.pa.us 2323 [ - + ]:GNC 27 : Assert(pid != InvalidPid);
2324 : :
2325 : 27 : QUEUE_BACKEND_WAKEUP_PENDING(i) = true;
2326 : 27 : signalPids[count] = pid;
2327 : 27 : signalProcnos[count] = i;
2328 : 27 : count++;
2329 : : }
2330 : :
2331 : 30 : dshash_release_lock(globalChannelTable, entry);
2332 : : }
2333 : :
2334 : : /*
2335 : : * Scan all listeners. Any that are not already pending wakeup must not
2336 : : * be interested in our notifications (else we'd have set their wakeup
2337 : : * flags above). Check to see if we can directly advance their queue
2338 : : * pointers to save a wakeup. Otherwise, if they are far behind, wake
2339 : : * them anyway so they will catch up.
2340 : : */
818 heikki.linnakangas@i 2341 [ + + ]:CBC 104 : for (ProcNumber i = QUEUE_FIRST_LISTENER; i != INVALID_PROC_NUMBER; i = QUEUE_NEXT_LISTENER(i))
2342 : : {
2343 : : int32 pid;
2344 : : QueuePosition pos;
2345 : :
135 tgl@sss.pgh.pa.us 2346 [ + + ]:GNC 45 : if (QUEUE_BACKEND_WAKEUP_PENDING(i))
2347 : 32 : continue;
2348 : :
2349 : : /* If it's currently advancing, we should not touch it */
2350 [ - + ]: 13 : if (QUEUE_BACKEND_IS_ADVANCING(i))
135 tgl@sss.pgh.pa.us 2351 :UNC 0 : continue;
2352 : :
135 tgl@sss.pgh.pa.us 2353 :GNC 13 : pid = QUEUE_BACKEND_PID(i);
2442 tgl@sss.pgh.pa.us 2354 :CBC 13 : pos = QUEUE_BACKEND_POS(i);
2355 : :
2356 : : /*
2357 : : * We can directly advance the other backend's queue pointer if it's
2358 : : * not currently advancing (else there are race conditions), and its
2359 : : * current pointer is not behind queueHeadBeforeWrite (else we'd make
2360 : : * it miss some older messages), and we'd not be moving the pointer
2361 : : * backward.
2362 : : */
135 tgl@sss.pgh.pa.us 2363 [ + - + - :GNC 26 : if (!QUEUE_POS_PRECEDES(pos, queueHeadBeforeWrite) &&
+ - + + ]
2364 [ + - + - ]: 15 : QUEUE_POS_PRECEDES(pos, queueHeadAfterWrite))
2365 : : {
2366 : : /* We can directly advance its pointer past what we wrote */
2367 : 13 : QUEUE_BACKEND_POS(i) = queueHeadAfterWrite;
2368 : : }
135 tgl@sss.pgh.pa.us 2369 [ # # ]:UNC 0 : else if (asyncQueuePageDiff(QUEUE_POS_PAGE(QUEUE_HEAD),
2370 : : QUEUE_POS_PAGE(pos)) >= QUEUE_CLEANUP_DELAY)
2371 : : {
2372 : : /* It's idle and far behind, so wake it up */
2373 [ # # ]: 0 : Assert(pid != InvalidPid);
2374 : :
2375 : 0 : QUEUE_BACKEND_WAKEUP_PENDING(i) = true;
2376 : 0 : signalPids[count] = pid;
2377 : 0 : signalProcnos[count] = i;
2378 : 0 : count++;
2379 : : }
2380 : : }
2381 : :
2206 tgl@sss.pgh.pa.us 2382 :CBC 59 : LWLockRelease(NotifyQueueLock);
2383 : :
2384 : : /* Now send signals */
2454 2385 [ + + ]: 86 : for (int i = 0; i < count; i++)
2386 : : {
135 tgl@sss.pgh.pa.us 2387 :GNC 27 : int32 pid = signalPids[i];
2388 : :
2389 : : /*
2390 : : * If we are signaling our own process, no need to involve the kernel;
2391 : : * just set the flag directly.
2392 : : */
1719 tgl@sss.pgh.pa.us 2393 [ + + ]:CBC 27 : if (pid == MyProcPid)
2394 : : {
2395 : 21 : notifyInterruptPending = true;
2396 : 21 : continue;
2397 : : }
2398 : :
2399 : : /*
2400 : : * Note: assuming things aren't broken, a signal failure here could
2401 : : * only occur if the target backend exited since we released
2402 : : * NotifyQueueLock; which is unlikely but certainly possible. So we
2403 : : * just log a low-level debug message if it happens.
2404 : : */
135 tgl@sss.pgh.pa.us 2405 [ - + ]:GNC 6 : if (SendProcSignal(pid, PROCSIG_NOTIFY_INTERRUPT, signalProcnos[i]) < 0)
5947 tgl@sss.pgh.pa.us 2406 [ # # ]:UBC 0 : elog(DEBUG3, "could not signal backend with PID %d: %m", pid);
2407 : : }
10098 tgl@sss.pgh.pa.us 2408 :CBC 59 : }
2409 : :
2410 : : /*
2411 : : * AtAbort_Notify
2412 : : *
2413 : : * This is called at transaction abort.
2414 : : *
2415 : : * Revert any staged listen/unlisten changes and clean up transaction state.
2416 : : * This only does anything if we abort after PreCommit_Notify has staged
2417 : : * some entries.
2418 : : */
2419 : : void
9113 2420 : 35350 : AtAbort_Notify(void)
2421 : : {
2422 : : /* Revert staged listen/unlisten changes */
135 tgl@sss.pgh.pa.us 2423 :GNC 35350 : ApplyPendingListenActions(false);
2424 : :
2425 : : /* If we're no longer listening on anything, unregister */
2426 [ - + - - : 35350 : if (amRegisteredListener && LocalChannelTableIsEmpty())
- - ]
4854 tgl@sss.pgh.pa.us 2427 :UBC 0 : asyncQueueUnregister();
2428 : :
2429 : : /* And clean up */
6653 tgl@sss.pgh.pa.us 2430 :CBC 35350 : ClearPendingActionsAndNotifies();
10098 2431 : 35350 : }
2432 : :
2433 : : /*
2434 : : * AtSubCommit_Notify() --- Take care of subtransaction commit.
2435 : : *
2436 : : * Reassign all items in the pending lists to the parent transaction.
2437 : : */
2438 : : void
8003 2439 : 7276 : AtSubCommit_Notify(void)
2440 : : {
2430 rhaas@postgresql.org 2441 : 7276 : int my_level = GetCurrentTransactionNestLevel();
2442 : :
2443 : : /* If there are actions at our nesting level, we must reparent them. */
2444 [ + + ]: 7276 : if (pendingActions != NULL &&
2430 rhaas@postgresql.org 2445 [ + - ]:GBC 2 : pendingActions->nestingLevel >= my_level)
2446 : : {
2447 [ + + ]: 2 : if (pendingActions->upper == NULL ||
2448 [ - + ]: 1 : pendingActions->upper->nestingLevel < my_level - 1)
2449 : : {
2450 : : /* nothing to merge; give the whole thing to the parent */
2451 : 1 : --pendingActions->nestingLevel;
2452 : : }
2453 : : else
2454 : : {
2455 : 1 : ActionList *childPendingActions = pendingActions;
2456 : :
2457 : 1 : pendingActions = pendingActions->upper;
2458 : :
2459 : : /*
2460 : : * Mustn't try to eliminate duplicates here --- see queue_listen()
2461 : : */
2462 : 2 : pendingActions->actions =
2463 : 1 : list_concat(pendingActions->actions,
2464 : 1 : childPendingActions->actions);
2465 : 1 : pfree(childPendingActions);
2466 : : }
2467 : : }
2468 : :
2469 : : /* If there are notifies at our nesting level, we must reparent them. */
2430 rhaas@postgresql.org 2470 [ + + ]:CBC 7276 : if (pendingNotifies != NULL &&
2471 [ + + ]: 3 : pendingNotifies->nestingLevel >= my_level)
2472 : : {
2473 [ - + ]: 2 : Assert(pendingNotifies->nestingLevel == my_level);
2474 : :
2475 [ + + ]: 2 : if (pendingNotifies->upper == NULL ||
2476 [ - + ]: 1 : pendingNotifies->upper->nestingLevel < my_level - 1)
2477 : : {
2478 : : /* nothing to merge; give the whole thing to the parent */
2430 rhaas@postgresql.org 2479 :GBC 1 : --pendingNotifies->nestingLevel;
2480 : : }
2481 : : else
2482 : : {
2483 : : /*
2484 : : * Formerly, we didn't bother to eliminate duplicates here, but
2485 : : * now we must, else we fall foul of "Assert(!found)", either here
2486 : : * or during a later attempt to build the parent-level hashtable.
2487 : : */
2430 rhaas@postgresql.org 2488 :CBC 1 : NotificationList *childPendingNotifies = pendingNotifies;
2489 : : ListCell *l;
2490 : :
2491 : 1 : pendingNotifies = pendingNotifies->upper;
2492 : : /* Insert all the subxact's events into parent, except for dups */
2493 [ + - + + : 5 : foreach(l, childPendingNotifies->events)
+ + ]
2494 : : {
2495 : 4 : Notification *childn = (Notification *) lfirst(l);
2496 : :
2497 [ + + ]: 4 : if (!AsyncExistsPendingNotify(childn))
2498 : 2 : AddEventToPendingNotifies(childn);
2499 : : }
2500 : 1 : pfree(childPendingNotifies);
2501 : : }
2502 : : }
8003 tgl@sss.pgh.pa.us 2503 : 7276 : }
2504 : :
2505 : : /*
2506 : : * AtSubAbort_Notify() --- Take care of subtransaction abort.
2507 : : */
2508 : : void
2509 : 5394 : AtSubAbort_Notify(void)
2510 : : {
7936 2511 : 5394 : int my_level = GetCurrentTransactionNestLevel();
2512 : :
2513 : : /*
2514 : : * All we have to do is pop the stack --- the actions/notifies made in
2515 : : * this subxact are no longer interesting, and the space will be freed
2516 : : * when CurTransactionContext is recycled. We still have to free the
2517 : : * ActionList and NotificationList objects themselves, though, because
2518 : : * those are allocated in TopTransactionContext.
2519 : : *
2520 : : * Note that there might be no entries at all, or no entries for the
2521 : : * current subtransaction level, either because none were ever created, or
2522 : : * because we reentered this routine due to trouble during subxact abort.
2523 : : */
2430 rhaas@postgresql.org 2524 [ + + ]: 5395 : while (pendingActions != NULL &&
2430 rhaas@postgresql.org 2525 [ + - ]:GBC 1 : pendingActions->nestingLevel >= my_level)
2526 : : {
2527 : 1 : ActionList *childPendingActions = pendingActions;
2528 : :
2529 : 1 : pendingActions = pendingActions->upper;
2530 : 1 : pfree(childPendingActions);
2531 : : }
2532 : :
2430 rhaas@postgresql.org 2533 [ + + ]:CBC 5395 : while (pendingNotifies != NULL &&
2534 [ + + ]: 2 : pendingNotifies->nestingLevel >= my_level)
2535 : : {
2536 : 1 : NotificationList *childPendingNotifies = pendingNotifies;
2537 : :
2538 : 1 : pendingNotifies = pendingNotifies->upper;
2539 : 1 : pfree(childPendingNotifies);
2540 : : }
8003 tgl@sss.pgh.pa.us 2541 : 5394 : }
2542 : :
2543 : : /*
2544 : : * HandleNotifyInterrupt
2545 : : *
2546 : : * Signal handler portion of interrupt handling. Let the backend know
2547 : : * that there's a pending notify interrupt. If we're currently reading
2548 : : * from the client, this will interrupt the read and
2549 : : * ProcessClientReadInterrupt() will call ProcessNotifyInterrupt().
2550 : : */
2551 : : void
6147 2552 : 6 : HandleNotifyInterrupt(void)
2553 : : {
2554 : : /*
2555 : : * Note: this is called by a SIGNAL HANDLER. You must be very wary what
2556 : : * you do here.
2557 : : */
2558 : :
2559 : : /* signal that work needs to be done */
4134 andres@anarazel.de 2560 : 6 : notifyInterruptPending = true;
2561 : :
2562 : : /* latch will be set by procsignal_sigusr1_handler */
10098 tgl@sss.pgh.pa.us 2563 : 6 : }
2564 : :
2565 : : /*
2566 : : * ProcessNotifyInterrupt
2567 : : *
2568 : : * This is called if we see notifyInterruptPending set, just before
2569 : : * transmitting ReadyForQuery at the end of a frontend command, and
2570 : : * also if a notify signal occurs while reading from the frontend.
2571 : : * HandleNotifyInterrupt() will cause the read to be interrupted
2572 : : * via the process's latch, and this routine will get called.
2573 : : * If we are truly idle (ie, *not* inside a transaction block),
2574 : : * process the incoming notifies.
2575 : : *
2576 : : * If "flush" is true, force any frontend messages out immediately.
2577 : : * This can be false when being called at the end of a frontend command,
2578 : : * since we'll flush after sending ReadyForQuery.
2579 : : */
2580 : : void
1719 2581 : 33 : ProcessNotifyInterrupt(bool flush)
2582 : : {
8262 2583 [ + + ]: 33 : if (IsTransactionOrTransactionBlock())
10098 2584 : 7 : return; /* not really idle */
2585 : :
2586 : : /* Loop in case another signal arrives while sending messages */
4134 andres@anarazel.de 2587 [ + + ]: 52 : while (notifyInterruptPending)
1719 tgl@sss.pgh.pa.us 2588 : 26 : ProcessIncomingNotify(flush);
2589 : : }
2590 : :
2591 : :
2592 : : /*
2593 : : * Read all pending notifications from the queue, and deliver appropriate
2594 : : * ones to my frontend. Stop when we reach queue head or an uncommitted
2595 : : * notification.
2596 : : */
2597 : : static void
5947 2598 : 44 : asyncQueueReadAllNotifications(void)
2599 : : {
2600 : : QueuePosition pos;
2601 : : QueuePosition head;
2602 : : Snapshot snapshot;
2603 : :
2604 : : /*
2605 : : * Fetch current state, indicate to others that we have woken up, and that
2606 : : * we are in process of advancing our position.
2607 : : */
2206 2608 : 44 : LWLockAcquire(NotifyQueueLock, LW_SHARED);
2609 : : /* Assert checks that we have a valid state entry */
818 heikki.linnakangas@i 2610 [ - + ]: 44 : Assert(MyProcPid == QUEUE_BACKEND_PID(MyProcNumber));
135 tgl@sss.pgh.pa.us 2611 :GNC 44 : QUEUE_BACKEND_WAKEUP_PENDING(MyProcNumber) = false;
818 heikki.linnakangas@i 2612 :CBC 44 : pos = QUEUE_BACKEND_POS(MyProcNumber);
5947 tgl@sss.pgh.pa.us 2613 : 44 : head = QUEUE_HEAD;
2614 : :
2615 [ + + - + ]: 44 : if (QUEUE_POS_EQUAL(pos, head))
2616 : : {
2617 : : /* Nothing to do, we have read all notifications already. */
135 tgl@sss.pgh.pa.us 2618 :UNC 0 : LWLockRelease(NotifyQueueLock);
5947 tgl@sss.pgh.pa.us 2619 :UBC 0 : return;
2620 : : }
2621 : :
135 tgl@sss.pgh.pa.us 2622 :GNC 44 : QUEUE_BACKEND_IS_ADVANCING(MyProcNumber) = true;
2623 : 44 : LWLockRelease(NotifyQueueLock);
2624 : :
2625 : : /*----------
2626 : : * Get snapshot we'll use to decide which xacts are still in progress.
2627 : : * This is trickier than it might seem, because of race conditions.
2628 : : * Consider the following example:
2629 : : *
2630 : : * Backend 1: Backend 2:
2631 : : *
2632 : : * transaction starts
2633 : : * UPDATE foo SET ...;
2634 : : * NOTIFY foo;
2635 : : * commit starts
2636 : : * queue the notify message
2637 : : * transaction starts
2638 : : * LISTEN foo; -- first LISTEN in session
2639 : : * SELECT * FROM foo WHERE ...;
2640 : : * commit to clog
2641 : : * commit starts
2642 : : * add backend 2 to array of listeners
2643 : : * advance to queue head (this code)
2644 : : * commit to clog
2645 : : *
2646 : : * Transaction 2's SELECT has not seen the UPDATE's effects, since that
2647 : : * wasn't committed yet. Ideally we'd ensure that client 2 would
2648 : : * eventually get transaction 1's notify message, but there's no way
2649 : : * to do that; until we're in the listener array, there's no guarantee
2650 : : * that the notify message doesn't get removed from the queue.
2651 : : *
2652 : : * Therefore the coding technique transaction 2 is using is unsafe:
2653 : : * applications must commit a LISTEN before inspecting database state,
2654 : : * if they want to ensure they will see notifications about subsequent
2655 : : * changes to that state.
2656 : : *
2657 : : * What we do guarantee is that we'll see all notifications from
2658 : : * transactions committing after the snapshot we take here.
2659 : : * BecomeRegisteredListener has already added us to the listener array,
2660 : : * so no not-yet-committed messages can be removed from the queue
2661 : : * before we see them.
2662 : : *----------
2663 : : */
2379 tgl@sss.pgh.pa.us 2664 :CBC 44 : snapshot = RegisterSnapshot(GetLatestSnapshot());
2665 : :
2666 : : /*
2667 : : * It is possible that we fail while trying to send a message to our
2668 : : * frontend (for example, because of encoding conversion failure). If
2669 : : * that happens it is critical that we not try to send the same message
2670 : : * over and over again. Therefore, we set ExitOnAnyError to upgrade any
2671 : : * ERRORs to FATAL, causing the client connection to be closed on error.
2672 : : *
2673 : : * We used to only skip over the offending message and try to soldier on,
2674 : : * but it was somewhat questionable to lose a notification and give the
2675 : : * client an ERROR instead. A client application is not be prepared for
2676 : : * that and can't tell that a notification was missed. It was also not
2677 : : * very useful in practice because notifications are often processed while
2678 : : * a connection is idle and reading a message from the client, and in that
2679 : : * state, any error is upgraded to FATAL anyway. Closing the connection
2680 : : * is a clear signal to the application that it might have missed
2681 : : * notifications.
2682 : : */
2683 : : {
199 heikki.linnakangas@i 2684 : 44 : bool save_ExitOnAnyError = ExitOnAnyError;
2685 : : bool reachedStop;
2686 : :
2687 : 44 : ExitOnAnyError = true;
2688 : :
2689 : : do
2690 : : {
2691 : : /*
2692 : : * Process messages up to the stop position, end of page, or an
2693 : : * uncommitted message.
2694 : : *
2695 : : * Our stop position is what we found to be the head's position
2696 : : * when we entered this function. It might have changed already.
2697 : : * But if it has, we will receive (or have already received and
2698 : : * queued) another signal and come here again.
2699 : : *
2700 : : * We are not holding NotifyQueueLock here! The queue can only
2701 : : * extend beyond the head pointer (see above) and we leave our
2702 : : * backend's pointer where it is so nobody will truncate or
2703 : : * rewrite pages under us. Especially we don't want to hold a lock
2704 : : * while sending the notifications to the frontend.
2705 : : */
2706 : 47 : reachedStop = asyncQueueProcessPageEntries(&pos, head, snapshot);
5947 tgl@sss.pgh.pa.us 2707 [ + + ]: 47 : } while (!reachedStop);
2708 : :
2709 : : /* Update shared state */
2206 2710 : 44 : LWLockAcquire(NotifyQueueLock, LW_SHARED);
818 heikki.linnakangas@i 2711 : 44 : QUEUE_BACKEND_POS(MyProcNumber) = pos;
135 tgl@sss.pgh.pa.us 2712 :GNC 44 : QUEUE_BACKEND_IS_ADVANCING(MyProcNumber) = false;
2206 tgl@sss.pgh.pa.us 2713 :CBC 44 : LWLockRelease(NotifyQueueLock);
2714 : :
199 heikki.linnakangas@i 2715 : 44 : ExitOnAnyError = save_ExitOnAnyError;
2716 : : }
2717 : :
2718 : : /* Done with snapshot */
3153 tgl@sss.pgh.pa.us 2719 : 44 : UnregisterSnapshot(snapshot);
2720 : : }
2721 : :
2722 : : /*
2723 : : * Fetch notifications from the shared queue, beginning at position current,
2724 : : * and deliver relevant ones to my frontend.
2725 : : *
2726 : : * The function returns true once we have reached the stop position or an
2727 : : * uncommitted notification, and false if we have finished with the page.
2728 : : * In other words: once it returns true there is no need to look further.
2729 : : * The QueuePosition *current is advanced past all processed messages.
2730 : : */
2731 : : static bool
199 heikki.linnakangas@i 2732 : 47 : asyncQueueProcessPageEntries(QueuePosition *current,
2733 : : QueuePosition stop,
2734 : : Snapshot snapshot)
2735 : : {
2736 : 47 : int64 curpage = QUEUE_POS_PAGE(*current);
2737 : : int slotno;
2738 : : char *page_buffer;
5947 tgl@sss.pgh.pa.us 2739 : 47 : bool reachedStop = false;
2740 : : bool reachedEndOfPage;
2741 : :
2742 : : /*
2743 : : * We copy the entries into a local buffer to avoid holding the SLRU lock
2744 : : * while we transmit them to our frontend. The local buffer must be
2745 : : * adequately aligned.
2746 : : */
2747 : : alignas(AsyncQueueEntry) char local_buf[QUEUE_PAGESIZE];
190 peter@eisentraut.org 2748 :GNC 47 : char *local_buf_end = local_buf;
2749 : :
78 heikki.linnakangas@i 2750 : 47 : slotno = SimpleLruReadPage_ReadOnly(NotifyCtl, curpage, current);
199 heikki.linnakangas@i 2751 :CBC 47 : page_buffer = NotifyCtl->shared->page_buffer[slotno];
2752 : :
2753 : : do
2754 : : {
5937 bruce@momjian.us 2755 : 1413 : QueuePosition thisentry = *current;
2756 : : AsyncQueueEntry *qe;
2757 : :
5946 tgl@sss.pgh.pa.us 2758 [ + + + + ]: 1413 : if (QUEUE_POS_EQUAL(thisentry, stop))
5947 2759 : 44 : break;
2760 : :
5946 2761 : 1369 : qe = (AsyncQueueEntry *) (page_buffer + QUEUE_POS_OFFSET(thisentry));
2762 : :
2763 : : /*
2764 : : * Advance *current over this message, possibly to the next page. As
2765 : : * noted in the comments for asyncQueueReadAllNotifications, we must
2766 : : * do this before possibly failing while processing the message.
2767 : : */
5947 2768 : 1369 : reachedEndOfPage = asyncQueueAdvance(current, qe->length);
2769 : :
2770 : : /* Ignore messages destined for other databases */
2771 [ + - ]: 1369 : if (qe->dboid == MyDatabaseId)
2772 : : {
3153 2773 [ - + ]: 1369 : if (XidInMVCCSnapshot(qe->xid, snapshot))
2774 : : {
2775 : : /*
2776 : : * The source transaction is still in progress, so we can't
2777 : : * process this message yet. Break out of the loop, but first
2778 : : * back up *current so we will reprocess the message next
2779 : : * time. (Note: it is unlikely but not impossible for
2780 : : * TransactionIdDidCommit to fail, so we can't really avoid
2781 : : * this advance-then-back-up behavior when dealing with an
2782 : : * uncommitted message.)
2783 : : *
2784 : : * Note that we must test XidInMVCCSnapshot before we test
2785 : : * TransactionIdDidCommit, else we might return a message from
2786 : : * a transaction that is not yet visible to snapshots; compare
2787 : : * the comments at the head of heapam_visibility.c.
2788 : : *
2789 : : * Also, while our own xact won't be listed in the snapshot,
2790 : : * we need not check for TransactionIdIsCurrentTransactionId
2791 : : * because our transaction cannot (yet) have queued any
2792 : : * messages.
2793 : : */
4461 tgl@sss.pgh.pa.us 2794 :UBC 0 : *current = thisentry;
2795 : 0 : reachedStop = true;
2796 : 0 : break;
2797 : : }
2798 : :
2799 : : /*
2800 : : * Quick check for the case that we're not listening on any
2801 : : * channels, before calling TransactionIdDidCommit(). This makes
2802 : : * that case a little faster, but more importantly, it ensures
2803 : : * that if there's a bad entry in the queue for which
2804 : : * TransactionIdDidCommit() fails for some reason, we can skip
2805 : : * over it on the first LISTEN in a session, and not get stuck on
2806 : : * it indefinitely. (This is a little trickier than it looks: it
2807 : : * works because BecomeRegisteredListener runs this code before we
2808 : : * have made the first entry in localChannelTable.)
2809 : : */
135 tgl@sss.pgh.pa.us 2810 [ + - + + ]:GNC 1369 : if (LocalChannelTableIsEmpty())
199 heikki.linnakangas@i 2811 :CBC 1314 : continue;
2812 : :
2813 [ + - ]: 55 : if (TransactionIdDidCommit(qe->xid))
2814 : : {
2815 : 55 : memcpy(local_buf_end, qe, qe->length);
2816 : 55 : local_buf_end += qe->length;
2817 : : }
2818 : : else
2819 : : {
2820 : : /*
2821 : : * The source transaction aborted or crashed, so we just
2822 : : * ignore its notifications.
2823 : : */
2824 : : }
2825 : : }
2826 : :
2827 : : /* Loop back if we're not at end of page */
5947 tgl@sss.pgh.pa.us 2828 [ + + ]: 1369 : } while (!reachedEndOfPage);
2829 : :
2830 : : /* Release lock that we got from SimpleLruReadPage_ReadOnly() */
199 heikki.linnakangas@i 2831 : 47 : LWLockRelease(SimpleLruGetBankLock(NotifyCtl, curpage));
2832 : :
2833 : : /*
2834 : : * Now that we have let go of the SLRU bank lock, send the notifications
2835 : : * to our backend
2836 : : */
190 peter@eisentraut.org 2837 [ - + ]:GNC 47 : Assert(local_buf_end - local_buf <= BLCKSZ);
2838 [ + + ]: 102 : for (char *p = local_buf; p < local_buf_end;)
2839 : : {
199 heikki.linnakangas@i 2840 :CBC 55 : AsyncQueueEntry *qe = (AsyncQueueEntry *) p;
2841 : :
2842 : : /* qe->data is the null-terminated channel name */
2843 : 55 : char *channel = qe->data;
2844 : :
2845 [ + + ]: 55 : if (IsListeningOn(channel))
2846 : : {
2847 : : /* payload follows channel name */
2848 : 53 : char *payload = qe->data + strlen(channel) + 1;
2849 : :
2850 : 53 : NotifyMyFrontEnd(channel, payload, qe->srcPid);
2851 : : }
2852 : :
2853 : 55 : p += qe->length;
2854 : : }
2855 : :
5947 tgl@sss.pgh.pa.us 2856 [ + + + + ]: 47 : if (QUEUE_POS_EQUAL(*current, stop))
2857 : 44 : reachedStop = true;
2858 : :
2859 : 47 : return reachedStop;
2860 : : }
2861 : :
2862 : : /*
2863 : : * Advance the shared queue tail variable to the minimum of all the
2864 : : * per-backend tail pointers. Truncate pg_notify space if possible.
2865 : : *
2866 : : * This is (usually) called during CommitTransaction(), so it's important for
2867 : : * it to have very low probability of failure.
2868 : : */
2869 : : static void
2870 : 14 : asyncQueueAdvanceTail(void)
2871 : : {
2872 : : QueuePosition min;
2873 : : int64 oldtailpage;
2874 : : int64 newtailpage;
2875 : : int64 boundary;
2876 : :
2877 : : /* Restrict task to one backend per cluster; see SimpleLruTruncate(). */
2114 noah@leadboat.com 2878 : 14 : LWLockAcquire(NotifyQueueTailLock, LW_EXCLUSIVE);
2879 : :
2880 : : /*
2881 : : * Compute the new tail. Pre-v13, it's essential that QUEUE_TAIL be exact
2882 : : * (ie, exactly match at least one backend's queue position), so it must
2883 : : * be updated atomically with the actual computation. Since v13, we could
2884 : : * get away with not doing it like that, but it seems prudent to keep it
2885 : : * so.
2886 : : *
2887 : : * Also, because incoming backends will scan forward from QUEUE_TAIL, that
2888 : : * must be advanced before we can truncate any data. Thus, QUEUE_TAIL is
2889 : : * the logical tail, while QUEUE_STOP_PAGE is the physical tail, or oldest
2890 : : * un-truncated page. When QUEUE_STOP_PAGE != QUEUE_POS_PAGE(QUEUE_TAIL),
2891 : : * there are pages we can truncate but haven't yet finished doing so.
2892 : : *
2893 : : * For concurrency's sake, we don't want to hold NotifyQueueLock while
2894 : : * performing SimpleLruTruncate. This is OK because no backend will try
2895 : : * to access the pages we are in the midst of truncating.
2896 : : */
2206 tgl@sss.pgh.pa.us 2897 : 14 : LWLockAcquire(NotifyQueueLock, LW_EXCLUSIVE);
5947 2898 : 14 : min = QUEUE_HEAD;
818 heikki.linnakangas@i 2899 [ + + ]: 24 : for (ProcNumber i = QUEUE_FIRST_LISTENER; i != INVALID_PROC_NUMBER; i = QUEUE_NEXT_LISTENER(i))
2900 : : {
2454 tgl@sss.pgh.pa.us 2901 [ - + ]: 10 : Assert(QUEUE_BACKEND_PID(i) != InvalidPid);
2902 [ + - + + : 10 : min = QUEUE_POS_MIN(min, QUEUE_BACKEND_POS(i));
+ - ]
2903 : : }
2009 2904 : 14 : QUEUE_TAIL = min;
2905 : 14 : oldtailpage = QUEUE_STOP_PAGE;
2206 2906 : 14 : LWLockRelease(NotifyQueueLock);
2907 : :
2908 : : /*
2909 : : * We can truncate something if the global tail advanced across an SLRU
2910 : : * segment boundary.
2911 : : *
2912 : : * XXX it might be better to truncate only once every several segments, to
2913 : : * reduce the number of directory scans.
2914 : : */
5947 2915 : 14 : newtailpage = QUEUE_POS_PAGE(min);
2916 : 14 : boundary = newtailpage - (newtailpage % SLRU_PAGES_PER_SEGMENT);
5358 alvherre@alvh.no-ip. 2917 [ + + ]: 14 : if (asyncQueuePagePrecedes(oldtailpage, boundary))
2918 : : {
2919 : : /*
2920 : : * SimpleLruTruncate() will ask for SLRU bank locks but will also
2921 : : * release the lock again.
2922 : : */
2206 tgl@sss.pgh.pa.us 2923 :GBC 1 : SimpleLruTruncate(NotifyCtl, newtailpage);
2924 : :
2009 2925 : 1 : LWLockAcquire(NotifyQueueLock, LW_EXCLUSIVE);
2926 : 1 : QUEUE_STOP_PAGE = newtailpage;
2927 : 1 : LWLockRelease(NotifyQueueLock);
2928 : : }
2929 : :
2114 noah@leadboat.com 2930 :CBC 14 : LWLockRelease(NotifyQueueTailLock);
5947 tgl@sss.pgh.pa.us 2931 : 14 : }
2932 : :
2933 : : /*
2934 : : * AsyncNotifyFreezeXids
2935 : : *
2936 : : * Prepare the async notification queue for CLOG truncation by freezing
2937 : : * transaction IDs that are about to become inaccessible.
2938 : : *
2939 : : * This function is called by VACUUM before advancing datfrozenxid. It scans
2940 : : * the notification queue and replaces XIDs that would become inaccessible
2941 : : * after CLOG truncation with special markers:
2942 : : * - Committed transactions are set to FrozenTransactionId
2943 : : * - Aborted/crashed transactions are set to InvalidTransactionId
2944 : : *
2945 : : * Only XIDs < newFrozenXid are processed, as those are the ones whose CLOG
2946 : : * pages will be truncated. If XID < newFrozenXid, it cannot still be running
2947 : : * (or it would have held back newFrozenXid through ProcArray).
2948 : : * Therefore, if TransactionIdDidCommit returns false, we know the transaction
2949 : : * either aborted explicitly or crashed, and we can safely mark it invalid.
2950 : : */
2951 : : void
199 heikki.linnakangas@i 2952 : 114 : AsyncNotifyFreezeXids(TransactionId newFrozenXid)
2953 : : {
2954 : : QueuePosition pos;
2955 : : QueuePosition head;
2956 : 114 : int64 curpage = -1;
2957 : 114 : int slotno = -1;
2958 : 114 : char *page_buffer = NULL;
2959 : 114 : bool page_dirty = false;
2960 : :
2961 : : /*
2962 : : * Acquire locks in the correct order to avoid deadlocks. As per the
2963 : : * locking protocol: NotifyQueueTailLock, then NotifyQueueLock, then SLRU
2964 : : * bank locks.
2965 : : *
2966 : : * We only need SHARED mode since we're just reading the head/tail
2967 : : * positions, not modifying them.
2968 : : */
2969 : 114 : LWLockAcquire(NotifyQueueTailLock, LW_SHARED);
2970 : 114 : LWLockAcquire(NotifyQueueLock, LW_SHARED);
2971 : :
2972 : 114 : pos = QUEUE_TAIL;
2973 : 114 : head = QUEUE_HEAD;
2974 : :
2975 : : /* Release NotifyQueueLock early, we only needed to read the positions */
2976 : 114 : LWLockRelease(NotifyQueueLock);
2977 : :
2978 : : /*
2979 : : * Scan the queue from tail to head, freezing XIDs as needed. We hold
2980 : : * NotifyQueueTailLock throughout to ensure the tail doesn't move while
2981 : : * we're working.
2982 : : */
2983 [ - + - + ]: 114 : while (!QUEUE_POS_EQUAL(pos, head))
2984 : : {
2985 : : AsyncQueueEntry *qe;
2986 : : TransactionId xid;
199 heikki.linnakangas@i 2987 :UBC 0 : int64 pageno = QUEUE_POS_PAGE(pos);
2988 : 0 : int offset = QUEUE_POS_OFFSET(pos);
2989 : :
2990 : : /* If we need a different page, release old lock and get new one */
2991 [ # # ]: 0 : if (pageno != curpage)
2992 : : {
2993 : : LWLock *lock;
2994 : :
2995 : : /* Release previous page if any */
2996 [ # # ]: 0 : if (slotno >= 0)
2997 : : {
2998 [ # # ]: 0 : if (page_dirty)
2999 : : {
3000 : 0 : NotifyCtl->shared->page_dirty[slotno] = true;
3001 : 0 : page_dirty = false;
3002 : : }
3003 : 0 : LWLockRelease(SimpleLruGetBankLock(NotifyCtl, curpage));
3004 : : }
3005 : :
3006 : 0 : lock = SimpleLruGetBankLock(NotifyCtl, pageno);
3007 : 0 : LWLockAcquire(lock, LW_EXCLUSIVE);
78 heikki.linnakangas@i 3008 :UNC 0 : slotno = SimpleLruReadPage(NotifyCtl, pageno, true, &pos);
199 heikki.linnakangas@i 3009 :UBC 0 : page_buffer = NotifyCtl->shared->page_buffer[slotno];
3010 : 0 : curpage = pageno;
3011 : : }
3012 : :
3013 : 0 : qe = (AsyncQueueEntry *) (page_buffer + offset);
3014 : 0 : xid = qe->xid;
3015 : :
3016 [ # # # # ]: 0 : if (TransactionIdIsNormal(xid) &&
3017 : 0 : TransactionIdPrecedes(xid, newFrozenXid))
3018 : : {
3019 [ # # ]: 0 : if (TransactionIdDidCommit(xid))
3020 : : {
3021 : 0 : qe->xid = FrozenTransactionId;
3022 : 0 : page_dirty = true;
3023 : : }
3024 : : else
3025 : : {
3026 : 0 : qe->xid = InvalidTransactionId;
3027 : 0 : page_dirty = true;
3028 : : }
3029 : : }
3030 : :
3031 : : /* Advance to next entry */
3032 : 0 : asyncQueueAdvance(&pos, qe->length);
3033 : : }
3034 : :
3035 : : /* Release final page lock if we acquired one */
199 heikki.linnakangas@i 3036 [ - + ]:CBC 114 : if (slotno >= 0)
3037 : : {
199 heikki.linnakangas@i 3038 [ # # ]:UBC 0 : if (page_dirty)
3039 : 0 : NotifyCtl->shared->page_dirty[slotno] = true;
3040 : 0 : LWLockRelease(SimpleLruGetBankLock(NotifyCtl, curpage));
3041 : : }
3042 : :
199 heikki.linnakangas@i 3043 :CBC 114 : LWLockRelease(NotifyQueueTailLock);
3044 : 114 : }
3045 : :
3046 : : /*
3047 : : * ProcessIncomingNotify
3048 : : *
3049 : : * Scan the queue for arriving notifications and report them to the front
3050 : : * end. The notifications might be from other sessions, or our own;
3051 : : * there's no need to distinguish here.
3052 : : *
3053 : : * If "flush" is true, force any frontend messages out immediately.
3054 : : *
3055 : : * NOTE: since we are outside any transaction, we must create our own.
3056 : : */
3057 : : static void
1719 tgl@sss.pgh.pa.us 3058 : 26 : ProcessIncomingNotify(bool flush)
3059 : : {
3060 : : /* We *must* reset the flag */
4134 andres@anarazel.de 3061 : 26 : notifyInterruptPending = false;
3062 : :
3063 : : /* Do nothing else if we aren't actively listening */
135 tgl@sss.pgh.pa.us 3064 [ + - - + ]:GNC 26 : if (LocalChannelTableIsEmpty())
5947 tgl@sss.pgh.pa.us 3065 :UBC 0 : return;
3066 : :
9495 peter_e@gmx.net 3067 [ - + ]:CBC 26 : if (Trace_notify)
8404 bruce@momjian.us 3068 [ # # ]:UBC 0 : elog(DEBUG1, "ProcessIncomingNotify");
3069 : :
2271 peter@eisentraut.org 3070 :CBC 26 : set_ps_display("notify interrupt");
3071 : :
3072 : : /*
3073 : : * We must run asyncQueueReadAllNotifications inside a transaction, else
3074 : : * bad things happen if it gets an error.
3075 : : */
5947 tgl@sss.pgh.pa.us 3076 : 26 : StartTransactionCommand();
3077 : :
3078 : 26 : asyncQueueReadAllNotifications();
3079 : :
8417 3080 : 26 : CommitTransactionCommand();
3081 : :
3082 : : /*
3083 : : * If this isn't an end-of-command case, we must flush the notify messages
3084 : : * to ensure frontend gets them promptly.
3085 : : */
1719 3086 [ + + ]: 26 : if (flush)
3087 : 4 : pq_flush();
3088 : :
2271 peter@eisentraut.org 3089 : 26 : set_ps_display("idle");
3090 : :
9495 peter_e@gmx.net 3091 [ - + ]: 26 : if (Trace_notify)
8404 bruce@momjian.us 3092 [ # # ]:UBC 0 : elog(DEBUG1, "ProcessIncomingNotify: done");
3093 : : }
3094 : :
3095 : : /*
3096 : : * Send NOTIFY message to my front end.
3097 : : */
3098 : : void
5947 tgl@sss.pgh.pa.us 3099 :CBC 53 : NotifyMyFrontEnd(const char *channel, const char *payload, int32 srcPid)
3100 : : {
7513 alvherre@alvh.no-ip. 3101 [ + - ]: 53 : if (whereToSendOutput == DestRemote)
3102 : : {
3103 : : StringInfoData buf;
3104 : :
1012 nathan@postgresql.or 3105 : 53 : pq_beginmessage(&buf, PqMsg_NotificationResponse);
3153 andres@anarazel.de 3106 : 53 : pq_sendint32(&buf, srcPid);
5947 tgl@sss.pgh.pa.us 3107 : 53 : pq_sendstring(&buf, channel);
1913 heikki.linnakangas@i 3108 : 53 : pq_sendstring(&buf, payload);
9897 tgl@sss.pgh.pa.us 3109 : 53 : pq_endmessage(&buf);
3110 : :
3111 : : /*
3112 : : * NOTE: we do not do pq_flush() here. Some level of caller will
3113 : : * handle it later, allowing this message to be combined into a packet
3114 : : * with other ones.
3115 : : */
3116 : : }
3117 : : else
5947 tgl@sss.pgh.pa.us 3118 [ # # ]:UBC 0 : elog(INFO, "NOTIFY for \"%s\" payload \"%s\"", channel, payload);
10098 tgl@sss.pgh.pa.us 3119 :CBC 53 : }
3120 : :
3121 : : /* Does pendingNotifies include a match for the given event? */
3122 : : static bool
2480 3123 : 1066 : AsyncExistsPendingNotify(Notification *n)
3124 : : {
3125 [ - + ]: 1066 : if (pendingNotifies == NULL)
5947 tgl@sss.pgh.pa.us 3126 :UBC 0 : return false;
3127 : :
2480 tgl@sss.pgh.pa.us 3128 [ + + ]:CBC 1066 : if (pendingNotifies->hashtab != NULL)
3129 : : {
3130 : : /* Use the hash table to probe for a match */
3131 [ + + ]: 984 : if (hash_search(pendingNotifies->hashtab,
3132 : : &n,
3133 : : HASH_FIND,
3134 : : NULL))
2480 tgl@sss.pgh.pa.us 3135 :GBC 1 : return true;
3136 : : }
3137 : : else
3138 : : {
3139 : : /* Must scan the event list */
3140 : : ListCell *l;
3141 : :
2480 tgl@sss.pgh.pa.us 3142 [ + - + + :CBC 425 : foreach(l, pendingNotifies->events)
+ + ]
3143 : : {
3144 : 357 : Notification *oldn = (Notification *) lfirst(l);
3145 : :
3146 [ + - ]: 357 : if (n->channel_len == oldn->channel_len &&
3147 [ + + ]: 357 : n->payload_len == oldn->payload_len &&
3148 : 190 : memcmp(n->data, oldn->data,
3149 [ + + ]: 190 : n->channel_len + n->payload_len + 2) == 0)
3150 : 14 : return true;
3151 : : }
3152 : : }
3153 : :
3154 : 1051 : return false;
3155 : : }
3156 : :
3157 : : /*
3158 : : * Add a notification event to a pre-existing pendingNotifies list.
3159 : : *
3160 : : * Because pendingNotifies->events is already nonempty, this works
3161 : : * correctly no matter what CurrentMemoryContext is.
3162 : : */
3163 : : static void
3164 : 1051 : AddEventToPendingNotifies(Notification *n)
3165 : : {
3166 [ - + ]: 1051 : Assert(pendingNotifies->events != NIL);
3167 : :
3168 : : /* Create the hash tables if it's time to */
3169 [ + + ]: 1051 : if (list_length(pendingNotifies->events) >= MIN_HASHABLE_NOTIFIES &&
3170 [ + + ]: 985 : pendingNotifies->hashtab == NULL)
3171 : : {
3172 : : HASHCTL hash_ctl;
3173 : : ListCell *l;
3174 : :
3175 : : /* Create the hash table */
3176 : 2 : hash_ctl.keysize = sizeof(Notification *);
743 peter@eisentraut.org 3177 : 2 : hash_ctl.entrysize = sizeof(struct NotificationHash);
2480 tgl@sss.pgh.pa.us 3178 : 2 : hash_ctl.hash = notification_hash;
3179 : 2 : hash_ctl.match = notification_match;
3180 : 2 : hash_ctl.hcxt = CurTransactionContext;
3181 : 4 : pendingNotifies->hashtab =
3182 : 2 : hash_create("Pending Notifies",
3183 : : 256L,
3184 : : &hash_ctl,
3185 : : HASH_ELEM | HASH_FUNCTION | HASH_COMPARE | HASH_CONTEXT);
3186 : :
3187 : : /* Create the unique channel name table */
135 tgl@sss.pgh.pa.us 3188 [ - + ]:GNC 2 : Assert(pendingNotifies->uniqueChannelHash == NULL);
3189 : 2 : hash_ctl.keysize = NAMEDATALEN;
3190 : 2 : hash_ctl.entrysize = sizeof(ChannelName);
3191 : 2 : hash_ctl.hcxt = CurTransactionContext;
3192 : 4 : pendingNotifies->uniqueChannelHash =
3193 : 2 : hash_create("Pending Notify Channel Names",
3194 : : 64L,
3195 : : &hash_ctl,
3196 : : HASH_ELEM | HASH_STRINGS | HASH_CONTEXT);
3197 : :
3198 : : /* Insert all the already-existing events */
2480 tgl@sss.pgh.pa.us 3199 [ + - + + :CBC 34 : foreach(l, pendingNotifies->events)
+ + ]
3200 : : {
3201 : 32 : Notification *oldn = (Notification *) lfirst(l);
135 tgl@sss.pgh.pa.us 3202 :GNC 32 : char *channel = oldn->data;
3203 : : bool found;
3204 : :
912 john.naylor@postgres 3205 :CBC 32 : (void) hash_search(pendingNotifies->hashtab,
3206 : : &oldn,
3207 : : HASH_ENTER,
3208 : : &found);
2480 tgl@sss.pgh.pa.us 3209 [ - + ]: 32 : Assert(!found);
3210 : :
3211 : : /* Add channel name to uniqueChannelHash; might be there already */
135 tgl@sss.pgh.pa.us 3212 :GNC 32 : (void) hash_search(pendingNotifies->uniqueChannelHash,
3213 : : channel,
3214 : : HASH_ENTER,
3215 : : NULL);
3216 : : }
3217 : : }
3218 : :
3219 : : /* Add new event to the list, in order */
2480 tgl@sss.pgh.pa.us 3220 :CBC 1051 : pendingNotifies->events = lappend(pendingNotifies->events, n);
3221 : :
3222 : : /* Add event to the hash tables if needed */
3223 [ + + ]: 1051 : if (pendingNotifies->hashtab != NULL)
3224 : : {
135 tgl@sss.pgh.pa.us 3225 :GNC 985 : char *channel = n->data;
3226 : : bool found;
3227 : :
912 john.naylor@postgres 3228 :CBC 985 : (void) hash_search(pendingNotifies->hashtab,
3229 : : &n,
3230 : : HASH_ENTER,
3231 : : &found);
2480 tgl@sss.pgh.pa.us 3232 [ - + ]: 985 : Assert(!found);
3233 : :
3234 : : /* Add channel name to uniqueChannelHash; might be there already */
135 tgl@sss.pgh.pa.us 3235 :GNC 985 : (void) hash_search(pendingNotifies->uniqueChannelHash,
3236 : : channel,
3237 : : HASH_ENTER,
3238 : : NULL);
3239 : : }
2480 tgl@sss.pgh.pa.us 3240 :CBC 1051 : }
3241 : :
3242 : : /*
3243 : : * notification_hash: hash function for notification hash table
3244 : : *
3245 : : * The hash "keys" are pointers to Notification structs.
3246 : : */
3247 : : static uint32
3248 : 2001 : notification_hash(const void *key, Size keysize)
3249 : : {
3250 : 2001 : const Notification *k = *(const Notification *const *) key;
3251 : :
3252 [ - + ]: 2001 : Assert(keysize == sizeof(Notification *));
3253 : : /* We don't bother to include the payload's trailing null in the hash */
3254 : 2001 : return DatumGetUInt32(hash_any((const unsigned char *) k->data,
3255 : 2001 : k->channel_len + k->payload_len + 1));
3256 : : }
3257 : :
3258 : : /*
3259 : : * notification_match: match function to use with notification_hash
3260 : : */
3261 : : static int
2480 tgl@sss.pgh.pa.us 3262 :GBC 1 : notification_match(const void *key1, const void *key2, Size keysize)
3263 : : {
3264 : 1 : const Notification *k1 = *(const Notification *const *) key1;
3265 : 1 : const Notification *k2 = *(const Notification *const *) key2;
3266 : :
3267 [ - + ]: 1 : Assert(keysize == sizeof(Notification *));
3268 [ + - ]: 1 : if (k1->channel_len == k2->channel_len &&
3269 [ + - ]: 1 : k1->payload_len == k2->payload_len &&
3270 : 1 : memcmp(k1->data, k2->data,
3271 [ + - ]: 1 : k1->channel_len + k1->payload_len + 2) == 0)
3272 : 1 : return 0; /* equal */
2480 tgl@sss.pgh.pa.us 3273 :UBC 0 : return 1; /* not equal */
3274 : : }
3275 : :
3276 : : /* Clear the pendingActions and pendingNotifies lists. */
3277 : : static void
6653 tgl@sss.pgh.pa.us 3278 :CBC 35491 : ClearPendingActionsAndNotifies(void)
3279 : : {
3280 : : /*
3281 : : * Everything's allocated in either TopTransactionContext or the context
3282 : : * for the subtransaction to which it corresponds. So, there's nothing to
3283 : : * do here except reset the pointers; the space will be reclaimed when the
3284 : : * contexts are deleted.
3285 : : */
2430 rhaas@postgresql.org 3286 : 35491 : pendingActions = NULL;
2480 tgl@sss.pgh.pa.us 3287 : 35491 : pendingNotifies = NULL;
3288 : : /* Also clear pendingListenActions, which is derived from pendingActions */
135 tgl@sss.pgh.pa.us 3289 :GNC 35491 : pendingListenActions = NULL;
10492 bruce@momjian.us 3290 :CBC 35491 : }
3291 : :
3292 : : /*
3293 : : * GUC check_hook for notify_buffers
3294 : : */
3295 : : bool
822 alvherre@alvh.no-ip. 3296 : 1292 : check_notify_buffers(int *newval, void **extra, GucSource source)
3297 : : {
3298 : 1292 : return check_slru_buffers("notify_buffers", newval);
3299 : : }
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