Age Owner Branch data TLA Line data Source code
1 : : /*-------------------------------------------------------------------------
2 : : * logicalctl.c
3 : : * Functionality to control logical decoding status online.
4 : : *
5 : : * This module enables dynamic control of logical decoding availability.
6 : : * Logical decoding becomes active under two conditions: when the wal_level
7 : : * parameter is set to 'logical', or when at least one valid logical replication
8 : : * slot exists with wal_level set to 'replica'. The system disables logical
9 : : * decoding when neither condition is met. Therefore, the dynamic control
10 : : * of logical decoding availability is required only when wal_level is set
11 : : * to 'replica'. Logical decoding is always enabled when wal_level='logical'
12 : : * and always disabled when wal_level='minimal'.
13 : : *
14 : : * The core concept of dynamically enabling and disabling logical decoding
15 : : * is to separately control two aspects: writing information required for
16 : : * logical decoding to WAL records, and using logical decoding itself. During
17 : : * activation, we first enable logical WAL writing while keeping logical
18 : : * decoding disabled. This change is reflected in the read-only
19 : : * effective_wal_level GUC parameter. Once we ensure that all processes have
20 : : * updated to the latest effective_wal_level value, we then enable logical
21 : : * decoding. Deactivation follows a similar careful, multi-step process
22 : : * in reverse order.
23 : : *
24 : : * While activation occurs synchronously right after creating the first
25 : : * logical slot, deactivation happens asynchronously through the checkpointer
26 : : * process. This design avoids a race condition at the end of recovery; see
27 : : * the comments in UpdateLogicalDecodingStatusEndOfRecovery() for details.
28 : : * Asynchronous deactivation also avoids excessive toggling of the logical
29 : : * decoding status in workloads that repeatedly create and drop a single
30 : : * logical slot. On the other hand, this lazy approach can delay changes
31 : : * to effective_wal_level and the disabling logical decoding, especially
32 : : * when the checkpointer is busy with other tasks. We chose this lazy approach
33 : : * in all deactivation paths to keep the implementation simple, even though
34 : : * laziness is strictly required only for end-of-recovery cases. Future work
35 : : * might address this limitation either by using a dedicated worker instead
36 : : * of the checkpointer, or by implementing synchronous waiting during slot
37 : : * drops if workloads are significantly affected by the lazy deactivation
38 : : * of logical decoding.
39 : : *
40 : : * Standby servers use the primary server's effective_wal_level and logical
41 : : * decoding status. Unlike normal activation and deactivation, these
42 : : * are updated simultaneously without status change coordination, solely by
43 : : * replaying XLOG_LOGICAL_DECODING_STATUS_CHANGE records. The local wal_level
44 : : * setting has no effect during this time. Upon promotion, we update the
45 : : * logical decoding status based on local conditions: the wal_level value and
46 : : * the presence of logical slots.
47 : : *
48 : : * In the future, we could extend support to include automatic transitions
49 : : * of effective_wal_level between 'minimal' and 'logical' WAL levels. However,
50 : : * this enhancement would require additional coordination mechanisms and
51 : : * careful implementation of operations such as terminating walsenders and
52 : : * archiver processes while carefully considering the sequence of operations
53 : : * to ensure system stability during these transitions.
54 : : *
55 : : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
56 : : * Portions Copyright (c) 1994, Regents of the University of California
57 : : *
58 : : * IDENTIFICATION
59 : : * src/backend/replication/logical/logicalctl.c
60 : : *
61 : : *-------------------------------------------------------------------------
62 : : */
63 : :
64 : : #include "postgres.h"
65 : :
66 : : #include "access/xloginsert.h"
67 : : #include "catalog/pg_control.h"
68 : : #include "miscadmin.h"
69 : : #include "replication/slot.h"
70 : : #include "storage/ipc.h"
71 : : #include "storage/lmgr.h"
72 : : #include "storage/proc.h"
73 : : #include "storage/procarray.h"
74 : : #include "storage/procsignal.h"
75 : : #include "storage/subsystems.h"
76 : : #include "utils/injection_point.h"
77 : :
78 : : /*
79 : : * Struct for controlling the logical decoding status.
80 : : *
81 : : * This struct is protected by LogicalDecodingControlLock.
82 : : */
83 : : typedef struct LogicalDecodingCtlData
84 : : {
85 : : /*
86 : : * This is the authoritative value used by all processes to determine
87 : : * whether to write additional information required by logical decoding to
88 : : * WAL. Since this information could be checked frequently, each process
89 : : * caches this value in XLogLogicalInfo for better performance.
90 : : */
91 : : bool xlog_logical_info;
92 : :
93 : : /* True if logical decoding is available in the system */
94 : : bool logical_decoding_enabled;
95 : :
96 : : /* True if logical decoding might need to be disabled */
97 : : bool pending_disable;
98 : : } LogicalDecodingCtlData;
99 : :
100 : : static LogicalDecodingCtlData *LogicalDecodingCtl = NULL;
101 : :
102 : : static void LogicalDecodingCtlShmemRequest(void *arg);
103 : :
104 : : const ShmemCallbacks LogicalDecodingCtlShmemCallbacks = {
105 : : .request_fn = LogicalDecodingCtlShmemRequest,
106 : : };
107 : :
108 : : /*
109 : : * A process-local cache of LogicalDecodingCtl->xlog_logical_info. This is
110 : : * initialized at process startup, and updated when processing the process
111 : : * barrier signal in ProcessBarrierUpdateXLogLogicalInfo(). If the process
112 : : * is in an XID-assigned transaction, the cache update is delayed until the
113 : : * transaction ends. See the comments for XLogLogicalInfoUpdatePending for details.
114 : : */
115 : : bool XLogLogicalInfo = false;
116 : :
117 : : /*
118 : : * When receiving the PROCSIGNAL_BARRIER_UPDATE_XLOG_LOGICAL_INFO signal, if
119 : : * an XID is assigned to the current transaction, the process sets this flag and
120 : : * delays the XLogLogicalInfo update until the transaction ends. This ensures
121 : : * that the XLogLogicalInfo value (typically accessed via XLogLogicalInfoActive)
122 : : * remains consistent throughout the transaction.
123 : : */
124 : : static bool XLogLogicalInfoUpdatePending = false;
125 : :
126 : : static void update_xlog_logical_info(void);
127 : : static void abort_logical_decoding_activation(int code, Datum arg);
128 : : static void write_logical_decoding_status_update_record(bool status);
129 : :
130 : : static void
29 heikki.linnakangas@i 131 :GNC 1244 : LogicalDecodingCtlShmemRequest(void *arg)
132 : : {
133 : 1244 : ShmemRequestStruct(.name = "Logical decoding control",
134 : : .size = sizeof(LogicalDecodingCtlData),
135 : : .ptr = (void **) &LogicalDecodingCtl,
136 : : );
133 msawada@postgresql.o 137 : 1244 : }
138 : :
139 : : /*
140 : : * Initialize the logical decoding status in shmem at server startup. This
141 : : * must be called ONCE during postmaster or standalone-backend startup.
142 : : */
143 : : void
144 : 1077 : StartupLogicalDecodingStatus(bool last_status)
145 : : {
146 : : /* Logical decoding is always disabled when 'minimal' WAL level */
147 [ + + ]: 1077 : if (wal_level == WAL_LEVEL_MINIMAL)
148 : 395 : return;
149 : :
150 : : /*
151 : : * Set the initial logical decoding status based on the last status. If
152 : : * logical decoding was enabled before the last shutdown, it remains
153 : : * enabled as we might have set wal_level='logical' or have at least one
154 : : * logical slot.
155 : : */
156 : 682 : LogicalDecodingCtl->xlog_logical_info = last_status;
157 : 682 : LogicalDecodingCtl->logical_decoding_enabled = last_status;
158 : : }
159 : :
160 : : /*
161 : : * Update the XLogLogicalInfo cache.
162 : : */
163 : : static inline void
164 : 24787 : update_xlog_logical_info(void)
165 : : {
166 : 24787 : XLogLogicalInfo = IsXLogLogicalInfoEnabled();
167 : 24787 : }
168 : :
169 : : /*
170 : : * Initialize XLogLogicalInfo backend-private cache. This routine is called
171 : : * during process initialization.
172 : : */
173 : : void
174 : 22952 : InitializeProcessXLogLogicalInfo(void)
175 : : {
176 : 22952 : update_xlog_logical_info();
177 : 22952 : }
178 : :
179 : : /*
180 : : * This routine is called when we are told to update XLogLogicalInfo
181 : : * by a ProcSignalBarrier.
182 : : */
183 : : bool
184 : 1835 : ProcessBarrierUpdateXLogLogicalInfo(void)
185 : : {
186 [ - + ]: 1835 : if (GetTopTransactionIdIfAny() != InvalidTransactionId)
187 : : {
188 : : /* Delay updating XLogLogicalInfo until the transaction end */
133 msawada@postgresql.o 189 :UNC 0 : XLogLogicalInfoUpdatePending = true;
190 : : }
191 : : else
133 msawada@postgresql.o 192 :GNC 1835 : update_xlog_logical_info();
193 : :
194 : 1835 : return true;
195 : : }
196 : :
197 : : /*
198 : : * Check the shared memory state and return true if logical decoding is
199 : : * enabled on the system.
200 : : */
201 : : bool
202 : 20350 : IsLogicalDecodingEnabled(void)
203 : : {
204 : : bool enabled;
205 : :
206 : 20350 : LWLockAcquire(LogicalDecodingControlLock, LW_SHARED);
207 : 20350 : enabled = LogicalDecodingCtl->logical_decoding_enabled;
208 : 20350 : LWLockRelease(LogicalDecodingControlLock);
209 : :
210 : 20350 : return enabled;
211 : : }
212 : :
213 : : /*
214 : : * Returns true if logical WAL logging is enabled based on the shared memory
215 : : * status.
216 : : */
217 : : bool
218 : 25211 : IsXLogLogicalInfoEnabled(void)
219 : : {
220 : : bool xlog_logical_info;
221 : :
222 : 25211 : LWLockAcquire(LogicalDecodingControlLock, LW_SHARED);
223 : 25211 : xlog_logical_info = LogicalDecodingCtl->xlog_logical_info;
224 : 25211 : LWLockRelease(LogicalDecodingControlLock);
225 : :
226 : 25211 : return xlog_logical_info;
227 : : }
228 : :
229 : : /*
230 : : * Reset the local cache at end of the transaction.
231 : : */
232 : : void
233 : 423274 : AtEOXact_LogicalCtl(void)
234 : : {
235 : : /* Update the local cache if there is a pending update */
236 [ - + ]: 423274 : if (XLogLogicalInfoUpdatePending)
237 : : {
133 msawada@postgresql.o 238 :UNC 0 : update_xlog_logical_info();
239 : 0 : XLogLogicalInfoUpdatePending = false;
240 : : }
133 msawada@postgresql.o 241 :GNC 423274 : }
242 : :
243 : : /*
244 : : * Writes an XLOG_LOGICAL_DECODING_STATUS_CHANGE WAL record with the given
245 : : * status.
246 : : */
247 : : static void
248 : 85 : write_logical_decoding_status_update_record(bool status)
249 : : {
250 : : XLogRecPtr recptr;
251 : :
252 : 85 : XLogBeginInsert();
253 : 85 : XLogRegisterData(&status, sizeof(bool));
254 : 85 : recptr = XLogInsert(RM_XLOG_ID, XLOG_LOGICAL_DECODING_STATUS_CHANGE);
255 : 85 : XLogFlush(recptr);
256 : 85 : }
257 : :
258 : : /*
259 : : * A PG_ENSURE_ERROR_CLEANUP callback for activating logical decoding, resetting
260 : : * the shared flags to revert the logical decoding activation process.
261 : : */
262 : : static void
263 : 1 : abort_logical_decoding_activation(int code, Datum arg)
264 : : {
265 [ - + ]: 1 : Assert(MyReplicationSlot);
266 [ - + ]: 1 : Assert(!LogicalDecodingCtl->logical_decoding_enabled);
267 : :
268 [ + - ]: 1 : elog(DEBUG1, "aborting logical decoding activation process");
269 : :
270 : : /*
271 : : * Abort the change to xlog_logical_info. We don't need to check
272 : : * CheckLogicalSlotExists() as we're still holding a logical slot.
273 : : */
274 : 1 : LWLockAcquire(LogicalDecodingControlLock, LW_EXCLUSIVE);
275 : 1 : LogicalDecodingCtl->xlog_logical_info = false;
276 : 1 : LWLockRelease(LogicalDecodingControlLock);
277 : :
278 : : /*
279 : : * Some processes might have already started logical info WAL logging, so
280 : : * tell all running processes to update their caches. We don't need to
281 : : * wait for all processes to disable xlog_logical_info locally as it's
282 : : * always safe to write logical information to WAL records, even when not
283 : : * strictly required.
284 : : */
285 : 1 : EmitProcSignalBarrier(PROCSIGNAL_BARRIER_UPDATE_XLOG_LOGICAL_INFO);
286 : 1 : }
287 : :
288 : : /*
289 : : * Enable logical decoding if disabled.
290 : : *
291 : : * If this function is called during recovery, it simply returns without
292 : : * action since the logical decoding status change is not allowed during
293 : : * this time. The logical decoding status depends on the status on the primary.
294 : : * The caller should use CheckLogicalDecodingRequirements() before calling this
295 : : * function to make sure that the logical decoding status can be modified.
296 : : *
297 : : * Note that there is no interlock between logical decoding activation
298 : : * and slot creation. To ensure enabling logical decoding, the caller
299 : : * needs to call this function after creating a logical slot before
300 : : * initializing the logical decoding context.
301 : : */
302 : : void
303 : 502 : EnsureLogicalDecodingEnabled(void)
304 : : {
305 [ - + ]: 502 : Assert(MyReplicationSlot);
306 [ - + ]: 502 : Assert(wal_level >= WAL_LEVEL_REPLICA);
307 : :
308 : : /* Logical decoding is always enabled */
309 [ + + ]: 502 : if (wal_level >= WAL_LEVEL_LOGICAL)
310 : 490 : return;
311 : :
312 [ + + ]: 12 : if (RecoveryInProgress())
313 : : {
314 : : /*
315 : : * CheckLogicalDecodingRequirements() must have already errored out if
316 : : * logical decoding is not enabled since we cannot enable the logical
317 : : * decoding status during recovery.
318 : : */
319 [ - + ]: 3 : Assert(IsLogicalDecodingEnabled());
320 : 3 : return;
321 : : }
322 : :
323 : : /*
324 : : * Ensure to abort the activation process in cases where there in an
325 : : * interruption during the wait.
326 : : */
327 [ + + ]: 9 : PG_ENSURE_ERROR_CLEANUP(abort_logical_decoding_activation, (Datum) 0);
328 : : {
329 : 9 : EnableLogicalDecoding();
330 : : }
331 [ - + ]: 9 : PG_END_ENSURE_ERROR_CLEANUP(abort_logical_decoding_activation, (Datum) 0);
332 : : }
333 : :
334 : : /*
335 : : * A workhorse function to enable logical decoding.
336 : : */
337 : : void
338 : 18 : EnableLogicalDecoding(void)
339 : : {
340 : : bool in_recovery;
341 : :
342 : 18 : LWLockAcquire(LogicalDecodingControlLock, LW_EXCLUSIVE);
343 : :
344 : : /* Return if it is already enabled */
345 [ + + ]: 18 : if (LogicalDecodingCtl->logical_decoding_enabled)
346 : : {
347 : 3 : LogicalDecodingCtl->pending_disable = false;
348 : 3 : LWLockRelease(LogicalDecodingControlLock);
349 : 3 : return;
350 : : }
351 : :
352 : : /*
353 : : * Set logical info WAL logging in shmem. All process starts after this
354 : : * point will include the information required by logical decoding to WAL
355 : : * records.
356 : : */
357 : 15 : LogicalDecodingCtl->xlog_logical_info = true;
358 : :
359 : 15 : LWLockRelease(LogicalDecodingControlLock);
360 : :
361 : : /*
362 : : * Tell all running processes to reflect the xlog_logical_info update, and
363 : : * wait. This ensures that all running processes have enabled logical
364 : : * information WAL logging.
365 : : */
366 : 15 : WaitForProcSignalBarrier(
367 : : EmitProcSignalBarrier(PROCSIGNAL_BARRIER_UPDATE_XLOG_LOGICAL_INFO));
368 : :
369 : 15 : INJECTION_POINT("logical-decoding-activation", NULL);
370 : :
371 : 14 : in_recovery = RecoveryInProgress();
372 : :
373 : : /*
374 : : * There could be some transactions that might have started with the old
375 : : * status, but we don't need to wait for these transactions to complete as
376 : : * long as they have valid XIDs. These transactions will appear in the
377 : : * xl_running_xacts record and therefore the snapshot builder will not try
378 : : * to decode the transaction during the logical decoding initialization.
379 : : *
380 : : * There is a theoretical case where a transaction decides whether to
381 : : * include logical-info to WAL records before getting an XID. In this
382 : : * case, the transaction won't appear in xl_running_xacts.
383 : : *
384 : : * For operations that do not require an XID assignment, the process
385 : : * starts including logical-info immediately upon receiving the signal
386 : : * (barrier). If such an operation checks the effective_wal_level multiple
387 : : * times within a single execution, the resulting WAL records might be
388 : : * inconsistent (i.e., logical-info is included in some records but not in
389 : : * others). However, this is harmless because logical decoding generally
390 : : * ignores WAL records that are not associated with an assigned XID.
391 : : *
392 : : * One might think we need to wait for all running transactions, including
393 : : * those without XIDs and read-only transactions, to finish before
394 : : * enabling logical decoding. However, such a requirement would force the
395 : : * slot creation to wait for a potentially very long time due to
396 : : * long-running read queries, which is practically unacceptable.
397 : : */
398 : :
399 : 14 : START_CRIT_SECTION();
400 : :
401 : : /*
402 : : * We enable logical decoding first, followed by writing the WAL record.
403 : : * This sequence ensures logical decoding becomes available on the primary
404 : : * first.
405 : : */
406 : 14 : LWLockAcquire(LogicalDecodingControlLock, LW_EXCLUSIVE);
407 : :
408 : 14 : LogicalDecodingCtl->logical_decoding_enabled = true;
409 : :
410 [ + + ]: 14 : if (!in_recovery)
411 : 5 : write_logical_decoding_status_update_record(true);
412 : :
413 : 14 : LogicalDecodingCtl->pending_disable = false;
414 : :
415 : 14 : LWLockRelease(LogicalDecodingControlLock);
416 : :
417 [ - + ]: 14 : END_CRIT_SECTION();
418 : :
419 [ + + ]: 14 : if (!in_recovery)
420 [ + - ]: 5 : ereport(LOG,
421 : : errmsg("logical decoding is enabled upon creating a new logical replication slot"));
422 : : }
423 : :
424 : : /*
425 : : * Initiate a request for disabling logical decoding.
426 : : *
427 : : * Note that this function does not verify whether logical slots exist. The
428 : : * checkpointer will verify if logical decoding should actually be disabled.
429 : : */
430 : : void
431 : 431 : RequestDisableLogicalDecoding(void)
432 : : {
433 [ + + ]: 431 : if (wal_level != WAL_LEVEL_REPLICA)
434 : 420 : return;
435 : :
436 : : /*
437 : : * It's possible that we might not actually need to disable logical
438 : : * decoding if someone creates a new logical slot concurrently. We set the
439 : : * flag anyway and the checkpointer will check it and disable logical
440 : : * decoding if necessary.
441 : : */
442 : 11 : LWLockAcquire(LogicalDecodingControlLock, LW_EXCLUSIVE);
443 : 11 : LogicalDecodingCtl->pending_disable = true;
444 : 11 : LWLockRelease(LogicalDecodingControlLock);
445 : :
446 : 11 : WakeupCheckpointer();
447 : :
448 [ + - ]: 11 : elog(DEBUG1, "requested disabling logical decoding");
449 : : }
450 : :
451 : : /*
452 : : * Disable logical decoding if necessary.
453 : : *
454 : : * This function disables logical decoding upon a request initiated by
455 : : * RequestDisableLogicalDecoding(). Otherwise, it performs no action.
456 : : */
457 : : void
458 : 5770 : DisableLogicalDecodingIfNecessary(void)
459 : : {
460 : : bool pending_disable;
461 : :
462 [ + + ]: 5770 : if (wal_level != WAL_LEVEL_REPLICA)
463 : 1324 : return;
464 : :
465 : : /*
466 : : * Sanity check as we cannot disable logical decoding while holding a
467 : : * logical slot.
468 : : */
469 [ - + ]: 4446 : Assert(!MyReplicationSlot);
470 : :
471 [ + + ]: 4446 : if (RecoveryInProgress())
472 : 1948 : return;
473 : :
474 : 2498 : LWLockAcquire(LogicalDecodingControlLock, LW_SHARED);
475 : 2498 : pending_disable = LogicalDecodingCtl->pending_disable;
476 : 2498 : LWLockRelease(LogicalDecodingControlLock);
477 : :
478 : : /* Quick return if no pending disable request */
479 [ + + ]: 2498 : if (!pending_disable)
480 : 2488 : return;
481 : :
482 : 10 : DisableLogicalDecoding();
483 : : }
484 : :
485 : : /*
486 : : * A workhorse function to disable logical decoding.
487 : : */
488 : : void
489 : 19 : DisableLogicalDecoding(void)
490 : : {
491 : 19 : bool in_recovery = RecoveryInProgress();
492 : :
493 : 19 : LWLockAcquire(LogicalDecodingControlLock, LW_EXCLUSIVE);
494 : :
495 : : /*
496 : : * Check if we can disable logical decoding.
497 : : *
498 : : * Skip CheckLogicalSlotExists() check during recovery because the
499 : : * existing slots will be invalidated after disabling logical decoding.
500 : : */
501 [ + + ]: 19 : if (!LogicalDecodingCtl->logical_decoding_enabled ||
502 [ + + + + ]: 16 : (!in_recovery && CheckLogicalSlotExists()))
503 : : {
504 : 4 : LogicalDecodingCtl->pending_disable = false;
505 : 4 : LWLockRelease(LogicalDecodingControlLock);
506 : 4 : return;
507 : : }
508 : :
509 : 15 : START_CRIT_SECTION();
510 : :
511 : : /*
512 : : * We need to disable logical decoding first and then disable logical
513 : : * information WAL logging in order to ensure that no logical decoding
514 : : * processes WAL records with insufficient information.
515 : : */
516 : 15 : LogicalDecodingCtl->logical_decoding_enabled = false;
517 : :
518 : : /* Write the WAL to disable logical decoding on standbys too */
519 [ + + ]: 15 : if (!in_recovery)
520 : 6 : write_logical_decoding_status_update_record(false);
521 : :
522 : : /* Now disable logical information WAL logging */
523 : 15 : LogicalDecodingCtl->xlog_logical_info = false;
524 : 15 : LogicalDecodingCtl->pending_disable = false;
525 : :
526 [ - + ]: 15 : END_CRIT_SECTION();
527 : :
528 [ + + ]: 15 : if (!in_recovery)
529 [ + - ]: 6 : ereport(LOG,
530 : : errmsg("logical decoding is disabled because there are no valid logical replication slots"));
531 : :
532 : 15 : LWLockRelease(LogicalDecodingControlLock);
533 : :
534 : : /*
535 : : * Tell all running processes to reflect the xlog_logical_info update.
536 : : * Unlike when enabling logical decoding, we don't need to wait for all
537 : : * processes to complete it in this case. We already disabled logical
538 : : * decoding and it's always safe to write logical information to WAL
539 : : * records, even when not strictly required. Therefore, we don't need to
540 : : * wait for all running transactions to finish either.
541 : : */
542 : 15 : EmitProcSignalBarrier(PROCSIGNAL_BARRIER_UPDATE_XLOG_LOGICAL_INFO);
543 : : }
544 : :
545 : : /*
546 : : * Updates the logical decoding status at end of recovery, and ensures that
547 : : * all running processes have the updated XLogLogicalInfo status. This
548 : : * function must be called before accepting writes.
549 : : */
550 : : void
551 : 1010 : UpdateLogicalDecodingStatusEndOfRecovery(void)
552 : : {
553 : 1010 : bool new_status = false;
554 : :
555 [ - + ]: 1010 : Assert(RecoveryInProgress());
556 : :
557 : : /*
558 : : * With 'minimal' WAL level, there are no logical replication slots during
559 : : * recovery. Logical decoding is always disabled, so there is no need to
560 : : * synchronize XLogLogicalInfo.
561 : : */
562 [ + + ]: 1010 : if (wal_level == WAL_LEVEL_MINIMAL)
563 : : {
564 [ + - - + ]: 395 : Assert(!IsXLogLogicalInfoEnabled() && !IsLogicalDecodingEnabled());
565 : 395 : return;
566 : : }
567 : :
568 : 615 : LWLockAcquire(LogicalDecodingControlLock, LW_EXCLUSIVE);
569 : :
570 [ + + + + ]: 615 : if (wal_level == WAL_LEVEL_LOGICAL || CheckLogicalSlotExists())
571 : 134 : new_status = true;
572 : :
573 : : /*
574 : : * When recovery ends, we need to either enable or disable logical
575 : : * decoding based on the wal_level setting and the presence of logical
576 : : * slots. We need to note that concurrent slot creation and deletion could
577 : : * happen but WAL writes are still not permitted until recovery fully
578 : : * completes. Here's how we handle concurrent toggling of logical
579 : : * decoding:
580 : : *
581 : : * For 'enable' case, if there's a concurrent disable request before
582 : : * recovery fully completes, the checkpointer will handle it after
583 : : * recovery is done. This means there might be a brief period after
584 : : * recovery where logical decoding remains enabled even with no logical
585 : : * replication slots present. This temporary state is not new - it can
586 : : * already occur due to the checkpointer's asynchronous deactivation
587 : : * process.
588 : : *
589 : : * For 'disable' case, backend cannot create logical replication slots
590 : : * during recovery (see checks in CheckLogicalDecodingRequirements()),
591 : : * which prevents a race condition between disabling logical decoding and
592 : : * concurrent slot creation.
593 : : */
594 [ + + ]: 615 : if (new_status != LogicalDecodingCtl->logical_decoding_enabled)
595 : : {
596 : : /*
597 : : * Update both the logical decoding status and logical WAL logging
598 : : * status. Unlike toggling these status during non-recovery, we don't
599 : : * need to worry about the operation order as WAL writes are still not
600 : : * permitted.
601 : : */
602 : 74 : LogicalDecodingCtl->xlog_logical_info = new_status;
603 : 74 : LogicalDecodingCtl->logical_decoding_enabled = new_status;
604 : :
605 [ + + ]: 74 : elog(DEBUG1,
606 : : "update logical decoding status to %d at the end of recovery",
607 : : new_status);
608 : :
609 : : /*
610 : : * Now that we updated the logical decoding status, clear the pending
611 : : * disable flag. It's possible that a concurrent process drops the
612 : : * last logical slot and initiates the pending disable again. The
613 : : * checkpointer process will check it.
614 : : */
615 : 74 : LogicalDecodingCtl->pending_disable = false;
616 : :
617 : 74 : LWLockRelease(LogicalDecodingControlLock);
618 : :
619 : 74 : write_logical_decoding_status_update_record(new_status);
620 : : }
621 : : else
622 : 541 : LWLockRelease(LogicalDecodingControlLock);
623 : :
624 : : /*
625 : : * Ensure all running processes have the updated status. We don't need to
626 : : * wait for running transactions to finish as we don't accept any writes
627 : : * yet. On the other hand, we need to wait for synchronizing
628 : : * XLogLogicalInfo even if we've not updated the status above as the
629 : : * status have been turned on and off during recovery, having running
630 : : * processes have different status on their local caches.
631 : : */
632 [ + + ]: 615 : if (IsUnderPostmaster)
633 : 482 : WaitForProcSignalBarrier(
634 : : EmitProcSignalBarrier(PROCSIGNAL_BARRIER_UPDATE_XLOG_LOGICAL_INFO));
635 : :
636 : 615 : INJECTION_POINT("startup-logical-decoding-status-change-end-of-recovery", NULL);
637 : : }
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