Branch data 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
131 : 1253 : LogicalDecodingCtlShmemRequest(void *arg)
132 : : {
133 : 1253 : ShmemRequestStruct(.name = "Logical decoding control",
134 : : .size = sizeof(LogicalDecodingCtlData),
135 : : .ptr = (void **) &LogicalDecodingCtl,
136 : : );
137 : 1253 : }
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 : 1088 : StartupLogicalDecodingStatus(bool last_status)
145 : : {
146 : : /* Logical decoding is always disabled when 'minimal' WAL level */
147 [ + + ]: 1088 : if (wal_level == WAL_LEVEL_MINIMAL)
148 : 394 : 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 : 694 : LogicalDecodingCtl->xlog_logical_info = last_status;
157 : 694 : LogicalDecodingCtl->logical_decoding_enabled = last_status;
158 : : }
159 : :
160 : : /*
161 : : * Update the XLogLogicalInfo cache.
162 : : */
163 : : static inline void
164 : 27704 : update_xlog_logical_info(void)
165 : : {
166 : 27704 : XLogLogicalInfo = IsXLogLogicalInfoEnabled();
167 : 27704 : }
168 : :
169 : : /*
170 : : * Initialize XLogLogicalInfo backend-private cache. This routine is called
171 : : * during process initialization.
172 : : */
173 : : void
174 : 24762 : InitializeProcessXLogLogicalInfo(void)
175 : : {
176 : 24762 : update_xlog_logical_info();
177 : 24762 : }
178 : :
179 : : /*
180 : : * This routine is called when we are told to update XLogLogicalInfo
181 : : * by a ProcSignalBarrier.
182 : : */
183 : : bool
184 : 2942 : ProcessBarrierUpdateXLogLogicalInfo(void)
185 : : {
186 [ + + ]: 2942 : if (GetTopTransactionIdIfAny() != InvalidTransactionId)
187 : : {
188 : : /* Delay updating XLogLogicalInfo until the transaction end */
189 : 4 : XLogLogicalInfoUpdatePending = true;
190 : : }
191 : : else
192 : 2938 : update_xlog_logical_info();
193 : :
194 : 2942 : 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 : 19799 : IsLogicalDecodingEnabled(void)
203 : : {
204 : : bool enabled;
205 : :
206 : 19799 : LWLockAcquire(LogicalDecodingControlLock, LW_SHARED);
207 : 19799 : enabled = LogicalDecodingCtl->logical_decoding_enabled;
208 : 19799 : LWLockRelease(LogicalDecodingControlLock);
209 : :
210 : 19799 : 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 : 27735 : IsXLogLogicalInfoEnabled(void)
219 : : {
220 : : bool xlog_logical_info;
221 : :
222 : 27735 : LWLockAcquire(LogicalDecodingControlLock, LW_SHARED);
223 : 27735 : xlog_logical_info = LogicalDecodingCtl->xlog_logical_info;
224 : 27735 : LWLockRelease(LogicalDecodingControlLock);
225 : :
226 : 27735 : return xlog_logical_info;
227 : : }
228 : :
229 : : /*
230 : : * Reset the local cache at end of the transaction.
231 : : */
232 : : void
233 : 650749 : AtEOXact_LogicalCtl(void)
234 : : {
235 : : /* Update the local cache if there is a pending update */
236 [ + + ]: 650749 : if (XLogLogicalInfoUpdatePending)
237 : : {
238 : 4 : update_xlog_logical_info();
239 : 4 : XLogLogicalInfoUpdatePending = false;
240 : : }
241 : 650749 : }
242 : :
243 : : /*
244 : : * Writes an XLOG_LOGICAL_DECODING_STATUS_CHANGE WAL record with the given
245 : : * status.
246 : : */
247 : : static void
248 : 95 : write_logical_decoding_status_update_record(bool status)
249 : : {
250 : : XLogRecPtr recptr;
251 : :
252 : 95 : XLogBeginInsert();
253 : 95 : XLogRegisterData(&status, sizeof(bool));
254 : 95 : recptr = XLogInsert(RM_XLOG_ID, XLOG_LOGICAL_DECODING_STATUS_CHANGE);
255 : 95 : XLogFlush(recptr);
256 : 95 : }
257 : :
258 : : /*
259 : : * A PG_ENSURE_ERROR_CLEANUP callback for activating logical decoding.
260 : : *
261 : : * Rather than directly reverting xlog_logical_info here, we request
262 : : * that the checkpointer handle it via the normal disable path. This
263 : : * avoids race conditions when multiple backends attempt concurrent
264 : : * activation: the checkpointer will reset xlog_logical_info when
265 : : * no valid logical slots exist.
266 : : */
267 : : static void
268 : 2 : abort_logical_decoding_activation(int code, Datum arg)
269 : : {
270 [ + - ]: 2 : elog(DEBUG1, "aborting logical decoding activation process");
271 : 2 : RequestDisableLogicalDecoding();
272 : 2 : }
273 : :
274 : : /*
275 : : * Enable logical decoding if disabled.
276 : : *
277 : : * If this function is called during recovery, it simply returns without
278 : : * action since the logical decoding status change is not allowed during
279 : : * this time. The logical decoding status depends on the status on the primary.
280 : : * The caller should use CheckLogicalDecodingRequirements() before calling this
281 : : * function to make sure that the logical decoding status can be modified.
282 : : *
283 : : * Note that there is no interlock between logical decoding activation
284 : : * and slot creation. To ensure enabling logical decoding, the caller
285 : : * needs to call this function after creating a logical slot before
286 : : * initializing the logical decoding context.
287 : : */
288 : : void
289 : 515 : EnsureLogicalDecodingEnabled(void)
290 : : {
291 : : Assert(MyReplicationSlot);
292 : : Assert(wal_level >= WAL_LEVEL_REPLICA);
293 : :
294 : : /* Logical decoding is always enabled */
295 [ + + ]: 515 : if (wal_level >= WAL_LEVEL_LOGICAL)
296 : 498 : return;
297 : :
298 [ + + ]: 17 : if (RecoveryInProgress())
299 : : {
300 : : /*
301 : : * CheckLogicalDecodingRequirements() must have already errored out if
302 : : * logical decoding is not enabled since we cannot enable the logical
303 : : * decoding status during recovery.
304 : : */
305 : : Assert(IsLogicalDecodingEnabled());
306 : 3 : return;
307 : : }
308 : :
309 : : /*
310 : : * Ensure to abort the activation process in cases where there in an
311 : : * interruption during the wait.
312 : : */
313 [ + + ]: 14 : PG_ENSURE_ERROR_CLEANUP(abort_logical_decoding_activation, (Datum) 0);
314 : : {
315 : 14 : EnableLogicalDecoding();
316 : : }
317 [ - + ]: 14 : PG_END_ENSURE_ERROR_CLEANUP(abort_logical_decoding_activation, (Datum) 0);
318 : : }
319 : :
320 : : /*
321 : : * A workhorse function to enable logical decoding.
322 : : */
323 : : void
324 : 23 : EnableLogicalDecoding(void)
325 : : {
326 : : bool in_recovery;
327 : :
328 : 23 : LWLockAcquire(LogicalDecodingControlLock, LW_EXCLUSIVE);
329 : :
330 : : /* Return if it is already enabled */
331 [ + + ]: 23 : if (LogicalDecodingCtl->logical_decoding_enabled)
332 : : {
333 : 2 : LogicalDecodingCtl->pending_disable = false;
334 : 2 : LWLockRelease(LogicalDecodingControlLock);
335 : 2 : return;
336 : : }
337 : :
338 : : /*
339 : : * Set logical info WAL logging in shmem. All process starts after this
340 : : * point will include the information required by logical decoding to WAL
341 : : * records.
342 : : */
343 : 21 : LogicalDecodingCtl->xlog_logical_info = true;
344 : :
345 : 21 : LWLockRelease(LogicalDecodingControlLock);
346 : :
347 : : /*
348 : : * Tell all running processes to reflect the xlog_logical_info update, and
349 : : * wait. This ensures that all running processes have enabled logical
350 : : * information WAL logging.
351 : : */
352 : 21 : WaitForProcSignalBarrier(
353 : : EmitProcSignalBarrier(PROCSIGNAL_BARRIER_UPDATE_XLOG_LOGICAL_INFO));
354 : :
355 : 21 : INJECTION_POINT("logical-decoding-activation", NULL);
356 : :
357 : 19 : in_recovery = RecoveryInProgress();
358 : :
359 : : /*
360 : : * There could be some transactions that might have started with the old
361 : : * status, but we don't need to wait for these transactions to complete as
362 : : * long as they have valid XIDs. These transactions will appear in the
363 : : * xl_running_xacts record and therefore the snapshot builder will not try
364 : : * to decode the transaction during the logical decoding initialization.
365 : : *
366 : : * There is a theoretical case where a transaction decides whether to
367 : : * include logical-info to WAL records before getting an XID. In this
368 : : * case, the transaction won't appear in xl_running_xacts.
369 : : *
370 : : * For operations that do not require an XID assignment, the process
371 : : * starts including logical-info immediately upon receiving the signal
372 : : * (barrier). If such an operation checks the effective_wal_level multiple
373 : : * times within a single execution, the resulting WAL records might be
374 : : * inconsistent (i.e., logical-info is included in some records but not in
375 : : * others). However, this is harmless because logical decoding generally
376 : : * ignores WAL records that are not associated with an assigned XID.
377 : : *
378 : : * One might think we need to wait for all running transactions, including
379 : : * those without XIDs and read-only transactions, to finish before
380 : : * enabling logical decoding. However, such a requirement would force the
381 : : * slot creation to wait for a potentially very long time due to
382 : : * long-running read queries, which is practically unacceptable.
383 : : */
384 : :
385 : 19 : LWLockAcquire(LogicalDecodingControlLock, LW_EXCLUSIVE);
386 : :
387 : 19 : START_CRIT_SECTION();
388 : :
389 : : /*
390 : : * We enable logical decoding first, followed by writing the WAL record.
391 : : * This sequence ensures logical decoding becomes available on the primary
392 : : * first.
393 : : */
394 : 19 : LogicalDecodingCtl->logical_decoding_enabled = true;
395 : :
396 [ + + ]: 19 : if (!in_recovery)
397 : 10 : write_logical_decoding_status_update_record(true);
398 : :
399 : 19 : LogicalDecodingCtl->pending_disable = false;
400 : :
401 : 19 : END_CRIT_SECTION();
402 : :
403 : 19 : LWLockRelease(LogicalDecodingControlLock);
404 : :
405 : : /*
406 : : * We log the activation message after releasing the slot lock. This is
407 : : * safe because the activation is performed while holding a logical slot,
408 : : * meaning, a concurrent deactivation cannot interleave its log message
409 : : * ahead of ours.
410 : : */
411 [ + + ]: 19 : if (!in_recovery)
412 [ + - ]: 10 : ereport(LOG,
413 : : errmsg("logical decoding is enabled upon creating a new logical replication slot"));
414 : : }
415 : :
416 : : /*
417 : : * Initiate a request for disabling logical decoding.
418 : : *
419 : : * Note that this function does not verify whether logical slots exist. The
420 : : * checkpointer will verify if logical decoding should actually be disabled.
421 : : */
422 : : void
423 : 446 : RequestDisableLogicalDecoding(void)
424 : : {
425 [ + + ]: 446 : if (wal_level != WAL_LEVEL_REPLICA)
426 : 427 : return;
427 : :
428 : : /*
429 : : * It's possible that we might not actually need to disable logical
430 : : * decoding if someone creates a new logical slot concurrently. We set the
431 : : * flag anyway and the checkpointer will check it and disable logical
432 : : * decoding if necessary.
433 : : */
434 : 19 : LWLockAcquire(LogicalDecodingControlLock, LW_EXCLUSIVE);
435 : 19 : LogicalDecodingCtl->pending_disable = true;
436 : 19 : LWLockRelease(LogicalDecodingControlLock);
437 : :
438 : 19 : WakeupCheckpointer();
439 : :
440 [ + + ]: 19 : elog(DEBUG1, "requested disabling logical decoding");
441 : : }
442 : :
443 : : /*
444 : : * Disable logical decoding if necessary.
445 : : *
446 : : * This function disables logical decoding upon a request initiated by
447 : : * RequestDisableLogicalDecoding(). Otherwise, it performs no action.
448 : : */
449 : : void
450 : 5721 : DisableLogicalDecodingIfNecessary(void)
451 : : {
452 : : bool pending_disable;
453 : :
454 [ + + ]: 5721 : if (wal_level != WAL_LEVEL_REPLICA)
455 : 1502 : return;
456 : :
457 : : /*
458 : : * Sanity check as we cannot disable logical decoding while holding a
459 : : * logical slot.
460 : : */
461 : : Assert(!MyReplicationSlot);
462 : :
463 [ + + ]: 4219 : if (RecoveryInProgress())
464 : 1803 : return;
465 : :
466 : 2416 : LWLockAcquire(LogicalDecodingControlLock, LW_SHARED);
467 : 2416 : pending_disable = LogicalDecodingCtl->pending_disable;
468 : 2416 : LWLockRelease(LogicalDecodingControlLock);
469 : :
470 : : /* Quick return if no pending disable request */
471 [ + + ]: 2416 : if (!pending_disable)
472 : 2400 : return;
473 : :
474 : 16 : DisableLogicalDecoding();
475 : : }
476 : :
477 : : /*
478 : : * A workhorse function to disable logical decoding.
479 : : */
480 : : void
481 : 25 : DisableLogicalDecoding(void)
482 : : {
483 : 25 : bool in_recovery = RecoveryInProgress();
484 : : bool was_enabled;
485 : :
486 : 25 : LWLockAcquire(LogicalDecodingControlLock, LW_EXCLUSIVE);
487 : :
488 : : /*
489 : : * Check if we can disable logical decoding.
490 : : *
491 : : * Nothing to do if both flags are already off, or if valid slots exist
492 : : * (skip the slot check during recovery because the existing slots will be
493 : : * invalidated after disabling logical decoding.)
494 : : */
495 [ + + ]: 25 : if ((!LogicalDecodingCtl->logical_decoding_enabled &&
496 [ + + ]: 3 : !LogicalDecodingCtl->xlog_logical_info) ||
497 [ + + + + ]: 23 : (!in_recovery && CheckLogicalSlotExists()))
498 : : {
499 : 4 : LogicalDecodingCtl->pending_disable = false;
500 : 4 : LWLockRelease(LogicalDecodingControlLock);
501 : 4 : return;
502 : : }
503 : :
504 : : /*
505 : : * Remember if logical decoding was enabled. An interrupted activation can
506 : : * leave xlog_logical_info=true while logical_decoding_enabled remains
507 : : * false.
508 : : */
509 : 21 : was_enabled = LogicalDecodingCtl->logical_decoding_enabled;
510 : :
511 : 21 : START_CRIT_SECTION();
512 : :
513 : : /*
514 : : * We need to disable logical decoding first and then disable logical
515 : : * information WAL logging in order to ensure that no logical decoding
516 : : * processes WAL records with insufficient information.
517 : : */
518 : 21 : LogicalDecodingCtl->logical_decoding_enabled = false;
519 : :
520 : : /* Write the WAL to disable logical decoding on standbys too */
521 [ + + + + ]: 21 : if (!in_recovery && was_enabled)
522 : 11 : write_logical_decoding_status_update_record(false);
523 : :
524 : : /* Now disable logical information WAL logging */
525 : 21 : LogicalDecodingCtl->xlog_logical_info = false;
526 : 21 : LogicalDecodingCtl->pending_disable = false;
527 : :
528 : 21 : END_CRIT_SECTION();
529 : :
530 : : /*
531 : : * Logging under the lock guarantees our "is disabled" message appears in
532 : : * the server log before its eventual "is enabled", making server log
533 : : * diagnostics easy.
534 : : */
535 [ + + + + ]: 21 : if (!in_recovery && was_enabled)
536 [ + - ]: 11 : ereport(LOG,
537 : : errmsg("logical decoding is disabled because there are no valid logical replication slots"));
538 : :
539 : 21 : LWLockRelease(LogicalDecodingControlLock);
540 : :
541 : : /*
542 : : * Tell all running processes to reflect the xlog_logical_info update.
543 : : * Unlike when enabling logical decoding, we don't need to wait for all
544 : : * processes to complete it in this case. We already disabled logical
545 : : * decoding and it's always safe to write logical information to WAL
546 : : * records, even when not strictly required. Therefore, we don't need to
547 : : * wait for all running transactions to finish either.
548 : : */
549 : 21 : EmitProcSignalBarrier(PROCSIGNAL_BARRIER_UPDATE_XLOG_LOGICAL_INFO);
550 : : }
551 : :
552 : : /*
553 : : * Updates the logical decoding status at end of recovery, and ensures that
554 : : * all running processes have the updated XLogLogicalInfo status. This
555 : : * function must be called before accepting writes.
556 : : */
557 : : void
558 : 1021 : UpdateLogicalDecodingStatusEndOfRecovery(void)
559 : : {
560 : 1021 : bool new_status = false;
561 : :
562 : : Assert(RecoveryInProgress());
563 : :
564 : 1021 : LWLockAcquire(LogicalDecodingControlLock, LW_EXCLUSIVE);
565 : :
566 : : /*
567 : : * With 'minimal' WAL level, no logical replication slot can exist (see
568 : : * RestoreSlotFromDisk()), so the new status is always false. However,
569 : : * logical decoding could have been enabled during recovery by replaying
570 : : * an XLOG_LOGICAL_DECODING_STATUS_CHANGE record from WAL generated with a
571 : : * higher wal_level, e.g. if the server crashed right after the last
572 : : * logical slot was dropped and then restarted with wal_level='minimal'.
573 : : * The code below disables logical decoding in that case.
574 : : */
575 [ + + + + ]: 1021 : if (wal_level == WAL_LEVEL_LOGICAL || CheckLogicalSlotExists())
576 : 137 : new_status = true;
577 : :
578 : : /*
579 : : * When recovery ends, we need to either enable or disable logical
580 : : * decoding based on the wal_level setting and the presence of logical
581 : : * slots. We need to note that concurrent slot creation and deletion could
582 : : * happen but WAL writes are still not permitted until recovery fully
583 : : * completes. Here's how we handle concurrent toggling of logical
584 : : * decoding:
585 : : *
586 : : * For 'enable' case, if there's a concurrent disable request before
587 : : * recovery fully completes, the checkpointer will handle it after
588 : : * recovery is done. This means there might be a brief period after
589 : : * recovery where logical decoding remains enabled even with no logical
590 : : * replication slots present. This temporary state is not new - it can
591 : : * already occur due to the checkpointer's asynchronous deactivation
592 : : * process.
593 : : *
594 : : * For 'disable' case, backend cannot create logical replication slots
595 : : * during recovery (see checks in CheckLogicalDecodingRequirements()),
596 : : * which prevents a race condition between disabling logical decoding and
597 : : * concurrent slot creation.
598 : : */
599 [ + + ]: 1021 : if (new_status != LogicalDecodingCtl->logical_decoding_enabled)
600 : : {
601 : : /*
602 : : * Update both the logical decoding status and logical WAL logging
603 : : * status. Unlike toggling these status during non-recovery, we don't
604 : : * need to worry about the operation order as WAL writes are still not
605 : : * permitted.
606 : : */
607 : 74 : LogicalDecodingCtl->xlog_logical_info = new_status;
608 : 74 : LogicalDecodingCtl->logical_decoding_enabled = new_status;
609 : :
610 [ + + ]: 74 : elog(DEBUG1,
611 : : "update logical decoding status to %d at the end of recovery",
612 : : new_status);
613 : :
614 : : /*
615 : : * Now that we updated the logical decoding status, clear the pending
616 : : * disable flag. It's possible that a concurrent process drops the
617 : : * last logical slot and initiates the pending disable again. The
618 : : * checkpointer process will check it.
619 : : */
620 : 74 : LogicalDecodingCtl->pending_disable = false;
621 : :
622 : 74 : LWLockRelease(LogicalDecodingControlLock);
623 : :
624 : 74 : write_logical_decoding_status_update_record(new_status);
625 : : }
626 : : else
627 : 947 : LWLockRelease(LogicalDecodingControlLock);
628 : :
629 : : /*
630 : : * Ensure all running processes have the updated status. We don't need to
631 : : * wait for running transactions to finish as we don't accept any writes
632 : : * yet. On the other hand, we need to wait for synchronizing
633 : : * XLogLogicalInfo even if we've not updated the status above as the
634 : : * status have been turned on and off during recovery, having running
635 : : * processes have different status on their local caches.
636 : : */
637 [ + + ]: 1021 : if (IsUnderPostmaster)
638 : 888 : WaitForProcSignalBarrier(
639 : : EmitProcSignalBarrier(PROCSIGNAL_BARRIER_UPDATE_XLOG_LOGICAL_INFO));
640 : :
641 : 1021 : INJECTION_POINT("startup-logical-decoding-status-change-end-of-recovery", NULL);
642 : 1021 : }
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