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 "utils/injection_point.h"
75 : :
76 : : /*
77 : : * Struct for controlling the logical decoding status.
78 : : *
79 : : * This struct is protected by LogicalDecodingControlLock.
80 : : */
81 : : typedef struct LogicalDecodingCtlData
82 : : {
83 : : /*
84 : : * This is the authoritative value used by all processes to determine
85 : : * whether to write additional information required by logical decoding to
86 : : * WAL. Since this information could be checked frequently, each process
87 : : * caches this value in XLogLogicalInfo for better performance.
88 : : */
89 : : bool xlog_logical_info;
90 : :
91 : : /* True if logical decoding is available in the system */
92 : : bool logical_decoding_enabled;
93 : :
94 : : /* True if logical decoding might need to be disabled */
95 : : bool pending_disable;
96 : : } LogicalDecodingCtlData;
97 : :
98 : : static LogicalDecodingCtlData *LogicalDecodingCtl = NULL;
99 : :
100 : : /*
101 : : * A process-local cache of LogicalDecodingCtl->xlog_logical_info. This is
102 : : * initialized at process startup, and updated when processing the process
103 : : * barrier signal in ProcessBarrierUpdateXLogLogicalInfo(). If the process
104 : : * is in an XID-assigned transaction, the cache update is delayed until the
105 : : * transaction ends. See the comments for XLogLogicalInfoUpdatePending for details.
106 : : */
107 : : bool XLogLogicalInfo = false;
108 : :
109 : : /*
110 : : * When receiving the PROCSIGNAL_BARRIER_UPDATE_XLOG_LOGICAL_INFO signal, if
111 : : * an XID is assigned to the current transaction, the process sets this flag and
112 : : * delays the XLogLogicalInfo update until the transaction ends. This ensures
113 : : * that the XLogLogicalInfo value (typically accessed via XLogLogicalInfoActive)
114 : : * remains consistent throughout the transaction.
115 : : */
116 : : static bool XLogLogicalInfoUpdatePending = false;
117 : :
118 : : static void update_xlog_logical_info(void);
119 : : static void abort_logical_decoding_activation(int code, Datum arg);
120 : : static void write_logical_decoding_status_update_record(bool status);
121 : :
122 : : Size
123 : 21 : LogicalDecodingCtlShmemSize(void)
124 : : {
125 : 21 : return sizeof(LogicalDecodingCtlData);
126 : : }
127 : :
128 : : void
129 : 6 : LogicalDecodingCtlShmemInit(void)
130 : : {
131 : 6 : bool found;
132 : :
133 : 6 : LogicalDecodingCtl = ShmemInitStruct("Logical decoding control",
134 : 6 : LogicalDecodingCtlShmemSize(),
135 : : &found);
136 : :
137 [ - + ]: 6 : if (!found)
138 [ + - - + : 6 : MemSet(LogicalDecodingCtl, 0, LogicalDecodingCtlShmemSize());
# # # # #
# ]
139 : 6 : }
140 : :
141 : : /*
142 : : * Initialize the logical decoding status in shmem at server startup. This
143 : : * must be called ONCE during postmaster or standalone-backend startup.
144 : : */
145 : : void
146 : 4 : StartupLogicalDecodingStatus(bool last_status)
147 : : {
148 : : /* Logical decoding is always disabled when 'minimal' WAL level */
149 [ + + ]: 4 : if (wal_level == WAL_LEVEL_MINIMAL)
150 : 1 : return;
151 : :
152 : : /*
153 : : * Set the initial logical decoding status based on the last status. If
154 : : * logical decoding was enabled before the last shutdown, it remains
155 : : * enabled as we might have set wal_level='logical' or have at least one
156 : : * logical slot.
157 : : */
158 : 3 : LogicalDecodingCtl->xlog_logical_info = last_status;
159 : 3 : LogicalDecodingCtl->logical_decoding_enabled = last_status;
160 : 4 : }
161 : :
162 : : /*
163 : : * Update the XLogLogicalInfo cache.
164 : : */
165 : : static inline void
166 : 812 : update_xlog_logical_info(void)
167 : : {
168 : 812 : XLogLogicalInfo = IsXLogLogicalInfoEnabled();
169 : 812 : }
170 : :
171 : : /*
172 : : * Initialize XLogLogicalInfo backend-private cache. This routine is called
173 : : * during process initialization.
174 : : */
175 : : void
176 : 806 : InitializeProcessXLogLogicalInfo(void)
177 : : {
178 : 806 : update_xlog_logical_info();
179 : 806 : }
180 : :
181 : : /*
182 : : * This routine is called when we are told to update XLogLogicalInfo
183 : : * by a ProcSignalBarrier.
184 : : */
185 : : bool
186 : 6 : ProcessBarrierUpdateXLogLogicalInfo(void)
187 : : {
188 [ - + ]: 6 : if (GetTopTransactionIdIfAny() != InvalidTransactionId)
189 : : {
190 : : /* Delay updating XLogLogicalInfo until the transaction end */
191 : 0 : XLogLogicalInfoUpdatePending = true;
192 : 0 : }
193 : : else
194 : 6 : update_xlog_logical_info();
195 : :
196 : 6 : return true;
197 : : }
198 : :
199 : : /*
200 : : * Check the shared memory state and return true if logical decoding is
201 : : * enabled on the system.
202 : : */
203 : : bool
204 : 12 : IsLogicalDecodingEnabled(void)
205 : : {
206 : 12 : bool enabled;
207 : :
208 : 12 : LWLockAcquire(LogicalDecodingControlLock, LW_SHARED);
209 : 12 : enabled = LogicalDecodingCtl->logical_decoding_enabled;
210 : 12 : LWLockRelease(LogicalDecodingControlLock);
211 : :
212 : 24 : return enabled;
213 : 12 : }
214 : :
215 : : /*
216 : : * Returns true if logical WAL logging is enabled based on the shared memory
217 : : * status.
218 : : */
219 : : bool
220 : 813 : IsXLogLogicalInfoEnabled(void)
221 : : {
222 : 813 : bool xlog_logical_info;
223 : :
224 : 813 : LWLockAcquire(LogicalDecodingControlLock, LW_SHARED);
225 : 813 : xlog_logical_info = LogicalDecodingCtl->xlog_logical_info;
226 : 813 : LWLockRelease(LogicalDecodingControlLock);
227 : :
228 : 1626 : return xlog_logical_info;
229 : 813 : }
230 : :
231 : : /*
232 : : * Reset the local cache at end of the transaction.
233 : : */
234 : : void
235 : 57914 : AtEOXact_LogicalCtl(void)
236 : : {
237 : : /* Update the local cache if there is a pending update */
238 [ + - ]: 57914 : if (XLogLogicalInfoUpdatePending)
239 : : {
240 : 0 : update_xlog_logical_info();
241 : 0 : XLogLogicalInfoUpdatePending = false;
242 : 0 : }
243 : 57914 : }
244 : :
245 : : /*
246 : : * Writes an XLOG_LOGICAL_DECODING_STATUS_CHANGE WAL record with the given
247 : : * status.
248 : : */
249 : : static void
250 : 0 : write_logical_decoding_status_update_record(bool status)
251 : : {
252 : 0 : XLogRecPtr recptr;
253 : :
254 : 0 : XLogBeginInsert();
255 : 0 : XLogRegisterData(&status, sizeof(bool));
256 : 0 : recptr = XLogInsert(RM_XLOG_ID, XLOG_LOGICAL_DECODING_STATUS_CHANGE);
257 : 0 : XLogFlush(recptr);
258 : 0 : }
259 : :
260 : : /*
261 : : * A PG_ENSURE_ERROR_CLEANUP callback for activating logical decoding, resetting
262 : : * the shared flags to revert the logical decoding activation process.
263 : : */
264 : : static void
265 : 0 : abort_logical_decoding_activation(int code, Datum arg)
266 : : {
267 [ # # ]: 0 : Assert(MyReplicationSlot);
268 [ # # ]: 0 : Assert(!LogicalDecodingCtl->logical_decoding_enabled);
269 : :
270 [ # # # # ]: 0 : elog(DEBUG1, "aborting logical decoding activation process");
271 : :
272 : : /*
273 : : * Abort the change to xlog_logical_info. We don't need to check
274 : : * CheckLogicalSlotExists() as we're still holding a logical slot.
275 : : */
276 : 0 : LWLockAcquire(LogicalDecodingControlLock, LW_EXCLUSIVE);
277 : 0 : LogicalDecodingCtl->xlog_logical_info = false;
278 : 0 : LWLockRelease(LogicalDecodingControlLock);
279 : :
280 : : /*
281 : : * Some processes might have already started logical info WAL logging, so
282 : : * tell all running processes to update their caches. We don't need to
283 : : * wait for all processes to disable xlog_logical_info locally as it's
284 : : * always safe to write logical information to WAL records, even when not
285 : : * strictly required.
286 : : */
287 : 0 : EmitProcSignalBarrier(PROCSIGNAL_BARRIER_UPDATE_XLOG_LOGICAL_INFO);
288 : 0 : }
289 : :
290 : : /*
291 : : * Enable logical decoding if disabled.
292 : : *
293 : : * If this function is called during recovery, it simply returns without
294 : : * action since the logical decoding status change is not allowed during
295 : : * this time. The logical decoding status depends on the status on the primary.
296 : : * The caller should use CheckLogicalDecodingRequirements() before calling this
297 : : * function to make sure that the logical decoding status can be modified.
298 : : *
299 : : * Note that there is no interlock between logical decoding activation
300 : : * and slot creation. To ensure enabling logical decoding, the caller
301 : : * needs to call this function after creating a logical slot before
302 : : * initializing the logical decoding context.
303 : : */
304 : : void
305 : 0 : EnsureLogicalDecodingEnabled(void)
306 : : {
307 [ # # ]: 0 : Assert(MyReplicationSlot);
308 [ # # ]: 0 : Assert(wal_level >= WAL_LEVEL_REPLICA);
309 : :
310 : : /* Logical decoding is always enabled */
311 [ # # ]: 0 : if (wal_level >= WAL_LEVEL_LOGICAL)
312 : 0 : return;
313 : :
314 [ # # ]: 0 : if (RecoveryInProgress())
315 : : {
316 : : /*
317 : : * CheckLogicalDecodingRequirements() must have already errored out if
318 : : * logical decoding is not enabled since we cannot enable the logical
319 : : * decoding status during recovery.
320 : : */
321 [ # # ]: 0 : Assert(IsLogicalDecodingEnabled());
322 : 0 : return;
323 : : }
324 : :
325 : : /*
326 : : * Ensure to abort the activation process in cases where there in an
327 : : * interruption during the wait.
328 : : */
329 [ # # ]: 0 : PG_ENSURE_ERROR_CLEANUP(abort_logical_decoding_activation, (Datum) 0);
330 : : {
331 : 0 : EnableLogicalDecoding();
332 : : }
333 [ # # ]: 0 : PG_END_ENSURE_ERROR_CLEANUP(abort_logical_decoding_activation, (Datum) 0);
334 : 0 : }
335 : :
336 : : /*
337 : : * A workhorse function to enable logical decoding.
338 : : */
339 : : void
340 : 0 : EnableLogicalDecoding(void)
341 : : {
342 : 0 : bool in_recovery;
343 : :
344 : 0 : LWLockAcquire(LogicalDecodingControlLock, LW_EXCLUSIVE);
345 : :
346 : : /* Return if it is already enabled */
347 [ # # ]: 0 : if (LogicalDecodingCtl->logical_decoding_enabled)
348 : : {
349 : 0 : LogicalDecodingCtl->pending_disable = false;
350 : 0 : LWLockRelease(LogicalDecodingControlLock);
351 : 0 : return;
352 : : }
353 : :
354 : : /*
355 : : * Set logical info WAL logging in shmem. All process starts after this
356 : : * point will include the information required by logical decoding to WAL
357 : : * records.
358 : : */
359 : 0 : LogicalDecodingCtl->xlog_logical_info = true;
360 : :
361 : 0 : LWLockRelease(LogicalDecodingControlLock);
362 : :
363 : : /*
364 : : * Tell all running processes to reflect the xlog_logical_info update, and
365 : : * wait. This ensures that all running processes have enabled logical
366 : : * information WAL logging.
367 : : */
368 : 0 : WaitForProcSignalBarrier(
369 : 0 : EmitProcSignalBarrier(PROCSIGNAL_BARRIER_UPDATE_XLOG_LOGICAL_INFO));
370 : :
371 : : INJECTION_POINT("logical-decoding-activation", NULL);
372 : :
373 : 0 : in_recovery = RecoveryInProgress();
374 : :
375 : : /*
376 : : * There could be some transactions that might have started with the old
377 : : * status, but we don't need to wait for these transactions to complete as
378 : : * long as they have valid XIDs. These transactions will appear in the
379 : : * xl_running_xacts record and therefore the snapshot builder will not try
380 : : * to decode the transaction during the logical decoding initialization.
381 : : *
382 : : * There is a theoretical case where a transaction decides whether to
383 : : * include logical-info to WAL records before getting an XID. In this
384 : : * case, the transaction won't appear in xl_running_xacts.
385 : : *
386 : : * For operations that do not require an XID assignment, the process
387 : : * starts including logical-info immediately upon receiving the signal
388 : : * (barrier). If such an operation checks the effective_wal_level multiple
389 : : * times within a single execution, the resulting WAL records might be
390 : : * inconsistent (i.e., logical-info is included in some records but not in
391 : : * others). However, this is harmless because logical decoding generally
392 : : * ignores WAL records that are not associated with an assigned XID.
393 : : *
394 : : * One might think we need to wait for all running transactions, including
395 : : * those without XIDs and read-only transactions, to finish before
396 : : * enabling logical decoding. However, such a requirement would force the
397 : : * slot creation to wait for a potentially very long time due to
398 : : * long-running read queries, which is practically unacceptable.
399 : : */
400 : :
401 : 0 : START_CRIT_SECTION();
402 : :
403 : : /*
404 : : * We enable logical decoding first, followed by writing the WAL record.
405 : : * This sequence ensures logical decoding becomes available on the primary
406 : : * first.
407 : : */
408 : 0 : LWLockAcquire(LogicalDecodingControlLock, LW_EXCLUSIVE);
409 : :
410 : 0 : LogicalDecodingCtl->logical_decoding_enabled = true;
411 : :
412 [ # # ]: 0 : if (!in_recovery)
413 : 0 : write_logical_decoding_status_update_record(true);
414 : :
415 : 0 : LogicalDecodingCtl->pending_disable = false;
416 : :
417 : 0 : LWLockRelease(LogicalDecodingControlLock);
418 : :
419 [ # # ]: 0 : END_CRIT_SECTION();
420 : :
421 [ # # ]: 0 : if (!in_recovery)
422 [ # # # # ]: 0 : ereport(LOG,
423 : : errmsg("logical decoding is enabled upon creating a new logical replication slot"));
424 [ # # ]: 0 : }
425 : :
426 : : /*
427 : : * Initiate a request for disabling logical decoding.
428 : : *
429 : : * Note that this function does not verify whether logical slots exist. The
430 : : * checkpointer will verify if logical decoding should actually be disabled.
431 : : */
432 : : void
433 : 0 : RequestDisableLogicalDecoding(void)
434 : : {
435 [ # # ]: 0 : if (wal_level != WAL_LEVEL_REPLICA)
436 : 0 : return;
437 : :
438 : : /*
439 : : * It's possible that we might not actually need to disable logical
440 : : * decoding if someone creates a new logical slot concurrently. We set the
441 : : * flag anyway and the checkpointer will check it and disable logical
442 : : * decoding if necessary.
443 : : */
444 : 0 : LWLockAcquire(LogicalDecodingControlLock, LW_EXCLUSIVE);
445 : 0 : LogicalDecodingCtl->pending_disable = true;
446 : 0 : LWLockRelease(LogicalDecodingControlLock);
447 : :
448 : 0 : WakeupCheckpointer();
449 : :
450 [ # # # # ]: 0 : elog(DEBUG1, "requested disabling logical decoding");
451 : 0 : }
452 : :
453 : : /*
454 : : * Disable logical decoding if necessary.
455 : : *
456 : : * This function disables logical decoding upon a request initiated by
457 : : * RequestDisableLogicalDecoding(). Otherwise, it performs no action.
458 : : */
459 : : void
460 : 3 : DisableLogicalDecodingIfNecessary(void)
461 : : {
462 : 3 : bool pending_disable;
463 : :
464 [ - + ]: 3 : if (wal_level != WAL_LEVEL_REPLICA)
465 : 0 : return;
466 : :
467 : : /*
468 : : * Sanity check as we cannot disable logical decoding while holding a
469 : : * logical slot.
470 : : */
471 [ + - ]: 3 : Assert(!MyReplicationSlot);
472 : :
473 [ + + ]: 3 : if (RecoveryInProgress())
474 : 2 : return;
475 : :
476 : 1 : LWLockAcquire(LogicalDecodingControlLock, LW_SHARED);
477 : 1 : pending_disable = LogicalDecodingCtl->pending_disable;
478 : 1 : LWLockRelease(LogicalDecodingControlLock);
479 : :
480 : : /* Quick return if no pending disable request */
481 [ - + ]: 1 : if (!pending_disable)
482 : 1 : return;
483 : :
484 : 0 : DisableLogicalDecoding();
485 [ - + ]: 3 : }
486 : :
487 : : /*
488 : : * A workhorse function to disable logical decoding.
489 : : */
490 : : void
491 : 0 : DisableLogicalDecoding(void)
492 : : {
493 : 0 : bool in_recovery = RecoveryInProgress();
494 : :
495 : 0 : LWLockAcquire(LogicalDecodingControlLock, LW_EXCLUSIVE);
496 : :
497 : : /*
498 : : * Check if we can disable logical decoding.
499 : : *
500 : : * Skip CheckLogicalSlotExists() check during recovery because the
501 : : * existing slots will be invalidated after disabling logical decoding.
502 : : */
503 [ # # # # ]: 0 : if (!LogicalDecodingCtl->logical_decoding_enabled ||
504 [ # # ]: 0 : (!in_recovery && CheckLogicalSlotExists()))
505 : : {
506 : 0 : LogicalDecodingCtl->pending_disable = false;
507 : 0 : LWLockRelease(LogicalDecodingControlLock);
508 : 0 : return;
509 : : }
510 : :
511 : 0 : 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 : 0 : LogicalDecodingCtl->logical_decoding_enabled = false;
519 : :
520 : : /* Write the WAL to disable logical decoding on standbys too */
521 [ # # ]: 0 : if (!in_recovery)
522 : 0 : write_logical_decoding_status_update_record(false);
523 : :
524 : : /* Now disable logical information WAL logging */
525 : 0 : LogicalDecodingCtl->xlog_logical_info = false;
526 : 0 : LogicalDecodingCtl->pending_disable = false;
527 : :
528 [ # # ]: 0 : END_CRIT_SECTION();
529 : :
530 [ # # ]: 0 : if (!in_recovery)
531 [ # # # # ]: 0 : ereport(LOG,
532 : : errmsg("logical decoding is disabled because there are no valid logical replication slots"));
533 : :
534 : 0 : LWLockRelease(LogicalDecodingControlLock);
535 : :
536 : : /*
537 : : * Tell all running processes to reflect the xlog_logical_info update.
538 : : * Unlike when enabling logical decoding, we don't need to wait for all
539 : : * processes to complete it in this case. We already disabled logical
540 : : * decoding and it's always safe to write logical information to WAL
541 : : * records, even when not strictly required. Therefore, we don't need to
542 : : * wait for all running transactions to finish either.
543 : : */
544 : 0 : EmitProcSignalBarrier(PROCSIGNAL_BARRIER_UPDATE_XLOG_LOGICAL_INFO);
545 [ # # ]: 0 : }
546 : :
547 : : /*
548 : : * Updates the logical decoding status at end of recovery, and ensures that
549 : : * all running processes have the updated XLogLogicalInfo status. This
550 : : * function must be called before accepting writes.
551 : : */
552 : : void
553 : 4 : UpdateLogicalDecodingStatusEndOfRecovery(void)
554 : : {
555 : 4 : bool new_status = false;
556 : :
557 [ + - ]: 4 : Assert(RecoveryInProgress());
558 : :
559 : : /*
560 : : * With 'minimal' WAL level, there are no logical replication slots during
561 : : * recovery. Logical decoding is always disabled, so there is no need to
562 : : * synchronize XLogLogicalInfo.
563 : : */
564 [ + + ]: 4 : if (wal_level == WAL_LEVEL_MINIMAL)
565 : : {
566 [ + - ]: 1 : Assert(!IsXLogLogicalInfoEnabled() && !IsLogicalDecodingEnabled());
567 : 1 : return;
568 : : }
569 : :
570 : 3 : LWLockAcquire(LogicalDecodingControlLock, LW_EXCLUSIVE);
571 : :
572 [ + - - + ]: 3 : if (wal_level == WAL_LEVEL_LOGICAL || CheckLogicalSlotExists())
573 : 0 : new_status = true;
574 : :
575 : : /*
576 : : * When recovery ends, we need to either enable or disable logical
577 : : * decoding based on the wal_level setting and the presence of logical
578 : : * slots. We need to note that concurrent slot creation and deletion could
579 : : * happen but WAL writes are still not permitted until recovery fully
580 : : * completes. Here's how we handle concurrent toggling of logical
581 : : * decoding:
582 : : *
583 : : * For 'enable' case, if there's a concurrent disable request before
584 : : * recovery fully completes, the checkpointer will handle it after
585 : : * recovery is done. This means there might be a brief period after
586 : : * recovery where logical decoding remains enabled even with no logical
587 : : * replication slots present. This temporary state is not new - it can
588 : : * already occur due to the checkpointer's asynchronous deactivation
589 : : * process.
590 : : *
591 : : * For 'disable' case, backend cannot create logical replication slots
592 : : * during recovery (see checks in CheckLogicalDecodingRequirements()),
593 : : * which prevents a race condition between disabling logical decoding and
594 : : * concurrent slot creation.
595 : : */
596 [ - + ]: 3 : if (new_status != LogicalDecodingCtl->logical_decoding_enabled)
597 : : {
598 : : /*
599 : : * Update both the logical decoding status and logical WAL logging
600 : : * status. Unlike toggling these status during non-recovery, we don't
601 : : * need to worry about the operation order as WAL writes are still not
602 : : * permitted.
603 : : */
604 : 0 : LogicalDecodingCtl->xlog_logical_info = new_status;
605 : 0 : LogicalDecodingCtl->logical_decoding_enabled = new_status;
606 : :
607 [ # # # # ]: 0 : elog(DEBUG1,
608 : : "update logical decoding status to %d at the end of recovery",
609 : : new_status);
610 : :
611 : : /*
612 : : * Now that we updated the logical decoding status, clear the pending
613 : : * disable flag. It's possible that a concurrent process drops the
614 : : * last logical slot and initiates the pending disable again. The
615 : : * checkpointer process will check it.
616 : : */
617 : 0 : LogicalDecodingCtl->pending_disable = false;
618 : :
619 : 0 : LWLockRelease(LogicalDecodingControlLock);
620 : :
621 : 0 : write_logical_decoding_status_update_record(new_status);
622 : 0 : }
623 : : else
624 : 3 : LWLockRelease(LogicalDecodingControlLock);
625 : :
626 : : /*
627 : : * Ensure all running processes have the updated status. We don't need to
628 : : * wait for running transactions to finish as we don't accept any writes
629 : : * yet. On the other hand, we need to wait for synchronizing
630 : : * XLogLogicalInfo even if we've not updated the status above as the
631 : : * status have been turned on and off during recovery, having running
632 : : * processes have different status on their local caches.
633 : : */
634 [ + + ]: 3 : if (IsUnderPostmaster)
635 : 1 : WaitForProcSignalBarrier(
636 : 1 : EmitProcSignalBarrier(PROCSIGNAL_BARRIER_UPDATE_XLOG_LOGICAL_INFO));
637 : :
638 : : INJECTION_POINT("startup-logical-decoding-status-change-end-of-recovery", NULL);
639 [ - + ]: 4 : }
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