Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * standby.c
4 : * Misc functions used in Hot Standby mode.
5 : *
6 : * All functions for handling RM_STANDBY_ID, which relate to
7 : * AccessExclusiveLocks and starting snapshots for Hot Standby mode.
8 : * Plus conflict recovery processing.
9 : *
10 : * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
11 : * Portions Copyright (c) 1994, Regents of the University of California
12 : *
13 : * IDENTIFICATION
14 : * src/backend/storage/ipc/standby.c
15 : *
16 : *-------------------------------------------------------------------------
17 : */
18 : #include "postgres.h"
19 : #include "access/transam.h"
20 : #include "access/twophase.h"
21 : #include "access/xact.h"
22 : #include "access/xloginsert.h"
23 : #include "access/xlogrecovery.h"
24 : #include "access/xlogutils.h"
25 : #include "miscadmin.h"
26 : #include "pgstat.h"
27 : #include "replication/slot.h"
28 : #include "storage/bufmgr.h"
29 : #include "storage/proc.h"
30 : #include "storage/procarray.h"
31 : #include "storage/sinvaladt.h"
32 : #include "storage/standby.h"
33 : #include "utils/hsearch.h"
34 : #include "utils/ps_status.h"
35 : #include "utils/timeout.h"
36 : #include "utils/timestamp.h"
37 :
38 : /* User-settable GUC parameters */
39 : int max_standby_archive_delay = 30 * 1000;
40 : int max_standby_streaming_delay = 30 * 1000;
41 : bool log_recovery_conflict_waits = false;
42 :
43 : /*
44 : * Keep track of all the exclusive locks owned by original transactions.
45 : * For each known exclusive lock, there is a RecoveryLockEntry in the
46 : * RecoveryLockHash hash table. All RecoveryLockEntrys belonging to a
47 : * given XID are chained together so that we can find them easily.
48 : * For each original transaction that is known to have any such locks,
49 : * there is a RecoveryLockXidEntry in the RecoveryLockXidHash hash table,
50 : * which stores the head of the chain of its locks.
51 : */
52 : typedef struct RecoveryLockEntry
53 : {
54 : xl_standby_lock key; /* hash key: xid, dbOid, relOid */
55 : struct RecoveryLockEntry *next; /* chain link */
56 : } RecoveryLockEntry;
57 :
58 : typedef struct RecoveryLockXidEntry
59 : {
60 : TransactionId xid; /* hash key -- must be first */
61 : struct RecoveryLockEntry *head; /* chain head */
62 : } RecoveryLockXidEntry;
63 :
64 : static HTAB *RecoveryLockHash = NULL;
65 : static HTAB *RecoveryLockXidHash = NULL;
66 :
67 : /* Flags set by timeout handlers */
68 : static volatile sig_atomic_t got_standby_deadlock_timeout = false;
69 : static volatile sig_atomic_t got_standby_delay_timeout = false;
70 : static volatile sig_atomic_t got_standby_lock_timeout = false;
71 :
72 : static void ResolveRecoveryConflictWithVirtualXIDs(VirtualTransactionId *waitlist,
73 : ProcSignalReason reason,
74 : uint32 wait_event_info,
75 : bool report_waiting);
76 : static void SendRecoveryConflictWithBufferPin(ProcSignalReason reason);
77 : static XLogRecPtr LogCurrentRunningXacts(RunningTransactions CurrRunningXacts);
78 : static void LogAccessExclusiveLocks(int nlocks, xl_standby_lock *locks);
79 : static const char *get_recovery_conflict_desc(ProcSignalReason reason);
80 :
81 : /*
82 : * InitRecoveryTransactionEnvironment
83 : * Initialize tracking of our primary's in-progress transactions.
84 : *
85 : * We need to issue shared invalidations and hold locks. Holding locks
86 : * means others may want to wait on us, so we need to make a lock table
87 : * vxact entry like a real transaction. We could create and delete
88 : * lock table entries for each transaction but its simpler just to create
89 : * one permanent entry and leave it there all the time. Locks are then
90 : * acquired and released as needed. Yes, this means you can see the
91 : * Startup process in pg_locks once we have run this.
92 : */
93 : void
94 186 : InitRecoveryTransactionEnvironment(void)
95 : {
96 : VirtualTransactionId vxid;
97 : HASHCTL hash_ctl;
98 :
99 : Assert(RecoveryLockHash == NULL); /* don't run this twice */
100 :
101 : /*
102 : * Initialize the hash tables for tracking the locks held by each
103 : * transaction.
104 : */
105 186 : hash_ctl.keysize = sizeof(xl_standby_lock);
106 186 : hash_ctl.entrysize = sizeof(RecoveryLockEntry);
107 186 : RecoveryLockHash = hash_create("RecoveryLockHash",
108 : 64,
109 : &hash_ctl,
110 : HASH_ELEM | HASH_BLOBS);
111 186 : hash_ctl.keysize = sizeof(TransactionId);
112 186 : hash_ctl.entrysize = sizeof(RecoveryLockXidEntry);
113 186 : RecoveryLockXidHash = hash_create("RecoveryLockXidHash",
114 : 64,
115 : &hash_ctl,
116 : HASH_ELEM | HASH_BLOBS);
117 :
118 : /*
119 : * Initialize shared invalidation management for Startup process, being
120 : * careful to register ourselves as a sendOnly process so we don't need to
121 : * read messages, nor will we get signaled when the queue starts filling
122 : * up.
123 : */
124 186 : SharedInvalBackendInit(true);
125 :
126 : /*
127 : * Lock a virtual transaction id for Startup process.
128 : *
129 : * We need to do GetNextLocalTransactionId() because
130 : * SharedInvalBackendInit() leaves localTransactionId invalid and the lock
131 : * manager doesn't like that at all.
132 : *
133 : * Note that we don't need to run XactLockTableInsert() because nobody
134 : * needs to wait on xids. That sounds a little strange, but table locks
135 : * are held by vxids and row level locks are held by xids. All queries
136 : * hold AccessShareLocks so never block while we write or lock new rows.
137 : */
138 186 : MyProc->vxid.procNumber = MyProcNumber;
139 186 : vxid.procNumber = MyProcNumber;
140 186 : vxid.localTransactionId = GetNextLocalTransactionId();
141 186 : VirtualXactLockTableInsert(vxid);
142 :
143 186 : standbyState = STANDBY_INITIALIZED;
144 186 : }
145 :
146 : /*
147 : * ShutdownRecoveryTransactionEnvironment
148 : * Shut down transaction tracking
149 : *
150 : * Prepare to switch from hot standby mode to normal operation. Shut down
151 : * recovery-time transaction tracking.
152 : *
153 : * This must be called even in shutdown of startup process if transaction
154 : * tracking has been initialized. Otherwise some locks the tracked
155 : * transactions were holding will not be released and may interfere with
156 : * the processes still running (but will exit soon later) at the exit of
157 : * startup process.
158 : */
159 : void
160 276 : ShutdownRecoveryTransactionEnvironment(void)
161 : {
162 : /*
163 : * Do nothing if RecoveryLockHash is NULL because that means that
164 : * transaction tracking has not yet been initialized or has already been
165 : * shut down. This makes it safe to have possibly-redundant calls of this
166 : * function during process exit.
167 : */
168 276 : if (RecoveryLockHash == NULL)
169 90 : return;
170 :
171 : /* Mark all tracked in-progress transactions as finished. */
172 186 : ExpireAllKnownAssignedTransactionIds();
173 :
174 : /* Release all locks the tracked transactions were holding */
175 186 : StandbyReleaseAllLocks();
176 :
177 : /* Destroy the lock hash tables. */
178 186 : hash_destroy(RecoveryLockHash);
179 186 : hash_destroy(RecoveryLockXidHash);
180 186 : RecoveryLockHash = NULL;
181 186 : RecoveryLockXidHash = NULL;
182 :
183 : /* Cleanup our VirtualTransaction */
184 186 : VirtualXactLockTableCleanup();
185 : }
186 :
187 :
188 : /*
189 : * -----------------------------------------------------
190 : * Standby wait timers and backend cancel logic
191 : * -----------------------------------------------------
192 : */
193 :
194 : /*
195 : * Determine the cutoff time at which we want to start canceling conflicting
196 : * transactions. Returns zero (a time safely in the past) if we are willing
197 : * to wait forever.
198 : */
199 : static TimestampTz
200 58 : GetStandbyLimitTime(void)
201 : {
202 : TimestampTz rtime;
203 : bool fromStream;
204 :
205 : /*
206 : * The cutoff time is the last WAL data receipt time plus the appropriate
207 : * delay variable. Delay of -1 means wait forever.
208 : */
209 58 : GetXLogReceiptTime(&rtime, &fromStream);
210 58 : if (fromStream)
211 : {
212 58 : if (max_standby_streaming_delay < 0)
213 0 : return 0; /* wait forever */
214 58 : return TimestampTzPlusMilliseconds(rtime, max_standby_streaming_delay);
215 : }
216 : else
217 : {
218 0 : if (max_standby_archive_delay < 0)
219 0 : return 0; /* wait forever */
220 0 : return TimestampTzPlusMilliseconds(rtime, max_standby_archive_delay);
221 : }
222 : }
223 :
224 : #define STANDBY_INITIAL_WAIT_US 1000
225 : static int standbyWait_us = STANDBY_INITIAL_WAIT_US;
226 :
227 : /*
228 : * Standby wait logic for ResolveRecoveryConflictWithVirtualXIDs.
229 : * We wait here for a while then return. If we decide we can't wait any
230 : * more then we return true, if we can wait some more return false.
231 : */
232 : static bool
233 30 : WaitExceedsMaxStandbyDelay(uint32 wait_event_info)
234 : {
235 : TimestampTz ltime;
236 :
237 30 : CHECK_FOR_INTERRUPTS();
238 :
239 : /* Are we past the limit time? */
240 30 : ltime = GetStandbyLimitTime();
241 30 : if (ltime && GetCurrentTimestamp() >= ltime)
242 6 : return true;
243 :
244 : /*
245 : * Sleep a bit (this is essential to avoid busy-waiting).
246 : */
247 24 : pgstat_report_wait_start(wait_event_info);
248 24 : pg_usleep(standbyWait_us);
249 24 : pgstat_report_wait_end();
250 :
251 : /*
252 : * Progressively increase the sleep times, but not to more than 1s, since
253 : * pg_usleep isn't interruptible on some platforms.
254 : */
255 24 : standbyWait_us *= 2;
256 24 : if (standbyWait_us > 1000000)
257 0 : standbyWait_us = 1000000;
258 :
259 24 : return false;
260 : }
261 :
262 : /*
263 : * Log the recovery conflict.
264 : *
265 : * wait_start is the timestamp when the caller started to wait.
266 : * now is the timestamp when this function has been called.
267 : * wait_list is the list of virtual transaction ids assigned to
268 : * conflicting processes. still_waiting indicates whether
269 : * the startup process is still waiting for the recovery conflict
270 : * to be resolved or not.
271 : */
272 : void
273 20 : LogRecoveryConflict(ProcSignalReason reason, TimestampTz wait_start,
274 : TimestampTz now, VirtualTransactionId *wait_list,
275 : bool still_waiting)
276 : {
277 : long secs;
278 : int usecs;
279 : long msecs;
280 : StringInfoData buf;
281 20 : int nprocs = 0;
282 :
283 : /*
284 : * There must be no conflicting processes when the recovery conflict has
285 : * already been resolved.
286 : */
287 : Assert(still_waiting || wait_list == NULL);
288 :
289 20 : TimestampDifference(wait_start, now, &secs, &usecs);
290 20 : msecs = secs * 1000 + usecs / 1000;
291 20 : usecs = usecs % 1000;
292 :
293 20 : if (wait_list)
294 : {
295 : VirtualTransactionId *vxids;
296 :
297 : /* Construct a string of list of the conflicting processes */
298 6 : vxids = wait_list;
299 12 : while (VirtualTransactionIdIsValid(*vxids))
300 : {
301 6 : PGPROC *proc = ProcNumberGetProc(vxids->procNumber);
302 :
303 : /* proc can be NULL if the target backend is not active */
304 6 : if (proc)
305 : {
306 6 : if (nprocs == 0)
307 : {
308 6 : initStringInfo(&buf);
309 6 : appendStringInfo(&buf, "%d", proc->pid);
310 : }
311 : else
312 0 : appendStringInfo(&buf, ", %d", proc->pid);
313 :
314 6 : nprocs++;
315 : }
316 :
317 6 : vxids++;
318 : }
319 : }
320 :
321 : /*
322 : * If wait_list is specified, report the list of PIDs of active
323 : * conflicting backends in a detail message. Note that if all the backends
324 : * in the list are not active, no detail message is logged.
325 : */
326 20 : if (still_waiting)
327 : {
328 10 : ereport(LOG,
329 : errmsg("recovery still waiting after %ld.%03d ms: %s",
330 : msecs, usecs, get_recovery_conflict_desc(reason)),
331 : nprocs > 0 ? errdetail_log_plural("Conflicting process: %s.",
332 : "Conflicting processes: %s.",
333 : nprocs, buf.data) : 0);
334 : }
335 : else
336 : {
337 10 : ereport(LOG,
338 : errmsg("recovery finished waiting after %ld.%03d ms: %s",
339 : msecs, usecs, get_recovery_conflict_desc(reason)));
340 : }
341 :
342 20 : if (nprocs > 0)
343 6 : pfree(buf.data);
344 20 : }
345 :
346 : /*
347 : * This is the main executioner for any query backend that conflicts with
348 : * recovery processing. Judgement has already been passed on it within
349 : * a specific rmgr. Here we just issue the orders to the procs. The procs
350 : * then throw the required error as instructed.
351 : *
352 : * If report_waiting is true, "waiting" is reported in PS display and the
353 : * wait for recovery conflict is reported in the log, if necessary. If
354 : * the caller is responsible for reporting them, report_waiting should be
355 : * false. Otherwise, both the caller and this function report the same
356 : * thing unexpectedly.
357 : */
358 : static void
359 17994 : ResolveRecoveryConflictWithVirtualXIDs(VirtualTransactionId *waitlist,
360 : ProcSignalReason reason, uint32 wait_event_info,
361 : bool report_waiting)
362 : {
363 17994 : TimestampTz waitStart = 0;
364 17994 : bool waiting = false;
365 17994 : bool logged_recovery_conflict = false;
366 :
367 : /* Fast exit, to avoid a kernel call if there's no work to be done. */
368 17994 : if (!VirtualTransactionIdIsValid(*waitlist))
369 17988 : return;
370 :
371 : /* Set the wait start timestamp for reporting */
372 6 : if (report_waiting && (log_recovery_conflict_waits || update_process_title))
373 4 : waitStart = GetCurrentTimestamp();
374 :
375 12 : while (VirtualTransactionIdIsValid(*waitlist))
376 : {
377 : /* reset standbyWait_us for each xact we wait for */
378 6 : standbyWait_us = STANDBY_INITIAL_WAIT_US;
379 :
380 : /* wait until the virtual xid is gone */
381 36 : while (!VirtualXactLock(*waitlist, false))
382 : {
383 : /* Is it time to kill it? */
384 30 : if (WaitExceedsMaxStandbyDelay(wait_event_info))
385 : {
386 : pid_t pid;
387 :
388 : /*
389 : * Now find out who to throw out of the balloon.
390 : */
391 : Assert(VirtualTransactionIdIsValid(*waitlist));
392 6 : pid = CancelVirtualTransaction(*waitlist, reason);
393 :
394 : /*
395 : * Wait a little bit for it to die so that we avoid flooding
396 : * an unresponsive backend when system is heavily loaded.
397 : */
398 6 : if (pid != 0)
399 6 : pg_usleep(5000L);
400 : }
401 :
402 30 : if (waitStart != 0 && (!logged_recovery_conflict || !waiting))
403 : {
404 28 : TimestampTz now = 0;
405 : bool maybe_log_conflict;
406 : bool maybe_update_title;
407 :
408 28 : maybe_log_conflict = (log_recovery_conflict_waits && !logged_recovery_conflict);
409 28 : maybe_update_title = (update_process_title && !waiting);
410 :
411 : /* Get the current timestamp if not report yet */
412 28 : if (maybe_log_conflict || maybe_update_title)
413 28 : now = GetCurrentTimestamp();
414 :
415 : /*
416 : * Report via ps if we have been waiting for more than 500
417 : * msec (should that be configurable?)
418 : */
419 56 : if (maybe_update_title &&
420 28 : TimestampDifferenceExceeds(waitStart, now, 500))
421 : {
422 0 : set_ps_display_suffix("waiting");
423 0 : waiting = true;
424 : }
425 :
426 : /*
427 : * Emit the log message if the startup process is waiting
428 : * longer than deadlock_timeout for recovery conflict.
429 : */
430 44 : if (maybe_log_conflict &&
431 16 : TimestampDifferenceExceeds(waitStart, now, DeadlockTimeout))
432 : {
433 4 : LogRecoveryConflict(reason, waitStart, now, waitlist, true);
434 4 : logged_recovery_conflict = true;
435 : }
436 : }
437 : }
438 :
439 : /* The virtual transaction is gone now, wait for the next one */
440 6 : waitlist++;
441 : }
442 :
443 : /*
444 : * Emit the log message if recovery conflict was resolved but the startup
445 : * process waited longer than deadlock_timeout for it.
446 : */
447 6 : if (logged_recovery_conflict)
448 4 : LogRecoveryConflict(reason, waitStart, GetCurrentTimestamp(),
449 : NULL, false);
450 :
451 : /* reset ps display to remove the suffix if we added one */
452 6 : if (waiting)
453 0 : set_ps_display_remove_suffix();
454 :
455 : }
456 :
457 : /*
458 : * Generate whatever recovery conflicts are needed to eliminate snapshots that
459 : * might see XIDs <= snapshotConflictHorizon as still running.
460 : *
461 : * snapshotConflictHorizon cutoffs are our standard approach to generating
462 : * granular recovery conflicts. Note that InvalidTransactionId values are
463 : * interpreted as "definitely don't need any conflicts" here, which is a
464 : * general convention that WAL records can (and often do) depend on.
465 : */
466 : void
467 21662 : ResolveRecoveryConflictWithSnapshot(TransactionId snapshotConflictHorizon,
468 : bool isCatalogRel,
469 : RelFileLocator locator)
470 : {
471 : VirtualTransactionId *backends;
472 :
473 : /*
474 : * If we get passed InvalidTransactionId then we do nothing (no conflict).
475 : *
476 : * This can happen when replaying already-applied WAL records after a
477 : * standby crash or restart, or when replaying an XLOG_HEAP2_VISIBLE
478 : * record that marks as frozen a page which was already all-visible. It's
479 : * also quite common with records generated during index deletion
480 : * (original execution of the deletion can reason that a recovery conflict
481 : * which is sufficient for the deletion operation must take place before
482 : * replay of the deletion record itself).
483 : */
484 21662 : if (!TransactionIdIsValid(snapshotConflictHorizon))
485 3672 : return;
486 :
487 : Assert(TransactionIdIsNormal(snapshotConflictHorizon));
488 17990 : backends = GetConflictingVirtualXIDs(snapshotConflictHorizon,
489 : locator.dbOid);
490 17990 : ResolveRecoveryConflictWithVirtualXIDs(backends,
491 : PROCSIG_RECOVERY_CONFLICT_SNAPSHOT,
492 : WAIT_EVENT_RECOVERY_CONFLICT_SNAPSHOT,
493 : true);
494 :
495 : /*
496 : * Note that WaitExceedsMaxStandbyDelay() is not taken into account here
497 : * (as opposed to ResolveRecoveryConflictWithVirtualXIDs() above). That
498 : * seems OK, given that this kind of conflict should not normally be
499 : * reached, e.g. due to using a physical replication slot.
500 : */
501 17990 : if (wal_level >= WAL_LEVEL_LOGICAL && isCatalogRel)
502 34 : InvalidateObsoleteReplicationSlots(RS_INVAL_HORIZON, 0, locator.dbOid,
503 : snapshotConflictHorizon);
504 : }
505 :
506 : /*
507 : * Variant of ResolveRecoveryConflictWithSnapshot that works with
508 : * FullTransactionId values
509 : */
510 : void
511 0 : ResolveRecoveryConflictWithSnapshotFullXid(FullTransactionId snapshotConflictHorizon,
512 : bool isCatalogRel,
513 : RelFileLocator locator)
514 : {
515 : /*
516 : * ResolveRecoveryConflictWithSnapshot operates on 32-bit TransactionIds,
517 : * so truncate the logged FullTransactionId. If the logged value is very
518 : * old, so that XID wrap-around already happened on it, there can't be any
519 : * snapshots that still see it.
520 : */
521 0 : FullTransactionId nextXid = ReadNextFullTransactionId();
522 : uint64 diff;
523 :
524 0 : diff = U64FromFullTransactionId(nextXid) -
525 0 : U64FromFullTransactionId(snapshotConflictHorizon);
526 0 : if (diff < MaxTransactionId / 2)
527 : {
528 : TransactionId truncated;
529 :
530 0 : truncated = XidFromFullTransactionId(snapshotConflictHorizon);
531 0 : ResolveRecoveryConflictWithSnapshot(truncated,
532 : isCatalogRel,
533 : locator);
534 : }
535 0 : }
536 :
537 : void
538 2 : ResolveRecoveryConflictWithTablespace(Oid tsid)
539 : {
540 : VirtualTransactionId *temp_file_users;
541 :
542 : /*
543 : * Standby users may be currently using this tablespace for their
544 : * temporary files. We only care about current users because
545 : * temp_tablespace parameter will just ignore tablespaces that no longer
546 : * exist.
547 : *
548 : * Ask everybody to cancel their queries immediately so we can ensure no
549 : * temp files remain and we can remove the tablespace. Nuke the entire
550 : * site from orbit, it's the only way to be sure.
551 : *
552 : * XXX: We could work out the pids of active backends using this
553 : * tablespace by examining the temp filenames in the directory. We would
554 : * then convert the pids into VirtualXIDs before attempting to cancel
555 : * them.
556 : *
557 : * We don't wait for commit because drop tablespace is non-transactional.
558 : */
559 2 : temp_file_users = GetConflictingVirtualXIDs(InvalidTransactionId,
560 : InvalidOid);
561 2 : ResolveRecoveryConflictWithVirtualXIDs(temp_file_users,
562 : PROCSIG_RECOVERY_CONFLICT_TABLESPACE,
563 : WAIT_EVENT_RECOVERY_CONFLICT_TABLESPACE,
564 : true);
565 2 : }
566 :
567 : void
568 22 : ResolveRecoveryConflictWithDatabase(Oid dbid)
569 : {
570 : /*
571 : * We don't do ResolveRecoveryConflictWithVirtualXIDs() here since that
572 : * only waits for transactions and completely idle sessions would block
573 : * us. This is rare enough that we do this as simply as possible: no wait,
574 : * just force them off immediately.
575 : *
576 : * No locking is required here because we already acquired
577 : * AccessExclusiveLock. Anybody trying to connect while we do this will
578 : * block during InitPostgres() and then disconnect when they see the
579 : * database has been removed.
580 : */
581 26 : while (CountDBBackends(dbid) > 0)
582 : {
583 4 : CancelDBBackends(dbid, PROCSIG_RECOVERY_CONFLICT_DATABASE, true);
584 :
585 : /*
586 : * Wait awhile for them to die so that we avoid flooding an
587 : * unresponsive backend when system is heavily loaded.
588 : */
589 4 : pg_usleep(10000);
590 : }
591 22 : }
592 :
593 : /*
594 : * ResolveRecoveryConflictWithLock is called from ProcSleep()
595 : * to resolve conflicts with other backends holding relation locks.
596 : *
597 : * The WaitLatch sleep normally done in ProcSleep()
598 : * (when not InHotStandby) is performed here, for code clarity.
599 : *
600 : * We either resolve conflicts immediately or set a timeout to wake us at
601 : * the limit of our patience.
602 : *
603 : * Resolve conflicts by canceling to all backends holding a conflicting
604 : * lock. As we are already queued to be granted the lock, no new lock
605 : * requests conflicting with ours will be granted in the meantime.
606 : *
607 : * We also must check for deadlocks involving the Startup process and
608 : * hot-standby backend processes. If deadlock_timeout is reached in
609 : * this function, all the backends holding the conflicting locks are
610 : * requested to check themselves for deadlocks.
611 : *
612 : * logging_conflict should be true if the recovery conflict has not been
613 : * logged yet even though logging is enabled. After deadlock_timeout is
614 : * reached and the request for deadlock check is sent, we wait again to
615 : * be signaled by the release of the lock if logging_conflict is false.
616 : * Otherwise we return without waiting again so that the caller can report
617 : * the recovery conflict. In this case, then, this function is called again
618 : * with logging_conflict=false (because the recovery conflict has already
619 : * been logged) and we will wait again for the lock to be released.
620 : */
621 : void
622 8 : ResolveRecoveryConflictWithLock(LOCKTAG locktag, bool logging_conflict)
623 : {
624 : TimestampTz ltime;
625 : TimestampTz now;
626 :
627 : Assert(InHotStandby);
628 :
629 8 : ltime = GetStandbyLimitTime();
630 8 : now = GetCurrentTimestamp();
631 :
632 : /*
633 : * Update waitStart if first time through after the startup process
634 : * started waiting for the lock. It should not be updated every time
635 : * ResolveRecoveryConflictWithLock() is called during the wait.
636 : *
637 : * Use the current time obtained for comparison with ltime as waitStart
638 : * (i.e., the time when this process started waiting for the lock). Since
639 : * getting the current time newly can cause overhead, we reuse the
640 : * already-obtained time to avoid that overhead.
641 : *
642 : * Note that waitStart is updated without holding the lock table's
643 : * partition lock, to avoid the overhead by additional lock acquisition.
644 : * This can cause "waitstart" in pg_locks to become NULL for a very short
645 : * period of time after the wait started even though "granted" is false.
646 : * This is OK in practice because we can assume that users are likely to
647 : * look at "waitstart" when waiting for the lock for a long time.
648 : */
649 8 : if (pg_atomic_read_u64(&MyProc->waitStart) == 0)
650 2 : pg_atomic_write_u64(&MyProc->waitStart, now);
651 :
652 8 : if (now >= ltime && ltime != 0)
653 2 : {
654 : /*
655 : * We're already behind, so clear a path as quickly as possible.
656 : */
657 : VirtualTransactionId *backends;
658 :
659 2 : backends = GetLockConflicts(&locktag, AccessExclusiveLock, NULL);
660 :
661 : /*
662 : * Prevent ResolveRecoveryConflictWithVirtualXIDs() from reporting
663 : * "waiting" in PS display by disabling its argument report_waiting
664 : * because the caller, WaitOnLock(), has already reported that.
665 : */
666 2 : ResolveRecoveryConflictWithVirtualXIDs(backends,
667 : PROCSIG_RECOVERY_CONFLICT_LOCK,
668 2 : PG_WAIT_LOCK | locktag.locktag_type,
669 : false);
670 : }
671 : else
672 : {
673 : /*
674 : * Wait (or wait again) until ltime, and check for deadlocks as well
675 : * if we will be waiting longer than deadlock_timeout
676 : */
677 : EnableTimeoutParams timeouts[2];
678 6 : int cnt = 0;
679 :
680 6 : if (ltime != 0)
681 : {
682 6 : got_standby_lock_timeout = false;
683 6 : timeouts[cnt].id = STANDBY_LOCK_TIMEOUT;
684 6 : timeouts[cnt].type = TMPARAM_AT;
685 6 : timeouts[cnt].fin_time = ltime;
686 6 : cnt++;
687 : }
688 :
689 6 : got_standby_deadlock_timeout = false;
690 6 : timeouts[cnt].id = STANDBY_DEADLOCK_TIMEOUT;
691 6 : timeouts[cnt].type = TMPARAM_AFTER;
692 6 : timeouts[cnt].delay_ms = DeadlockTimeout;
693 6 : cnt++;
694 :
695 6 : enable_timeouts(timeouts, cnt);
696 : }
697 :
698 : /* Wait to be signaled by the release of the Relation Lock */
699 8 : ProcWaitForSignal(PG_WAIT_LOCK | locktag.locktag_type);
700 :
701 : /*
702 : * Exit if ltime is reached. Then all the backends holding conflicting
703 : * locks will be canceled in the next ResolveRecoveryConflictWithLock()
704 : * call.
705 : */
706 8 : if (got_standby_lock_timeout)
707 0 : goto cleanup;
708 :
709 8 : if (got_standby_deadlock_timeout)
710 : {
711 : VirtualTransactionId *backends;
712 :
713 4 : backends = GetLockConflicts(&locktag, AccessExclusiveLock, NULL);
714 :
715 : /* Quick exit if there's no work to be done */
716 4 : if (!VirtualTransactionIdIsValid(*backends))
717 0 : goto cleanup;
718 :
719 : /*
720 : * Send signals to all the backends holding the conflicting locks, to
721 : * ask them to check themselves for deadlocks.
722 : */
723 8 : while (VirtualTransactionIdIsValid(*backends))
724 : {
725 4 : SignalVirtualTransaction(*backends,
726 : PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK,
727 : false);
728 4 : backends++;
729 : }
730 :
731 : /*
732 : * Exit if the recovery conflict has not been logged yet even though
733 : * logging is enabled, so that the caller can log that. Then
734 : * RecoveryConflictWithLock() is called again and we will wait again
735 : * for the lock to be released.
736 : */
737 4 : if (logging_conflict)
738 2 : goto cleanup;
739 :
740 : /*
741 : * Wait again here to be signaled by the release of the Relation Lock,
742 : * to prevent the subsequent RecoveryConflictWithLock() from causing
743 : * deadlock_timeout and sending a request for deadlocks check again.
744 : * Otherwise the request continues to be sent every deadlock_timeout
745 : * until the relation locks are released or ltime is reached.
746 : */
747 2 : got_standby_deadlock_timeout = false;
748 2 : ProcWaitForSignal(PG_WAIT_LOCK | locktag.locktag_type);
749 : }
750 :
751 4 : cleanup:
752 :
753 : /*
754 : * Clear any timeout requests established above. We assume here that the
755 : * Startup process doesn't have any other outstanding timeouts than those
756 : * used by this function. If that stops being true, we could cancel the
757 : * timeouts individually, but that'd be slower.
758 : */
759 8 : disable_all_timeouts(false);
760 8 : got_standby_lock_timeout = false;
761 8 : got_standby_deadlock_timeout = false;
762 8 : }
763 :
764 : /*
765 : * ResolveRecoveryConflictWithBufferPin is called from LockBufferForCleanup()
766 : * to resolve conflicts with other backends holding buffer pins.
767 : *
768 : * The ProcWaitForSignal() sleep normally done in LockBufferForCleanup()
769 : * (when not InHotStandby) is performed here, for code clarity.
770 : *
771 : * We either resolve conflicts immediately or set a timeout to wake us at
772 : * the limit of our patience.
773 : *
774 : * Resolve conflicts by sending a PROCSIG signal to all backends to check if
775 : * they hold one of the buffer pins that is blocking Startup process. If so,
776 : * those backends will take an appropriate error action, ERROR or FATAL.
777 : *
778 : * We also must check for deadlocks. Deadlocks occur because if queries
779 : * wait on a lock, that must be behind an AccessExclusiveLock, which can only
780 : * be cleared if the Startup process replays a transaction completion record.
781 : * If Startup process is also waiting then that is a deadlock. The deadlock
782 : * can occur if the query is waiting and then the Startup sleeps, or if
783 : * Startup is sleeping and the query waits on a lock. We protect against
784 : * only the former sequence here, the latter sequence is checked prior to
785 : * the query sleeping, in CheckRecoveryConflictDeadlock().
786 : *
787 : * Deadlocks are extremely rare, and relatively expensive to check for,
788 : * so we don't do a deadlock check right away ... only if we have had to wait
789 : * at least deadlock_timeout.
790 : */
791 : void
792 20 : ResolveRecoveryConflictWithBufferPin(void)
793 : {
794 : TimestampTz ltime;
795 :
796 : Assert(InHotStandby);
797 :
798 20 : ltime = GetStandbyLimitTime();
799 :
800 20 : if (GetCurrentTimestamp() >= ltime && ltime != 0)
801 : {
802 : /*
803 : * We're already behind, so clear a path as quickly as possible.
804 : */
805 2 : SendRecoveryConflictWithBufferPin(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN);
806 : }
807 : else
808 : {
809 : /*
810 : * Wake up at ltime, and check for deadlocks as well if we will be
811 : * waiting longer than deadlock_timeout
812 : */
813 : EnableTimeoutParams timeouts[2];
814 18 : int cnt = 0;
815 :
816 18 : if (ltime != 0)
817 : {
818 18 : timeouts[cnt].id = STANDBY_TIMEOUT;
819 18 : timeouts[cnt].type = TMPARAM_AT;
820 18 : timeouts[cnt].fin_time = ltime;
821 18 : cnt++;
822 : }
823 :
824 18 : got_standby_deadlock_timeout = false;
825 18 : timeouts[cnt].id = STANDBY_DEADLOCK_TIMEOUT;
826 18 : timeouts[cnt].type = TMPARAM_AFTER;
827 18 : timeouts[cnt].delay_ms = DeadlockTimeout;
828 18 : cnt++;
829 :
830 18 : enable_timeouts(timeouts, cnt);
831 : }
832 :
833 : /*
834 : * Wait to be signaled by UnpinBuffer() or for the wait to be interrupted
835 : * by one of the timeouts established above.
836 : *
837 : * We assume that only UnpinBuffer() and the timeout requests established
838 : * above can wake us up here. WakeupRecovery() called by walreceiver or
839 : * SIGHUP signal handler, etc cannot do that because it uses the different
840 : * latch from that ProcWaitForSignal() waits on.
841 : */
842 20 : ProcWaitForSignal(WAIT_EVENT_BUFFER_PIN);
843 :
844 20 : if (got_standby_delay_timeout)
845 2 : SendRecoveryConflictWithBufferPin(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN);
846 18 : else if (got_standby_deadlock_timeout)
847 : {
848 : /*
849 : * Send out a request for hot-standby backends to check themselves for
850 : * deadlocks.
851 : *
852 : * XXX The subsequent ResolveRecoveryConflictWithBufferPin() will wait
853 : * to be signaled by UnpinBuffer() again and send a request for
854 : * deadlocks check if deadlock_timeout happens. This causes the
855 : * request to continue to be sent every deadlock_timeout until the
856 : * buffer is unpinned or ltime is reached. This would increase the
857 : * workload in the startup process and backends. In practice it may
858 : * not be so harmful because the period that the buffer is kept pinned
859 : * is basically no so long. But we should fix this?
860 : */
861 12 : SendRecoveryConflictWithBufferPin(PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK);
862 : }
863 :
864 : /*
865 : * Clear any timeout requests established above. We assume here that the
866 : * Startup process doesn't have any other timeouts than what this function
867 : * uses. If that stops being true, we could cancel the timeouts
868 : * individually, but that'd be slower.
869 : */
870 20 : disable_all_timeouts(false);
871 20 : got_standby_delay_timeout = false;
872 20 : got_standby_deadlock_timeout = false;
873 20 : }
874 :
875 : static void
876 16 : SendRecoveryConflictWithBufferPin(ProcSignalReason reason)
877 : {
878 : Assert(reason == PROCSIG_RECOVERY_CONFLICT_BUFFERPIN ||
879 : reason == PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK);
880 :
881 : /*
882 : * We send signal to all backends to ask them if they are holding the
883 : * buffer pin which is delaying the Startup process. We must not set the
884 : * conflict flag yet, since most backends will be innocent. Let the
885 : * SIGUSR1 handling in each backend decide their own fate.
886 : */
887 16 : CancelDBBackends(InvalidOid, reason, false);
888 16 : }
889 :
890 : /*
891 : * In Hot Standby perform early deadlock detection. We abort the lock
892 : * wait if we are about to sleep while holding the buffer pin that Startup
893 : * process is waiting for.
894 : *
895 : * Note: this code is pessimistic, because there is no way for it to
896 : * determine whether an actual deadlock condition is present: the lock we
897 : * need to wait for might be unrelated to any held by the Startup process.
898 : * Sooner or later, this mechanism should get ripped out in favor of somehow
899 : * accounting for buffer locks in DeadLockCheck(). However, errors here
900 : * seem to be very low-probability in practice, so for now it's not worth
901 : * the trouble.
902 : */
903 : void
904 2 : CheckRecoveryConflictDeadlock(void)
905 : {
906 : Assert(!InRecovery); /* do not call in Startup process */
907 :
908 2 : if (!HoldingBufferPinThatDelaysRecovery())
909 2 : return;
910 :
911 : /*
912 : * Error message should match ProcessInterrupts() but we avoid calling
913 : * that because we aren't handling an interrupt at this point. Note that
914 : * we only cancel the current transaction here, so if we are in a
915 : * subtransaction and the pin is held by a parent, then the Startup
916 : * process will continue to wait even though we have avoided deadlock.
917 : */
918 0 : ereport(ERROR,
919 : (errcode(ERRCODE_T_R_DEADLOCK_DETECTED),
920 : errmsg("canceling statement due to conflict with recovery"),
921 : errdetail("User transaction caused buffer deadlock with recovery.")));
922 : }
923 :
924 :
925 : /* --------------------------------
926 : * timeout handler routines
927 : * --------------------------------
928 : */
929 :
930 : /*
931 : * StandbyDeadLockHandler() will be called if STANDBY_DEADLOCK_TIMEOUT is
932 : * exceeded.
933 : */
934 : void
935 16 : StandbyDeadLockHandler(void)
936 : {
937 16 : got_standby_deadlock_timeout = true;
938 16 : }
939 :
940 : /*
941 : * StandbyTimeoutHandler() will be called if STANDBY_TIMEOUT is exceeded.
942 : */
943 : void
944 2 : StandbyTimeoutHandler(void)
945 : {
946 2 : got_standby_delay_timeout = true;
947 2 : }
948 :
949 : /*
950 : * StandbyLockTimeoutHandler() will be called if STANDBY_LOCK_TIMEOUT is exceeded.
951 : */
952 : void
953 2 : StandbyLockTimeoutHandler(void)
954 : {
955 2 : got_standby_lock_timeout = true;
956 2 : }
957 :
958 : /*
959 : * -----------------------------------------------------
960 : * Locking in Recovery Mode
961 : * -----------------------------------------------------
962 : *
963 : * All locks are held by the Startup process using a single virtual
964 : * transaction. This implementation is both simpler and in some senses,
965 : * more correct. The locks held mean "some original transaction held
966 : * this lock, so query access is not allowed at this time". So the Startup
967 : * process is the proxy by which the original locks are implemented.
968 : *
969 : * We only keep track of AccessExclusiveLocks, which are only ever held by
970 : * one transaction on one relation.
971 : *
972 : * We keep a table of known locks in the RecoveryLockHash hash table.
973 : * The point of that table is to let us efficiently de-duplicate locks,
974 : * which is important because checkpoints will re-report the same locks
975 : * already held. There is also a RecoveryLockXidHash table with one entry
976 : * per xid, which allows us to efficiently find all the locks held by a
977 : * given original transaction.
978 : *
979 : * We use session locks rather than normal locks so we don't need
980 : * ResourceOwners.
981 : */
982 :
983 :
984 : void
985 43256 : StandbyAcquireAccessExclusiveLock(TransactionId xid, Oid dbOid, Oid relOid)
986 : {
987 : RecoveryLockXidEntry *xidentry;
988 : RecoveryLockEntry *lockentry;
989 : xl_standby_lock key;
990 : LOCKTAG locktag;
991 : bool found;
992 :
993 : /* Already processed? */
994 86512 : if (!TransactionIdIsValid(xid) ||
995 86504 : TransactionIdDidCommit(xid) ||
996 43248 : TransactionIdDidAbort(xid))
997 8 : return;
998 :
999 43248 : elog(DEBUG4, "adding recovery lock: db %u rel %u", dbOid, relOid);
1000 :
1001 : /* dbOid is InvalidOid when we are locking a shared relation. */
1002 : Assert(OidIsValid(relOid));
1003 :
1004 : /* Create a hash entry for this xid, if we don't have one already. */
1005 43248 : xidentry = hash_search(RecoveryLockXidHash, &xid, HASH_ENTER, &found);
1006 43248 : if (!found)
1007 : {
1008 : Assert(xidentry->xid == xid); /* dynahash should have set this */
1009 19318 : xidentry->head = NULL;
1010 : }
1011 :
1012 : /* Create a hash entry for this lock, unless we have one already. */
1013 43248 : key.xid = xid;
1014 43248 : key.dbOid = dbOid;
1015 43248 : key.relOid = relOid;
1016 43248 : lockentry = hash_search(RecoveryLockHash, &key, HASH_ENTER, &found);
1017 43248 : if (!found)
1018 : {
1019 : /* It's new, so link it into the XID's list ... */
1020 43072 : lockentry->next = xidentry->head;
1021 43072 : xidentry->head = lockentry;
1022 :
1023 : /* ... and acquire the lock locally. */
1024 43072 : SET_LOCKTAG_RELATION(locktag, dbOid, relOid);
1025 :
1026 43072 : (void) LockAcquire(&locktag, AccessExclusiveLock, true, false);
1027 : }
1028 : }
1029 :
1030 : /*
1031 : * Release all the locks associated with this RecoveryLockXidEntry.
1032 : */
1033 : static void
1034 19318 : StandbyReleaseXidEntryLocks(RecoveryLockXidEntry *xidentry)
1035 : {
1036 : RecoveryLockEntry *entry;
1037 : RecoveryLockEntry *next;
1038 :
1039 62390 : for (entry = xidentry->head; entry != NULL; entry = next)
1040 : {
1041 : LOCKTAG locktag;
1042 :
1043 43072 : elog(DEBUG4,
1044 : "releasing recovery lock: xid %u db %u rel %u",
1045 : entry->key.xid, entry->key.dbOid, entry->key.relOid);
1046 : /* Release the lock ... */
1047 43072 : SET_LOCKTAG_RELATION(locktag, entry->key.dbOid, entry->key.relOid);
1048 43072 : if (!LockRelease(&locktag, AccessExclusiveLock, true))
1049 : {
1050 0 : elog(LOG,
1051 : "RecoveryLockHash contains entry for lock no longer recorded by lock manager: xid %u database %u relation %u",
1052 : entry->key.xid, entry->key.dbOid, entry->key.relOid);
1053 : Assert(false);
1054 : }
1055 : /* ... and remove the per-lock hash entry */
1056 43072 : next = entry->next;
1057 43072 : hash_search(RecoveryLockHash, entry, HASH_REMOVE, NULL);
1058 : }
1059 :
1060 19318 : xidentry->head = NULL; /* just for paranoia */
1061 19318 : }
1062 :
1063 : /*
1064 : * Release locks for specific XID, or all locks if it's InvalidXid.
1065 : */
1066 : static void
1067 20668 : StandbyReleaseLocks(TransactionId xid)
1068 : {
1069 : RecoveryLockXidEntry *entry;
1070 :
1071 20668 : if (TransactionIdIsValid(xid))
1072 : {
1073 20668 : if ((entry = hash_search(RecoveryLockXidHash, &xid, HASH_FIND, NULL)))
1074 : {
1075 19318 : StandbyReleaseXidEntryLocks(entry);
1076 19318 : hash_search(RecoveryLockXidHash, entry, HASH_REMOVE, NULL);
1077 : }
1078 : }
1079 : else
1080 0 : StandbyReleaseAllLocks();
1081 20668 : }
1082 :
1083 : /*
1084 : * Release locks for a transaction tree, starting at xid down, from
1085 : * RecoveryLockXidHash.
1086 : *
1087 : * Called during WAL replay of COMMIT/ROLLBACK when in hot standby mode,
1088 : * to remove any AccessExclusiveLocks requested by a transaction.
1089 : */
1090 : void
1091 19668 : StandbyReleaseLockTree(TransactionId xid, int nsubxids, TransactionId *subxids)
1092 : {
1093 : int i;
1094 :
1095 19668 : StandbyReleaseLocks(xid);
1096 :
1097 20668 : for (i = 0; i < nsubxids; i++)
1098 1000 : StandbyReleaseLocks(subxids[i]);
1099 19668 : }
1100 :
1101 : /*
1102 : * Called at end of recovery and when we see a shutdown checkpoint.
1103 : */
1104 : void
1105 186 : StandbyReleaseAllLocks(void)
1106 : {
1107 : HASH_SEQ_STATUS status;
1108 : RecoveryLockXidEntry *entry;
1109 :
1110 186 : elog(DEBUG2, "release all standby locks");
1111 :
1112 186 : hash_seq_init(&status, RecoveryLockXidHash);
1113 186 : while ((entry = hash_seq_search(&status)))
1114 : {
1115 0 : StandbyReleaseXidEntryLocks(entry);
1116 0 : hash_search(RecoveryLockXidHash, entry, HASH_REMOVE, NULL);
1117 : }
1118 186 : }
1119 :
1120 : /*
1121 : * StandbyReleaseOldLocks
1122 : * Release standby locks held by top-level XIDs that aren't running,
1123 : * as long as they're not prepared transactions.
1124 : */
1125 : void
1126 508 : StandbyReleaseOldLocks(TransactionId oldxid)
1127 : {
1128 : HASH_SEQ_STATUS status;
1129 : RecoveryLockXidEntry *entry;
1130 :
1131 508 : hash_seq_init(&status, RecoveryLockXidHash);
1132 548 : while ((entry = hash_seq_search(&status)))
1133 : {
1134 : Assert(TransactionIdIsValid(entry->xid));
1135 :
1136 : /* Skip if prepared transaction. */
1137 40 : if (StandbyTransactionIdIsPrepared(entry->xid))
1138 0 : continue;
1139 :
1140 : /* Skip if >= oldxid. */
1141 40 : if (!TransactionIdPrecedes(entry->xid, oldxid))
1142 40 : continue;
1143 :
1144 : /* Remove all locks and hash table entry. */
1145 0 : StandbyReleaseXidEntryLocks(entry);
1146 0 : hash_search(RecoveryLockXidHash, entry, HASH_REMOVE, NULL);
1147 : }
1148 508 : }
1149 :
1150 : /*
1151 : * --------------------------------------------------------------------
1152 : * Recovery handling for Rmgr RM_STANDBY_ID
1153 : *
1154 : * These record types will only be created if XLogStandbyInfoActive()
1155 : * --------------------------------------------------------------------
1156 : */
1157 :
1158 : void
1159 44892 : standby_redo(XLogReaderState *record)
1160 : {
1161 44892 : uint8 info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;
1162 :
1163 : /* Backup blocks are not used in standby records */
1164 : Assert(!XLogRecHasAnyBlockRefs(record));
1165 :
1166 : /* Do nothing if we're not in hot standby mode */
1167 44892 : if (standbyState == STANDBY_DISABLED)
1168 280 : return;
1169 :
1170 44612 : if (info == XLOG_STANDBY_LOCK)
1171 : {
1172 43156 : xl_standby_locks *xlrec = (xl_standby_locks *) XLogRecGetData(record);
1173 : int i;
1174 :
1175 86412 : for (i = 0; i < xlrec->nlocks; i++)
1176 43256 : StandbyAcquireAccessExclusiveLock(xlrec->locks[i].xid,
1177 : xlrec->locks[i].dbOid,
1178 : xlrec->locks[i].relOid);
1179 : }
1180 1456 : else if (info == XLOG_RUNNING_XACTS)
1181 : {
1182 408 : xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record);
1183 : RunningTransactionsData running;
1184 :
1185 408 : running.xcnt = xlrec->xcnt;
1186 408 : running.subxcnt = xlrec->subxcnt;
1187 408 : running.subxid_overflow = xlrec->subxid_overflow;
1188 408 : running.nextXid = xlrec->nextXid;
1189 408 : running.latestCompletedXid = xlrec->latestCompletedXid;
1190 408 : running.oldestRunningXid = xlrec->oldestRunningXid;
1191 408 : running.xids = xlrec->xids;
1192 :
1193 408 : ProcArrayApplyRecoveryInfo(&running);
1194 :
1195 : /*
1196 : * The startup process currently has no convenient way to schedule
1197 : * stats to be reported. XLOG_RUNNING_XACTS records issued at a
1198 : * regular cadence, making this a convenient location to report stats.
1199 : * While these records aren't generated with wal_level=minimal, stats
1200 : * also cannot be accessed during WAL replay.
1201 : */
1202 408 : pgstat_report_stat(true);
1203 : }
1204 1048 : else if (info == XLOG_INVALIDATIONS)
1205 : {
1206 1048 : xl_invalidations *xlrec = (xl_invalidations *) XLogRecGetData(record);
1207 :
1208 1048 : ProcessCommittedInvalidationMessages(xlrec->msgs,
1209 : xlrec->nmsgs,
1210 1048 : xlrec->relcacheInitFileInval,
1211 : xlrec->dbId,
1212 : xlrec->tsId);
1213 : }
1214 : else
1215 0 : elog(PANIC, "standby_redo: unknown op code %u", info);
1216 : }
1217 :
1218 : /*
1219 : * Log details of the current snapshot to WAL. This allows the snapshot state
1220 : * to be reconstructed on the standby and for logical decoding.
1221 : *
1222 : * This is used for Hot Standby as follows:
1223 : *
1224 : * We can move directly to STANDBY_SNAPSHOT_READY at startup if we
1225 : * start from a shutdown checkpoint because we know nothing was running
1226 : * at that time and our recovery snapshot is known empty. In the more
1227 : * typical case of an online checkpoint we need to jump through a few
1228 : * hoops to get a correct recovery snapshot and this requires a two or
1229 : * sometimes a three stage process.
1230 : *
1231 : * The initial snapshot must contain all running xids and all current
1232 : * AccessExclusiveLocks at a point in time on the standby. Assembling
1233 : * that information while the server is running requires many and
1234 : * various LWLocks, so we choose to derive that information piece by
1235 : * piece and then re-assemble that info on the standby. When that
1236 : * information is fully assembled we move to STANDBY_SNAPSHOT_READY.
1237 : *
1238 : * Since locking on the primary when we derive the information is not
1239 : * strict, we note that there is a time window between the derivation and
1240 : * writing to WAL of the derived information. That allows race conditions
1241 : * that we must resolve, since xids and locks may enter or leave the
1242 : * snapshot during that window. This creates the issue that an xid or
1243 : * lock may start *after* the snapshot has been derived yet *before* the
1244 : * snapshot is logged in the running xacts WAL record. We resolve this by
1245 : * starting to accumulate changes at a point just prior to when we derive
1246 : * the snapshot on the primary, then ignore duplicates when we later apply
1247 : * the snapshot from the running xacts record. This is implemented during
1248 : * CreateCheckPoint() where we use the logical checkpoint location as
1249 : * our starting point and then write the running xacts record immediately
1250 : * before writing the main checkpoint WAL record. Since we always start
1251 : * up from a checkpoint and are immediately at our starting point, we
1252 : * unconditionally move to STANDBY_INITIALIZED. After this point we
1253 : * must do 4 things:
1254 : * * move shared nextXid forwards as we see new xids
1255 : * * extend the clog and subtrans with each new xid
1256 : * * keep track of uncommitted known assigned xids
1257 : * * keep track of uncommitted AccessExclusiveLocks
1258 : *
1259 : * When we see a commit/abort we must remove known assigned xids and locks
1260 : * from the completing transaction. Attempted removals that cannot locate
1261 : * an entry are expected and must not cause an error when we are in state
1262 : * STANDBY_INITIALIZED. This is implemented in StandbyReleaseLocks() and
1263 : * KnownAssignedXidsRemove().
1264 : *
1265 : * Later, when we apply the running xact data we must be careful to ignore
1266 : * transactions already committed, since those commits raced ahead when
1267 : * making WAL entries.
1268 : *
1269 : * The loose timing also means that locks may be recorded that have a
1270 : * zero xid, since xids are removed from procs before locks are removed.
1271 : * So we must prune the lock list down to ensure we hold locks only for
1272 : * currently running xids, performed by StandbyReleaseOldLocks().
1273 : * Zero xids should no longer be possible, but we may be replaying WAL
1274 : * from a time when they were possible.
1275 : *
1276 : * For logical decoding only the running xacts information is needed;
1277 : * there's no need to look at the locking information, but it's logged anyway,
1278 : * as there's no independent knob to just enable logical decoding. For
1279 : * details of how this is used, check snapbuild.c's introductory comment.
1280 : *
1281 : *
1282 : * Returns the RecPtr of the last inserted record.
1283 : */
1284 : XLogRecPtr
1285 1482 : LogStandbySnapshot(void)
1286 : {
1287 : XLogRecPtr recptr;
1288 : RunningTransactions running;
1289 : xl_standby_lock *locks;
1290 : int nlocks;
1291 :
1292 : Assert(XLogStandbyInfoActive());
1293 :
1294 : /*
1295 : * Get details of any AccessExclusiveLocks being held at the moment.
1296 : */
1297 1482 : locks = GetRunningTransactionLocks(&nlocks);
1298 1482 : if (nlocks > 0)
1299 50 : LogAccessExclusiveLocks(nlocks, locks);
1300 1482 : pfree(locks);
1301 :
1302 : /*
1303 : * Log details of all in-progress transactions. This should be the last
1304 : * record we write, because standby will open up when it sees this.
1305 : */
1306 1482 : running = GetRunningTransactionData();
1307 :
1308 : /*
1309 : * GetRunningTransactionData() acquired ProcArrayLock, we must release it.
1310 : * For Hot Standby this can be done before inserting the WAL record
1311 : * because ProcArrayApplyRecoveryInfo() rechecks the commit status using
1312 : * the clog. For logical decoding, though, the lock can't be released
1313 : * early because the clog might be "in the future" from the POV of the
1314 : * historic snapshot. This would allow for situations where we're waiting
1315 : * for the end of a transaction listed in the xl_running_xacts record
1316 : * which, according to the WAL, has committed before the xl_running_xacts
1317 : * record. Fortunately this routine isn't executed frequently, and it's
1318 : * only a shared lock.
1319 : */
1320 1482 : if (wal_level < WAL_LEVEL_LOGICAL)
1321 612 : LWLockRelease(ProcArrayLock);
1322 :
1323 1482 : recptr = LogCurrentRunningXacts(running);
1324 :
1325 : /* Release lock if we kept it longer ... */
1326 1482 : if (wal_level >= WAL_LEVEL_LOGICAL)
1327 870 : LWLockRelease(ProcArrayLock);
1328 :
1329 : /* GetRunningTransactionData() acquired XidGenLock, we must release it */
1330 1482 : LWLockRelease(XidGenLock);
1331 :
1332 1482 : return recptr;
1333 : }
1334 :
1335 : /*
1336 : * Record an enhanced snapshot of running transactions into WAL.
1337 : *
1338 : * The definitions of RunningTransactionsData and xl_running_xacts are
1339 : * similar. We keep them separate because xl_running_xacts is a contiguous
1340 : * chunk of memory and never exists fully until it is assembled in WAL.
1341 : * The inserted records are marked as not being important for durability,
1342 : * to avoid triggering superfluous checkpoint / archiving activity.
1343 : */
1344 : static XLogRecPtr
1345 1482 : LogCurrentRunningXacts(RunningTransactions CurrRunningXacts)
1346 : {
1347 : xl_running_xacts xlrec;
1348 : XLogRecPtr recptr;
1349 :
1350 1482 : xlrec.xcnt = CurrRunningXacts->xcnt;
1351 1482 : xlrec.subxcnt = CurrRunningXacts->subxcnt;
1352 1482 : xlrec.subxid_overflow = CurrRunningXacts->subxid_overflow;
1353 1482 : xlrec.nextXid = CurrRunningXacts->nextXid;
1354 1482 : xlrec.oldestRunningXid = CurrRunningXacts->oldestRunningXid;
1355 1482 : xlrec.latestCompletedXid = CurrRunningXacts->latestCompletedXid;
1356 :
1357 : /* Header */
1358 1482 : XLogBeginInsert();
1359 1482 : XLogSetRecordFlags(XLOG_MARK_UNIMPORTANT);
1360 1482 : XLogRegisterData((char *) (&xlrec), MinSizeOfXactRunningXacts);
1361 :
1362 : /* array of TransactionIds */
1363 1482 : if (xlrec.xcnt > 0)
1364 464 : XLogRegisterData((char *) CurrRunningXacts->xids,
1365 464 : (xlrec.xcnt + xlrec.subxcnt) * sizeof(TransactionId));
1366 :
1367 1482 : recptr = XLogInsert(RM_STANDBY_ID, XLOG_RUNNING_XACTS);
1368 :
1369 1482 : if (CurrRunningXacts->subxid_overflow)
1370 4 : elog(DEBUG2,
1371 : "snapshot of %d running transactions overflowed (lsn %X/%X oldest xid %u latest complete %u next xid %u)",
1372 : CurrRunningXacts->xcnt,
1373 : LSN_FORMAT_ARGS(recptr),
1374 : CurrRunningXacts->oldestRunningXid,
1375 : CurrRunningXacts->latestCompletedXid,
1376 : CurrRunningXacts->nextXid);
1377 : else
1378 1478 : elog(DEBUG2,
1379 : "snapshot of %d+%d running transaction ids (lsn %X/%X oldest xid %u latest complete %u next xid %u)",
1380 : CurrRunningXacts->xcnt, CurrRunningXacts->subxcnt,
1381 : LSN_FORMAT_ARGS(recptr),
1382 : CurrRunningXacts->oldestRunningXid,
1383 : CurrRunningXacts->latestCompletedXid,
1384 : CurrRunningXacts->nextXid);
1385 :
1386 : /*
1387 : * Ensure running_xacts information is synced to disk not too far in the
1388 : * future. We don't want to stall anything though (i.e. use XLogFlush()),
1389 : * so we let the wal writer do it during normal operation.
1390 : * XLogSetAsyncXactLSN() conveniently will mark the LSN as to-be-synced
1391 : * and nudge the WALWriter into action if sleeping. Check
1392 : * XLogBackgroundFlush() for details why a record might not be flushed
1393 : * without it.
1394 : */
1395 1482 : XLogSetAsyncXactLSN(recptr);
1396 :
1397 1482 : return recptr;
1398 : }
1399 :
1400 : /*
1401 : * Wholesale logging of AccessExclusiveLocks. Other lock types need not be
1402 : * logged, as described in backend/storage/lmgr/README.
1403 : */
1404 : static void
1405 163860 : LogAccessExclusiveLocks(int nlocks, xl_standby_lock *locks)
1406 : {
1407 : xl_standby_locks xlrec;
1408 :
1409 163860 : xlrec.nlocks = nlocks;
1410 :
1411 163860 : XLogBeginInsert();
1412 163860 : XLogRegisterData((char *) &xlrec, offsetof(xl_standby_locks, locks));
1413 163860 : XLogRegisterData((char *) locks, nlocks * sizeof(xl_standby_lock));
1414 163860 : XLogSetRecordFlags(XLOG_MARK_UNIMPORTANT);
1415 :
1416 163860 : (void) XLogInsert(RM_STANDBY_ID, XLOG_STANDBY_LOCK);
1417 163860 : }
1418 :
1419 : /*
1420 : * Individual logging of AccessExclusiveLocks for use during LockAcquire()
1421 : */
1422 : void
1423 163810 : LogAccessExclusiveLock(Oid dbOid, Oid relOid)
1424 : {
1425 : xl_standby_lock xlrec;
1426 :
1427 163810 : xlrec.xid = GetCurrentTransactionId();
1428 :
1429 163810 : xlrec.dbOid = dbOid;
1430 163810 : xlrec.relOid = relOid;
1431 :
1432 163810 : LogAccessExclusiveLocks(1, &xlrec);
1433 163810 : MyXactFlags |= XACT_FLAGS_ACQUIREDACCESSEXCLUSIVELOCK;
1434 163810 : }
1435 :
1436 : /*
1437 : * Prepare to log an AccessExclusiveLock, for use during LockAcquire()
1438 : */
1439 : void
1440 164234 : LogAccessExclusiveLockPrepare(void)
1441 : {
1442 : /*
1443 : * Ensure that a TransactionId has been assigned to this transaction, for
1444 : * two reasons, both related to lock release on the standby. First, we
1445 : * must assign an xid so that RecordTransactionCommit() and
1446 : * RecordTransactionAbort() do not optimise away the transaction
1447 : * completion record which recovery relies upon to release locks. It's a
1448 : * hack, but for a corner case not worth adding code for into the main
1449 : * commit path. Second, we must assign an xid before the lock is recorded
1450 : * in shared memory, otherwise a concurrently executing
1451 : * GetRunningTransactionLocks() might see a lock associated with an
1452 : * InvalidTransactionId which we later assert cannot happen.
1453 : */
1454 164234 : (void) GetCurrentTransactionId();
1455 164234 : }
1456 :
1457 : /*
1458 : * Emit WAL for invalidations. This currently is only used for commits without
1459 : * an xid but which contain invalidations.
1460 : */
1461 : void
1462 13940 : LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs,
1463 : bool relcacheInitFileInval)
1464 : {
1465 : xl_invalidations xlrec;
1466 :
1467 : /* prepare record */
1468 13940 : memset(&xlrec, 0, sizeof(xlrec));
1469 13940 : xlrec.dbId = MyDatabaseId;
1470 13940 : xlrec.tsId = MyDatabaseTableSpace;
1471 13940 : xlrec.relcacheInitFileInval = relcacheInitFileInval;
1472 13940 : xlrec.nmsgs = nmsgs;
1473 :
1474 : /* perform insertion */
1475 13940 : XLogBeginInsert();
1476 13940 : XLogRegisterData((char *) (&xlrec), MinSizeOfInvalidations);
1477 13940 : XLogRegisterData((char *) msgs,
1478 : nmsgs * sizeof(SharedInvalidationMessage));
1479 13940 : XLogInsert(RM_STANDBY_ID, XLOG_INVALIDATIONS);
1480 13940 : }
1481 :
1482 : /* Return the description of recovery conflict */
1483 : static const char *
1484 20 : get_recovery_conflict_desc(ProcSignalReason reason)
1485 : {
1486 20 : const char *reasonDesc = _("unknown reason");
1487 :
1488 20 : switch (reason)
1489 : {
1490 8 : case PROCSIG_RECOVERY_CONFLICT_BUFFERPIN:
1491 8 : reasonDesc = _("recovery conflict on buffer pin");
1492 8 : break;
1493 4 : case PROCSIG_RECOVERY_CONFLICT_LOCK:
1494 4 : reasonDesc = _("recovery conflict on lock");
1495 4 : break;
1496 4 : case PROCSIG_RECOVERY_CONFLICT_TABLESPACE:
1497 4 : reasonDesc = _("recovery conflict on tablespace");
1498 4 : break;
1499 4 : case PROCSIG_RECOVERY_CONFLICT_SNAPSHOT:
1500 4 : reasonDesc = _("recovery conflict on snapshot");
1501 4 : break;
1502 0 : case PROCSIG_RECOVERY_CONFLICT_LOGICALSLOT:
1503 0 : reasonDesc = _("recovery conflict on replication slot");
1504 0 : break;
1505 0 : case PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK:
1506 0 : reasonDesc = _("recovery conflict on buffer deadlock");
1507 0 : break;
1508 0 : case PROCSIG_RECOVERY_CONFLICT_DATABASE:
1509 0 : reasonDesc = _("recovery conflict on database");
1510 0 : break;
1511 0 : default:
1512 0 : break;
1513 : }
1514 :
1515 20 : return reasonDesc;
1516 : }
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