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launcher.c
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1 /*-------------------------------------------------------------------------
2  * launcher.c
3  * PostgreSQL logical replication worker launcher process
4  *
5  * Copyright (c) 2016-2021, PostgreSQL Global Development Group
6  *
7  * IDENTIFICATION
8  * src/backend/replication/logical/launcher.c
9  *
10  * NOTES
11  * This module contains the logical replication worker launcher which
12  * uses the background worker infrastructure to start the logical
13  * replication workers for every enabled subscription.
14  *
15  *-------------------------------------------------------------------------
16  */
17 
18 #include "postgres.h"
19 
20 #include "access/heapam.h"
21 #include "access/htup.h"
22 #include "access/htup_details.h"
23 #include "access/tableam.h"
24 #include "access/xact.h"
27 #include "funcapi.h"
28 #include "libpq/pqsignal.h"
29 #include "miscadmin.h"
30 #include "pgstat.h"
31 #include "postmaster/bgworker.h"
33 #include "postmaster/interrupt.h"
34 #include "postmaster/postmaster.h"
37 #include "replication/slot.h"
40 #include "storage/ipc.h"
41 #include "storage/proc.h"
42 #include "storage/procarray.h"
43 #include "storage/procsignal.h"
44 #include "tcop/tcopprot.h"
45 #include "utils/memutils.h"
46 #include "utils/pg_lsn.h"
47 #include "utils/ps_status.h"
48 #include "utils/snapmgr.h"
49 #include "utils/timeout.h"
50 
51 /* max sleep time between cycles (3min) */
52 #define DEFAULT_NAPTIME_PER_CYCLE 180000L
53 
56 
58 
59 typedef struct LogicalRepCtxStruct
60 {
61  /* Supervisor process. */
62  pid_t launcher_pid;
63 
64  /* Background workers. */
67 
69 
70 static void ApplyLauncherWakeup(void);
71 static void logicalrep_launcher_onexit(int code, Datum arg);
72 static void logicalrep_worker_onexit(int code, Datum arg);
73 static void logicalrep_worker_detach(void);
74 static void logicalrep_worker_cleanup(LogicalRepWorker *worker);
75 
76 static bool on_commit_launcher_wakeup = false;
77 
79 
80 
81 /*
82  * Load the list of subscriptions.
83  *
84  * Only the fields interesting for worker start/stop functions are filled for
85  * each subscription.
86  */
87 static List *
89 {
90  List *res = NIL;
91  Relation rel;
92  TableScanDesc scan;
93  HeapTuple tup;
94  MemoryContext resultcxt;
95 
96  /* This is the context that we will allocate our output data in */
97  resultcxt = CurrentMemoryContext;
98 
99  /*
100  * Start a transaction so we can access pg_database, and get a snapshot.
101  * We don't have a use for the snapshot itself, but we're interested in
102  * the secondary effect that it sets RecentGlobalXmin. (This is critical
103  * for anything that reads heap pages, because HOT may decide to prune
104  * them even if the process doesn't attempt to modify any tuples.)
105  *
106  * FIXME: This comment is inaccurate / the code buggy. A snapshot that is
107  * not pushed/active does not reliably prevent HOT pruning (->xmin could
108  * e.g. be cleared when cache invalidations are processed).
109  */
111  (void) GetTransactionSnapshot();
112 
113  rel = table_open(SubscriptionRelationId, AccessShareLock);
114  scan = table_beginscan_catalog(rel, 0, NULL);
115 
117  {
119  Subscription *sub;
120  MemoryContext oldcxt;
121 
122  /*
123  * Allocate our results in the caller's context, not the
124  * transaction's. We do this inside the loop, and restore the original
125  * context at the end, so that leaky things like heap_getnext() are
126  * not called in a potentially long-lived context.
127  */
128  oldcxt = MemoryContextSwitchTo(resultcxt);
129 
130  sub = (Subscription *) palloc0(sizeof(Subscription));
131  sub->oid = subform->oid;
132  sub->dbid = subform->subdbid;
133  sub->owner = subform->subowner;
134  sub->enabled = subform->subenabled;
135  sub->name = pstrdup(NameStr(subform->subname));
136  /* We don't fill fields we are not interested in. */
137 
138  res = lappend(res, sub);
139  MemoryContextSwitchTo(oldcxt);
140  }
141 
142  table_endscan(scan);
144 
146 
147  return res;
148 }
149 
150 /*
151  * Wait for a background worker to start up and attach to the shmem context.
152  *
153  * This is only needed for cleaning up the shared memory in case the worker
154  * fails to attach.
155  */
156 static void
158  uint16 generation,
159  BackgroundWorkerHandle *handle)
160 {
162  int rc;
163 
164  for (;;)
165  {
166  pid_t pid;
167 
169 
170  LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
171 
172  /* Worker either died or has started; no need to do anything. */
173  if (!worker->in_use || worker->proc)
174  {
175  LWLockRelease(LogicalRepWorkerLock);
176  return;
177  }
178 
179  LWLockRelease(LogicalRepWorkerLock);
180 
181  /* Check if worker has died before attaching, and clean up after it. */
182  status = GetBackgroundWorkerPid(handle, &pid);
183 
184  if (status == BGWH_STOPPED)
185  {
186  LWLockAcquire(LogicalRepWorkerLock, LW_EXCLUSIVE);
187  /* Ensure that this was indeed the worker we waited for. */
188  if (generation == worker->generation)
190  LWLockRelease(LogicalRepWorkerLock);
191  return;
192  }
193 
194  /*
195  * We need timeout because we generally don't get notified via latch
196  * about the worker attach. But we don't expect to have to wait long.
197  */
198  rc = WaitLatch(MyLatch,
201 
202  if (rc & WL_LATCH_SET)
203  {
206  }
207  }
208 }
209 
210 /*
211  * Walks the workers array and searches for one that matches given
212  * subscription id and relid.
213  */
215 logicalrep_worker_find(Oid subid, Oid relid, bool only_running)
216 {
217  int i;
218  LogicalRepWorker *res = NULL;
219 
220  Assert(LWLockHeldByMe(LogicalRepWorkerLock));
221 
222  /* Search for attached worker for a given subscription id. */
223  for (i = 0; i < max_logical_replication_workers; i++)
224  {
225  LogicalRepWorker *w = &LogicalRepCtx->workers[i];
226 
227  if (w->in_use && w->subid == subid && w->relid == relid &&
228  (!only_running || w->proc))
229  {
230  res = w;
231  break;
232  }
233  }
234 
235  return res;
236 }
237 
238 /*
239  * Similar to logicalrep_worker_find(), but returns list of all workers for
240  * the subscription, instead just one.
241  */
242 List *
243 logicalrep_workers_find(Oid subid, bool only_running)
244 {
245  int i;
246  List *res = NIL;
247 
248  Assert(LWLockHeldByMe(LogicalRepWorkerLock));
249 
250  /* Search for attached worker for a given subscription id. */
251  for (i = 0; i < max_logical_replication_workers; i++)
252  {
253  LogicalRepWorker *w = &LogicalRepCtx->workers[i];
254 
255  if (w->in_use && w->subid == subid && (!only_running || w->proc))
256  res = lappend(res, w);
257  }
258 
259  return res;
260 }
261 
262 /*
263  * Start new apply background worker, if possible.
264  */
265 void
266 logicalrep_worker_launch(Oid dbid, Oid subid, const char *subname, Oid userid,
267  Oid relid)
268 {
269  BackgroundWorker bgw;
270  BackgroundWorkerHandle *bgw_handle;
271  uint16 generation;
272  int i;
273  int slot = 0;
274  LogicalRepWorker *worker = NULL;
275  int nsyncworkers;
277 
278  ereport(DEBUG1,
279  (errmsg_internal("starting logical replication worker for subscription \"%s\"",
280  subname)));
281 
282  /* Report this after the initial starting message for consistency. */
283  if (max_replication_slots == 0)
284  ereport(ERROR,
285  (errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
286  errmsg("cannot start logical replication workers when max_replication_slots = 0")));
287 
288  /*
289  * We need to do the modification of the shared memory under lock so that
290  * we have consistent view.
291  */
292  LWLockAcquire(LogicalRepWorkerLock, LW_EXCLUSIVE);
293 
294 retry:
295  /* Find unused worker slot. */
296  for (i = 0; i < max_logical_replication_workers; i++)
297  {
298  LogicalRepWorker *w = &LogicalRepCtx->workers[i];
299 
300  if (!w->in_use)
301  {
302  worker = w;
303  slot = i;
304  break;
305  }
306  }
307 
308  nsyncworkers = logicalrep_sync_worker_count(subid);
309 
310  now = GetCurrentTimestamp();
311 
312  /*
313  * If we didn't find a free slot, try to do garbage collection. The
314  * reason we do this is because if some worker failed to start up and its
315  * parent has crashed while waiting, the in_use state was never cleared.
316  */
317  if (worker == NULL || nsyncworkers >= max_sync_workers_per_subscription)
318  {
319  bool did_cleanup = false;
320 
321  for (i = 0; i < max_logical_replication_workers; i++)
322  {
323  LogicalRepWorker *w = &LogicalRepCtx->workers[i];
324 
325  /*
326  * If the worker was marked in use but didn't manage to attach in
327  * time, clean it up.
328  */
329  if (w->in_use && !w->proc &&
332  {
333  elog(WARNING,
334  "logical replication worker for subscription %u took too long to start; canceled",
335  w->subid);
336 
338  did_cleanup = true;
339  }
340  }
341 
342  if (did_cleanup)
343  goto retry;
344  }
345 
346  /*
347  * If we reached the sync worker limit per subscription, just exit
348  * silently as we might get here because of an otherwise harmless race
349  * condition.
350  */
351  if (nsyncworkers >= max_sync_workers_per_subscription)
352  {
353  LWLockRelease(LogicalRepWorkerLock);
354  return;
355  }
356 
357  /*
358  * However if there are no more free worker slots, inform user about it
359  * before exiting.
360  */
361  if (worker == NULL)
362  {
363  LWLockRelease(LogicalRepWorkerLock);
365  (errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
366  errmsg("out of logical replication worker slots"),
367  errhint("You might need to increase max_logical_replication_workers.")));
368  return;
369  }
370 
371  /* Prepare the worker slot. */
372  worker->launch_time = now;
373  worker->in_use = true;
374  worker->generation++;
375  worker->proc = NULL;
376  worker->dbid = dbid;
377  worker->userid = userid;
378  worker->subid = subid;
379  worker->relid = relid;
380  worker->relstate = SUBREL_STATE_UNKNOWN;
382  worker->last_lsn = InvalidXLogRecPtr;
385  worker->reply_lsn = InvalidXLogRecPtr;
386  TIMESTAMP_NOBEGIN(worker->reply_time);
387 
388  /* Before releasing lock, remember generation for future identification. */
389  generation = worker->generation;
390 
391  LWLockRelease(LogicalRepWorkerLock);
392 
393  /* Register the new dynamic worker. */
394  memset(&bgw, 0, sizeof(bgw));
398  snprintf(bgw.bgw_library_name, BGW_MAXLEN, "postgres");
399  snprintf(bgw.bgw_function_name, BGW_MAXLEN, "ApplyWorkerMain");
400  if (OidIsValid(relid))
402  "logical replication worker for subscription %u sync %u", subid, relid);
403  else
405  "logical replication worker for subscription %u", subid);
406  snprintf(bgw.bgw_type, BGW_MAXLEN, "logical replication worker");
407 
410  bgw.bgw_main_arg = Int32GetDatum(slot);
411 
412  if (!RegisterDynamicBackgroundWorker(&bgw, &bgw_handle))
413  {
414  /* Failed to start worker, so clean up the worker slot. */
415  LWLockAcquire(LogicalRepWorkerLock, LW_EXCLUSIVE);
416  Assert(generation == worker->generation);
418  LWLockRelease(LogicalRepWorkerLock);
419 
421  (errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
422  errmsg("out of background worker slots"),
423  errhint("You might need to increase max_worker_processes.")));
424  return;
425  }
426 
427  /* Now wait until it attaches. */
428  WaitForReplicationWorkerAttach(worker, generation, bgw_handle);
429 }
430 
431 /*
432  * Stop the logical replication worker for subid/relid, if any, and wait until
433  * it detaches from the slot.
434  */
435 void
437 {
438  LogicalRepWorker *worker;
439  uint16 generation;
440 
441  LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
442 
443  worker = logicalrep_worker_find(subid, relid, false);
444 
445  /* No worker, nothing to do. */
446  if (!worker)
447  {
448  LWLockRelease(LogicalRepWorkerLock);
449  return;
450  }
451 
452  /*
453  * Remember which generation was our worker so we can check if what we see
454  * is still the same one.
455  */
456  generation = worker->generation;
457 
458  /*
459  * If we found a worker but it does not have proc set then it is still
460  * starting up; wait for it to finish starting and then kill it.
461  */
462  while (worker->in_use && !worker->proc)
463  {
464  int rc;
465 
466  LWLockRelease(LogicalRepWorkerLock);
467 
468  /* Wait a bit --- we don't expect to have to wait long. */
469  rc = WaitLatch(MyLatch,
472 
473  if (rc & WL_LATCH_SET)
474  {
477  }
478 
479  /* Recheck worker status. */
480  LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
481 
482  /*
483  * Check whether the worker slot is no longer used, which would mean
484  * that the worker has exited, or whether the worker generation is
485  * different, meaning that a different worker has taken the slot.
486  */
487  if (!worker->in_use || worker->generation != generation)
488  {
489  LWLockRelease(LogicalRepWorkerLock);
490  return;
491  }
492 
493  /* Worker has assigned proc, so it has started. */
494  if (worker->proc)
495  break;
496  }
497 
498  /* Now terminate the worker ... */
499  kill(worker->proc->pid, SIGTERM);
500 
501  /* ... and wait for it to die. */
502  for (;;)
503  {
504  int rc;
505 
506  /* is it gone? */
507  if (!worker->proc || worker->generation != generation)
508  break;
509 
510  LWLockRelease(LogicalRepWorkerLock);
511 
512  /* Wait a bit --- we don't expect to have to wait long. */
513  rc = WaitLatch(MyLatch,
516 
517  if (rc & WL_LATCH_SET)
518  {
521  }
522 
523  LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
524  }
525 
526  LWLockRelease(LogicalRepWorkerLock);
527 }
528 
529 /*
530  * Wake up (using latch) any logical replication worker for specified sub/rel.
531  */
532 void
534 {
535  LogicalRepWorker *worker;
536 
537  LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
538 
539  worker = logicalrep_worker_find(subid, relid, true);
540 
541  if (worker)
543 
544  LWLockRelease(LogicalRepWorkerLock);
545 }
546 
547 /*
548  * Wake up (using latch) the specified logical replication worker.
549  *
550  * Caller must hold lock, else worker->proc could change under us.
551  */
552 void
554 {
555  Assert(LWLockHeldByMe(LogicalRepWorkerLock));
556 
557  SetLatch(&worker->proc->procLatch);
558 }
559 
560 /*
561  * Attach to a slot.
562  */
563 void
565 {
566  /* Block concurrent access. */
567  LWLockAcquire(LogicalRepWorkerLock, LW_EXCLUSIVE);
568 
569  Assert(slot >= 0 && slot < max_logical_replication_workers);
570  MyLogicalRepWorker = &LogicalRepCtx->workers[slot];
571 
572  if (!MyLogicalRepWorker->in_use)
573  {
574  LWLockRelease(LogicalRepWorkerLock);
575  ereport(ERROR,
576  (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
577  errmsg("logical replication worker slot %d is empty, cannot attach",
578  slot)));
579  }
580 
581  if (MyLogicalRepWorker->proc)
582  {
583  LWLockRelease(LogicalRepWorkerLock);
584  ereport(ERROR,
585  (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
586  errmsg("logical replication worker slot %d is already used by "
587  "another worker, cannot attach", slot)));
588  }
589 
590  MyLogicalRepWorker->proc = MyProc;
592 
593  LWLockRelease(LogicalRepWorkerLock);
594 }
595 
596 /*
597  * Detach the worker (cleans up the worker info).
598  */
599 static void
601 {
602  /* Block concurrent access. */
603  LWLockAcquire(LogicalRepWorkerLock, LW_EXCLUSIVE);
604 
605  logicalrep_worker_cleanup(MyLogicalRepWorker);
606 
607  LWLockRelease(LogicalRepWorkerLock);
608 }
609 
610 /*
611  * Clean up worker info.
612  */
613 static void
615 {
616  Assert(LWLockHeldByMeInMode(LogicalRepWorkerLock, LW_EXCLUSIVE));
617 
618  worker->in_use = false;
619  worker->proc = NULL;
620  worker->dbid = InvalidOid;
621  worker->userid = InvalidOid;
622  worker->subid = InvalidOid;
623  worker->relid = InvalidOid;
624 }
625 
626 /*
627  * Cleanup function for logical replication launcher.
628  *
629  * Called on logical replication launcher exit.
630  */
631 static void
633 {
634  LogicalRepCtx->launcher_pid = 0;
635 }
636 
637 /*
638  * Cleanup function.
639  *
640  * Called on logical replication worker exit.
641  */
642 static void
644 {
645  /* Disconnect gracefully from the remote side. */
648 
650 
652 }
653 
654 /*
655  * Count the number of registered (not necessarily running) sync workers
656  * for a subscription.
657  */
658 int
660 {
661  int i;
662  int res = 0;
663 
664  Assert(LWLockHeldByMe(LogicalRepWorkerLock));
665 
666  /* Search for attached worker for a given subscription id. */
667  for (i = 0; i < max_logical_replication_workers; i++)
668  {
669  LogicalRepWorker *w = &LogicalRepCtx->workers[i];
670 
671  if (w->subid == subid && OidIsValid(w->relid))
672  res++;
673  }
674 
675  return res;
676 }
677 
678 /*
679  * ApplyLauncherShmemSize
680  * Compute space needed for replication launcher shared memory
681  */
682 Size
684 {
685  Size size;
686 
687  /*
688  * Need the fixed struct and the array of LogicalRepWorker.
689  */
690  size = sizeof(LogicalRepCtxStruct);
691  size = MAXALIGN(size);
693  sizeof(LogicalRepWorker)));
694  return size;
695 }
696 
697 /*
698  * ApplyLauncherRegister
699  * Register a background worker running the logical replication launcher.
700  */
701 void
703 {
704  BackgroundWorker bgw;
705 
707  return;
708 
709  memset(&bgw, 0, sizeof(bgw));
713  snprintf(bgw.bgw_library_name, BGW_MAXLEN, "postgres");
714  snprintf(bgw.bgw_function_name, BGW_MAXLEN, "ApplyLauncherMain");
716  "logical replication launcher");
718  "logical replication launcher");
719  bgw.bgw_restart_time = 5;
720  bgw.bgw_notify_pid = 0;
721  bgw.bgw_main_arg = (Datum) 0;
722 
724 }
725 
726 /*
727  * ApplyLauncherShmemInit
728  * Allocate and initialize replication launcher shared memory
729  */
730 void
732 {
733  bool found;
734 
735  LogicalRepCtx = (LogicalRepCtxStruct *)
736  ShmemInitStruct("Logical Replication Launcher Data",
738  &found);
739 
740  if (!found)
741  {
742  int slot;
743 
744  memset(LogicalRepCtx, 0, ApplyLauncherShmemSize());
745 
746  /* Initialize memory and spin locks for each worker slot. */
747  for (slot = 0; slot < max_logical_replication_workers; slot++)
748  {
749  LogicalRepWorker *worker = &LogicalRepCtx->workers[slot];
750 
751  memset(worker, 0, sizeof(LogicalRepWorker));
752  SpinLockInit(&worker->relmutex);
753  }
754  }
755 }
756 
757 /*
758  * Wakeup the launcher on commit if requested.
759  */
760 void
762 {
763  if (isCommit)
764  {
767  }
768 
770 }
771 
772 /*
773  * Request wakeup of the launcher on commit of the transaction.
774  *
775  * This is used to send launcher signal to stop sleeping and process the
776  * subscriptions when current transaction commits. Should be used when new
777  * tuple was added to the pg_subscription catalog.
778 */
779 void
781 {
784 }
785 
786 static void
788 {
789  if (LogicalRepCtx->launcher_pid != 0)
790  kill(LogicalRepCtx->launcher_pid, SIGUSR1);
791 }
792 
793 /*
794  * Main loop for the apply launcher process.
795  */
796 void
798 {
799  TimestampTz last_start_time = 0;
800 
801  ereport(DEBUG1,
802  (errmsg_internal("logical replication launcher started")));
803 
805 
806  Assert(LogicalRepCtx->launcher_pid == 0);
807  LogicalRepCtx->launcher_pid = MyProcPid;
808 
809  /* Establish signal handlers. */
811  pqsignal(SIGTERM, die);
813 
814  /*
815  * Establish connection to nailed catalogs (we only ever access
816  * pg_subscription).
817  */
819 
820  /* Enter main loop */
821  for (;;)
822  {
823  int rc;
824  List *sublist;
825  ListCell *lc;
826  MemoryContext subctx;
827  MemoryContext oldctx;
829  long wait_time = DEFAULT_NAPTIME_PER_CYCLE;
830 
832 
833  now = GetCurrentTimestamp();
834 
835  /* Limit the start retry to once a wal_retrieve_retry_interval */
836  if (TimestampDifferenceExceeds(last_start_time, now,
838  {
839  /* Use temporary context for the database list and worker info. */
841  "Logical Replication Launcher sublist",
843  oldctx = MemoryContextSwitchTo(subctx);
844 
845  /* search for subscriptions to start or stop. */
846  sublist = get_subscription_list();
847 
848  /* Start the missing workers for enabled subscriptions. */
849  foreach(lc, sublist)
850  {
851  Subscription *sub = (Subscription *) lfirst(lc);
852  LogicalRepWorker *w;
853 
854  if (!sub->enabled)
855  continue;
856 
857  LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
858  w = logicalrep_worker_find(sub->oid, InvalidOid, false);
859  LWLockRelease(LogicalRepWorkerLock);
860 
861  if (w == NULL)
862  {
863  last_start_time = now;
864  wait_time = wal_retrieve_retry_interval;
865 
866  logicalrep_worker_launch(sub->dbid, sub->oid, sub->name,
867  sub->owner, InvalidOid);
868  }
869  }
870 
871  /* Switch back to original memory context. */
872  MemoryContextSwitchTo(oldctx);
873  /* Clean the temporary memory. */
874  MemoryContextDelete(subctx);
875  }
876  else
877  {
878  /*
879  * The wait in previous cycle was interrupted in less than
880  * wal_retrieve_retry_interval since last worker was started, this
881  * usually means crash of the worker, so we should retry in
882  * wal_retrieve_retry_interval again.
883  */
884  wait_time = wal_retrieve_retry_interval;
885  }
886 
887  /* Wait for more work. */
888  rc = WaitLatch(MyLatch,
890  wait_time,
892 
893  if (rc & WL_LATCH_SET)
894  {
897  }
898 
900  {
901  ConfigReloadPending = false;
903  }
904  }
905 
906  /* Not reachable */
907 }
908 
909 /*
910  * Is current process the logical replication launcher?
911  */
912 bool
914 {
915  return LogicalRepCtx->launcher_pid == MyProcPid;
916 }
917 
918 /*
919  * Returns state of the subscriptions.
920  */
921 Datum
923 {
924 #define PG_STAT_GET_SUBSCRIPTION_COLS 8
925  Oid subid = PG_ARGISNULL(0) ? InvalidOid : PG_GETARG_OID(0);
926  int i;
927  ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
928  TupleDesc tupdesc;
929  Tuplestorestate *tupstore;
930  MemoryContext per_query_ctx;
931  MemoryContext oldcontext;
932 
933  /* check to see if caller supports us returning a tuplestore */
934  if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
935  ereport(ERROR,
936  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
937  errmsg("set-valued function called in context that cannot accept a set")));
938  if (!(rsinfo->allowedModes & SFRM_Materialize))
939  ereport(ERROR,
940  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
941  errmsg("materialize mode required, but it is not allowed in this context")));
942 
943  /* Build a tuple descriptor for our result type */
944  if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
945  elog(ERROR, "return type must be a row type");
946 
947  per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
948  oldcontext = MemoryContextSwitchTo(per_query_ctx);
949 
950  tupstore = tuplestore_begin_heap(true, false, work_mem);
951  rsinfo->returnMode = SFRM_Materialize;
952  rsinfo->setResult = tupstore;
953  rsinfo->setDesc = tupdesc;
954 
955  MemoryContextSwitchTo(oldcontext);
956 
957  /* Make sure we get consistent view of the workers. */
958  LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
959 
960  for (i = 0; i <= max_logical_replication_workers; i++)
961  {
962  /* for each row */
964  bool nulls[PG_STAT_GET_SUBSCRIPTION_COLS];
965  int worker_pid;
966  LogicalRepWorker worker;
967 
968  memcpy(&worker, &LogicalRepCtx->workers[i],
969  sizeof(LogicalRepWorker));
970  if (!worker.proc || !IsBackendPid(worker.proc->pid))
971  continue;
972 
973  if (OidIsValid(subid) && worker.subid != subid)
974  continue;
975 
976  worker_pid = worker.proc->pid;
977 
978  MemSet(values, 0, sizeof(values));
979  MemSet(nulls, 0, sizeof(nulls));
980 
981  values[0] = ObjectIdGetDatum(worker.subid);
982  if (OidIsValid(worker.relid))
983  values[1] = ObjectIdGetDatum(worker.relid);
984  else
985  nulls[1] = true;
986  values[2] = Int32GetDatum(worker_pid);
987  if (XLogRecPtrIsInvalid(worker.last_lsn))
988  nulls[3] = true;
989  else
990  values[3] = LSNGetDatum(worker.last_lsn);
991  if (worker.last_send_time == 0)
992  nulls[4] = true;
993  else
994  values[4] = TimestampTzGetDatum(worker.last_send_time);
995  if (worker.last_recv_time == 0)
996  nulls[5] = true;
997  else
998  values[5] = TimestampTzGetDatum(worker.last_recv_time);
999  if (XLogRecPtrIsInvalid(worker.reply_lsn))
1000  nulls[6] = true;
1001  else
1002  values[6] = LSNGetDatum(worker.reply_lsn);
1003  if (worker.reply_time == 0)
1004  nulls[7] = true;
1005  else
1006  values[7] = TimestampTzGetDatum(worker.reply_time);
1007 
1008  tuplestore_putvalues(tupstore, tupdesc, values, nulls);
1009 
1010  /*
1011  * If only a single subscription was requested, and we found it,
1012  * break.
1013  */
1014  if (OidIsValid(subid))
1015  break;
1016  }
1017 
1018  LWLockRelease(LogicalRepWorkerLock);
1019 
1020  /* clean up and return the tuplestore */
1021  tuplestore_donestoring(tupstore);
1022 
1023  return (Datum) 0;
1024 }
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