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logical.c
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1 /*-------------------------------------------------------------------------
2  * logical.c
3  * PostgreSQL logical decoding coordination
4  *
5  * Copyright (c) 2012-2017, PostgreSQL Global Development Group
6  *
7  * IDENTIFICATION
8  * src/backend/replication/logical/logical.c
9  *
10  * NOTES
11  * This file coordinates interaction between the various modules that
12  * together provide logical decoding, primarily by providing so
13  * called LogicalDecodingContexts. The goal is to encapsulate most of the
14  * internal complexity for consumers of logical decoding, so they can
15  * create and consume a changestream with a low amount of code. Builtin
16  * consumers are the walsender and SQL SRF interface, but it's possible to
17  * add further ones without changing core code, e.g. to consume changes in
18  * a bgworker.
19  *
20  * The idea is that a consumer provides three callbacks, one to read WAL,
21  * one to prepare a data write, and a final one for actually writing since
22  * their implementation depends on the type of consumer. Check
23  * logicalfuncs.c for an example implementation of a fairly simple consumer
24  * and an implementation of a WAL reading callback that's suitable for
25  * simple consumers.
26  *-------------------------------------------------------------------------
27  */
28 
29 #include "postgres.h"
30 
31 #include "miscadmin.h"
32 
33 #include "access/xact.h"
34 #include "access/xlog_internal.h"
35 
36 #include "replication/decode.h"
37 #include "replication/logical.h"
39 #include "replication/origin.h"
40 #include "replication/snapbuild.h"
41 
42 #include "storage/proc.h"
43 #include "storage/procarray.h"
44 
45 #include "utils/memutils.h"
46 
47 /* data for errcontext callback */
49 {
51  const char *callback_name;
54 
55 /* wrappers around output plugin callbacks */
56 static void output_plugin_error_callback(void *arg);
58  bool is_init);
60 static void begin_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn);
61 static void commit_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
62  XLogRecPtr commit_lsn);
63 static void change_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
64  Relation relation, ReorderBufferChange *change);
65 static void message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
66  XLogRecPtr message_lsn, bool transactional,
67  const char *prefix, Size message_size, const char *message);
68 
69 static void LoadOutputPlugin(OutputPluginCallbacks *callbacks, char *plugin);
70 
71 /*
72  * Make sure the current settings & environment are capable of doing logical
73  * decoding.
74  */
75 void
77 {
79 
81  ereport(ERROR,
82  (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
83  errmsg("logical decoding requires wal_level >= logical")));
84 
85  if (MyDatabaseId == InvalidOid)
86  ereport(ERROR,
87  (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
88  errmsg("logical decoding requires a database connection")));
89 
90  /* ----
91  * TODO: We got to change that someday soon...
92  *
93  * There's basically three things missing to allow this:
94  * 1) We need to be able to correctly and quickly identify the timeline a
95  * LSN belongs to
96  * 2) We need to force hot_standby_feedback to be enabled at all times so
97  * the primary cannot remove rows we need.
98  * 3) support dropping replication slots referring to a database, in
99  * dbase_redo. There can't be any active ones due to HS recovery
100  * conflicts, so that should be relatively easy.
101  * ----
102  */
103  if (RecoveryInProgress())
104  ereport(ERROR,
105  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
106  errmsg("logical decoding cannot be used while in recovery")));
107 }
108 
109 /*
110  * Helper function for CreateInitialDecodingContext() and
111  * CreateDecodingContext() performing common tasks.
112  */
113 static LogicalDecodingContext *
114 StartupDecodingContext(List *output_plugin_options,
115  XLogRecPtr start_lsn,
116  TransactionId xmin_horizon,
117  bool need_full_snapshot,
118  XLogPageReadCB read_page,
122 {
123  ReplicationSlot *slot;
124  MemoryContext context,
125  old_context;
127 
128  /* shorter lines... */
129  slot = MyReplicationSlot;
130 
132  "Logical decoding context",
134  old_context = MemoryContextSwitchTo(context);
135  ctx = palloc0(sizeof(LogicalDecodingContext));
136 
137  ctx->context = context;
138 
139  /*
140  * (re-)load output plugins, so we detect a bad (removed) output plugin
141  * now.
142  */
144 
145  /*
146  * Now that the slot's xmin has been set, we can announce ourselves as a
147  * logical decoding backend which doesn't need to be checked individually
148  * when computing the xmin horizon because the xmin is enforced via
149  * replication slots.
150  *
151  * We can only do so if we're outside of a transaction (i.e. the case when
152  * streaming changes via walsender), otherwise an already setup
153  * snapshot/xid would end up being ignored. That's not a particularly
154  * bothersome restriction since the SQL interface can't be used for
155  * streaming anyway.
156  */
158  {
159  LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
161  LWLockRelease(ProcArrayLock);
162  }
163 
164  ctx->slot = slot;
165 
166  ctx->reader = XLogReaderAllocate(wal_segment_size, read_page, ctx);
167  if (!ctx->reader)
168  ereport(ERROR,
169  (errcode(ERRCODE_OUT_OF_MEMORY),
170  errmsg("out of memory")));
171 
172  ctx->reader->private_data = ctx;
173 
175  ctx->snapshot_builder =
176  AllocateSnapshotBuilder(ctx->reorder, xmin_horizon, start_lsn,
177  need_full_snapshot);
178 
179  ctx->reorder->private_data = ctx;
180 
181  /* wrap output plugin callbacks, so we can add error context information */
186 
187  ctx->out = makeStringInfo();
188  ctx->prepare_write = prepare_write;
189  ctx->write = do_write;
190  ctx->update_progress = update_progress;
191 
192  ctx->output_plugin_options = output_plugin_options;
193 
194  MemoryContextSwitchTo(old_context);
195 
196  return ctx;
197 }
198 
199 /*
200  * Create a new decoding context, for a new logical slot.
201  *
202  * plugin contains the name of the output plugin
203  * output_plugin_options contains options passed to the output plugin
204  * read_page, prepare_write, do_write, update_progress
205  * callbacks that have to be filled to perform the use-case dependent,
206  * actual, work.
207  *
208  * Needs to be called while in a memory context that's at least as long lived
209  * as the decoding context because further memory contexts will be created
210  * inside it.
211  *
212  * Returns an initialized decoding context after calling the output plugin's
213  * startup function.
214  */
217  List *output_plugin_options,
218  bool need_full_snapshot,
219  XLogPageReadCB read_page,
223 {
224  TransactionId xmin_horizon = InvalidTransactionId;
225  ReplicationSlot *slot;
227  MemoryContext old_context;
228 
229  /* shorter lines... */
230  slot = MyReplicationSlot;
231 
232  /* first some sanity checks that are unlikely to be violated */
233  if (slot == NULL)
234  elog(ERROR, "cannot perform logical decoding without an acquired slot");
235 
236  if (plugin == NULL)
237  elog(ERROR, "cannot initialize logical decoding without a specified plugin");
238 
239  /* Make sure the passed slot is suitable. These are user facing errors. */
240  if (SlotIsPhysical(slot))
241  ereport(ERROR,
242  (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
243  errmsg("cannot use physical replication slot for logical decoding")));
244 
245  if (slot->data.database != MyDatabaseId)
246  ereport(ERROR,
247  (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
248  errmsg("replication slot \"%s\" was not created in this database",
249  NameStr(slot->data.name))));
250 
251  if (IsTransactionState() &&
253  ereport(ERROR,
254  (errcode(ERRCODE_ACTIVE_SQL_TRANSACTION),
255  errmsg("cannot create logical replication slot in transaction that has performed writes")));
256 
257  /* register output plugin name with slot */
258  SpinLockAcquire(&slot->mutex);
259  StrNCpy(NameStr(slot->data.plugin), plugin, NAMEDATALEN);
260  SpinLockRelease(&slot->mutex);
261 
263 
264  /* ----
265  * This is a bit tricky: We need to determine a safe xmin horizon to start
266  * decoding from, to avoid starting from a running xacts record referring
267  * to xids whose rows have been vacuumed or pruned
268  * already. GetOldestSafeDecodingTransactionId() returns such a value, but
269  * without further interlock its return value might immediately be out of
270  * date.
271  *
272  * So we have to acquire the ProcArrayLock to prevent computation of new
273  * xmin horizons by other backends, get the safe decoding xid, and inform
274  * the slot machinery about the new limit. Once that's done the
275  * ProcArrayLock can be released as the slot machinery now is
276  * protecting against vacuum.
277  *
278  * Note that, temporarily, the data, not just the catalog, xmin has to be
279  * reserved if a data snapshot is to be exported. Otherwise the initial
280  * data snapshot created here is not guaranteed to be valid. After that
281  * the data xmin doesn't need to be managed anymore and the global xmin
282  * should be recomputed. As we are fine with losing the pegged data xmin
283  * after crash - no chance a snapshot would get exported anymore - we can
284  * get away with just setting the slot's
285  * effective_xmin. ReplicationSlotRelease will reset it again.
286  *
287  * ----
288  */
289  LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
290 
291  xmin_horizon = GetOldestSafeDecodingTransactionId(!need_full_snapshot);
292 
293  slot->effective_catalog_xmin = xmin_horizon;
294  slot->data.catalog_xmin = xmin_horizon;
295  if (need_full_snapshot)
296  slot->effective_xmin = xmin_horizon;
297 
299 
300  LWLockRelease(ProcArrayLock);
301 
304 
305  ctx = StartupDecodingContext(NIL, InvalidXLogRecPtr, xmin_horizon,
306  need_full_snapshot, read_page, prepare_write,
307  do_write, update_progress);
308 
309  /* call output plugin initialization callback */
310  old_context = MemoryContextSwitchTo(ctx->context);
311  if (ctx->callbacks.startup_cb != NULL)
312  startup_cb_wrapper(ctx, &ctx->options, true);
313  MemoryContextSwitchTo(old_context);
314 
315  return ctx;
316 }
317 
318 /*
319  * Create a new decoding context, for a logical slot that has previously been
320  * used already.
321  *
322  * start_lsn
323  * The LSN at which to start decoding. If InvalidXLogRecPtr, restart
324  * from the slot's confirmed_flush; otherwise, start from the specified
325  * location (but move it forwards to confirmed_flush if it's older than
326  * that, see below).
327  *
328  * output_plugin_options
329  * contains options passed to the output plugin.
330  *
331  * read_page, prepare_write, do_write, update_progress
332  * callbacks that have to be filled to perform the use-case dependent,
333  * actual work.
334  *
335  * Needs to be called while in a memory context that's at least as long lived
336  * as the decoding context because further memory contexts will be created
337  * inside it.
338  *
339  * Returns an initialized decoding context after calling the output plugin's
340  * startup function.
341  */
344  List *output_plugin_options,
345  XLogPageReadCB read_page,
349 {
351  ReplicationSlot *slot;
352  MemoryContext old_context;
353 
354  /* shorter lines... */
355  slot = MyReplicationSlot;
356 
357  /* first some sanity checks that are unlikely to be violated */
358  if (slot == NULL)
359  elog(ERROR, "cannot perform logical decoding without an acquired slot");
360 
361  /* make sure the passed slot is suitable, these are user facing errors */
362  if (SlotIsPhysical(slot))
363  ereport(ERROR,
364  (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
365  (errmsg("cannot use physical replication slot for logical decoding"))));
366 
367  if (slot->data.database != MyDatabaseId)
368  ereport(ERROR,
369  (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
370  (errmsg("replication slot \"%s\" was not created in this database",
371  NameStr(slot->data.name)))));
372 
373  if (start_lsn == InvalidXLogRecPtr)
374  {
375  /* continue from last position */
376  start_lsn = slot->data.confirmed_flush;
377  }
378  else if (start_lsn < slot->data.confirmed_flush)
379  {
380  /*
381  * It might seem like we should error out in this case, but it's
382  * pretty common for a client to acknowledge a LSN it doesn't have to
383  * do anything for, and thus didn't store persistently, because the
384  * xlog records didn't result in anything relevant for logical
385  * decoding. Clients have to be able to do that to support synchronous
386  * replication.
387  */
388  elog(DEBUG1, "cannot stream from %X/%X, minimum is %X/%X, forwarding",
389  (uint32) (start_lsn >> 32), (uint32) start_lsn,
390  (uint32) (slot->data.confirmed_flush >> 32),
391  (uint32) slot->data.confirmed_flush);
392 
393  start_lsn = slot->data.confirmed_flush;
394  }
395 
396  ctx = StartupDecodingContext(output_plugin_options,
397  start_lsn, InvalidTransactionId, false,
398  read_page, prepare_write, do_write,
399  update_progress);
400 
401  /* call output plugin initialization callback */
402  old_context = MemoryContextSwitchTo(ctx->context);
403  if (ctx->callbacks.startup_cb != NULL)
404  startup_cb_wrapper(ctx, &ctx->options, false);
405  MemoryContextSwitchTo(old_context);
406 
407  ereport(LOG,
408  (errmsg("starting logical decoding for slot \"%s\"",
409  NameStr(slot->data.name)),
410  errdetail("streaming transactions committing after %X/%X, reading WAL from %X/%X",
411  (uint32) (slot->data.confirmed_flush >> 32),
412  (uint32) slot->data.confirmed_flush,
413  (uint32) (slot->data.restart_lsn >> 32),
414  (uint32) slot->data.restart_lsn)));
415 
416  return ctx;
417 }
418 
419 /*
420  * Returns true if a consistent initial decoding snapshot has been built.
421  */
422 bool
424 {
426 }
427 
428 /*
429  * Read from the decoding slot, until it is ready to start extracting changes.
430  */
431 void
433 {
434  XLogRecPtr startptr;
435 
436  /* Initialize from where to start reading WAL. */
437  startptr = ctx->slot->data.restart_lsn;
438 
439  elog(DEBUG1, "searching for logical decoding starting point, starting at %X/%X",
440  (uint32) (ctx->slot->data.restart_lsn >> 32),
441  (uint32) ctx->slot->data.restart_lsn);
442 
443  /* Wait for a consistent starting point */
444  for (;;)
445  {
446  XLogRecord *record;
447  char *err = NULL;
448 
449  /* the read_page callback waits for new WAL */
450  record = XLogReadRecord(ctx->reader, startptr, &err);
451  if (err)
452  elog(ERROR, "%s", err);
453  if (!record)
454  elog(ERROR, "no record found"); /* shouldn't happen */
455 
456  startptr = InvalidXLogRecPtr;
457 
459 
460  /* only continue till we found a consistent spot */
461  if (DecodingContextReady(ctx))
462  break;
463 
465  }
466 
467  ctx->slot->data.confirmed_flush = ctx->reader->EndRecPtr;
468 }
469 
470 /*
471  * Free a previously allocated decoding context, invoking the shutdown
472  * callback if necessary.
473  */
474 void
476 {
477  if (ctx->callbacks.shutdown_cb != NULL)
478  shutdown_cb_wrapper(ctx);
479 
482  XLogReaderFree(ctx->reader);
484 }
485 
486 /*
487  * Prepare a write using the context's output routine.
488  */
489 void
491 {
492  if (!ctx->accept_writes)
493  elog(ERROR, "writes are only accepted in commit, begin and change callbacks");
494 
495  ctx->prepare_write(ctx, ctx->write_location, ctx->write_xid, last_write);
496  ctx->prepared_write = true;
497 }
498 
499 /*
500  * Perform a write using the context's output routine.
501  */
502 void
504 {
505  if (!ctx->prepared_write)
506  elog(ERROR, "OutputPluginPrepareWrite needs to be called before OutputPluginWrite");
507 
508  ctx->write(ctx, ctx->write_location, ctx->write_xid, last_write);
509  ctx->prepared_write = false;
510 }
511 
512 /*
513  * Update progress tracking (if supported).
514  */
515 void
517 {
518  if (!ctx->update_progress)
519  return;
520 
521  ctx->update_progress(ctx, ctx->write_location, ctx->write_xid);
522 }
523 
524 /*
525  * Load the output plugin, lookup its output plugin init function, and check
526  * that it provides the required callbacks.
527  */
528 static void
530 {
531  LogicalOutputPluginInit plugin_init;
532 
533  plugin_init = (LogicalOutputPluginInit)
534  load_external_function(plugin, "_PG_output_plugin_init", false, NULL);
535 
536  if (plugin_init == NULL)
537  elog(ERROR, "output plugins have to declare the _PG_output_plugin_init symbol");
538 
539  /* ask the output plugin to fill the callback struct */
540  plugin_init(callbacks);
541 
542  if (callbacks->begin_cb == NULL)
543  elog(ERROR, "output plugins have to register a begin callback");
544  if (callbacks->change_cb == NULL)
545  elog(ERROR, "output plugins have to register a change callback");
546  if (callbacks->commit_cb == NULL)
547  elog(ERROR, "output plugins have to register a commit callback");
548 }
549 
550 static void
552 {
554 
555  /* not all callbacks have an associated LSN */
556  if (state->report_location != InvalidXLogRecPtr)
557  errcontext("slot \"%s\", output plugin \"%s\", in the %s callback, associated LSN %X/%X",
558  NameStr(state->ctx->slot->data.name),
559  NameStr(state->ctx->slot->data.plugin),
560  state->callback_name,
561  (uint32) (state->report_location >> 32),
562  (uint32) state->report_location);
563  else
564  errcontext("slot \"%s\", output plugin \"%s\", in the %s callback",
565  NameStr(state->ctx->slot->data.name),
566  NameStr(state->ctx->slot->data.plugin),
567  state->callback_name);
568 }
569 
570 static void
572 {
574  ErrorContextCallback errcallback;
575 
576  /* Push callback + info on the error context stack */
577  state.ctx = ctx;
578  state.callback_name = "startup";
581  errcallback.arg = (void *) &state;
582  errcallback.previous = error_context_stack;
583  error_context_stack = &errcallback;
584 
585  /* set output state */
586  ctx->accept_writes = false;
587 
588  /* do the actual work: call callback */
589  ctx->callbacks.startup_cb(ctx, opt, is_init);
590 
591  /* Pop the error context stack */
592  error_context_stack = errcallback.previous;
593 }
594 
595 static void
597 {
599  ErrorContextCallback errcallback;
600 
601  /* Push callback + info on the error context stack */
602  state.ctx = ctx;
603  state.callback_name = "shutdown";
606  errcallback.arg = (void *) &state;
607  errcallback.previous = error_context_stack;
608  error_context_stack = &errcallback;
609 
610  /* set output state */
611  ctx->accept_writes = false;
612 
613  /* do the actual work: call callback */
614  ctx->callbacks.shutdown_cb(ctx);
615 
616  /* Pop the error context stack */
617  error_context_stack = errcallback.previous;
618 }
619 
620 
621 /*
622  * Callbacks for ReorderBuffer which add in some more information and then call
623  * output_plugin.h plugins.
624  */
625 static void
627 {
630  ErrorContextCallback errcallback;
631 
632  /* Push callback + info on the error context stack */
633  state.ctx = ctx;
634  state.callback_name = "begin";
635  state.report_location = txn->first_lsn;
637  errcallback.arg = (void *) &state;
638  errcallback.previous = error_context_stack;
639  error_context_stack = &errcallback;
640 
641  /* set output state */
642  ctx->accept_writes = true;
643  ctx->write_xid = txn->xid;
644  ctx->write_location = txn->first_lsn;
645 
646  /* do the actual work: call callback */
647  ctx->callbacks.begin_cb(ctx, txn);
648 
649  /* Pop the error context stack */
650  error_context_stack = errcallback.previous;
651 }
652 
653 static void
655  XLogRecPtr commit_lsn)
656 {
659  ErrorContextCallback errcallback;
660 
661  /* Push callback + info on the error context stack */
662  state.ctx = ctx;
663  state.callback_name = "commit";
664  state.report_location = txn->final_lsn; /* beginning of commit record */
666  errcallback.arg = (void *) &state;
667  errcallback.previous = error_context_stack;
668  error_context_stack = &errcallback;
669 
670  /* set output state */
671  ctx->accept_writes = true;
672  ctx->write_xid = txn->xid;
673  ctx->write_location = txn->end_lsn; /* points to the end of the record */
674 
675  /* do the actual work: call callback */
676  ctx->callbacks.commit_cb(ctx, txn, commit_lsn);
677 
678  /* Pop the error context stack */
679  error_context_stack = errcallback.previous;
680 }
681 
682 static void
684  Relation relation, ReorderBufferChange *change)
685 {
688  ErrorContextCallback errcallback;
689 
690  /* Push callback + info on the error context stack */
691  state.ctx = ctx;
692  state.callback_name = "change";
693  state.report_location = change->lsn;
695  errcallback.arg = (void *) &state;
696  errcallback.previous = error_context_stack;
697  error_context_stack = &errcallback;
698 
699  /* set output state */
700  ctx->accept_writes = true;
701  ctx->write_xid = txn->xid;
702 
703  /*
704  * report this change's lsn so replies from clients can give an up2date
705  * answer. This won't ever be enough (and shouldn't be!) to confirm
706  * receipt of this transaction, but it might allow another transaction's
707  * commit to be confirmed with one message.
708  */
709  ctx->write_location = change->lsn;
710 
711  ctx->callbacks.change_cb(ctx, txn, relation, change);
712 
713  /* Pop the error context stack */
714  error_context_stack = errcallback.previous;
715 }
716 
717 bool
719 {
721  ErrorContextCallback errcallback;
722  bool ret;
723 
724  /* Push callback + info on the error context stack */
725  state.ctx = ctx;
726  state.callback_name = "filter_by_origin";
729  errcallback.arg = (void *) &state;
730  errcallback.previous = error_context_stack;
731  error_context_stack = &errcallback;
732 
733  /* set output state */
734  ctx->accept_writes = false;
735 
736  /* do the actual work: call callback */
737  ret = ctx->callbacks.filter_by_origin_cb(ctx, origin_id);
738 
739  /* Pop the error context stack */
740  error_context_stack = errcallback.previous;
741 
742  return ret;
743 }
744 
745 static void
747  XLogRecPtr message_lsn, bool transactional,
748  const char *prefix, Size message_size, const char *message)
749 {
752  ErrorContextCallback errcallback;
753 
754  if (ctx->callbacks.message_cb == NULL)
755  return;
756 
757  /* Push callback + info on the error context stack */
758  state.ctx = ctx;
759  state.callback_name = "message";
760  state.report_location = message_lsn;
762  errcallback.arg = (void *) &state;
763  errcallback.previous = error_context_stack;
764  error_context_stack = &errcallback;
765 
766  /* set output state */
767  ctx->accept_writes = true;
768  ctx->write_xid = txn != NULL ? txn->xid : InvalidTransactionId;
769  ctx->write_location = message_lsn;
770 
771  /* do the actual work: call callback */
772  ctx->callbacks.message_cb(ctx, txn, message_lsn, transactional, prefix,
773  message_size, message);
774 
775  /* Pop the error context stack */
776  error_context_stack = errcallback.previous;
777 }
778 
779 /*
780  * Set the required catalog xmin horizon for historic snapshots in the current
781  * replication slot.
782  *
783  * Note that in the most cases, we won't be able to immediately use the xmin
784  * to increase the xmin horizon: we need to wait till the client has confirmed
785  * receiving current_lsn with LogicalConfirmReceivedLocation().
786  */
787 void
789 {
790  bool updated_xmin = false;
791  ReplicationSlot *slot;
792 
793  slot = MyReplicationSlot;
794 
795  Assert(slot != NULL);
796 
797  SpinLockAcquire(&slot->mutex);
798 
799  /*
800  * don't overwrite if we already have a newer xmin. This can happen if we
801  * restart decoding in a slot.
802  */
804  {
805  }
806 
807  /*
808  * If the client has already confirmed up to this lsn, we directly can
809  * mark this as accepted. This can happen if we restart decoding in a
810  * slot.
811  */
812  else if (current_lsn <= slot->data.confirmed_flush)
813  {
814  slot->candidate_catalog_xmin = xmin;
815  slot->candidate_xmin_lsn = current_lsn;
816 
817  /* our candidate can directly be used */
818  updated_xmin = true;
819  }
820 
821  /*
822  * Only increase if the previous values have been applied, otherwise we
823  * might never end up updating if the receiver acks too slowly.
824  */
825  else if (slot->candidate_xmin_lsn == InvalidXLogRecPtr)
826  {
827  slot->candidate_catalog_xmin = xmin;
828  slot->candidate_xmin_lsn = current_lsn;
829  }
830  SpinLockRelease(&slot->mutex);
831 
832  /* candidate already valid with the current flush position, apply */
833  if (updated_xmin)
835 }
836 
837 /*
838  * Mark the minimal LSN (restart_lsn) we need to read to replay all
839  * transactions that have not yet committed at current_lsn.
840  *
841  * Just like IncreaseRestartDecodingForSlot this only takes effect when the
842  * client has confirmed to have received current_lsn.
843  */
844 void
846 {
847  bool updated_lsn = false;
848  ReplicationSlot *slot;
849 
850  slot = MyReplicationSlot;
851 
852  Assert(slot != NULL);
853  Assert(restart_lsn != InvalidXLogRecPtr);
854  Assert(current_lsn != InvalidXLogRecPtr);
855 
856  SpinLockAcquire(&slot->mutex);
857 
858  /* don't overwrite if have a newer restart lsn */
859  if (restart_lsn <= slot->data.restart_lsn)
860  {
861  }
862 
863  /*
864  * We might have already flushed far enough to directly accept this lsn,
865  * in this case there is no need to check for existing candidate LSNs
866  */
867  else if (current_lsn <= slot->data.confirmed_flush)
868  {
869  slot->candidate_restart_valid = current_lsn;
870  slot->candidate_restart_lsn = restart_lsn;
871 
872  /* our candidate can directly be used */
873  updated_lsn = true;
874  }
875 
876  /*
877  * Only increase if the previous values have been applied, otherwise we
878  * might never end up updating if the receiver acks too slowly. A missed
879  * value here will just cause some extra effort after reconnecting.
880  */
882  {
883  slot->candidate_restart_valid = current_lsn;
884  slot->candidate_restart_lsn = restart_lsn;
885 
886  elog(DEBUG1, "got new restart lsn %X/%X at %X/%X",
887  (uint32) (restart_lsn >> 32), (uint32) restart_lsn,
888  (uint32) (current_lsn >> 32), (uint32) current_lsn);
889  }
890  else
891  {
892  elog(DEBUG1, "failed to increase restart lsn: proposed %X/%X, after %X/%X, current candidate %X/%X, current after %X/%X, flushed up to %X/%X",
893  (uint32) (restart_lsn >> 32), (uint32) restart_lsn,
894  (uint32) (current_lsn >> 32), (uint32) current_lsn,
895  (uint32) (slot->candidate_restart_lsn >> 32),
897  (uint32) (slot->candidate_restart_valid >> 32),
899  (uint32) (slot->data.confirmed_flush >> 32),
900  (uint32) slot->data.confirmed_flush
901  );
902  }
903  SpinLockRelease(&slot->mutex);
904 
905  /* candidates are already valid with the current flush position, apply */
906  if (updated_lsn)
908 }
909 
910 /*
911  * Handle a consumer's confirmation having received all changes up to lsn.
912  */
913 void
915 {
916  Assert(lsn != InvalidXLogRecPtr);
917 
918  /* Do an unlocked check for candidate_lsn first. */
921  {
922  bool updated_xmin = false;
923  bool updated_restart = false;
924 
926 
928 
929  /* if we're past the location required for bumping xmin, do so */
932  {
933  /*
934  * We have to write the changed xmin to disk *before* we change
935  * the in-memory value, otherwise after a crash we wouldn't know
936  * that some catalog tuples might have been removed already.
937  *
938  * Ensure that by first writing to ->xmin and only update
939  * ->effective_xmin once the new state is synced to disk. After a
940  * crash ->effective_xmin is set to ->xmin.
941  */
944  {
948  updated_xmin = true;
949  }
950  }
951 
954  {
956 
960  updated_restart = true;
961  }
962 
964 
965  /* first write new xmin to disk, so we know what's up after a crash */
966  if (updated_xmin || updated_restart)
967  {
970  elog(DEBUG1, "updated xmin: %u restart: %u", updated_xmin, updated_restart);
971  }
972 
973  /*
974  * Now the new xmin is safely on disk, we can let the global value
975  * advance. We do not take ProcArrayLock or similar since we only
976  * advance xmin here and there's not much harm done by a concurrent
977  * computation missing that.
978  */
979  if (updated_xmin)
980  {
984 
987  }
988  }
989  else
990  {
994  }
995 }
XLogRecPtr first_lsn
#define NIL
Definition: pg_list.h:69
TransactionId write_xid
Definition: logical.h:84
static const char * plugin
void CheckSlotRequirements(void)
Definition: slot.c:965
TransactionId candidate_catalog_xmin
Definition: slot.h:135
#define InvalidXLogRecPtr
Definition: xlogdefs.h:28
TransactionId GetOldestSafeDecodingTransactionId(bool catalogOnly)
Definition: procarray.c:2158
ReorderBufferApplyChangeCB apply_change
void MemoryContextDelete(MemoryContext context)
Definition: mcxt.c:200
void * private_data
#define DEBUG1
Definition: elog.h:25
static void change_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn, Relation relation, ReorderBufferChange *change)
Definition: logical.c:683
struct ReorderBuffer * reorder
Definition: logical.h:45
#define PROC_IN_LOGICAL_DECODING
Definition: proc.h:57
int wal_segment_size
Definition: xlog.c:113
uint32 TransactionId
Definition: c.h:445
SnapBuildState SnapBuildCurrentState(SnapBuild *builder)
Definition: snapbuild.c:401
static void LoadOutputPlugin(OutputPluginCallbacks *callbacks, char *plugin)
Definition: logical.c:529
bool DecodingContextReady(LogicalDecodingContext *ctx)
Definition: logical.c:423
struct LogicalErrorCallbackState LogicalErrorCallbackState
static void commit_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn, XLogRecPtr commit_lsn)
Definition: logical.c:654
OutputPluginOptions options
Definition: logical.h:49
void LogicalIncreaseRestartDecodingForSlot(XLogRecPtr current_lsn, XLogRecPtr restart_lsn)
Definition: logical.c:845
int wal_level
Definition: xlog.c:104
StringInfo makeStringInfo(void)
Definition: stringinfo.c:28
LogicalDecodeMessageCB message_cb
OutputPluginCallbacks callbacks
Definition: logical.h:48
static MemoryContext MemoryContextSwitchTo(MemoryContext context)
Definition: palloc.h:109
void ReorderBufferFree(ReorderBuffer *rb)
uint16 RepOriginId
Definition: xlogdefs.h:51
int errcode(int sqlerrcode)
Definition: elog.c:575
bool IsTransactionOrTransactionBlock(void)
Definition: xact.c:4465
MemoryContext context
Definition: logical.h:38
void ReplicationSlotSave(void)
Definition: slot.c:638
LogicalDecodingContext * CreateInitDecodingContext(char *plugin, List *output_plugin_options, bool need_full_snapshot, XLogPageReadCB read_page, LogicalOutputPluginWriterPrepareWrite prepare_write, LogicalOutputPluginWriterWrite do_write, LogicalOutputPluginWriterUpdateProgress update_progress)
Definition: logical.c:216
List * output_plugin_options
Definition: logical.h:54
ReorderBufferCommitCB commit
ReplicationSlotPersistentData data
Definition: slot.h:120
void * private_data
Definition: xlogreader.h:113
#define LOG
Definition: elog.h:26
bool RecoveryInProgress(void)
Definition: xlog.c:7929
void(* callback)(void *arg)
Definition: elog.h:239
struct ErrorContextCallback * previous
Definition: elog.h:238
#define SlotIsPhysical(slot)
Definition: slot.h:141
LogicalOutputPluginWriterWrite LogicalOutputPluginWriterPrepareWrite
Definition: logical.h:27
void(* LogicalOutputPluginWriterUpdateProgress)(struct LogicalDecodingContext *lr, XLogRecPtr Ptr, TransactionId xid)
Definition: logical.h:29
const char * callback_name
Definition: logical.c:51
XLogRecord * XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg)
Definition: xlogreader.c:195
XLogRecPtr confirmed_flush
Definition: slot.h:81
PGXACT * MyPgXact
Definition: proc.c:68
XLogRecPtr write_location
Definition: logical.h:83
XLogRecPtr EndRecPtr
Definition: xlogreader.h:120
uint8 vacuumFlags
Definition: proc.h:230
static LogicalDecodingContext * StartupDecodingContext(List *output_plugin_options, XLogRecPtr start_lsn, TransactionId xmin_horizon, bool need_full_snapshot, XLogPageReadCB read_page, LogicalOutputPluginWriterPrepareWrite prepare_write, LogicalOutputPluginWriterWrite do_write, LogicalOutputPluginWriterUpdateProgress update_progress)
Definition: logical.c:114
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1721
ErrorContextCallback * error_context_stack
Definition: elog.c:88
#define NAMEDATALEN
#define SpinLockAcquire(lock)
Definition: spin.h:62
void ReplicationSlotReserveWal(void)
Definition: slot.c:985
void DecodingContextFindStartpoint(LogicalDecodingContext *ctx)
Definition: logical.c:432
void ReplicationSlotsComputeRequiredLSN(void)
Definition: slot.c:741
bool TransactionIdPrecedesOrEquals(TransactionId id1, TransactionId id2)
Definition: transam.c:319
#define ERROR
Definition: elog.h:43
void LogicalDecodingProcessRecord(LogicalDecodingContext *ctx, XLogReaderState *record)
Definition: decode.c:93
static void startup_cb_wrapper(LogicalDecodingContext *ctx, OutputPluginOptions *opt, bool is_init)
Definition: logical.c:571
LogicalOutputPluginWriterPrepareWrite prepare_write
Definition: logical.h:59
LogicalDecodeCommitCB commit_cb
TransactionId effective_xmin
Definition: slot.h:116
void(* LogicalOutputPluginInit)(struct OutputPluginCallbacks *cb)
Definition: output_plugin.h:35
#define ALLOCSET_DEFAULT_SIZES
Definition: memutils.h:165
static void shutdown_cb_wrapper(LogicalDecodingContext *ctx)
Definition: logical.c:596
XLogRecPtr candidate_restart_valid
Definition: slot.h:137
int errdetail(const char *fmt,...)
Definition: elog.c:873
TransactionId catalog_xmin
Definition: slot.h:70
#define InvalidTransactionId
Definition: transam.h:31
LogicalOutputPluginWriterUpdateProgress update_progress
Definition: logical.h:61
unsigned int uint32
Definition: c.h:296
XLogRecPtr final_lsn
MemoryContext CurrentMemoryContext
Definition: mcxt.c:37
bool filter_by_origin_cb_wrapper(LogicalDecodingContext *ctx, RepOriginId origin_id)
Definition: logical.c:718
TransactionId GetTopTransactionIdIfAny(void)
Definition: xact.c:405
ReorderBufferMessageCB message
PGFunction load_external_function(const char *filename, const char *funcname, bool signalNotFound, void **filehandle)
Definition: dfmgr.c:94
#define ereport(elevel, rest)
Definition: elog.h:122
void XLogReaderFree(XLogReaderState *state)
Definition: xlogreader.c:127
#define SpinLockRelease(lock)
Definition: spin.h:64
XLogReaderState * XLogReaderAllocate(int wal_segment_size, XLogPageReadCB pagereadfunc, void *private_data)
Definition: xlogreader.c:67
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Definition: logical.c:516
MemoryContext AllocSetContextCreate(MemoryContext parent, const char *name, Size minContextSize, Size initBlockSize, Size maxBlockSize)
Definition: aset.c:322
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Definition: mcxt.c:877
LogicalDecodeChangeCB change_cb
Definition: output_plugin.h:99
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Definition: slot.h:117
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Definition: globals.c:77
#define InvalidOid
Definition: postgres_ext.h:36
LogicalDecodingContext * CreateDecodingContext(XLogRecPtr start_lsn, List *output_plugin_options, XLogPageReadCB read_page, LogicalOutputPluginWriterPrepareWrite prepare_write, LogicalOutputPluginWriterWrite do_write, LogicalOutputPluginWriterUpdateProgress update_progress)
Definition: logical.c:343
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Definition: snapbuild.c:357
static void begin_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn)
Definition: logical.c:626
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Definition: logical.c:490
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Definition: logical.h:46
ReplicationSlot * MyReplicationSlot
Definition: slot.c:96
uint64 XLogRecPtr
Definition: xlogdefs.h:21
#define Assert(condition)
Definition: c.h:670
#define StrNCpy(dst, src, len)
Definition: c.h:826
Definition: regguts.h:298
void FreeDecodingContext(LogicalDecodingContext *ctx)
Definition: logical.c:475
XLogRecPtr restart_lsn
Definition: slot.h:73
void LogicalIncreaseXminForSlot(XLogRecPtr current_lsn, TransactionId xmin)
Definition: logical.c:788
XLogRecPtr end_lsn
size_t Size
Definition: c.h:404
int(* XLogPageReadCB)(XLogReaderState *xlogreader, XLogRecPtr targetPagePtr, int reqLen, XLogRecPtr targetRecPtr, char *readBuf, TimeLineID *pageTLI)
Definition: xlogreader.h:33
LogicalDecodeShutdownCB shutdown_cb
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Definition: lwlock.c:1117
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Definition: xact.c:351
ReorderBuffer * ReorderBufferAllocate(void)
void(* LogicalOutputPluginWriterWrite)(struct LogicalDecodingContext *lr, XLogRecPtr Ptr, TransactionId xid, bool last_write)
Definition: logical.h:20
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Definition: logical.c:914
LogicalDecodeStartupCB startup_cb
Definition: output_plugin.h:97
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Definition: slot.h:136
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Definition: logical.c:52
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Definition: elog.c:797
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Definition: logical.h:44
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Definition: logical.h:41
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Definition: logical.c:503
LogicalOutputPluginWriterWrite write
Definition: logical.h:60
StringInfo out
Definition: logical.h:66
#define errcontext
Definition: elog.h:164
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Definition: c.h:547
void * arg
LogicalDecodeBeginCB begin_cb
Definition: output_plugin.h:98
#define CHECK_FOR_INTERRUPTS()
Definition: miscadmin.h:98
static void message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn, XLogRecPtr message_lsn, bool transactional, const char *prefix, Size message_size, const char *message)
Definition: logical.c:746
#define elog
Definition: elog.h:219
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Definition: slot.h:93
#define TransactionIdIsValid(xid)
Definition: transam.h:41
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Definition: logical.c:50
ReorderBufferBeginCB begin
static void output_plugin_error_callback(void *arg)
Definition: logical.c:551
LogicalDecodeFilterByOriginCB filter_by_origin_cb
Definition: pg_list.h:45
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Definition: logical.c:76
SnapBuild * AllocateSnapshotBuilder(ReorderBuffer *reorder, TransactionId xmin_horizon, XLogRecPtr start_lsn, bool need_full_snapshot)
Definition: snapbuild.c:316
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Definition: slot.c:695
XLogRecPtr candidate_restart_lsn
Definition: slot.h:138
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Definition: slot.c:656