Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * slotfuncs.c
4 : * Support functions for replication slots
5 : *
6 : * Copyright (c) 2012-2025, PostgreSQL Global Development Group
7 : *
8 : * IDENTIFICATION
9 : * src/backend/replication/slotfuncs.c
10 : *
11 : *-------------------------------------------------------------------------
12 : */
13 : #include "postgres.h"
14 :
15 : #include "access/htup_details.h"
16 : #include "access/xlog_internal.h"
17 : #include "access/xlogrecovery.h"
18 : #include "access/xlogutils.h"
19 : #include "funcapi.h"
20 : #include "replication/logical.h"
21 : #include "replication/slot.h"
22 : #include "replication/slotsync.h"
23 : #include "utils/builtins.h"
24 : #include "utils/guc.h"
25 : #include "utils/pg_lsn.h"
26 :
27 : /*
28 : * Helper function for creating a new physical replication slot with
29 : * given arguments. Note that this function doesn't release the created
30 : * slot.
31 : *
32 : * If restart_lsn is a valid value, we use it without WAL reservation
33 : * routine. So the caller must guarantee that WAL is available.
34 : */
35 : static void
36 74 : create_physical_replication_slot(char *name, bool immediately_reserve,
37 : bool temporary, XLogRecPtr restart_lsn)
38 : {
39 : Assert(!MyReplicationSlot);
40 :
41 : /* acquire replication slot, this will check for conflicting names */
42 74 : ReplicationSlotCreate(name, false,
43 : temporary ? RS_TEMPORARY : RS_PERSISTENT, false,
44 : false, false);
45 :
46 74 : if (immediately_reserve)
47 : {
48 : /* Reserve WAL as the user asked for it */
49 34 : if (XLogRecPtrIsInvalid(restart_lsn))
50 26 : ReplicationSlotReserveWal();
51 : else
52 8 : MyReplicationSlot->data.restart_lsn = restart_lsn;
53 :
54 : /* Write this slot to disk */
55 34 : ReplicationSlotMarkDirty();
56 34 : ReplicationSlotSave();
57 : }
58 74 : }
59 :
60 : /*
61 : * SQL function for creating a new physical (streaming replication)
62 : * replication slot.
63 : */
64 : Datum
65 66 : pg_create_physical_replication_slot(PG_FUNCTION_ARGS)
66 : {
67 66 : Name name = PG_GETARG_NAME(0);
68 66 : bool immediately_reserve = PG_GETARG_BOOL(1);
69 66 : bool temporary = PG_GETARG_BOOL(2);
70 : Datum values[2];
71 : bool nulls[2];
72 : TupleDesc tupdesc;
73 : HeapTuple tuple;
74 : Datum result;
75 :
76 66 : if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
77 0 : elog(ERROR, "return type must be a row type");
78 :
79 66 : CheckSlotPermissions();
80 :
81 66 : CheckSlotRequirements();
82 :
83 66 : create_physical_replication_slot(NameStr(*name),
84 : immediately_reserve,
85 : temporary,
86 : InvalidXLogRecPtr);
87 :
88 66 : values[0] = NameGetDatum(&MyReplicationSlot->data.name);
89 66 : nulls[0] = false;
90 :
91 66 : if (immediately_reserve)
92 : {
93 26 : values[1] = LSNGetDatum(MyReplicationSlot->data.restart_lsn);
94 26 : nulls[1] = false;
95 : }
96 : else
97 40 : nulls[1] = true;
98 :
99 66 : tuple = heap_form_tuple(tupdesc, values, nulls);
100 66 : result = HeapTupleGetDatum(tuple);
101 :
102 66 : ReplicationSlotRelease();
103 :
104 66 : PG_RETURN_DATUM(result);
105 : }
106 :
107 :
108 : /*
109 : * Helper function for creating a new logical replication slot with
110 : * given arguments. Note that this function doesn't release the created
111 : * slot.
112 : *
113 : * When find_startpoint is false, the slot's confirmed_flush is not set; it's
114 : * caller's responsibility to ensure it's set to something sensible.
115 : */
116 : static void
117 250 : create_logical_replication_slot(char *name, char *plugin,
118 : bool temporary, bool two_phase,
119 : bool failover,
120 : XLogRecPtr restart_lsn,
121 : bool find_startpoint)
122 : {
123 250 : LogicalDecodingContext *ctx = NULL;
124 :
125 : Assert(!MyReplicationSlot);
126 :
127 : /*
128 : * Acquire a logical decoding slot, this will check for conflicting names.
129 : * Initially create persistent slot as ephemeral - that allows us to
130 : * nicely handle errors during initialization because it'll get dropped if
131 : * this transaction fails. We'll make it persistent at the end. Temporary
132 : * slots can be created as temporary from beginning as they get dropped on
133 : * error as well.
134 : */
135 250 : ReplicationSlotCreate(name, true,
136 : temporary ? RS_TEMPORARY : RS_EPHEMERAL, two_phase,
137 : failover, false);
138 :
139 : /*
140 : * Create logical decoding context to find start point or, if we don't
141 : * need it, to 1) bump slot's restart_lsn and xmin 2) check plugin sanity.
142 : *
143 : * Note: when !find_startpoint this is still important, because it's at
144 : * this point that the output plugin is validated.
145 : */
146 240 : ctx = CreateInitDecodingContext(plugin, NIL,
147 : false, /* just catalogs is OK */
148 : restart_lsn,
149 240 : XL_ROUTINE(.page_read = read_local_xlog_page,
150 : .segment_open = wal_segment_open,
151 : .segment_close = wal_segment_close),
152 : NULL, NULL, NULL);
153 :
154 : /*
155 : * If caller needs us to determine the decoding start point, do so now.
156 : * This might take a while.
157 : */
158 234 : if (find_startpoint)
159 222 : DecodingContextFindStartpoint(ctx);
160 :
161 : /* don't need the decoding context anymore */
162 230 : FreeDecodingContext(ctx);
163 230 : }
164 :
165 : /*
166 : * SQL function for creating a new logical replication slot.
167 : */
168 : Datum
169 238 : pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
170 : {
171 238 : Name name = PG_GETARG_NAME(0);
172 238 : Name plugin = PG_GETARG_NAME(1);
173 238 : bool temporary = PG_GETARG_BOOL(2);
174 238 : bool two_phase = PG_GETARG_BOOL(3);
175 238 : bool failover = PG_GETARG_BOOL(4);
176 : Datum result;
177 : TupleDesc tupdesc;
178 : HeapTuple tuple;
179 : Datum values[2];
180 : bool nulls[2];
181 :
182 238 : if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
183 0 : elog(ERROR, "return type must be a row type");
184 :
185 238 : CheckSlotPermissions();
186 :
187 236 : CheckLogicalDecodingRequirements();
188 :
189 236 : create_logical_replication_slot(NameStr(*name),
190 236 : NameStr(*plugin),
191 : temporary,
192 : two_phase,
193 : failover,
194 : InvalidXLogRecPtr,
195 : true);
196 :
197 218 : values[0] = NameGetDatum(&MyReplicationSlot->data.name);
198 218 : values[1] = LSNGetDatum(MyReplicationSlot->data.confirmed_flush);
199 :
200 218 : memset(nulls, 0, sizeof(nulls));
201 :
202 218 : tuple = heap_form_tuple(tupdesc, values, nulls);
203 218 : result = HeapTupleGetDatum(tuple);
204 :
205 : /* ok, slot is now fully created, mark it as persistent if needed */
206 218 : if (!temporary)
207 208 : ReplicationSlotPersist();
208 218 : ReplicationSlotRelease();
209 :
210 218 : PG_RETURN_DATUM(result);
211 : }
212 :
213 :
214 : /*
215 : * SQL function for dropping a replication slot.
216 : */
217 : Datum
218 262 : pg_drop_replication_slot(PG_FUNCTION_ARGS)
219 : {
220 262 : Name name = PG_GETARG_NAME(0);
221 :
222 262 : CheckSlotPermissions();
223 :
224 258 : CheckSlotRequirements();
225 :
226 258 : ReplicationSlotDrop(NameStr(*name), true);
227 :
228 246 : PG_RETURN_VOID();
229 : }
230 :
231 : /*
232 : * pg_get_replication_slots - SQL SRF showing all replication slots
233 : * that currently exist on the database cluster.
234 : */
235 : Datum
236 588 : pg_get_replication_slots(PG_FUNCTION_ARGS)
237 : {
238 : #define PG_GET_REPLICATION_SLOTS_COLS 19
239 588 : ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
240 : XLogRecPtr currlsn;
241 : int slotno;
242 :
243 : /*
244 : * We don't require any special permission to see this function's data
245 : * because nothing should be sensitive. The most critical being the slot
246 : * name, which shouldn't contain anything particularly sensitive.
247 : */
248 :
249 588 : InitMaterializedSRF(fcinfo, 0);
250 :
251 588 : currlsn = GetXLogWriteRecPtr();
252 :
253 588 : LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
254 4892 : for (slotno = 0; slotno < max_replication_slots; slotno++)
255 : {
256 4304 : ReplicationSlot *slot = &ReplicationSlotCtl->replication_slots[slotno];
257 : ReplicationSlot slot_contents;
258 : Datum values[PG_GET_REPLICATION_SLOTS_COLS];
259 : bool nulls[PG_GET_REPLICATION_SLOTS_COLS];
260 : WALAvailability walstate;
261 : int i;
262 : ReplicationSlotInvalidationCause cause;
263 :
264 4304 : if (!slot->in_use)
265 3364 : continue;
266 :
267 : /* Copy slot contents while holding spinlock, then examine at leisure */
268 940 : SpinLockAcquire(&slot->mutex);
269 940 : slot_contents = *slot;
270 940 : SpinLockRelease(&slot->mutex);
271 :
272 940 : memset(values, 0, sizeof(values));
273 940 : memset(nulls, 0, sizeof(nulls));
274 :
275 940 : i = 0;
276 940 : values[i++] = NameGetDatum(&slot_contents.data.name);
277 :
278 940 : if (slot_contents.data.database == InvalidOid)
279 266 : nulls[i++] = true;
280 : else
281 674 : values[i++] = NameGetDatum(&slot_contents.data.plugin);
282 :
283 940 : if (slot_contents.data.database == InvalidOid)
284 266 : values[i++] = CStringGetTextDatum("physical");
285 : else
286 674 : values[i++] = CStringGetTextDatum("logical");
287 :
288 940 : if (slot_contents.data.database == InvalidOid)
289 266 : nulls[i++] = true;
290 : else
291 674 : values[i++] = ObjectIdGetDatum(slot_contents.data.database);
292 :
293 940 : values[i++] = BoolGetDatum(slot_contents.data.persistency == RS_TEMPORARY);
294 940 : values[i++] = BoolGetDatum(slot_contents.active_pid != 0);
295 :
296 940 : if (slot_contents.active_pid != 0)
297 294 : values[i++] = Int32GetDatum(slot_contents.active_pid);
298 : else
299 646 : nulls[i++] = true;
300 :
301 940 : if (slot_contents.data.xmin != InvalidTransactionId)
302 126 : values[i++] = TransactionIdGetDatum(slot_contents.data.xmin);
303 : else
304 814 : nulls[i++] = true;
305 :
306 940 : if (slot_contents.data.catalog_xmin != InvalidTransactionId)
307 738 : values[i++] = TransactionIdGetDatum(slot_contents.data.catalog_xmin);
308 : else
309 202 : nulls[i++] = true;
310 :
311 940 : if (slot_contents.data.restart_lsn != InvalidXLogRecPtr)
312 910 : values[i++] = LSNGetDatum(slot_contents.data.restart_lsn);
313 : else
314 30 : nulls[i++] = true;
315 :
316 940 : if (slot_contents.data.confirmed_flush != InvalidXLogRecPtr)
317 626 : values[i++] = LSNGetDatum(slot_contents.data.confirmed_flush);
318 : else
319 314 : nulls[i++] = true;
320 :
321 : /*
322 : * If the slot has not been invalidated, test availability from
323 : * restart_lsn.
324 : */
325 940 : if (slot_contents.data.invalidated != RS_INVAL_NONE)
326 70 : walstate = WALAVAIL_REMOVED;
327 : else
328 870 : walstate = GetWALAvailability(slot_contents.data.restart_lsn);
329 :
330 940 : switch (walstate)
331 : {
332 24 : case WALAVAIL_INVALID_LSN:
333 24 : nulls[i++] = true;
334 24 : break;
335 :
336 840 : case WALAVAIL_RESERVED:
337 840 : values[i++] = CStringGetTextDatum("reserved");
338 840 : break;
339 :
340 4 : case WALAVAIL_EXTENDED:
341 4 : values[i++] = CStringGetTextDatum("extended");
342 4 : break;
343 :
344 2 : case WALAVAIL_UNRESERVED:
345 2 : values[i++] = CStringGetTextDatum("unreserved");
346 2 : break;
347 :
348 70 : case WALAVAIL_REMOVED:
349 :
350 : /*
351 : * If we read the restart_lsn long enough ago, maybe that file
352 : * has been removed by now. However, the walsender could have
353 : * moved forward enough that it jumped to another file after
354 : * we looked. If checkpointer signalled the process to
355 : * termination, then it's definitely lost; but if a process is
356 : * still alive, then "unreserved" seems more appropriate.
357 : *
358 : * If we do change it, save the state for safe_wal_size below.
359 : */
360 70 : if (!XLogRecPtrIsInvalid(slot_contents.data.restart_lsn))
361 : {
362 : int pid;
363 :
364 64 : SpinLockAcquire(&slot->mutex);
365 64 : pid = slot->active_pid;
366 64 : slot_contents.data.restart_lsn = slot->data.restart_lsn;
367 64 : SpinLockRelease(&slot->mutex);
368 64 : if (pid != 0)
369 : {
370 0 : values[i++] = CStringGetTextDatum("unreserved");
371 0 : walstate = WALAVAIL_UNRESERVED;
372 0 : break;
373 : }
374 : }
375 70 : values[i++] = CStringGetTextDatum("lost");
376 70 : break;
377 : }
378 :
379 : /*
380 : * safe_wal_size is only computed for slots that have not been lost,
381 : * and only if there's a configured maximum size.
382 : */
383 940 : if (walstate == WALAVAIL_REMOVED || max_slot_wal_keep_size_mb < 0)
384 930 : nulls[i++] = true;
385 : else
386 : {
387 : XLogSegNo targetSeg;
388 : uint64 slotKeepSegs;
389 : uint64 keepSegs;
390 : XLogSegNo failSeg;
391 : XLogRecPtr failLSN;
392 :
393 10 : XLByteToSeg(slot_contents.data.restart_lsn, targetSeg, wal_segment_size);
394 :
395 : /* determine how many segments can be kept by slots */
396 10 : slotKeepSegs = XLogMBVarToSegs(max_slot_wal_keep_size_mb, wal_segment_size);
397 : /* ditto for wal_keep_size */
398 10 : keepSegs = XLogMBVarToSegs(wal_keep_size_mb, wal_segment_size);
399 :
400 : /* if currpos reaches failLSN, we lose our segment */
401 10 : failSeg = targetSeg + Max(slotKeepSegs, keepSegs) + 1;
402 10 : XLogSegNoOffsetToRecPtr(failSeg, 0, wal_segment_size, failLSN);
403 :
404 10 : values[i++] = Int64GetDatum(failLSN - currlsn);
405 : }
406 :
407 940 : values[i++] = BoolGetDatum(slot_contents.data.two_phase);
408 :
409 940 : if (slot_contents.inactive_since > 0)
410 660 : values[i++] = TimestampTzGetDatum(slot_contents.inactive_since);
411 : else
412 280 : nulls[i++] = true;
413 :
414 940 : cause = slot_contents.data.invalidated;
415 :
416 940 : if (SlotIsPhysical(&slot_contents))
417 266 : nulls[i++] = true;
418 : else
419 : {
420 : /*
421 : * rows_removed and wal_level_insufficient are the only two
422 : * reasons for the logical slot's conflict with recovery.
423 : */
424 674 : if (cause == RS_INVAL_HORIZON ||
425 : cause == RS_INVAL_WAL_LEVEL)
426 56 : values[i++] = BoolGetDatum(true);
427 : else
428 618 : values[i++] = BoolGetDatum(false);
429 : }
430 :
431 940 : if (cause == RS_INVAL_NONE)
432 870 : nulls[i++] = true;
433 : else
434 70 : values[i++] = CStringGetTextDatum(GetSlotInvalidationCauseName(cause));
435 :
436 940 : values[i++] = BoolGetDatum(slot_contents.data.failover);
437 :
438 940 : values[i++] = BoolGetDatum(slot_contents.data.synced);
439 :
440 : Assert(i == PG_GET_REPLICATION_SLOTS_COLS);
441 :
442 940 : tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
443 : values, nulls);
444 : }
445 :
446 588 : LWLockRelease(ReplicationSlotControlLock);
447 :
448 588 : return (Datum) 0;
449 : }
450 :
451 : /*
452 : * Helper function for advancing our physical replication slot forward.
453 : *
454 : * The LSN position to move to is compared simply to the slot's restart_lsn,
455 : * knowing that any position older than that would be removed by successive
456 : * checkpoints.
457 : */
458 : static XLogRecPtr
459 2 : pg_physical_replication_slot_advance(XLogRecPtr moveto)
460 : {
461 2 : XLogRecPtr startlsn = MyReplicationSlot->data.restart_lsn;
462 2 : XLogRecPtr retlsn = startlsn;
463 :
464 : Assert(moveto != InvalidXLogRecPtr);
465 :
466 2 : if (startlsn < moveto)
467 : {
468 2 : SpinLockAcquire(&MyReplicationSlot->mutex);
469 2 : MyReplicationSlot->data.restart_lsn = moveto;
470 2 : SpinLockRelease(&MyReplicationSlot->mutex);
471 2 : retlsn = moveto;
472 :
473 : /*
474 : * Dirty the slot so as it is written out at the next checkpoint. Note
475 : * that the LSN position advanced may still be lost in the event of a
476 : * crash, but this makes the data consistent after a clean shutdown.
477 : */
478 2 : ReplicationSlotMarkDirty();
479 :
480 : /*
481 : * Wake up logical walsenders holding logical failover slots after
482 : * updating the restart_lsn of the physical slot.
483 : */
484 2 : PhysicalWakeupLogicalWalSnd();
485 : }
486 :
487 2 : return retlsn;
488 : }
489 :
490 : /*
491 : * Advance our logical replication slot forward. See
492 : * LogicalSlotAdvanceAndCheckSnapState for details.
493 : */
494 : static XLogRecPtr
495 10 : pg_logical_replication_slot_advance(XLogRecPtr moveto)
496 : {
497 10 : return LogicalSlotAdvanceAndCheckSnapState(moveto, NULL);
498 : }
499 :
500 : /*
501 : * SQL function for moving the position in a replication slot.
502 : */
503 : Datum
504 16 : pg_replication_slot_advance(PG_FUNCTION_ARGS)
505 : {
506 16 : Name slotname = PG_GETARG_NAME(0);
507 16 : XLogRecPtr moveto = PG_GETARG_LSN(1);
508 : XLogRecPtr endlsn;
509 : XLogRecPtr minlsn;
510 : TupleDesc tupdesc;
511 : Datum values[2];
512 : bool nulls[2];
513 : HeapTuple tuple;
514 : Datum result;
515 :
516 : Assert(!MyReplicationSlot);
517 :
518 16 : CheckSlotPermissions();
519 :
520 16 : if (XLogRecPtrIsInvalid(moveto))
521 2 : ereport(ERROR,
522 : (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
523 : errmsg("invalid target WAL LSN")));
524 :
525 : /* Build a tuple descriptor for our result type */
526 14 : if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
527 0 : elog(ERROR, "return type must be a row type");
528 :
529 : /*
530 : * We can't move slot past what's been flushed/replayed so clamp the
531 : * target position accordingly.
532 : */
533 14 : if (!RecoveryInProgress())
534 14 : moveto = Min(moveto, GetFlushRecPtr(NULL));
535 : else
536 0 : moveto = Min(moveto, GetXLogReplayRecPtr(NULL));
537 :
538 : /* Acquire the slot so we "own" it */
539 14 : ReplicationSlotAcquire(NameStr(*slotname), true, true);
540 :
541 : /* A slot whose restart_lsn has never been reserved cannot be advanced */
542 14 : if (XLogRecPtrIsInvalid(MyReplicationSlot->data.restart_lsn))
543 2 : ereport(ERROR,
544 : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
545 : errmsg("replication slot \"%s\" cannot be advanced",
546 : NameStr(*slotname)),
547 : errdetail("This slot has never previously reserved WAL, or it has been invalidated.")));
548 :
549 : /*
550 : * Check if the slot is not moving backwards. Physical slots rely simply
551 : * on restart_lsn as a minimum point, while logical slots have confirmed
552 : * consumption up to confirmed_flush, meaning that in both cases data
553 : * older than that is not available anymore.
554 : */
555 12 : if (OidIsValid(MyReplicationSlot->data.database))
556 10 : minlsn = MyReplicationSlot->data.confirmed_flush;
557 : else
558 2 : minlsn = MyReplicationSlot->data.restart_lsn;
559 :
560 12 : if (moveto < minlsn)
561 0 : ereport(ERROR,
562 : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
563 : errmsg("cannot advance replication slot to %X/%X, minimum is %X/%X",
564 : LSN_FORMAT_ARGS(moveto), LSN_FORMAT_ARGS(minlsn))));
565 :
566 : /* Do the actual slot update, depending on the slot type */
567 12 : if (OidIsValid(MyReplicationSlot->data.database))
568 10 : endlsn = pg_logical_replication_slot_advance(moveto);
569 : else
570 2 : endlsn = pg_physical_replication_slot_advance(moveto);
571 :
572 12 : values[0] = NameGetDatum(&MyReplicationSlot->data.name);
573 12 : nulls[0] = false;
574 :
575 : /*
576 : * Recompute the minimum LSN and xmin across all slots to adjust with the
577 : * advancing potentially done.
578 : */
579 12 : ReplicationSlotsComputeRequiredXmin(false);
580 12 : ReplicationSlotsComputeRequiredLSN();
581 :
582 12 : ReplicationSlotRelease();
583 :
584 : /* Return the reached position. */
585 12 : values[1] = LSNGetDatum(endlsn);
586 12 : nulls[1] = false;
587 :
588 12 : tuple = heap_form_tuple(tupdesc, values, nulls);
589 12 : result = HeapTupleGetDatum(tuple);
590 :
591 12 : PG_RETURN_DATUM(result);
592 : }
593 :
594 : /*
595 : * Helper function of copying a replication slot.
596 : */
597 : static Datum
598 28 : copy_replication_slot(FunctionCallInfo fcinfo, bool logical_slot)
599 : {
600 28 : Name src_name = PG_GETARG_NAME(0);
601 28 : Name dst_name = PG_GETARG_NAME(1);
602 28 : ReplicationSlot *src = NULL;
603 : ReplicationSlot first_slot_contents;
604 : ReplicationSlot second_slot_contents;
605 : XLogRecPtr src_restart_lsn;
606 : bool src_islogical;
607 : bool temporary;
608 : char *plugin;
609 : Datum values[2];
610 : bool nulls[2];
611 : Datum result;
612 : TupleDesc tupdesc;
613 : HeapTuple tuple;
614 :
615 28 : if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
616 0 : elog(ERROR, "return type must be a row type");
617 :
618 28 : CheckSlotPermissions();
619 :
620 28 : if (logical_slot)
621 16 : CheckLogicalDecodingRequirements();
622 : else
623 12 : CheckSlotRequirements();
624 :
625 28 : LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
626 :
627 : /*
628 : * We need to prevent the source slot's reserved WAL from being removed,
629 : * but we don't want to lock that slot for very long, and it can advance
630 : * in the meantime. So obtain the source slot's data, and create a new
631 : * slot using its restart_lsn. Afterwards we lock the source slot again
632 : * and verify that the data we copied (name, type) has not changed
633 : * incompatibly. No inconvenient WAL removal can occur once the new slot
634 : * is created -- but since WAL removal could have occurred before we
635 : * managed to create the new slot, we advance the new slot's restart_lsn
636 : * to the source slot's updated restart_lsn the second time we lock it.
637 : */
638 30 : for (int i = 0; i < max_replication_slots; i++)
639 : {
640 30 : ReplicationSlot *s = &ReplicationSlotCtl->replication_slots[i];
641 :
642 30 : if (s->in_use && strcmp(NameStr(s->data.name), NameStr(*src_name)) == 0)
643 : {
644 : /* Copy the slot contents while holding spinlock */
645 28 : SpinLockAcquire(&s->mutex);
646 28 : first_slot_contents = *s;
647 28 : SpinLockRelease(&s->mutex);
648 28 : src = s;
649 28 : break;
650 : }
651 : }
652 :
653 28 : LWLockRelease(ReplicationSlotControlLock);
654 :
655 28 : if (src == NULL)
656 0 : ereport(ERROR,
657 : (errcode(ERRCODE_UNDEFINED_OBJECT),
658 : errmsg("replication slot \"%s\" does not exist", NameStr(*src_name))));
659 :
660 28 : src_islogical = SlotIsLogical(&first_slot_contents);
661 28 : src_restart_lsn = first_slot_contents.data.restart_lsn;
662 28 : temporary = (first_slot_contents.data.persistency == RS_TEMPORARY);
663 28 : plugin = logical_slot ? NameStr(first_slot_contents.data.plugin) : NULL;
664 :
665 : /* Check type of replication slot */
666 28 : if (src_islogical != logical_slot)
667 4 : ereport(ERROR,
668 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
669 : src_islogical ?
670 : errmsg("cannot copy physical replication slot \"%s\" as a logical replication slot",
671 : NameStr(*src_name)) :
672 : errmsg("cannot copy logical replication slot \"%s\" as a physical replication slot",
673 : NameStr(*src_name))));
674 :
675 : /* Copying non-reserved slot doesn't make sense */
676 24 : if (XLogRecPtrIsInvalid(src_restart_lsn))
677 2 : ereport(ERROR,
678 : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
679 : errmsg("cannot copy a replication slot that doesn't reserve WAL")));
680 :
681 : /* Overwrite params from optional arguments */
682 22 : if (PG_NARGS() >= 3)
683 12 : temporary = PG_GETARG_BOOL(2);
684 22 : if (PG_NARGS() >= 4)
685 : {
686 : Assert(logical_slot);
687 8 : plugin = NameStr(*(PG_GETARG_NAME(3)));
688 : }
689 :
690 : /* Create new slot and acquire it */
691 22 : if (logical_slot)
692 : {
693 : /*
694 : * We must not try to read WAL, since we haven't reserved it yet --
695 : * hence pass find_startpoint false. confirmed_flush will be set
696 : * below, by copying from the source slot.
697 : *
698 : * We don't copy the failover option to prevent potential issues with
699 : * slot synchronization. For instance, if a slot was synchronized to
700 : * the standby, then dropped on the primary, and immediately recreated
701 : * by copying from another existing slot with much earlier restart_lsn
702 : * and confirmed_flush_lsn, the slot synchronization would only
703 : * observe the LSN of the same slot moving backward. As slot
704 : * synchronization does not copy the restart_lsn and
705 : * confirmed_flush_lsn backward (see update_local_synced_slot() for
706 : * details), if a failover happens before the primary's slot catches
707 : * up, logical replication cannot continue using the synchronized slot
708 : * on the promoted standby because the slot retains the restart_lsn
709 : * and confirmed_flush_lsn that are much later than expected.
710 : */
711 14 : create_logical_replication_slot(NameStr(*dst_name),
712 : plugin,
713 : temporary,
714 : false,
715 : false,
716 : src_restart_lsn,
717 : false);
718 : }
719 : else
720 8 : create_physical_replication_slot(NameStr(*dst_name),
721 : true,
722 : temporary,
723 : src_restart_lsn);
724 :
725 : /*
726 : * Update the destination slot to current values of the source slot;
727 : * recheck that the source slot is still the one we saw previously.
728 : */
729 : {
730 : TransactionId copy_effective_xmin;
731 : TransactionId copy_effective_catalog_xmin;
732 : TransactionId copy_xmin;
733 : TransactionId copy_catalog_xmin;
734 : XLogRecPtr copy_restart_lsn;
735 : XLogRecPtr copy_confirmed_flush;
736 : bool copy_islogical;
737 : char *copy_name;
738 :
739 : /* Copy data of source slot again */
740 20 : SpinLockAcquire(&src->mutex);
741 20 : second_slot_contents = *src;
742 20 : SpinLockRelease(&src->mutex);
743 :
744 20 : copy_effective_xmin = second_slot_contents.effective_xmin;
745 20 : copy_effective_catalog_xmin = second_slot_contents.effective_catalog_xmin;
746 :
747 20 : copy_xmin = second_slot_contents.data.xmin;
748 20 : copy_catalog_xmin = second_slot_contents.data.catalog_xmin;
749 20 : copy_restart_lsn = second_slot_contents.data.restart_lsn;
750 20 : copy_confirmed_flush = second_slot_contents.data.confirmed_flush;
751 :
752 : /* for existence check */
753 20 : copy_name = NameStr(second_slot_contents.data.name);
754 20 : copy_islogical = SlotIsLogical(&second_slot_contents);
755 :
756 : /*
757 : * Check if the source slot still exists and is valid. We regard it as
758 : * invalid if the type of replication slot or name has been changed,
759 : * or the restart_lsn either is invalid or has gone backward. (The
760 : * restart_lsn could go backwards if the source slot is dropped and
761 : * copied from an older slot during installation.)
762 : *
763 : * Since erroring out will release and drop the destination slot we
764 : * don't need to release it here.
765 : */
766 20 : if (copy_restart_lsn < src_restart_lsn ||
767 20 : src_islogical != copy_islogical ||
768 20 : strcmp(copy_name, NameStr(*src_name)) != 0)
769 0 : ereport(ERROR,
770 : (errmsg("could not copy replication slot \"%s\"",
771 : NameStr(*src_name)),
772 : errdetail("The source replication slot was modified incompatibly during the copy operation.")));
773 :
774 : /* The source slot must have a consistent snapshot */
775 20 : if (src_islogical && XLogRecPtrIsInvalid(copy_confirmed_flush))
776 0 : ereport(ERROR,
777 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
778 : errmsg("cannot copy unfinished logical replication slot \"%s\"",
779 : NameStr(*src_name)),
780 : errhint("Retry when the source replication slot's confirmed_flush_lsn is valid.")));
781 :
782 : /* Install copied values again */
783 20 : SpinLockAcquire(&MyReplicationSlot->mutex);
784 20 : MyReplicationSlot->effective_xmin = copy_effective_xmin;
785 20 : MyReplicationSlot->effective_catalog_xmin = copy_effective_catalog_xmin;
786 :
787 20 : MyReplicationSlot->data.xmin = copy_xmin;
788 20 : MyReplicationSlot->data.catalog_xmin = copy_catalog_xmin;
789 20 : MyReplicationSlot->data.restart_lsn = copy_restart_lsn;
790 20 : MyReplicationSlot->data.confirmed_flush = copy_confirmed_flush;
791 20 : SpinLockRelease(&MyReplicationSlot->mutex);
792 :
793 20 : ReplicationSlotMarkDirty();
794 20 : ReplicationSlotsComputeRequiredXmin(false);
795 20 : ReplicationSlotsComputeRequiredLSN();
796 20 : ReplicationSlotSave();
797 :
798 : #ifdef USE_ASSERT_CHECKING
799 : /* Check that the restart_lsn is available */
800 : {
801 : XLogSegNo segno;
802 :
803 : XLByteToSeg(copy_restart_lsn, segno, wal_segment_size);
804 : Assert(XLogGetLastRemovedSegno() < segno);
805 : }
806 : #endif
807 : }
808 :
809 : /* target slot fully created, mark as persistent if needed */
810 20 : if (logical_slot && !temporary)
811 6 : ReplicationSlotPersist();
812 :
813 : /* All done. Set up the return values */
814 20 : values[0] = NameGetDatum(dst_name);
815 20 : nulls[0] = false;
816 20 : if (!XLogRecPtrIsInvalid(MyReplicationSlot->data.confirmed_flush))
817 : {
818 12 : values[1] = LSNGetDatum(MyReplicationSlot->data.confirmed_flush);
819 12 : nulls[1] = false;
820 : }
821 : else
822 8 : nulls[1] = true;
823 :
824 20 : tuple = heap_form_tuple(tupdesc, values, nulls);
825 20 : result = HeapTupleGetDatum(tuple);
826 :
827 20 : ReplicationSlotRelease();
828 :
829 20 : PG_RETURN_DATUM(result);
830 : }
831 :
832 : /* The wrappers below are all to appease opr_sanity */
833 : Datum
834 8 : pg_copy_logical_replication_slot_a(PG_FUNCTION_ARGS)
835 : {
836 8 : return copy_replication_slot(fcinfo, true);
837 : }
838 :
839 : Datum
840 0 : pg_copy_logical_replication_slot_b(PG_FUNCTION_ARGS)
841 : {
842 0 : return copy_replication_slot(fcinfo, true);
843 : }
844 :
845 : Datum
846 8 : pg_copy_logical_replication_slot_c(PG_FUNCTION_ARGS)
847 : {
848 8 : return copy_replication_slot(fcinfo, true);
849 : }
850 :
851 : Datum
852 4 : pg_copy_physical_replication_slot_a(PG_FUNCTION_ARGS)
853 : {
854 4 : return copy_replication_slot(fcinfo, false);
855 : }
856 :
857 : Datum
858 8 : pg_copy_physical_replication_slot_b(PG_FUNCTION_ARGS)
859 : {
860 8 : return copy_replication_slot(fcinfo, false);
861 : }
862 :
863 : /*
864 : * Synchronize failover enabled replication slots to a standby server
865 : * from the primary server.
866 : */
867 : Datum
868 22 : pg_sync_replication_slots(PG_FUNCTION_ARGS)
869 : {
870 : WalReceiverConn *wrconn;
871 : char *err;
872 : StringInfoData app_name;
873 :
874 22 : CheckSlotPermissions();
875 :
876 20 : if (!RecoveryInProgress())
877 2 : ereport(ERROR,
878 : errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
879 : errmsg("replication slots can only be synchronized to a standby server"));
880 :
881 18 : ValidateSlotSyncParams(ERROR);
882 :
883 : /* Load the libpq-specific functions */
884 18 : load_file("libpqwalreceiver", false);
885 :
886 18 : (void) CheckAndGetDbnameFromConninfo();
887 :
888 16 : initStringInfo(&app_name);
889 16 : if (cluster_name[0])
890 16 : appendStringInfo(&app_name, "%s_slotsync", cluster_name);
891 : else
892 0 : appendStringInfoString(&app_name, "slotsync");
893 :
894 : /* Connect to the primary server. */
895 16 : wrconn = walrcv_connect(PrimaryConnInfo, false, false, false,
896 : app_name.data, &err);
897 16 : pfree(app_name.data);
898 :
899 16 : if (!wrconn)
900 0 : ereport(ERROR,
901 : errcode(ERRCODE_CONNECTION_FAILURE),
902 : errmsg("synchronization worker \"%s\" could not connect to the primary server: %s",
903 : app_name.data, err));
904 :
905 16 : SyncReplicationSlots(wrconn);
906 :
907 14 : walrcv_disconnect(wrconn);
908 :
909 14 : PG_RETURN_VOID();
910 : }
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