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 72 : 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 72 : ReplicationSlotCreate(name, false,
43 : temporary ? RS_TEMPORARY : RS_PERSISTENT, false,
44 : false, false);
45 :
46 72 : if (immediately_reserve)
47 : {
48 : /* Reserve WAL as the user asked for it */
49 32 : if (XLogRecPtrIsInvalid(restart_lsn))
50 24 : ReplicationSlotReserveWal();
51 : else
52 8 : MyReplicationSlot->data.restart_lsn = restart_lsn;
53 :
54 : /* Write this slot to disk */
55 32 : ReplicationSlotMarkDirty();
56 32 : ReplicationSlotSave();
57 : }
58 72 : }
59 :
60 : /*
61 : * SQL function for creating a new physical (streaming replication)
62 : * replication slot.
63 : */
64 : Datum
65 64 : pg_create_physical_replication_slot(PG_FUNCTION_ARGS)
66 : {
67 64 : Name name = PG_GETARG_NAME(0);
68 64 : bool immediately_reserve = PG_GETARG_BOOL(1);
69 64 : 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 64 : if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
77 0 : elog(ERROR, "return type must be a row type");
78 :
79 64 : CheckSlotPermissions();
80 :
81 64 : CheckSlotRequirements();
82 :
83 64 : create_physical_replication_slot(NameStr(*name),
84 : immediately_reserve,
85 : temporary,
86 : InvalidXLogRecPtr);
87 :
88 64 : values[0] = NameGetDatum(&MyReplicationSlot->data.name);
89 64 : nulls[0] = false;
90 :
91 64 : if (immediately_reserve)
92 : {
93 24 : values[1] = LSNGetDatum(MyReplicationSlot->data.restart_lsn);
94 24 : nulls[1] = false;
95 : }
96 : else
97 40 : nulls[1] = true;
98 :
99 64 : tuple = heap_form_tuple(tupdesc, values, nulls);
100 64 : result = HeapTupleGetDatum(tuple);
101 :
102 64 : ReplicationSlotRelease();
103 :
104 64 : 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
117 246 : 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 : {
123 246 : 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 : */
135 246 : 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 : */
146 236 : ctx = CreateInitDecodingContext(plugin, NIL,
147 : false, /* just catalogs is OK */
148 : restart_lsn,
149 236 : 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 : */
158 230 : if (find_startpoint)
159 218 : DecodingContextFindStartpoint(ctx);
160 :
161 : /* don't need the decoding context anymore */
162 226 : FreeDecodingContext(ctx);
163 226 : }
164 :
165 : /*
166 : * SQL function for creating a new logical replication slot.
167 : */
168 : Datum
169 234 : pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
170 : {
171 234 : Name name = PG_GETARG_NAME(0);
172 234 : Name plugin = PG_GETARG_NAME(1);
173 234 : bool temporary = PG_GETARG_BOOL(2);
174 234 : bool two_phase = PG_GETARG_BOOL(3);
175 234 : bool failover = PG_GETARG_BOOL(4);
176 : Datum result;
177 : TupleDesc tupdesc;
178 : HeapTuple tuple;
179 : Datum values[2];
180 : bool nulls[2];
181 :
182 234 : if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
183 0 : elog(ERROR, "return type must be a row type");
184 :
185 234 : CheckSlotPermissions();
186 :
187 232 : CheckLogicalDecodingRequirements();
188 :
189 232 : create_logical_replication_slot(NameStr(*name),
190 232 : NameStr(*plugin),
191 : temporary,
192 : two_phase,
193 : failover,
194 : InvalidXLogRecPtr,
195 : true);
196 :
197 214 : values[0] = NameGetDatum(&MyReplicationSlot->data.name);
198 214 : values[1] = LSNGetDatum(MyReplicationSlot->data.confirmed_flush);
199 :
200 214 : memset(nulls, 0, sizeof(nulls));
201 :
202 214 : tuple = heap_form_tuple(tupdesc, values, nulls);
203 214 : result = HeapTupleGetDatum(tuple);
204 :
205 : /* ok, slot is now fully created, mark it as persistent if needed */
206 214 : if (!temporary)
207 204 : ReplicationSlotPersist();
208 214 : ReplicationSlotRelease();
209 :
210 214 : PG_RETURN_DATUM(result);
211 : }
212 :
213 :
214 : /*
215 : * SQL function for dropping a replication slot.
216 : */
217 : Datum
218 256 : pg_drop_replication_slot(PG_FUNCTION_ARGS)
219 : {
220 256 : Name name = PG_GETARG_NAME(0);
221 :
222 256 : CheckSlotPermissions();
223 :
224 252 : CheckSlotRequirements();
225 :
226 252 : ReplicationSlotDrop(NameStr(*name), true);
227 :
228 240 : 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
236 536 : pg_get_replication_slots(PG_FUNCTION_ARGS)
237 : {
238 : #define PG_GET_REPLICATION_SLOTS_COLS 19
239 536 : 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 :
249 536 : InitMaterializedSRF(fcinfo, 0);
250 :
251 536 : currlsn = GetXLogWriteRecPtr();
252 :
253 536 : LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
254 4376 : for (slotno = 0; slotno < max_replication_slots; slotno++)
255 : {
256 3840 : 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 3840 : if (!slot->in_use)
265 2932 : continue;
266 :
267 : /* Copy slot contents while holding spinlock, then examine at leisure */
268 908 : SpinLockAcquire(&slot->mutex);
269 908 : slot_contents = *slot;
270 908 : SpinLockRelease(&slot->mutex);
271 :
272 908 : memset(values, 0, sizeof(values));
273 908 : memset(nulls, 0, sizeof(nulls));
274 :
275 908 : i = 0;
276 908 : values[i++] = NameGetDatum(&slot_contents.data.name);
277 :
278 908 : if (slot_contents.data.database == InvalidOid)
279 256 : nulls[i++] = true;
280 : else
281 652 : values[i++] = NameGetDatum(&slot_contents.data.plugin);
282 :
283 908 : if (slot_contents.data.database == InvalidOid)
284 256 : values[i++] = CStringGetTextDatum("physical");
285 : else
286 652 : values[i++] = CStringGetTextDatum("logical");
287 :
288 908 : if (slot_contents.data.database == InvalidOid)
289 256 : nulls[i++] = true;
290 : else
291 652 : values[i++] = ObjectIdGetDatum(slot_contents.data.database);
292 :
293 908 : values[i++] = BoolGetDatum(slot_contents.data.persistency == RS_TEMPORARY);
294 908 : values[i++] = BoolGetDatum(slot_contents.active_pid != 0);
295 :
296 908 : if (slot_contents.active_pid != 0)
297 280 : values[i++] = Int32GetDatum(slot_contents.active_pid);
298 : else
299 628 : nulls[i++] = true;
300 :
301 908 : if (slot_contents.data.xmin != InvalidTransactionId)
302 118 : values[i++] = TransactionIdGetDatum(slot_contents.data.xmin);
303 : else
304 790 : nulls[i++] = true;
305 :
306 908 : if (slot_contents.data.catalog_xmin != InvalidTransactionId)
307 714 : values[i++] = TransactionIdGetDatum(slot_contents.data.catalog_xmin);
308 : else
309 194 : nulls[i++] = true;
310 :
311 908 : if (slot_contents.data.restart_lsn != InvalidXLogRecPtr)
312 874 : values[i++] = LSNGetDatum(slot_contents.data.restart_lsn);
313 : else
314 34 : nulls[i++] = true;
315 :
316 908 : if (slot_contents.data.confirmed_flush != InvalidXLogRecPtr)
317 604 : values[i++] = LSNGetDatum(slot_contents.data.confirmed_flush);
318 : else
319 304 : nulls[i++] = true;
320 :
321 : /*
322 : * If the slot has not been invalidated, test availability from
323 : * restart_lsn.
324 : */
325 908 : if (slot_contents.data.invalidated != RS_INVAL_NONE)
326 62 : walstate = WALAVAIL_REMOVED;
327 : else
328 846 : walstate = GetWALAvailability(slot_contents.data.restart_lsn);
329 :
330 908 : switch (walstate)
331 : {
332 28 : case WALAVAIL_INVALID_LSN:
333 28 : nulls[i++] = true;
334 28 : break;
335 :
336 812 : case WALAVAIL_RESERVED:
337 812 : values[i++] = CStringGetTextDatum("reserved");
338 812 : 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 62 : 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 62 : if (!XLogRecPtrIsInvalid(slot_contents.data.restart_lsn))
361 : {
362 : int pid;
363 :
364 56 : SpinLockAcquire(&slot->mutex);
365 56 : pid = slot->active_pid;
366 56 : slot_contents.data.restart_lsn = slot->data.restart_lsn;
367 56 : SpinLockRelease(&slot->mutex);
368 56 : if (pid != 0)
369 : {
370 0 : values[i++] = CStringGetTextDatum("unreserved");
371 0 : walstate = WALAVAIL_UNRESERVED;
372 0 : break;
373 : }
374 : }
375 62 : values[i++] = CStringGetTextDatum("lost");
376 62 : 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 : */
383 908 : if (walstate == WALAVAIL_REMOVED || max_slot_wal_keep_size_mb < 0)
384 898 : 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 :
407 908 : values[i++] = BoolGetDatum(slot_contents.data.two_phase);
408 :
409 908 : if (slot_contents.inactive_since > 0)
410 654 : values[i++] = TimestampTzGetDatum(slot_contents.inactive_since);
411 : else
412 254 : nulls[i++] = true;
413 :
414 908 : cause = slot_contents.data.invalidated;
415 :
416 908 : if (SlotIsPhysical(&slot_contents))
417 256 : 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 : */
424 652 : if (cause == RS_INVAL_HORIZON ||
425 : cause == RS_INVAL_WAL_LEVEL)
426 56 : values[i++] = BoolGetDatum(true);
427 : else
428 596 : values[i++] = BoolGetDatum(false);
429 : }
430 :
431 908 : if (cause == RS_INVAL_NONE)
432 846 : nulls[i++] = true;
433 : else
434 62 : values[i++] = CStringGetTextDatum(SlotInvalidationCauses[cause]);
435 :
436 908 : values[i++] = BoolGetDatum(slot_contents.data.failover);
437 :
438 908 : values[i++] = BoolGetDatum(slot_contents.data.synced);
439 :
440 : Assert(i == PG_GET_REPLICATION_SLOTS_COLS);
441 :
442 908 : tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
443 : values, nulls);
444 : }
445 :
446 536 : LWLockRelease(ReplicationSlotControlLock);
447 :
448 536 : 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);
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 : * To avoid potential issues with the slot synchronization where the
699 : * restart_lsn of a replication slot can go backward, we set the
700 : * failover option to false here. This situation occurs when a slot
701 : * on the primary server is dropped and immediately replaced with a
702 : * new slot of the same name, created by copying from another existing
703 : * slot. However, the slot synchronization will only observe the
704 : * restart_lsn of the same slot going backward.
705 : */
706 14 : create_logical_replication_slot(NameStr(*dst_name),
707 : plugin,
708 : temporary,
709 : false,
710 : false,
711 : src_restart_lsn,
712 : false);
713 : }
714 : else
715 8 : create_physical_replication_slot(NameStr(*dst_name),
716 : true,
717 : temporary,
718 : src_restart_lsn);
719 :
720 : /*
721 : * Update the destination slot to current values of the source slot;
722 : * recheck that the source slot is still the one we saw previously.
723 : */
724 : {
725 : TransactionId copy_effective_xmin;
726 : TransactionId copy_effective_catalog_xmin;
727 : TransactionId copy_xmin;
728 : TransactionId copy_catalog_xmin;
729 : XLogRecPtr copy_restart_lsn;
730 : XLogRecPtr copy_confirmed_flush;
731 : bool copy_islogical;
732 : char *copy_name;
733 :
734 : /* Copy data of source slot again */
735 20 : SpinLockAcquire(&src->mutex);
736 20 : second_slot_contents = *src;
737 20 : SpinLockRelease(&src->mutex);
738 :
739 20 : copy_effective_xmin = second_slot_contents.effective_xmin;
740 20 : copy_effective_catalog_xmin = second_slot_contents.effective_catalog_xmin;
741 :
742 20 : copy_xmin = second_slot_contents.data.xmin;
743 20 : copy_catalog_xmin = second_slot_contents.data.catalog_xmin;
744 20 : copy_restart_lsn = second_slot_contents.data.restart_lsn;
745 20 : copy_confirmed_flush = second_slot_contents.data.confirmed_flush;
746 :
747 : /* for existence check */
748 20 : copy_name = NameStr(second_slot_contents.data.name);
749 20 : copy_islogical = SlotIsLogical(&second_slot_contents);
750 :
751 : /*
752 : * Check if the source slot still exists and is valid. We regard it as
753 : * invalid if the type of replication slot or name has been changed,
754 : * or the restart_lsn either is invalid or has gone backward. (The
755 : * restart_lsn could go backwards if the source slot is dropped and
756 : * copied from an older slot during installation.)
757 : *
758 : * Since erroring out will release and drop the destination slot we
759 : * don't need to release it here.
760 : */
761 20 : if (copy_restart_lsn < src_restart_lsn ||
762 20 : src_islogical != copy_islogical ||
763 20 : strcmp(copy_name, NameStr(*src_name)) != 0)
764 0 : ereport(ERROR,
765 : (errmsg("could not copy replication slot \"%s\"",
766 : NameStr(*src_name)),
767 : errdetail("The source replication slot was modified incompatibly during the copy operation.")));
768 :
769 : /* The source slot must have a consistent snapshot */
770 20 : if (src_islogical && XLogRecPtrIsInvalid(copy_confirmed_flush))
771 0 : ereport(ERROR,
772 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
773 : errmsg("cannot copy unfinished logical replication slot \"%s\"",
774 : NameStr(*src_name)),
775 : errhint("Retry when the source replication slot's confirmed_flush_lsn is valid.")));
776 :
777 : /* Install copied values again */
778 20 : SpinLockAcquire(&MyReplicationSlot->mutex);
779 20 : MyReplicationSlot->effective_xmin = copy_effective_xmin;
780 20 : MyReplicationSlot->effective_catalog_xmin = copy_effective_catalog_xmin;
781 :
782 20 : MyReplicationSlot->data.xmin = copy_xmin;
783 20 : MyReplicationSlot->data.catalog_xmin = copy_catalog_xmin;
784 20 : MyReplicationSlot->data.restart_lsn = copy_restart_lsn;
785 20 : MyReplicationSlot->data.confirmed_flush = copy_confirmed_flush;
786 20 : SpinLockRelease(&MyReplicationSlot->mutex);
787 :
788 20 : ReplicationSlotMarkDirty();
789 20 : ReplicationSlotsComputeRequiredXmin(false);
790 20 : ReplicationSlotsComputeRequiredLSN();
791 20 : ReplicationSlotSave();
792 :
793 : #ifdef USE_ASSERT_CHECKING
794 : /* Check that the restart_lsn is available */
795 : {
796 : XLogSegNo segno;
797 :
798 : XLByteToSeg(copy_restart_lsn, segno, wal_segment_size);
799 : Assert(XLogGetLastRemovedSegno() < segno);
800 : }
801 : #endif
802 : }
803 :
804 : /* target slot fully created, mark as persistent if needed */
805 20 : if (logical_slot && !temporary)
806 6 : ReplicationSlotPersist();
807 :
808 : /* All done. Set up the return values */
809 20 : values[0] = NameGetDatum(dst_name);
810 20 : nulls[0] = false;
811 20 : if (!XLogRecPtrIsInvalid(MyReplicationSlot->data.confirmed_flush))
812 : {
813 12 : values[1] = LSNGetDatum(MyReplicationSlot->data.confirmed_flush);
814 12 : nulls[1] = false;
815 : }
816 : else
817 8 : nulls[1] = true;
818 :
819 20 : tuple = heap_form_tuple(tupdesc, values, nulls);
820 20 : result = HeapTupleGetDatum(tuple);
821 :
822 20 : ReplicationSlotRelease();
823 :
824 20 : PG_RETURN_DATUM(result);
825 : }
826 :
827 : /* The wrappers below are all to appease opr_sanity */
828 : Datum
829 8 : pg_copy_logical_replication_slot_a(PG_FUNCTION_ARGS)
830 : {
831 8 : return copy_replication_slot(fcinfo, true);
832 : }
833 :
834 : Datum
835 0 : pg_copy_logical_replication_slot_b(PG_FUNCTION_ARGS)
836 : {
837 0 : return copy_replication_slot(fcinfo, true);
838 : }
839 :
840 : Datum
841 8 : pg_copy_logical_replication_slot_c(PG_FUNCTION_ARGS)
842 : {
843 8 : return copy_replication_slot(fcinfo, true);
844 : }
845 :
846 : Datum
847 4 : pg_copy_physical_replication_slot_a(PG_FUNCTION_ARGS)
848 : {
849 4 : return copy_replication_slot(fcinfo, false);
850 : }
851 :
852 : Datum
853 8 : pg_copy_physical_replication_slot_b(PG_FUNCTION_ARGS)
854 : {
855 8 : return copy_replication_slot(fcinfo, false);
856 : }
857 :
858 : /*
859 : * Synchronize failover enabled replication slots to a standby server
860 : * from the primary server.
861 : */
862 : Datum
863 22 : pg_sync_replication_slots(PG_FUNCTION_ARGS)
864 : {
865 : WalReceiverConn *wrconn;
866 : char *err;
867 : StringInfoData app_name;
868 :
869 22 : CheckSlotPermissions();
870 :
871 20 : if (!RecoveryInProgress())
872 2 : ereport(ERROR,
873 : errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
874 : errmsg("replication slots can only be synchronized to a standby server"));
875 :
876 18 : ValidateSlotSyncParams(ERROR);
877 :
878 : /* Load the libpq-specific functions */
879 18 : load_file("libpqwalreceiver", false);
880 :
881 18 : (void) CheckAndGetDbnameFromConninfo();
882 :
883 16 : initStringInfo(&app_name);
884 16 : if (cluster_name[0])
885 16 : appendStringInfo(&app_name, "%s_slotsync", cluster_name);
886 : else
887 0 : appendStringInfoString(&app_name, "slotsync");
888 :
889 : /* Connect to the primary server. */
890 16 : wrconn = walrcv_connect(PrimaryConnInfo, false, false, false,
891 : app_name.data, &err);
892 16 : pfree(app_name.data);
893 :
894 16 : if (!wrconn)
895 0 : ereport(ERROR,
896 : errcode(ERRCODE_CONNECTION_FAILURE),
897 : errmsg("synchronization worker \"%s\" could not connect to the primary server: %s",
898 : app_name.data, err));
899 :
900 16 : SyncReplicationSlots(wrconn);
901 :
902 14 : walrcv_disconnect(wrconn);
903 :
904 14 : PG_RETURN_VOID();
905 : }
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