Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * autoprewarm.c
4 : * Periodically dump information about the blocks present in
5 : * shared_buffers, and reload them on server restart.
6 : *
7 : * Due to locking considerations, we can't actually begin prewarming
8 : * until the server reaches a consistent state. We need the catalogs
9 : * to be consistent so that we can figure out which relation to lock,
10 : * and we need to lock the relations so that we don't try to prewarm
11 : * pages from a relation that is in the process of being dropped.
12 : *
13 : * While prewarming, autoprewarm will use two workers. There's a
14 : * leader worker that reads and sorts the list of blocks to be
15 : * prewarmed and then launches a per-database worker for each
16 : * relevant database in turn. The former keeps running after the
17 : * initial prewarm is complete to update the dump file periodically.
18 : *
19 : * Copyright (c) 2016-2025, PostgreSQL Global Development Group
20 : *
21 : * IDENTIFICATION
22 : * contrib/pg_prewarm/autoprewarm.c
23 : *
24 : *-------------------------------------------------------------------------
25 : */
26 :
27 : #include "postgres.h"
28 :
29 : #include <unistd.h>
30 :
31 : #include "access/relation.h"
32 : #include "access/xact.h"
33 : #include "pgstat.h"
34 : #include "postmaster/bgworker.h"
35 : #include "postmaster/interrupt.h"
36 : #include "storage/buf_internals.h"
37 : #include "storage/dsm.h"
38 : #include "storage/dsm_registry.h"
39 : #include "storage/fd.h"
40 : #include "storage/ipc.h"
41 : #include "storage/latch.h"
42 : #include "storage/lwlock.h"
43 : #include "storage/procsignal.h"
44 : #include "storage/read_stream.h"
45 : #include "storage/smgr.h"
46 : #include "tcop/tcopprot.h"
47 : #include "utils/guc.h"
48 : #include "utils/rel.h"
49 : #include "utils/relfilenumbermap.h"
50 : #include "utils/timestamp.h"
51 :
52 : #define AUTOPREWARM_FILE "autoprewarm.blocks"
53 :
54 : /* Metadata for each block we dump. */
55 : typedef struct BlockInfoRecord
56 : {
57 : Oid database;
58 : Oid tablespace;
59 : RelFileNumber filenumber;
60 : ForkNumber forknum;
61 : BlockNumber blocknum;
62 : } BlockInfoRecord;
63 :
64 : /* Shared state information for autoprewarm bgworker. */
65 : typedef struct AutoPrewarmSharedState
66 : {
67 : LWLock lock; /* mutual exclusion */
68 : pid_t bgworker_pid; /* for main bgworker */
69 : pid_t pid_using_dumpfile; /* for autoprewarm or block dump */
70 :
71 : /* Following items are for communication with per-database worker */
72 : dsm_handle block_info_handle;
73 : Oid database;
74 : int prewarm_start_idx;
75 : int prewarm_stop_idx;
76 : int prewarmed_blocks;
77 : } AutoPrewarmSharedState;
78 :
79 : /*
80 : * Private data passed through the read stream API for our use in the
81 : * callback.
82 : */
83 : typedef struct AutoPrewarmReadStreamData
84 : {
85 : /* The array of records containing the blocks we should prewarm. */
86 : BlockInfoRecord *block_info;
87 :
88 : /*
89 : * pos is the read stream callback's index into block_info. Because the
90 : * read stream may read ahead, pos is likely to be ahead of the index in
91 : * the main loop in autoprewarm_database_main().
92 : */
93 : int pos;
94 : Oid tablespace;
95 : RelFileNumber filenumber;
96 : ForkNumber forknum;
97 : BlockNumber nblocks;
98 : } AutoPrewarmReadStreamData;
99 :
100 :
101 : PGDLLEXPORT void autoprewarm_main(Datum main_arg);
102 : PGDLLEXPORT void autoprewarm_database_main(Datum main_arg);
103 :
104 4 : PG_FUNCTION_INFO_V1(autoprewarm_start_worker);
105 6 : PG_FUNCTION_INFO_V1(autoprewarm_dump_now);
106 :
107 : static void apw_load_buffers(void);
108 : static int apw_dump_now(bool is_bgworker, bool dump_unlogged);
109 : static void apw_start_leader_worker(void);
110 : static void apw_start_database_worker(void);
111 : static bool apw_init_shmem(void);
112 : static void apw_detach_shmem(int code, Datum arg);
113 : static int apw_compare_blockinfo(const void *p, const void *q);
114 :
115 : /* Pointer to shared-memory state. */
116 : static AutoPrewarmSharedState *apw_state = NULL;
117 :
118 : /* GUC variables. */
119 : static bool autoprewarm = true; /* start worker? */
120 : static int autoprewarm_interval = 300; /* dump interval */
121 :
122 : /*
123 : * Module load callback.
124 : */
125 : void
126 10 : _PG_init(void)
127 : {
128 10 : DefineCustomIntVariable("pg_prewarm.autoprewarm_interval",
129 : "Sets the interval between dumps of shared buffers",
130 : "If set to zero, time-based dumping is disabled.",
131 : &autoprewarm_interval,
132 : 300,
133 : 0, INT_MAX / 1000,
134 : PGC_SIGHUP,
135 : GUC_UNIT_S,
136 : NULL,
137 : NULL,
138 : NULL);
139 :
140 10 : if (!process_shared_preload_libraries_in_progress)
141 6 : return;
142 :
143 : /* can't define PGC_POSTMASTER variable after startup */
144 4 : DefineCustomBoolVariable("pg_prewarm.autoprewarm",
145 : "Starts the autoprewarm worker.",
146 : NULL,
147 : &autoprewarm,
148 : true,
149 : PGC_POSTMASTER,
150 : 0,
151 : NULL,
152 : NULL,
153 : NULL);
154 :
155 4 : MarkGUCPrefixReserved("pg_prewarm");
156 :
157 : /* Register autoprewarm worker, if enabled. */
158 4 : if (autoprewarm)
159 4 : apw_start_leader_worker();
160 : }
161 :
162 : /*
163 : * Main entry point for the leader autoprewarm process. Per-database workers
164 : * have a separate entry point.
165 : */
166 : void
167 4 : autoprewarm_main(Datum main_arg)
168 : {
169 4 : bool first_time = true;
170 4 : bool final_dump_allowed = true;
171 4 : TimestampTz last_dump_time = 0;
172 :
173 : /* Establish signal handlers; once that's done, unblock signals. */
174 4 : pqsignal(SIGTERM, SignalHandlerForShutdownRequest);
175 4 : pqsignal(SIGHUP, SignalHandlerForConfigReload);
176 4 : pqsignal(SIGUSR1, procsignal_sigusr1_handler);
177 4 : BackgroundWorkerUnblockSignals();
178 :
179 : /* Create (if necessary) and attach to our shared memory area. */
180 4 : if (apw_init_shmem())
181 0 : first_time = false;
182 :
183 : /*
184 : * Set on-detach hook so that our PID will be cleared on exit.
185 : *
186 : * NB: Autoprewarm's state is stored in a DSM segment, and DSM segments
187 : * are detached before calling the on_shmem_exit callbacks, so we must put
188 : * apw_detach_shmem in the before_shmem_exit callback list.
189 : */
190 4 : before_shmem_exit(apw_detach_shmem, 0);
191 :
192 : /*
193 : * Store our PID in the shared memory area --- unless there's already
194 : * another worker running, in which case just exit.
195 : */
196 4 : LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE);
197 4 : if (apw_state->bgworker_pid != InvalidPid)
198 : {
199 0 : LWLockRelease(&apw_state->lock);
200 0 : ereport(LOG,
201 : (errmsg("autoprewarm worker is already running under PID %d",
202 : (int) apw_state->bgworker_pid)));
203 0 : return;
204 : }
205 4 : apw_state->bgworker_pid = MyProcPid;
206 4 : LWLockRelease(&apw_state->lock);
207 :
208 : /*
209 : * Preload buffers from the dump file only if we just created the shared
210 : * memory region. Otherwise, it's either already been done or shouldn't
211 : * be done - e.g. because the old dump file has been overwritten since the
212 : * server was started.
213 : *
214 : * There's not much point in performing a dump immediately after we finish
215 : * preloading; so, if we do end up preloading, consider the last dump time
216 : * to be equal to the current time.
217 : *
218 : * If apw_load_buffers() is terminated early by a shutdown request,
219 : * prevent dumping out our state below the loop, because we'd effectively
220 : * just truncate the saved state to however much we'd managed to preload.
221 : */
222 4 : if (first_time)
223 : {
224 4 : apw_load_buffers();
225 4 : final_dump_allowed = !ShutdownRequestPending;
226 4 : last_dump_time = GetCurrentTimestamp();
227 : }
228 :
229 : /* Periodically dump buffers until terminated. */
230 10 : while (!ShutdownRequestPending)
231 : {
232 : /* In case of a SIGHUP, just reload the configuration. */
233 6 : if (ConfigReloadPending)
234 : {
235 0 : ConfigReloadPending = false;
236 0 : ProcessConfigFile(PGC_SIGHUP);
237 : }
238 :
239 6 : if (autoprewarm_interval <= 0)
240 : {
241 : /* We're only dumping at shutdown, so just wait forever. */
242 6 : (void) WaitLatch(MyLatch,
243 : WL_LATCH_SET | WL_EXIT_ON_PM_DEATH,
244 : -1L,
245 : PG_WAIT_EXTENSION);
246 : }
247 : else
248 : {
249 : TimestampTz next_dump_time;
250 : long delay_in_ms;
251 :
252 : /* Compute the next dump time. */
253 0 : next_dump_time =
254 0 : TimestampTzPlusMilliseconds(last_dump_time,
255 : autoprewarm_interval * 1000);
256 : delay_in_ms =
257 0 : TimestampDifferenceMilliseconds(GetCurrentTimestamp(),
258 : next_dump_time);
259 :
260 : /* Perform a dump if it's time. */
261 0 : if (delay_in_ms <= 0)
262 : {
263 0 : last_dump_time = GetCurrentTimestamp();
264 0 : apw_dump_now(true, false);
265 0 : continue;
266 : }
267 :
268 : /* Sleep until the next dump time. */
269 0 : (void) WaitLatch(MyLatch,
270 : WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
271 : delay_in_ms,
272 : PG_WAIT_EXTENSION);
273 : }
274 :
275 : /* Reset the latch, loop. */
276 6 : ResetLatch(MyLatch);
277 : }
278 :
279 : /*
280 : * Dump one last time. We assume this is probably the result of a system
281 : * shutdown, although it's possible that we've merely been terminated.
282 : */
283 4 : if (final_dump_allowed)
284 4 : apw_dump_now(true, true);
285 : }
286 :
287 : /*
288 : * Read the dump file and launch per-database workers one at a time to
289 : * prewarm the buffers found there.
290 : */
291 : static void
292 4 : apw_load_buffers(void)
293 : {
294 4 : FILE *file = NULL;
295 : int num_elements,
296 : i;
297 : BlockInfoRecord *blkinfo;
298 : dsm_segment *seg;
299 :
300 : /*
301 : * Skip the prewarm if the dump file is in use; otherwise, prevent any
302 : * other process from writing it while we're using it.
303 : */
304 4 : LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE);
305 4 : if (apw_state->pid_using_dumpfile == InvalidPid)
306 4 : apw_state->pid_using_dumpfile = MyProcPid;
307 : else
308 : {
309 0 : LWLockRelease(&apw_state->lock);
310 0 : ereport(LOG,
311 : (errmsg("skipping prewarm because block dump file is being written by PID %d",
312 : (int) apw_state->pid_using_dumpfile)));
313 2 : return;
314 : }
315 4 : LWLockRelease(&apw_state->lock);
316 :
317 : /*
318 : * Open the block dump file. Exit quietly if it doesn't exist, but report
319 : * any other error.
320 : */
321 4 : file = AllocateFile(AUTOPREWARM_FILE, "r");
322 4 : if (!file)
323 : {
324 2 : if (errno == ENOENT)
325 : {
326 2 : LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE);
327 2 : apw_state->pid_using_dumpfile = InvalidPid;
328 2 : LWLockRelease(&apw_state->lock);
329 2 : return; /* No file to load. */
330 : }
331 0 : ereport(ERROR,
332 : (errcode_for_file_access(),
333 : errmsg("could not read file \"%s\": %m",
334 : AUTOPREWARM_FILE)));
335 : }
336 :
337 : /* First line of the file is a record count. */
338 2 : if (fscanf(file, "<<%d>>\n", &num_elements) != 1)
339 0 : ereport(ERROR,
340 : (errcode_for_file_access(),
341 : errmsg("could not read from file \"%s\": %m",
342 : AUTOPREWARM_FILE)));
343 :
344 : /* Allocate a dynamic shared memory segment to store the record data. */
345 2 : seg = dsm_create(sizeof(BlockInfoRecord) * num_elements, 0);
346 2 : blkinfo = (BlockInfoRecord *) dsm_segment_address(seg);
347 :
348 : /* Read records, one per line. */
349 430 : for (i = 0; i < num_elements; i++)
350 : {
351 : unsigned forknum;
352 :
353 428 : if (fscanf(file, "%u,%u,%u,%u,%u\n", &blkinfo[i].database,
354 428 : &blkinfo[i].tablespace, &blkinfo[i].filenumber,
355 428 : &forknum, &blkinfo[i].blocknum) != 5)
356 0 : ereport(ERROR,
357 : (errmsg("autoprewarm block dump file is corrupted at line %d",
358 : i + 1)));
359 428 : blkinfo[i].forknum = forknum;
360 : }
361 :
362 2 : FreeFile(file);
363 :
364 : /* Sort the blocks to be loaded. */
365 2 : qsort(blkinfo, num_elements, sizeof(BlockInfoRecord),
366 : apw_compare_blockinfo);
367 :
368 : /* Populate shared memory state. */
369 2 : apw_state->block_info_handle = dsm_segment_handle(seg);
370 2 : apw_state->prewarm_start_idx = apw_state->prewarm_stop_idx = 0;
371 2 : apw_state->prewarmed_blocks = 0;
372 :
373 : /* Get the info position of the first block of the next database. */
374 4 : while (apw_state->prewarm_start_idx < num_elements)
375 : {
376 2 : int j = apw_state->prewarm_start_idx;
377 2 : Oid current_db = blkinfo[j].database;
378 :
379 : /*
380 : * Advance the prewarm_stop_idx to the first BlockInfoRecord that does
381 : * not belong to this database.
382 : */
383 2 : j++;
384 428 : while (j < num_elements)
385 : {
386 426 : if (current_db != blkinfo[j].database)
387 : {
388 : /*
389 : * Combine BlockInfoRecords for global objects with those of
390 : * the database.
391 : */
392 2 : if (current_db != InvalidOid)
393 0 : break;
394 2 : current_db = blkinfo[j].database;
395 : }
396 :
397 426 : j++;
398 : }
399 :
400 : /*
401 : * If we reach this point with current_db == InvalidOid, then only
402 : * BlockInfoRecords belonging to global objects exist. We can't
403 : * prewarm without a database connection, so just bail out.
404 : */
405 2 : if (current_db == InvalidOid)
406 0 : break;
407 :
408 : /* Configure stop point and database for next per-database worker. */
409 2 : apw_state->prewarm_stop_idx = j;
410 2 : apw_state->database = current_db;
411 : Assert(apw_state->prewarm_start_idx < apw_state->prewarm_stop_idx);
412 :
413 : /* If we've run out of free buffers, don't launch another worker. */
414 2 : if (!have_free_buffer())
415 0 : break;
416 :
417 : /*
418 : * Likewise, don't launch if we've already been told to shut down.
419 : * (The launch would fail anyway, but we might as well skip it.)
420 : */
421 2 : if (ShutdownRequestPending)
422 0 : break;
423 :
424 : /*
425 : * Start a per-database worker to load blocks for this database; this
426 : * function will return once the per-database worker exits.
427 : */
428 2 : apw_start_database_worker();
429 :
430 : /* Prepare for next database. */
431 2 : apw_state->prewarm_start_idx = apw_state->prewarm_stop_idx;
432 : }
433 :
434 : /* Clean up. */
435 2 : dsm_detach(seg);
436 2 : LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE);
437 2 : apw_state->block_info_handle = DSM_HANDLE_INVALID;
438 2 : apw_state->pid_using_dumpfile = InvalidPid;
439 2 : LWLockRelease(&apw_state->lock);
440 :
441 : /* Report our success, if we were able to finish. */
442 2 : if (!ShutdownRequestPending)
443 2 : ereport(LOG,
444 : (errmsg("autoprewarm successfully prewarmed %d of %d previously-loaded blocks",
445 : apw_state->prewarmed_blocks, num_elements)));
446 : }
447 :
448 : /*
449 : * Return the next block number of a specific relation and fork to read
450 : * according to the array of BlockInfoRecord.
451 : */
452 : static BlockNumber
453 554 : apw_read_stream_next_block(ReadStream *stream,
454 : void *callback_private_data,
455 : void *per_buffer_data)
456 : {
457 554 : AutoPrewarmReadStreamData *p = callback_private_data;
458 :
459 554 : CHECK_FOR_INTERRUPTS();
460 :
461 554 : while (p->pos < apw_state->prewarm_stop_idx)
462 : {
463 552 : BlockInfoRecord blk = p->block_info[p->pos];
464 :
465 552 : if (!have_free_buffer())
466 : {
467 0 : p->pos = apw_state->prewarm_stop_idx;
468 552 : return InvalidBlockNumber;
469 : }
470 :
471 552 : if (blk.tablespace != p->tablespace)
472 2 : return InvalidBlockNumber;
473 :
474 550 : if (blk.filenumber != p->filenumber)
475 94 : return InvalidBlockNumber;
476 :
477 456 : if (blk.forknum != p->forknum)
478 28 : return InvalidBlockNumber;
479 :
480 428 : p->pos++;
481 :
482 : /*
483 : * Check whether blocknum is valid and within fork file size.
484 : * Fast-forward through any invalid blocks. We want p->pos to reflect
485 : * the location of the next relation or fork before ending the stream.
486 : */
487 428 : if (blk.blocknum >= p->nblocks)
488 0 : continue;
489 :
490 428 : return blk.blocknum;
491 : }
492 :
493 2 : return InvalidBlockNumber;
494 : }
495 :
496 : /*
497 : * Prewarm all blocks for one database (and possibly also global objects, if
498 : * those got grouped with this database).
499 : */
500 : void
501 2 : autoprewarm_database_main(Datum main_arg)
502 : {
503 : BlockInfoRecord *block_info;
504 : int i;
505 : BlockInfoRecord blk;
506 : dsm_segment *seg;
507 :
508 : /* Establish signal handlers; once that's done, unblock signals. */
509 2 : pqsignal(SIGTERM, die);
510 2 : BackgroundWorkerUnblockSignals();
511 :
512 : /* Connect to correct database and get block information. */
513 2 : apw_init_shmem();
514 2 : seg = dsm_attach(apw_state->block_info_handle);
515 2 : if (seg == NULL)
516 0 : ereport(ERROR,
517 : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
518 : errmsg("could not map dynamic shared memory segment")));
519 2 : BackgroundWorkerInitializeConnectionByOid(apw_state->database, InvalidOid, 0);
520 2 : block_info = (BlockInfoRecord *) dsm_segment_address(seg);
521 :
522 2 : i = apw_state->prewarm_start_idx;
523 2 : blk = block_info[i];
524 :
525 : /*
526 : * Loop until we run out of blocks to prewarm or until we run out of free
527 : * buffers.
528 : */
529 100 : while (i < apw_state->prewarm_stop_idx && have_free_buffer())
530 : {
531 98 : Oid tablespace = blk.tablespace;
532 98 : RelFileNumber filenumber = blk.filenumber;
533 : Oid reloid;
534 : Relation rel;
535 :
536 : /*
537 : * All blocks between prewarm_start_idx and prewarm_stop_idx should
538 : * belong either to global objects or the same database.
539 : */
540 : Assert(blk.database == apw_state->database || blk.database == 0);
541 :
542 98 : StartTransactionCommand();
543 :
544 98 : reloid = RelidByRelfilenumber(blk.tablespace, blk.filenumber);
545 196 : if (!OidIsValid(reloid) ||
546 98 : (rel = try_relation_open(reloid, AccessShareLock)) == NULL)
547 : {
548 : /* We failed to open the relation, so there is nothing to close. */
549 0 : CommitTransactionCommand();
550 :
551 : /*
552 : * Fast-forward to the next relation. We want to skip all of the
553 : * other records referencing this relation since we know we can't
554 : * open it. That way, we avoid repeatedly trying and failing to
555 : * open the same relation.
556 : */
557 0 : for (; i < apw_state->prewarm_stop_idx; i++)
558 : {
559 0 : blk = block_info[i];
560 0 : if (blk.tablespace != tablespace ||
561 0 : blk.filenumber != filenumber)
562 : break;
563 : }
564 :
565 : /* Time to try and open our newfound relation */
566 0 : continue;
567 : }
568 :
569 : /*
570 : * We have a relation; now let's loop until we find a valid fork of
571 : * the relation or we run out of free buffers. Once we've read from
572 : * all valid forks or run out of options, we'll close the relation and
573 : * move on.
574 : */
575 224 : while (i < apw_state->prewarm_stop_idx &&
576 222 : blk.tablespace == tablespace &&
577 346 : blk.filenumber == filenumber &&
578 126 : have_free_buffer())
579 : {
580 126 : ForkNumber forknum = blk.forknum;
581 : BlockNumber nblocks;
582 : struct AutoPrewarmReadStreamData p;
583 : ReadStream *stream;
584 : Buffer buf;
585 :
586 : /*
587 : * smgrexists is not safe for illegal forknum, hence check whether
588 : * the passed forknum is valid before using it in smgrexists.
589 : */
590 126 : if (blk.forknum <= InvalidForkNumber ||
591 126 : blk.forknum > MAX_FORKNUM ||
592 126 : !smgrexists(RelationGetSmgr(rel), blk.forknum))
593 : {
594 : /*
595 : * Fast-forward to the next fork. We want to skip all of the
596 : * other records referencing this fork since we already know
597 : * it's not valid.
598 : */
599 0 : for (; i < apw_state->prewarm_stop_idx; i++)
600 : {
601 0 : blk = block_info[i];
602 0 : if (blk.tablespace != tablespace ||
603 0 : blk.filenumber != filenumber ||
604 0 : blk.forknum != forknum)
605 : break;
606 : }
607 :
608 : /* Time to check if this newfound fork is valid */
609 0 : continue;
610 : }
611 :
612 126 : nblocks = RelationGetNumberOfBlocksInFork(rel, blk.forknum);
613 :
614 126 : p = (struct AutoPrewarmReadStreamData)
615 : {
616 : .block_info = block_info,
617 : .pos = i,
618 : .tablespace = tablespace,
619 : .filenumber = filenumber,
620 : .forknum = forknum,
621 : .nblocks = nblocks,
622 : };
623 :
624 126 : stream = read_stream_begin_relation(READ_STREAM_DEFAULT |
625 : READ_STREAM_USE_BATCHING,
626 : NULL,
627 : rel,
628 : p.forknum,
629 : apw_read_stream_next_block,
630 : &p,
631 : 0);
632 :
633 : /*
634 : * Loop until we've prewarmed all the blocks from this fork. The
635 : * read stream callback will check that we still have free buffers
636 : * before requesting each block from the read stream API.
637 : */
638 554 : while ((buf = read_stream_next_buffer(stream, NULL)) != InvalidBuffer)
639 : {
640 428 : apw_state->prewarmed_blocks++;
641 428 : ReleaseBuffer(buf);
642 : }
643 :
644 126 : read_stream_end(stream);
645 :
646 : /* Advance i past all the blocks just prewarmed. */
647 126 : i = p.pos;
648 126 : blk = block_info[i];
649 : }
650 :
651 98 : relation_close(rel, AccessShareLock);
652 98 : CommitTransactionCommand();
653 : }
654 :
655 2 : dsm_detach(seg);
656 2 : }
657 :
658 : /*
659 : * Dump information on blocks in shared buffers. We use a text format here
660 : * so that it's easy to understand and even change the file contents if
661 : * necessary.
662 : * Returns the number of blocks dumped.
663 : */
664 : static int
665 6 : apw_dump_now(bool is_bgworker, bool dump_unlogged)
666 : {
667 : int num_blocks;
668 : int i;
669 : int ret;
670 : BlockInfoRecord *block_info_array;
671 : BufferDesc *bufHdr;
672 : FILE *file;
673 : char transient_dump_file_path[MAXPGPATH];
674 : pid_t pid;
675 :
676 6 : LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE);
677 6 : pid = apw_state->pid_using_dumpfile;
678 6 : if (apw_state->pid_using_dumpfile == InvalidPid)
679 6 : apw_state->pid_using_dumpfile = MyProcPid;
680 6 : LWLockRelease(&apw_state->lock);
681 :
682 6 : if (pid != InvalidPid)
683 : {
684 0 : if (!is_bgworker)
685 0 : ereport(ERROR,
686 : (errmsg("could not perform block dump because dump file is being used by PID %d",
687 : (int) apw_state->pid_using_dumpfile)));
688 :
689 0 : ereport(LOG,
690 : (errmsg("skipping block dump because it is already being performed by PID %d",
691 : (int) apw_state->pid_using_dumpfile)));
692 0 : return 0;
693 : }
694 :
695 : block_info_array =
696 6 : (BlockInfoRecord *) palloc(sizeof(BlockInfoRecord) * NBuffers);
697 :
698 98310 : for (num_blocks = 0, i = 0; i < NBuffers; i++)
699 : {
700 : uint32 buf_state;
701 :
702 98304 : CHECK_FOR_INTERRUPTS();
703 :
704 98304 : bufHdr = GetBufferDescriptor(i);
705 :
706 : /* Lock each buffer header before inspecting. */
707 98304 : buf_state = LockBufHdr(bufHdr);
708 :
709 : /*
710 : * Unlogged tables will be automatically truncated after a crash or
711 : * unclean shutdown. In such cases we need not prewarm them. Dump them
712 : * only if requested by caller.
713 : */
714 98304 : if (buf_state & BM_TAG_VALID &&
715 1284 : ((buf_state & BM_PERMANENT) || dump_unlogged))
716 : {
717 1284 : block_info_array[num_blocks].database = bufHdr->tag.dbOid;
718 1284 : block_info_array[num_blocks].tablespace = bufHdr->tag.spcOid;
719 2568 : block_info_array[num_blocks].filenumber =
720 1284 : BufTagGetRelNumber(&bufHdr->tag);
721 2568 : block_info_array[num_blocks].forknum =
722 1284 : BufTagGetForkNum(&bufHdr->tag);
723 1284 : block_info_array[num_blocks].blocknum = bufHdr->tag.blockNum;
724 1284 : ++num_blocks;
725 : }
726 :
727 98304 : UnlockBufHdr(bufHdr, buf_state);
728 : }
729 :
730 6 : snprintf(transient_dump_file_path, MAXPGPATH, "%s.tmp", AUTOPREWARM_FILE);
731 6 : file = AllocateFile(transient_dump_file_path, "w");
732 6 : if (!file)
733 0 : ereport(ERROR,
734 : (errcode_for_file_access(),
735 : errmsg("could not open file \"%s\": %m",
736 : transient_dump_file_path)));
737 :
738 6 : ret = fprintf(file, "<<%d>>\n", num_blocks);
739 6 : if (ret < 0)
740 : {
741 0 : int save_errno = errno;
742 :
743 0 : FreeFile(file);
744 0 : unlink(transient_dump_file_path);
745 0 : errno = save_errno;
746 0 : ereport(ERROR,
747 : (errcode_for_file_access(),
748 : errmsg("could not write to file \"%s\": %m",
749 : transient_dump_file_path)));
750 : }
751 :
752 1290 : for (i = 0; i < num_blocks; i++)
753 : {
754 1284 : CHECK_FOR_INTERRUPTS();
755 :
756 1284 : ret = fprintf(file, "%u,%u,%u,%u,%u\n",
757 1284 : block_info_array[i].database,
758 1284 : block_info_array[i].tablespace,
759 1284 : block_info_array[i].filenumber,
760 1284 : (uint32) block_info_array[i].forknum,
761 1284 : block_info_array[i].blocknum);
762 1284 : if (ret < 0)
763 : {
764 0 : int save_errno = errno;
765 :
766 0 : FreeFile(file);
767 0 : unlink(transient_dump_file_path);
768 0 : errno = save_errno;
769 0 : ereport(ERROR,
770 : (errcode_for_file_access(),
771 : errmsg("could not write to file \"%s\": %m",
772 : transient_dump_file_path)));
773 : }
774 : }
775 :
776 6 : pfree(block_info_array);
777 :
778 : /*
779 : * Rename transient_dump_file_path to AUTOPREWARM_FILE to make things
780 : * permanent.
781 : */
782 6 : ret = FreeFile(file);
783 6 : if (ret != 0)
784 : {
785 0 : int save_errno = errno;
786 :
787 0 : unlink(transient_dump_file_path);
788 0 : errno = save_errno;
789 0 : ereport(ERROR,
790 : (errcode_for_file_access(),
791 : errmsg("could not close file \"%s\": %m",
792 : transient_dump_file_path)));
793 : }
794 :
795 6 : (void) durable_rename(transient_dump_file_path, AUTOPREWARM_FILE, ERROR);
796 6 : apw_state->pid_using_dumpfile = InvalidPid;
797 :
798 6 : ereport(DEBUG1,
799 : (errmsg_internal("wrote block details for %d blocks", num_blocks)));
800 6 : return num_blocks;
801 : }
802 :
803 : /*
804 : * SQL-callable function to launch autoprewarm.
805 : */
806 : Datum
807 0 : autoprewarm_start_worker(PG_FUNCTION_ARGS)
808 : {
809 : pid_t pid;
810 :
811 0 : if (!autoprewarm)
812 0 : ereport(ERROR,
813 : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
814 : errmsg("autoprewarm is disabled")));
815 :
816 0 : apw_init_shmem();
817 0 : LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE);
818 0 : pid = apw_state->bgworker_pid;
819 0 : LWLockRelease(&apw_state->lock);
820 :
821 0 : if (pid != InvalidPid)
822 0 : ereport(ERROR,
823 : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
824 : errmsg("autoprewarm worker is already running under PID %d",
825 : (int) pid)));
826 :
827 0 : apw_start_leader_worker();
828 :
829 0 : PG_RETURN_VOID();
830 : }
831 :
832 : /*
833 : * SQL-callable function to perform an immediate block dump.
834 : *
835 : * Note: this is declared to return int8, as insurance against some
836 : * very distant day when we might make NBuffers wider than int.
837 : */
838 : Datum
839 2 : autoprewarm_dump_now(PG_FUNCTION_ARGS)
840 : {
841 : int num_blocks;
842 :
843 2 : apw_init_shmem();
844 :
845 2 : PG_ENSURE_ERROR_CLEANUP(apw_detach_shmem, 0);
846 : {
847 2 : num_blocks = apw_dump_now(false, true);
848 : }
849 2 : PG_END_ENSURE_ERROR_CLEANUP(apw_detach_shmem, 0);
850 :
851 2 : PG_RETURN_INT64((int64) num_blocks);
852 : }
853 :
854 : static void
855 4 : apw_init_state(void *ptr)
856 : {
857 4 : AutoPrewarmSharedState *state = (AutoPrewarmSharedState *) ptr;
858 :
859 4 : LWLockInitialize(&state->lock, LWLockNewTrancheId());
860 4 : state->bgworker_pid = InvalidPid;
861 4 : state->pid_using_dumpfile = InvalidPid;
862 4 : }
863 :
864 : /*
865 : * Allocate and initialize autoprewarm related shared memory, if not already
866 : * done, and set up backend-local pointer to that state. Returns true if an
867 : * existing shared memory segment was found.
868 : */
869 : static bool
870 8 : apw_init_shmem(void)
871 : {
872 : bool found;
873 :
874 8 : apw_state = GetNamedDSMSegment("autoprewarm",
875 : sizeof(AutoPrewarmSharedState),
876 : apw_init_state,
877 : &found);
878 8 : LWLockRegisterTranche(apw_state->lock.tranche, "autoprewarm");
879 :
880 8 : return found;
881 : }
882 :
883 : /*
884 : * Clear our PID from autoprewarm shared state.
885 : */
886 : static void
887 4 : apw_detach_shmem(int code, Datum arg)
888 : {
889 4 : LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE);
890 4 : if (apw_state->pid_using_dumpfile == MyProcPid)
891 0 : apw_state->pid_using_dumpfile = InvalidPid;
892 4 : if (apw_state->bgworker_pid == MyProcPid)
893 4 : apw_state->bgworker_pid = InvalidPid;
894 4 : LWLockRelease(&apw_state->lock);
895 4 : }
896 :
897 : /*
898 : * Start autoprewarm leader worker process.
899 : */
900 : static void
901 4 : apw_start_leader_worker(void)
902 : {
903 4 : BackgroundWorker worker = {0};
904 : BackgroundWorkerHandle *handle;
905 : BgwHandleStatus status;
906 : pid_t pid;
907 :
908 4 : worker.bgw_flags = BGWORKER_SHMEM_ACCESS;
909 4 : worker.bgw_start_time = BgWorkerStart_ConsistentState;
910 4 : strcpy(worker.bgw_library_name, "pg_prewarm");
911 4 : strcpy(worker.bgw_function_name, "autoprewarm_main");
912 4 : strcpy(worker.bgw_name, "autoprewarm leader");
913 4 : strcpy(worker.bgw_type, "autoprewarm leader");
914 :
915 4 : if (process_shared_preload_libraries_in_progress)
916 : {
917 4 : RegisterBackgroundWorker(&worker);
918 4 : return;
919 : }
920 :
921 : /* must set notify PID to wait for startup */
922 0 : worker.bgw_notify_pid = MyProcPid;
923 :
924 0 : if (!RegisterDynamicBackgroundWorker(&worker, &handle))
925 0 : ereport(ERROR,
926 : (errcode(ERRCODE_INSUFFICIENT_RESOURCES),
927 : errmsg("could not register background process"),
928 : errhint("You may need to increase \"max_worker_processes\".")));
929 :
930 0 : status = WaitForBackgroundWorkerStartup(handle, &pid);
931 0 : if (status != BGWH_STARTED)
932 0 : ereport(ERROR,
933 : (errcode(ERRCODE_INSUFFICIENT_RESOURCES),
934 : errmsg("could not start background process"),
935 : errhint("More details may be available in the server log.")));
936 : }
937 :
938 : /*
939 : * Start autoprewarm per-database worker process.
940 : */
941 : static void
942 2 : apw_start_database_worker(void)
943 : {
944 2 : BackgroundWorker worker = {0};
945 : BackgroundWorkerHandle *handle;
946 :
947 2 : worker.bgw_flags =
948 : BGWORKER_SHMEM_ACCESS | BGWORKER_BACKEND_DATABASE_CONNECTION;
949 2 : worker.bgw_start_time = BgWorkerStart_ConsistentState;
950 2 : worker.bgw_restart_time = BGW_NEVER_RESTART;
951 2 : strcpy(worker.bgw_library_name, "pg_prewarm");
952 2 : strcpy(worker.bgw_function_name, "autoprewarm_database_main");
953 2 : strcpy(worker.bgw_name, "autoprewarm worker");
954 2 : strcpy(worker.bgw_type, "autoprewarm worker");
955 :
956 : /* must set notify PID to wait for shutdown */
957 2 : worker.bgw_notify_pid = MyProcPid;
958 :
959 2 : if (!RegisterDynamicBackgroundWorker(&worker, &handle))
960 0 : ereport(ERROR,
961 : (errcode(ERRCODE_INSUFFICIENT_RESOURCES),
962 : errmsg("registering dynamic bgworker autoprewarm failed"),
963 : errhint("Consider increasing the configuration parameter \"%s\".", "max_worker_processes")));
964 :
965 : /*
966 : * Ignore return value; if it fails, postmaster has died, but we have
967 : * checks for that elsewhere.
968 : */
969 2 : WaitForBackgroundWorkerShutdown(handle);
970 2 : }
971 :
972 : /* Compare member elements to check whether they are not equal. */
973 : #define cmp_member_elem(fld) \
974 : do { \
975 : if (a->fld < b->fld) \
976 : return -1; \
977 : else if (a->fld > b->fld) \
978 : return 1; \
979 : } while(0)
980 :
981 : /*
982 : * apw_compare_blockinfo
983 : *
984 : * We depend on all records for a particular database being consecutive
985 : * in the dump file; each per-database worker will preload blocks until
986 : * it sees a block for some other database. Sorting by tablespace,
987 : * filenumber, forknum, and blocknum isn't critical for correctness, but
988 : * helps us get a sequential I/O pattern.
989 : */
990 : static int
991 3516 : apw_compare_blockinfo(const void *p, const void *q)
992 : {
993 3516 : const BlockInfoRecord *a = (const BlockInfoRecord *) p;
994 3516 : const BlockInfoRecord *b = (const BlockInfoRecord *) q;
995 :
996 3516 : cmp_member_elem(database);
997 3390 : cmp_member_elem(tablespace);
998 3390 : cmp_member_elem(filenumber);
999 1400 : cmp_member_elem(forknum);
1000 1192 : cmp_member_elem(blocknum);
1001 :
1002 0 : return 0;
1003 : }
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