-
Notifications
You must be signed in to change notification settings - Fork 5
/
pg_hibernate_9.3.c
1011 lines (834 loc) · 26.5 KB
/
pg_hibernate_9.3.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
#include "postgres.h"
#if PG_VERSION_NUM >= 90300 && PG_VERSION_NUM < 90400
#include "pg_hibernator.h"
PG_MODULE_MAGIC;
/*
* Overall flow of control:
*
* _PG_init() registers a BGWorker for BufferSaver process, and one BGWorker
* each for the save-files it finds in $PGDATA/pg_hibernator/.
*
* On shutdown request, the BufferSaver scans the shared buffers and saves the
* list of blocks currently in memory to the $PGDATA/pg_hibernator/ directory;
* one save-file for each database.
*
* When launched, the BlockReader reads the save-file assigned to it, connects
* to the database represented by that save-file, and restores the blocks
* identified by the list of blocks in save-file.
*
* Database numbers (and hence save-files with names) 0 and 1 are reserved;
* In _PG_init() 0 is used to identify and register the BufferSaver, and 1 is
* reserved in BufferSaver for save-file that contains global objects.
*/
typedef struct SharedState
{
LWLockId lock;
} SharedState;
static void SharedStateSetup(void);
static void shmem_startup(void);
static shmem_startup_hook_type prev_shmem_startup_hook = NULL;
static SharedState *shared_mem = NULL;
typedef struct SavedBuffer
{
Oid database;
Oid filenode; /* On-disk marker: 'r', for Relfilenode */
ForkNumber forknum; /* On-disk marker: 'f' */
BlockNumber blocknum; /* On-disk marker: 'b' */
/* On-disk marker: 'N', for range of N blocks */
} SavedBuffer;
/* Primary functions */
void _PG_init(void);
static void DefineGUCs(void);
static void CreateDirectory(void);
static void RegisterBlockReaders(void);
static bool RegisterWorker(int id);
static void BlockReaderMain(Datum main_arg);
static void ReadBlocks(int filenum);
static void BufferSaverMain(Datum main_arg);
static void SaveBuffers(void);
/* Secondary/supporting functions */
static void sigtermHandler(SIGNAL_ARGS);
static void sighupHandler(SIGNAL_ARGS);
static void WorkerCommon(void);
static int SavedBufferCmp(const void *a, const void *b);
static Oid GetRelOid(Oid filenode);
/* flags set by signal handlers */
static volatile sig_atomic_t got_sighup = false;
static volatile sig_atomic_t got_sigterm = false;
/* GUC variables */
static bool guc_enabled = true; /* Is the extension enabled? */
static bool guc_parallel_enabled = false; /* Can we restore databases in parallel? */
static char* guc_default_database = "postgres"; /* Default DB to connect to. */
/*
* Signal handler for SIGTERM
*
* Set a flag to notify the main loop of the signal received, and set our latch
* to wake it up.
*/
static void
sigtermHandler(SIGNAL_ARGS)
{
int save_errno = errno;
got_sigterm = true;
if (MyProc)
SetLatch(&MyProc->procLatch);
errno = save_errno;
}
/*
* Signal handler for SIGHUP
*
* Used only in BufferSaver. Set a flag to notify the main loop of the signal
* received, and set our latch to wake it up.
*/
static void
sighupHandler(SIGNAL_ARGS)
{
got_sighup = true;
if (MyProc)
SetLatch(&MyProc->procLatch);
}
/* This extension's entry point. */
void
_PG_init(void)
{
SharedStateSetup();
DefineGUCs();
CreateDirectory();
/*
* Create the BufferSaver irrespective of whether the extension is enabled.
* The BufferSaver will check the parameter when it receives SIGTERM, and act
* accordingly. This way the user can start the server with the extension
* disabled (pg_hibernator.enabled=false), enable the extension while
* server is running, and expect the save-files to be created when the server
* shuts down.
*/
/* Register the BufferSaver worker */
RegisterWorker(0);
/*
* In Postgres version 9.4 and above, we use the dynamic background worker
* infrastructure for BlockReaders, and the BufferSaver process does the
* legwork of registering the BlockReader workers.
*/
/*
* In Postgres 9.3 we use regular workers for BlockReader processes, and
* they are registered right here.
*/
RegisterBlockReaders(); /* Register the BlockReader worker processes */
}
static void
SharedStateSetup()
{
/* Request one LWLock */
RequestAddinLWLocks(1);
/* Register our hook for Shared Memory initialization */
prev_shmem_startup_hook = shmem_startup_hook;
shmem_startup_hook = shmem_startup;
}
static void
shmem_startup()
{
bool found;
/* reset in case this is a restart within the postmaster */
shared_mem = NULL;
if (prev_shmem_startup_hook)
prev_shmem_startup_hook();
LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);
shared_mem = ShmemInitStruct("pg_hibernator",
sizeof(SharedState),
&found);
if (!found)
{
/* First time through */
shared_mem->lock = LWLockAssign();
}
LWLockRelease(AddinShmemInitLock);
}
/* Declare the parameters */
static void
DefineGUCs(void)
{
DefineCustomBoolVariable("pg_hibernator.enabled",
"Enable/disable automatic hibernation.",
NULL,
&guc_enabled,
guc_enabled,
PGC_SIGHUP,
0,
NULL,
NULL,
NULL);
DefineCustomBoolVariable("pg_hibernator.parallel",
"Enable/disable restoring databases in parallel.",
NULL,
&guc_parallel_enabled,
guc_parallel_enabled,
PGC_SIGHUP,
0,
NULL,
NULL,
NULL);
DefineCustomStringVariable("pg_hibernator.default_database",
"Database to connect to, by default.",
"Postgres Hibernator will connect to this database when saving buffers, and when reading blocks of global objects.",
&guc_default_database,
guc_default_database,
PGC_POSTMASTER,
0,
NULL,
NULL,
NULL);
}
/*
* Create the directory to save files in, if it doesn't already exist.
*/
static void
CreateDirectory(void)
{
struct stat st;
const char *hibernate_dir = SAVE_LOCATION;
if (stat(hibernate_dir, &st) == 0)
{
/* Is it not a directory? */
if (!S_ISDIR(st.st_mode))
ereport(ERROR,
(errmsg("\"%s\" exists but is not a directory, hence disabling hibernation",
hibernate_dir)));
}
else
{
/* Directory does not exist? */
if (errno == ENOENT)
{
/* Create directory */
if (mkdir(hibernate_dir, S_IRWXU) < 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not create directory \"%s\": %m",
hibernate_dir)));
}
else
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not stat directory \"%s\": %m", hibernate_dir)));
}
/* XXX: Should we make sure we have write permissions on this directory? */
}
static void
RegisterBlockReaders(void)
{
DIR *dir;
const char *hibernate_dir;
struct dirent *dent;
/* Don't create BlockReaders if the extension is disabled. */
if (!guc_enabled)
return;
hibernate_dir = SAVE_LOCATION;
dir = opendir(hibernate_dir);
if (dir == NULL)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not open directory \"%s\": %m", hibernate_dir)));
errno = 0;
while ((dent = readdir(dir)) != NULL)
{
int filenum;
/* Skip worker creation if we can't parse the file name. */
if (!parseSavefileName(dent->d_name, &filenum))
continue;
RegisterWorker(filenum);
}
if (errno != 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("error encountered during readdir \"%s\": %m", hibernate_dir)));
closedir(dir);
}
static bool
RegisterWorker(int id)
{
BackgroundWorker worker;
/*
* Protect against the possibility of more members being added to the
* structure than we are using below.
*/
MemSet(&worker, 0, sizeof(worker));
worker.bgw_main_arg = Int32GetDatum(id);
worker.bgw_flags = BGWORKER_SHMEM_ACCESS | BGWORKER_BACKEND_DATABASE_CONNECTION;
if (id == 0)
{
/* Register the BufferSaver background worker */
worker.bgw_start_time = BgWorkerStart_ConsistentState;
worker.bgw_restart_time = 0; /* Keep the BufferSaver running */
worker.bgw_main = BufferSaverMain;
snprintf(worker.bgw_name, BGW_MAXLEN, "Buffer Saver");
}
else
{
/* Register a BlockReader background worker process */
worker.bgw_start_time = BgWorkerStart_ConsistentState;
worker.bgw_restart_time = BGW_NEVER_RESTART; /* Don't restart BlockReaders upon error */
worker.bgw_main = BlockReaderMain;
snprintf(worker.bgw_name, BGW_MAXLEN, "Block Reader %d", id);
}
/*
* This API is deficient as it can't report failure; it just does an
* ereport(LOG) on failure.
*/
RegisterBackgroundWorker(&worker);
return true;
}
static void
WorkerCommon(void)
{
/* Establish signal handlers before unblocking signals. */
pqsignal(SIGHUP, sighupHandler);
pqsignal(SIGTERM, sigtermHandler);
/* We're now ready to receive signals */
BackgroundWorkerUnblockSignals();
}
static void
BlockReaderMain(Datum main_arg)
{
int id = DatumGetInt32(main_arg);
DIR *dir;
const char *hibernate_dir = SAVE_LOCATION;
struct dirent *dent;
int filenum;
WorkerCommon();
dir = opendir(hibernate_dir);
if (dir == NULL)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("Block Reader %d: could not open directory \"%s\": %m",
id, hibernate_dir)));
/*
* Reset errno before making system call, so that we don't trip over an
* error that occurred earlier.
*/
errno = 0;
/* Scan the directory looking for file this worker is assigned to. */
while ((dent = readdir(dir)) != NULL)
{
if (!parseSavefileName(dent->d_name, &filenum))
continue;
/* Stop if this is the file assigned to this worker. */
if (filenum == id)
break;
}
if (dent == NULL)
{
closedir(dir);
if (errno != 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("Block Reader %d: encountered error during readdir \"%s\": %m",
filenum, hibernate_dir)));
ereport(ERROR,
(errmsg("Block Reader %d: could not find its save-file", filenum)));
}
closedir(dir);
/* We found the file we're supposed to restore. */
/* If parallelism is disabled, wait until it's our turn to read blocks. */
/*
* Despite the warning on LWLockAcquire() that an LWLock should not be held
* for more than a few seconds, because holding one causes the query-cancel
* and die signals are blocked, I think it's safe to hold an LWLock around
* a database buffer restore operation since we're a background worker and
* query-cancel is intended for regular backends, and die() (a.k.a SIGTERM)
* is handled by us, and we promptly honor it.
*/
if (!guc_parallel_enabled)
LWLockAcquire(shared_mem->lock, LW_EXCLUSIVE);
ReadBlocks(filenum);
if (!guc_parallel_enabled)
LWLockRelease(shared_mem->lock);
/*
* Exit with non-zero status to ensure that this worker is not restarted.
*
* For any backend connected to shared-buffers, an exit code other than 0 or 1
* causes a system-wide restart, so we have no choice but to use 1. Since an
* ERROR also causes exit code 1, it would've been nice if we could use some
* other code to signal normal exit, so that a monitor could differentiate
* between a successful exit, and an exit due to an ERROR.
*
* To get around this ambiguity we resort to logging a message to server log;
* this message should console the user that everything went okay, even though
* the exit code is 1.
*/
ereport(LOG, (errmsg("Block Reader %d: all blocks read successfully", filenum)));
proc_exit(1);
}
static void
ReadBlocks(int filenum)
{
FILE *file;
char record_type;
char *dbname;
Oid record_filenode;
ForkNumber record_forknum;
BlockNumber record_blocknum;
BlockNumber record_range;
int log_level = DEBUG3;
Oid relOid = InvalidOid;
Relation rel = NULL;
bool skip_relation = false;
bool skip_fork = false;
bool skip_block = false;
BlockNumber nblocks = 0;
BlockNumber blocks_restored = 0;
const char *filepath;
/*
* If this condition changes, then this code, and the code in the writer
* will need to be changed; especially the format specifiers in log and
* error messages.
*/
StaticAssertStmt(MaxBlockNumber == 0xFFFFFFFE, "Code may need review.");
filepath = getSavefileName(filenum);
file = fileOpen(filepath, PG_BINARY_R);
dbname = readDBName(file, filepath);
/*
* When restoring global objects, the dbname is zero-length string, and non-
* zero length otherwise. And filenum is never expected to be smaller than 1.
*/
Assert(filenum >= 1);
Assert(filenum == 1 ? strlen(dbname) == 0 : strlen(dbname) > 0);
/* To restore the global objects, use default database */
BackgroundWorkerInitializeConnection(filenum == 1 ? guc_default_database : dbname, NULL);
SetCurrentStatementStartTimestamp();
StartTransactionCommand();
SPI_connect();
PushActiveSnapshot(GetTransactionSnapshot());
pgstat_report_activity(STATE_RUNNING, "restoring buffers");
/*
* Note that in case of a read error, we will leak relcache entry that we may
* currently have open. In case of EOF, we close the relation after the loop.
*/
while (fileRead(&record_type, 1, file, true, filepath))
{
/*
* If we want to process the signals, this seems to be the best place
* to do it. Generally the backends refrain from processing config file
* while in transaction, but that's more for the fear of allowing GUC
* changes to affect expression evaluation, causing different results
* for the same expression in a transaction. Since this worker is not
* processing any queries, it is okay to process the config file here.
*
* Even though it's okay to process SIGHUP here, doing so doesn't add
* any value. The only reason we might want to process config file here
* would be to allow the user to interrupt the BlockReader's operation
* by changing this extenstion's GUC parameter. But the user can do that
* anyway, using SIGTERM or pg_terminate_backend().
*/
/* Stop processing the save-file if the Postmaster wants us to die. */
if (got_sigterm)
break;
ereport(log_level,
(errmsg("record type %x - %c", record_type, record_type)));
switch (record_type)
{
case 'r':
{
/* Close the previous relation, if any. */
if (rel)
{
relation_close(rel, AccessShareLock);
rel = NULL;
}
record_forknum = InvalidForkNumber;
record_blocknum = InvalidBlockNumber;
nblocks = 0;
fileRead(&record_filenode, sizeof(Oid), file, false, filepath);
relOid = GetRelOid(record_filenode);
ereport(log_level, (errmsg("processing filenode %u, relation %u",
record_filenode, relOid)));
/*
* If the relation has been rewritten/dropped since we saved it,
* just skip it and process the next relation.
*/
if (relOid == InvalidOid)
skip_relation = true;
else
{
skip_relation = false;
/* Open the relation */
rel = relation_open(relOid, AccessShareLock);
RelationOpenSmgr(rel);
}
}
break;
case 'f':
{
record_blocknum = InvalidBlockNumber;
nblocks = 0;
fileRead(&record_forknum, sizeof(ForkNumber), file, false, filepath);
if (skip_relation)
continue;
if (rel == NULL)
ereport(ERROR,
(errmsg("found a fork record without a preceeding relation record")));
ereport(log_level, (errmsg("processing fork %d", record_forknum)));
if (!smgrexists(rel->rd_smgr, record_forknum))
skip_fork = true;
else
{
skip_fork = false;
nblocks = RelationGetNumberOfBlocksInFork(rel, record_forknum);
}
}
break;
case 'b':
{
if (record_forknum == InvalidForkNumber)
ereport(ERROR,
(errmsg("found a block record without a preceeding fork record")));
fileRead(&record_blocknum, sizeof(BlockNumber), file, false, filepath);
if (skip_relation || skip_fork)
continue;
/*
* Don't try to read past the file; the file may have been shrunk
* by a vaccum/truncate operation.
*/
if (record_blocknum >= nblocks)
{
ereport(log_level,
(errmsg("reader %d skipping block filenode %u forknum %d blocknum %u",
filenum, record_filenode, record_forknum, record_blocknum)));
skip_block = true;
continue;
}
else
{
Buffer buf;
skip_block = false;
ereport(log_level,
(errmsg("reader %d reading block filenode %u forknum %d blocknum %u",
filenum, record_filenode, record_forknum, record_blocknum)));
buf = ReadBufferExtended(rel, record_forknum, record_blocknum, RBM_NORMAL, NULL);
ReleaseBuffer(buf);
++blocks_restored;
}
}
break;
case 'N':
{
BlockNumber block;
Assert(record_blocknum != InvalidBlockNumber);
if (record_blocknum == InvalidBlockNumber)
ereport(ERROR,
(errmsg("found a block range record without a preceeding block record")));
fileRead(&record_range, sizeof(int), file, false, filepath);
if (skip_relation || skip_fork || skip_block)
continue;
ereport(log_level,
(errmsg("reader %d reading range filenode %u forknum %d blocknum %u range %u",
filenum, record_filenode, record_forknum, record_blocknum, record_range)));
for (block = record_blocknum + 1; block <= (record_blocknum + record_range); ++block)
{
Buffer buf;
/*
* Don't try to read past the file; the file may have been
* shrunk by a vaccum operation.
*/
if (block >= nblocks)
{
ereport(log_level,
(errmsg("reader %d skipping block range filenode %u forknum %d start %u end %u",
filenum, record_filenode, record_forknum,
block, record_blocknum + record_range)));
break;
}
buf = ReadBufferExtended(rel, record_forknum, block, RBM_NORMAL, NULL);
ReleaseBuffer(buf);
++blocks_restored;
}
}
break;
default:
{
ereport(ERROR,
(errmsg("found unexpected save-file marker %x - %c)", record_type, record_type)));
Assert(false);
}
break;
}
}
if (rel)
relation_close(rel, AccessShareLock);
ereport(LOG,
(errmsg("Block Reader %d: restored %u blocks",
filenum, blocks_restored)));
SPI_finish();
PopActiveSnapshot();
CommitTransactionCommand();
pgstat_report_activity(STATE_IDLE, NULL);
fileClose(file, filepath);
/* Remove the save-file */
if (remove(filepath) != 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("error removing file \"%s\" : %m", filepath)));
}
static void
BufferSaverMain(Datum main_arg)
{
WorkerCommon();
/*
* Main loop: do this until the SIGTERM handler tells us to terminate
*/
while (!got_sigterm)
{
int rc;
ResetLatch(&MyProc->procLatch);
/*
* Wait on the process latch, which sleeps as necessary, but is awakened
* if postmaster dies. This way the background process goes away
* immediately in case of an emergency.
*/
rc = WaitLatch(&MyProc->procLatch,
WL_LATCH_SET | WL_TIMEOUT | WL_POSTMASTER_DEATH,
10 * 1000L);
/* emergency bailout if postmaster has died */
if (rc & WL_POSTMASTER_DEATH)
proc_exit(1);
/*
* In case of a SIGHUP, just reload the configuration.
*/
if (got_sighup)
{
got_sighup = false;
ProcessConfigFile(PGC_SIGHUP);
}
}
/*
* We recieved the SIGTERM; Shutdown is in progress, so save the
* shared-buffer contents.
*/
/* Save the buffers only if the extension is enabled. */
if (guc_enabled)
SaveBuffers();
/*
* The worker exits here. A proc_exit(0) is not necessary, we'll let the
* caller do that.
*/
}
static void
SaveBuffers(void)
{
int i;
int num_buffers;
int log_level = DEBUG3;
SavedBuffer *saved_buffers;
volatile BufferDesc *bufHdr; // XXX: Do we really need volatile here?
FILE *file = NULL;
int database_counter= 0;
Oid prev_database = InvalidOid;
Oid prev_filenode = InvalidOid;
ForkNumber prev_forknum = InvalidForkNumber;
BlockNumber prev_blocknum = InvalidBlockNumber;
BlockNumber range_counter = 0;
const char *savefile_path;
/*
* XXX: If the memory request fails, ask for a smaller memory chunk, and use
* it to create chunks of save-files, and make the workers read those chunks.
*
* This is not a concern as of now, so deferred; there's at least one other
* place that allocates (NBuffers * (much_bigger_struct)), so this seems to
* be an acceptable practice.
*/
saved_buffers = (SavedBuffer *) palloc(sizeof(SavedBuffer) * NBuffers);
/* Lock the buffer partitions for reading. */
for (i = 0; i < NUM_BUFFER_PARTITIONS; ++i)
LWLockAcquire(FirstBufMappingLock + i, LW_SHARED);
/* Scan and save a list of valid buffers. */
for (num_buffers = 0, i = 0, bufHdr = BufferDescriptors; i < NBuffers; ++i, ++bufHdr)
{
/* Lock each buffer header before inspecting. */
LockBufHdr(bufHdr);
/* Skip invalid buffers */
if ((bufHdr->flags & BM_VALID) && (bufHdr->flags & BM_TAG_VALID))
{
saved_buffers[num_buffers].database = bufHdr->tag.rnode.dbNode;
saved_buffers[num_buffers].filenode = bufHdr->tag.rnode.relNode;
saved_buffers[num_buffers].forknum = bufHdr->tag.forkNum;
saved_buffers[num_buffers].blocknum = bufHdr->tag.blockNum;
++num_buffers;
}
UnlockBufHdr(bufHdr);
}
/* Unlock the buffer partitions in reverse order, to avoid a deadlock. */
for (i = NUM_BUFFER_PARTITIONS - 1; i >= 0; --i)
LWLockRelease(FirstBufMappingLock + i);
/*
* Sort the list, so that we can optimize the storage of these buffers.
*
* The side-effect of this storage optimization is that when reading the
* blocks back from relation forks, it leads to sequential reads, which
* improve the restore speeds quite considerably as compared to random reads
* from different blocks all over the data directory.
*/
pg_qsort(saved_buffers, num_buffers, sizeof(SavedBuffer), SavedBufferCmp);
/* Connect to the database and start a transaction for database name lookups. */
BackgroundWorkerInitializeConnection(guc_default_database, NULL);
SetCurrentStatementStartTimestamp();
StartTransactionCommand();
PushActiveSnapshot(GetTransactionSnapshot());
pgstat_report_activity(STATE_RUNNING, "saving buffers");
for (i = 0; i < num_buffers; ++i)
{
int j;
SavedBuffer *buf = &saved_buffers[i];
if (i == 0)
{
/*
* Special case for global objects. The sort brings them to the
* front of the list.
*/
/* Make sure the first buffer we save belongs to global object. */
Assert(buf->database == InvalidOid);
/*
* Database number (and save-file name) 1 is reserverd for storing
* list of buffers of global objects.
*/
database_counter = 1;
savefile_path = getSavefileName(database_counter);
file = fileOpen(savefile_path, PG_BINARY_W);
writeDBName("", file, savefile_path);
prev_database = buf->database;
}
if (buf->database != prev_database)
{
char *dbname;
/*
* We are beginning to process a different database than the
* previous one; close the save-file of previous database, and open
* a new one.
*/
++database_counter;
dbname = get_database_name(buf->database);
Assert(dbname != NULL);
if (file != NULL)
fileClose(file, savefile_path);
savefile_path = getSavefileName(database_counter);
file = fileOpen(savefile_path, PG_BINARY_W);
writeDBName(dbname, file, savefile_path);
pfree(dbname);
/* Reset trackers appropriately */
prev_database = buf->database;
prev_filenode = InvalidOid;
prev_forknum = InvalidForkNumber;
prev_blocknum = InvalidBlockNumber;
range_counter = 0;
}
if (buf->filenode != prev_filenode)
{
/* We're beginning to process a new relation; emit a record for it. */
fileWrite("r", 1, file, savefile_path);
fileWrite(&(buf->filenode), sizeof(Oid), file, savefile_path);
/* Reset trackers appropriately */
prev_filenode = buf->filenode;
prev_forknum = InvalidForkNumber;
prev_blocknum = InvalidBlockNumber;
range_counter = 0;
}
if (buf->forknum != prev_forknum)
{
/*
* We're beginning to process a new fork of this relation; add a
* record for it.
*/
fileWrite("f", 1, file, savefile_path);
fileWrite(&(buf->forknum), sizeof(ForkNumber), file, savefile_path);
/* Reset trackers appropriately */
prev_forknum = buf->forknum;
prev_blocknum = InvalidBlockNumber;
range_counter = 0;
}
ereport(log_level,
(errmsg("writer: writing block db %d filenode %d forknum %d blocknum %d",
database_counter, prev_filenode, prev_forknum, buf->blocknum)));
fileWrite("b", 1, file, savefile_path);
fileWrite(&(buf->blocknum), sizeof(BlockNumber), file, savefile_path);
prev_blocknum = buf->blocknum;
/*
* If a continuous range of blocks follows this block, then emit one
* entry for the range, instead of one for each block.
*/
range_counter = 0;
for ( j = i+1; j < num_buffers; ++j)
{
SavedBuffer *tmp = &saved_buffers[j];
if (tmp->database == prev_database
&& tmp->filenode == prev_filenode
&& tmp->forknum == prev_forknum
&& tmp->blocknum == (prev_blocknum + range_counter + 1))
{
++range_counter;
}
}
if (range_counter != 0)
{
ereport(log_level,
(errmsg("writer: writing range db %d filenode %d forknum %d blocknum %d range %d",
database_counter, prev_filenode, prev_forknum, prev_blocknum, range_counter)));
fileWrite("N", 1, file, savefile_path);
fileWrite(&range_counter, sizeof(range_counter), file, savefile_path);
i += range_counter;
}
}
ereport(LOG,
(errmsg("Buffer Saver: saved metadata of %d blocks", num_buffers)));
Assert(file != NULL);
fileClose(file, savefile_path);
pfree(saved_buffers);
PopActiveSnapshot();
CommitTransactionCommand();
pgstat_report_activity(STATE_IDLE, NULL);
}
#define svdbfrcmp(fld) \
if (a->fld < b->fld) \
return -1; \
else if (a->fld > b->fld) \
return 1;
static int
SavedBufferCmp(const void *p, const void *q)
{
SavedBuffer *a = (SavedBuffer *) p;
SavedBuffer *b = (SavedBuffer *) q;
svdbfrcmp(database);
svdbfrcmp(filenode);
svdbfrcmp(forknum);
svdbfrcmp(blocknum);
Assert(false); // No two buffers should be storing identical page
return 0; // Keep compiler happy.
}
static Oid
GetRelOid(Oid filenode)
{
int ret;
Oid relid;
bool isnull;
Datum value[1] = { ObjectIdGetDatum(filenode) };
static SPIPlanPtr plan = NULL;
/* If this is our first time here, create a plan and save it for later calls. */
if (plan == NULL)
{
StringInfoData buf;
Oid paramType[1] = {OIDOID};
initStringInfo(&buf);
appendStringInfo(&buf, "select oid from pg_class where pg_relation_filenode(oid) = $1");
plan = SPI_prepare(buf.data, 1, (Oid*)¶mType);
if (plan == NULL)
elog(ERROR, "SPI_prepare returned %d", SPI_result);
}
ret = SPI_execute_plan(plan, (Datum*)&value, NULL, true, 1);
if (ret != SPI_OK_SELECT)
ereport(FATAL, (errmsg("SPI_execute_plan failed: error code %d", ret)));
if (SPI_processed < 1)