Branch data Line data Source code
1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * walsummarizer.c
4 : : *
5 : : * Background process to perform WAL summarization, if it is enabled.
6 : : * It continuously scans the write-ahead log and periodically emits a
7 : : * summary file which indicates which blocks in which relation forks
8 : : * were modified by WAL records in the LSN range covered by the summary
9 : : * file. See walsummary.c and blkreftable.c for more details on the
10 : : * naming and contents of WAL summary files.
11 : : *
12 : : * If configured to do, this background process will also remove WAL
13 : : * summary files when the file timestamp is older than a configurable
14 : : * threshold (but only if the WAL has been removed first).
15 : : *
16 : : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
17 : : *
18 : : * IDENTIFICATION
19 : : * src/backend/postmaster/walsummarizer.c
20 : : *
21 : : *-------------------------------------------------------------------------
22 : : */
23 : : #include "postgres.h"
24 : :
25 : : #include "access/timeline.h"
26 : : #include "access/xlog.h"
27 : : #include "access/xlog_internal.h"
28 : : #include "access/xlogrecovery.h"
29 : : #include "access/xlogutils.h"
30 : : #include "backup/walsummary.h"
31 : : #include "catalog/storage_xlog.h"
32 : : #include "commands/dbcommands_xlog.h"
33 : : #include "common/blkreftable.h"
34 : : #include "libpq/pqsignal.h"
35 : : #include "miscadmin.h"
36 : : #include "pgstat.h"
37 : : #include "postmaster/auxprocess.h"
38 : : #include "postmaster/interrupt.h"
39 : : #include "postmaster/walsummarizer.h"
40 : : #include "replication/walreceiver.h"
41 : : #include "storage/aio_subsys.h"
42 : : #include "storage/fd.h"
43 : : #include "storage/ipc.h"
44 : : #include "storage/latch.h"
45 : : #include "storage/lwlock.h"
46 : : #include "storage/proc.h"
47 : : #include "storage/procsignal.h"
48 : : #include "storage/shmem.h"
49 : : #include "utils/guc.h"
50 : : #include "utils/memutils.h"
51 : : #include "utils/wait_event.h"
52 : :
53 : : /*
54 : : * Data in shared memory related to WAL summarization.
55 : : */
56 : : typedef struct
57 : : {
58 : : /*
59 : : * These fields are protected by WALSummarizerLock.
60 : : *
61 : : * Until we've discovered what summary files already exist on disk and
62 : : * stored that information in shared memory, initialized is false and the
63 : : * other fields here contain no meaningful information. After that has
64 : : * been done, initialized is true.
65 : : *
66 : : * summarized_tli and summarized_lsn indicate the last LSN and TLI at
67 : : * which the next summary file will start. Normally, these are the LSN and
68 : : * TLI at which the last file ended; in such case, lsn_is_exact is true.
69 : : * If, however, the LSN is just an approximation, then lsn_is_exact is
70 : : * false. This can happen if, for example, there are no existing WAL
71 : : * summary files at startup. In that case, we have to derive the position
72 : : * at which to start summarizing from the WAL files that exist on disk,
73 : : * and so the LSN might point to the start of the next file even though
74 : : * that might happen to be in the middle of a WAL record.
75 : : *
76 : : * summarizer_pgprocno is the proc number of the summarizer process, if
77 : : * one is running, or else INVALID_PROC_NUMBER.
78 : : *
79 : : * pending_lsn is used by the summarizer to advertise the ending LSN of a
80 : : * record it has recently read. It shouldn't ever be less than
81 : : * summarized_lsn, but might be greater, because the summarizer buffers
82 : : * data for a range of LSNs in memory before writing out a new file.
83 : : */
84 : : bool initialized;
85 : : TimeLineID summarized_tli;
86 : : XLogRecPtr summarized_lsn;
87 : : bool lsn_is_exact;
88 : : ProcNumber summarizer_pgprocno;
89 : : XLogRecPtr pending_lsn;
90 : :
91 : : /*
92 : : * This field handles its own synchronization.
93 : : */
94 : : ConditionVariable summary_file_cv;
95 : : } WalSummarizerData;
96 : :
97 : : /*
98 : : * Private data for our xlogreader's page read callback.
99 : : */
100 : : typedef struct
101 : : {
102 : : TimeLineID tli;
103 : : bool historic;
104 : : XLogRecPtr read_upto;
105 : : bool end_of_wal;
106 : : } SummarizerReadLocalXLogPrivate;
107 : :
108 : : /* Pointer to shared memory state. */
109 : : static WalSummarizerData *WalSummarizerCtl;
110 : :
111 : : /*
112 : : * When we reach end of WAL and need to read more, we sleep for a number of
113 : : * milliseconds that is an integer multiple of MS_PER_SLEEP_QUANTUM. This is
114 : : * the multiplier. It should vary between 1 and MAX_SLEEP_QUANTA, depending
115 : : * on system activity. See summarizer_wait_for_wal() for how we adjust this.
116 : : */
117 : : static long sleep_quanta = 1;
118 : :
119 : : /*
120 : : * The sleep time will always be a multiple of 200ms and will not exceed
121 : : * thirty seconds (150 * 200 = 30 * 1000). Note that the timeout here needs
122 : : * to be substantially less than the maximum amount of time for which an
123 : : * incremental backup will wait for this process to catch up. Otherwise, an
124 : : * incremental backup might time out on an idle system just because we sleep
125 : : * for too long.
126 : : */
127 : : #define MAX_SLEEP_QUANTA 150
128 : : #define MS_PER_SLEEP_QUANTUM 200
129 : :
130 : : /*
131 : : * This is a count of the number of pages of WAL that we've read since the
132 : : * last time we waited for more WAL to appear.
133 : : */
134 : : static long pages_read_since_last_sleep = 0;
135 : :
136 : : /*
137 : : * Most recent RedoRecPtr value observed by MaybeRemoveOldWalSummaries.
138 : : */
139 : : static XLogRecPtr redo_pointer_at_last_summary_removal = InvalidXLogRecPtr;
140 : :
141 : : /*
142 : : * GUC parameters
143 : : */
144 : : bool summarize_wal = false;
145 : : int wal_summary_keep_time = 10 * HOURS_PER_DAY * MINS_PER_HOUR;
146 : :
147 : : static void WalSummarizerShutdown(int code, Datum arg);
148 : : static XLogRecPtr GetLatestLSN(TimeLineID *tli);
149 : : static void ProcessWalSummarizerInterrupts(void);
150 : : static XLogRecPtr SummarizeWAL(TimeLineID tli, XLogRecPtr start_lsn,
151 : : bool exact, XLogRecPtr switch_lsn,
152 : : XLogRecPtr maximum_lsn);
153 : : static void SummarizeDbaseRecord(XLogReaderState *xlogreader,
154 : : BlockRefTable *brtab);
155 : : static void SummarizeSmgrRecord(XLogReaderState *xlogreader,
156 : : BlockRefTable *brtab);
157 : : static void SummarizeXactRecord(XLogReaderState *xlogreader,
158 : : BlockRefTable *brtab);
159 : : static bool SummarizeXlogRecord(XLogReaderState *xlogreader,
160 : : bool *new_fast_forward);
161 : : static int summarizer_read_local_xlog_page(XLogReaderState *state,
162 : : XLogRecPtr targetPagePtr,
163 : : int reqLen,
164 : : XLogRecPtr targetRecPtr,
165 : : char *cur_page);
166 : : static void summarizer_wait_for_wal(void);
167 : : static void MaybeRemoveOldWalSummaries(void);
168 : :
169 : : /*
170 : : * Amount of shared memory required for this module.
171 : : */
172 : : Size
173 : 15 : WalSummarizerShmemSize(void)
174 : : {
175 : 15 : return sizeof(WalSummarizerData);
176 : : }
177 : :
178 : : /*
179 : : * Create or attach to shared memory segment for this module.
180 : : */
181 : : void
182 : 6 : WalSummarizerShmemInit(void)
183 : : {
184 : 6 : bool found;
185 : :
186 : 6 : WalSummarizerCtl = (WalSummarizerData *)
187 : 6 : ShmemInitStruct("Wal Summarizer Ctl", WalSummarizerShmemSize(),
188 : : &found);
189 : :
190 [ - + ]: 6 : if (!found)
191 : : {
192 : : /*
193 : : * First time through, so initialize.
194 : : *
195 : : * We're just filling in dummy values here -- the real initialization
196 : : * will happen when GetOldestUnsummarizedLSN() is called for the first
197 : : * time.
198 : : */
199 : 6 : WalSummarizerCtl->initialized = false;
200 : 6 : WalSummarizerCtl->summarized_tli = 0;
201 : 6 : WalSummarizerCtl->summarized_lsn = InvalidXLogRecPtr;
202 : 6 : WalSummarizerCtl->lsn_is_exact = false;
203 : 6 : WalSummarizerCtl->summarizer_pgprocno = INVALID_PROC_NUMBER;
204 : 6 : WalSummarizerCtl->pending_lsn = InvalidXLogRecPtr;
205 : 6 : ConditionVariableInit(&WalSummarizerCtl->summary_file_cv);
206 : 6 : }
207 : 6 : }
208 : :
209 : : /*
210 : : * Entry point for walsummarizer process.
211 : : */
212 : : void
213 : 0 : WalSummarizerMain(const void *startup_data, size_t startup_data_len)
214 : : {
215 : 0 : sigjmp_buf local_sigjmp_buf;
216 : 0 : MemoryContext context;
217 : :
218 : : /*
219 : : * Within this function, 'current_lsn' and 'current_tli' refer to the
220 : : * point from which the next WAL summary file should start. 'exact' is
221 : : * true if 'current_lsn' is known to be the start of a WAL record or WAL
222 : : * segment, and false if it might be in the middle of a record someplace.
223 : : *
224 : : * 'switch_lsn' and 'switch_tli', if set, are the LSN at which we need to
225 : : * switch to a new timeline and the timeline to which we need to switch.
226 : : * If not set, we either haven't figured out the answers yet or we're
227 : : * already on the latest timeline.
228 : : */
229 : 0 : XLogRecPtr current_lsn;
230 : 0 : TimeLineID current_tli;
231 : 0 : bool exact;
232 : 0 : XLogRecPtr switch_lsn = InvalidXLogRecPtr;
233 : 0 : TimeLineID switch_tli = 0;
234 : :
235 [ # # ]: 0 : Assert(startup_data_len == 0);
236 : :
237 : 0 : MyBackendType = B_WAL_SUMMARIZER;
238 : 0 : AuxiliaryProcessMainCommon();
239 : :
240 [ # # # # ]: 0 : ereport(DEBUG1,
241 : : (errmsg_internal("WAL summarizer started")));
242 : :
243 : : /*
244 : : * Properly accept or ignore signals the postmaster might send us
245 : : *
246 : : * We have no particular use for SIGINT at the moment, but seems
247 : : * reasonable to treat like SIGTERM.
248 : : */
249 : 0 : pqsignal(SIGHUP, SignalHandlerForConfigReload);
250 : 0 : pqsignal(SIGINT, SignalHandlerForShutdownRequest);
251 : 0 : pqsignal(SIGTERM, SignalHandlerForShutdownRequest);
252 : : /* SIGQUIT handler was already set up by InitPostmasterChild */
253 : 0 : pqsignal(SIGALRM, SIG_IGN);
254 : 0 : pqsignal(SIGPIPE, SIG_IGN);
255 : 0 : pqsignal(SIGUSR1, procsignal_sigusr1_handler);
256 : 0 : pqsignal(SIGUSR2, SIG_IGN); /* not used */
257 : :
258 : : /* Advertise ourselves. */
259 : 0 : on_shmem_exit(WalSummarizerShutdown, (Datum) 0);
260 : 0 : LWLockAcquire(WALSummarizerLock, LW_EXCLUSIVE);
261 : 0 : WalSummarizerCtl->summarizer_pgprocno = MyProcNumber;
262 : 0 : LWLockRelease(WALSummarizerLock);
263 : :
264 : : /* Create and switch to a memory context that we can reset on error. */
265 : 0 : context = AllocSetContextCreate(TopMemoryContext,
266 : : "Wal Summarizer",
267 : : ALLOCSET_DEFAULT_SIZES);
268 : 0 : MemoryContextSwitchTo(context);
269 : :
270 : : /*
271 : : * Reset some signals that are accepted by postmaster but not here
272 : : */
273 : 0 : pqsignal(SIGCHLD, SIG_DFL);
274 : :
275 : : /*
276 : : * If an exception is encountered, processing resumes here.
277 : : */
278 [ # # ]: 0 : if (sigsetjmp(local_sigjmp_buf, 1) != 0)
279 : : {
280 : : /* Since not using PG_TRY, must reset error stack by hand */
281 : 0 : error_context_stack = NULL;
282 : :
283 : : /* Prevent interrupts while cleaning up */
284 : 0 : HOLD_INTERRUPTS();
285 : :
286 : : /* Report the error to the server log */
287 : 0 : EmitErrorReport();
288 : :
289 : : /* Release resources we might have acquired. */
290 : 0 : LWLockReleaseAll();
291 : 0 : ConditionVariableCancelSleep();
292 : 0 : pgstat_report_wait_end();
293 : 0 : pgaio_error_cleanup();
294 : 0 : ReleaseAuxProcessResources(false);
295 : 0 : AtEOXact_Files(false);
296 : 0 : AtEOXact_HashTables(false);
297 : :
298 : : /*
299 : : * Now return to normal top-level context and clear ErrorContext for
300 : : * next time.
301 : : */
302 : 0 : MemoryContextSwitchTo(context);
303 : 0 : FlushErrorState();
304 : :
305 : : /* Flush any leaked data in the top-level context */
306 : 0 : MemoryContextReset(context);
307 : :
308 : : /* Now we can allow interrupts again */
309 [ # # ]: 0 : RESUME_INTERRUPTS();
310 : :
311 : : /*
312 : : * Sleep for 10 seconds before attempting to resume operations in
313 : : * order to avoid excessive logging.
314 : : *
315 : : * Many of the likely error conditions are things that will repeat
316 : : * every time. For example, if the WAL can't be read or the summary
317 : : * can't be written, only administrator action will cure the problem.
318 : : * So a really fast retry time doesn't seem to be especially
319 : : * beneficial, and it will clutter the logs.
320 : : */
321 : 0 : (void) WaitLatch(NULL,
322 : : WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
323 : : 10000,
324 : : WAIT_EVENT_WAL_SUMMARIZER_ERROR);
325 : 0 : }
326 : :
327 : : /* We can now handle ereport(ERROR) */
328 : 0 : PG_exception_stack = &local_sigjmp_buf;
329 : :
330 : : /*
331 : : * Unblock signals (they were blocked when the postmaster forked us)
332 : : */
333 : 0 : sigprocmask(SIG_SETMASK, &UnBlockSig, NULL);
334 : :
335 : : /*
336 : : * Fetch information about previous progress from shared memory, and ask
337 : : * GetOldestUnsummarizedLSN to reset pending_lsn to summarized_lsn. We
338 : : * might be recovering from an error, and if so, pending_lsn might have
339 : : * advanced past summarized_lsn, but any WAL we read previously has been
340 : : * lost and will need to be reread.
341 : : *
342 : : * If we discover that WAL summarization is not enabled, just exit.
343 : : */
344 : 0 : current_lsn = GetOldestUnsummarizedLSN(¤t_tli, &exact);
345 [ # # ]: 0 : if (!XLogRecPtrIsValid(current_lsn))
346 : 0 : proc_exit(0);
347 : :
348 : : /*
349 : : * Loop forever
350 : : */
351 : 0 : for (;;)
352 : : {
353 : 0 : XLogRecPtr latest_lsn;
354 : 0 : TimeLineID latest_tli;
355 : 0 : XLogRecPtr end_of_summary_lsn;
356 : :
357 : : /* Flush any leaked data in the top-level context */
358 : 0 : MemoryContextReset(context);
359 : :
360 : : /* Process any signals received recently. */
361 : 0 : ProcessWalSummarizerInterrupts();
362 : :
363 : : /* If it's time to remove any old WAL summaries, do that now. */
364 : 0 : MaybeRemoveOldWalSummaries();
365 : :
366 : : /* Find the LSN and TLI up to which we can safely summarize. */
367 : 0 : latest_lsn = GetLatestLSN(&latest_tli);
368 : :
369 : : /*
370 : : * If we're summarizing a historic timeline and we haven't yet
371 : : * computed the point at which to switch to the next timeline, do that
372 : : * now.
373 : : *
374 : : * Note that if this is a standby, what was previously the current
375 : : * timeline could become historic at any time.
376 : : *
377 : : * We could try to make this more efficient by caching the results of
378 : : * readTimeLineHistory when latest_tli has not changed, but since we
379 : : * only have to do this once per timeline switch, we probably wouldn't
380 : : * save any significant amount of work in practice.
381 : : */
382 [ # # # # ]: 0 : if (current_tli != latest_tli && !XLogRecPtrIsValid(switch_lsn))
383 : : {
384 : 0 : List *tles = readTimeLineHistory(latest_tli);
385 : :
386 : 0 : switch_lsn = tliSwitchPoint(current_tli, tles, &switch_tli);
387 [ # # # # ]: 0 : ereport(DEBUG1,
388 : : errmsg_internal("switch point from TLI %u to TLI %u is at %X/%08X",
389 : : current_tli, switch_tli, LSN_FORMAT_ARGS(switch_lsn)));
390 : 0 : }
391 : :
392 : : /*
393 : : * If we've reached the switch LSN, we can't summarize anything else
394 : : * on this timeline. Switch to the next timeline and go around again,
395 : : * backing up to the exact switch point if we passed it.
396 : : */
397 [ # # # # ]: 0 : if (XLogRecPtrIsValid(switch_lsn) && current_lsn >= switch_lsn)
398 : : {
399 : : /* Restart summarization from switch point. */
400 : 0 : current_tli = switch_tli;
401 : 0 : current_lsn = switch_lsn;
402 : :
403 : : /* Next timeline and switch point, if any, not yet known. */
404 : 0 : switch_lsn = InvalidXLogRecPtr;
405 : 0 : switch_tli = 0;
406 : :
407 : : /* Update (really, rewind, if needed) state in shared memory. */
408 : 0 : LWLockAcquire(WALSummarizerLock, LW_EXCLUSIVE);
409 : 0 : WalSummarizerCtl->summarized_lsn = current_lsn;
410 : 0 : WalSummarizerCtl->summarized_tli = current_tli;
411 : 0 : WalSummarizerCtl->lsn_is_exact = true;
412 : 0 : WalSummarizerCtl->pending_lsn = current_lsn;
413 : 0 : LWLockRelease(WALSummarizerLock);
414 : :
415 : 0 : continue;
416 : : }
417 : :
418 : : /* Summarize WAL. */
419 : 0 : end_of_summary_lsn = SummarizeWAL(current_tli,
420 : 0 : current_lsn, exact,
421 : 0 : switch_lsn, latest_lsn);
422 [ # # ]: 0 : Assert(XLogRecPtrIsValid(end_of_summary_lsn));
423 [ # # ]: 0 : Assert(end_of_summary_lsn >= current_lsn);
424 : :
425 : : /*
426 : : * Update state for next loop iteration.
427 : : *
428 : : * Next summary file should start from exactly where this one ended.
429 : : */
430 : 0 : current_lsn = end_of_summary_lsn;
431 : 0 : exact = true;
432 : :
433 : : /* Update state in shared memory. */
434 : 0 : LWLockAcquire(WALSummarizerLock, LW_EXCLUSIVE);
435 : 0 : WalSummarizerCtl->summarized_lsn = end_of_summary_lsn;
436 : 0 : WalSummarizerCtl->summarized_tli = current_tli;
437 : 0 : WalSummarizerCtl->lsn_is_exact = true;
438 : 0 : WalSummarizerCtl->pending_lsn = end_of_summary_lsn;
439 : 0 : LWLockRelease(WALSummarizerLock);
440 : :
441 : : /* Wake up anyone waiting for more summary files to be written. */
442 : 0 : ConditionVariableBroadcast(&WalSummarizerCtl->summary_file_cv);
443 [ # # # ]: 0 : }
444 : : }
445 : :
446 : : /*
447 : : * Get information about the state of the WAL summarizer.
448 : : */
449 : : void
450 : 0 : GetWalSummarizerState(TimeLineID *summarized_tli, XLogRecPtr *summarized_lsn,
451 : : XLogRecPtr *pending_lsn, int *summarizer_pid)
452 : : {
453 : 0 : LWLockAcquire(WALSummarizerLock, LW_SHARED);
454 [ # # ]: 0 : if (!WalSummarizerCtl->initialized)
455 : : {
456 : : /*
457 : : * If initialized is false, the rest of the structure contents are
458 : : * undefined.
459 : : */
460 : 0 : *summarized_tli = 0;
461 : 0 : *summarized_lsn = InvalidXLogRecPtr;
462 : 0 : *pending_lsn = InvalidXLogRecPtr;
463 : 0 : *summarizer_pid = -1;
464 : 0 : }
465 : : else
466 : : {
467 : 0 : int summarizer_pgprocno = WalSummarizerCtl->summarizer_pgprocno;
468 : :
469 : 0 : *summarized_tli = WalSummarizerCtl->summarized_tli;
470 : 0 : *summarized_lsn = WalSummarizerCtl->summarized_lsn;
471 [ # # ]: 0 : if (summarizer_pgprocno == INVALID_PROC_NUMBER)
472 : : {
473 : : /*
474 : : * If the summarizer has exited, the fact that it had processed
475 : : * beyond summarized_lsn is irrelevant now.
476 : : */
477 : 0 : *pending_lsn = WalSummarizerCtl->summarized_lsn;
478 : 0 : *summarizer_pid = -1;
479 : 0 : }
480 : : else
481 : : {
482 : 0 : *pending_lsn = WalSummarizerCtl->pending_lsn;
483 : :
484 : : /*
485 : : * We're not fussed about inexact answers here, since they could
486 : : * become stale instantly, so we don't bother taking the lock, but
487 : : * make sure that invalid PID values are normalized to -1.
488 : : */
489 : 0 : *summarizer_pid = GetPGProcByNumber(summarizer_pgprocno)->pid;
490 [ # # ]: 0 : if (*summarizer_pid <= 0)
491 : 0 : *summarizer_pid = -1;
492 : : }
493 : 0 : }
494 : 0 : LWLockRelease(WALSummarizerLock);
495 : 0 : }
496 : :
497 : : /*
498 : : * Get the oldest LSN in this server's timeline history that has not yet been
499 : : * summarized, and update shared memory state as appropriate.
500 : : *
501 : : * If *tli != NULL, it will be set to the TLI for the LSN that is returned.
502 : : *
503 : : * If *lsn_is_exact != NULL, it will be set to true if the returned LSN is
504 : : * necessarily the start of a WAL record and false if it's just the beginning
505 : : * of a WAL segment.
506 : : */
507 : : XLogRecPtr
508 : 7 : GetOldestUnsummarizedLSN(TimeLineID *tli, bool *lsn_is_exact)
509 : : {
510 : 7 : TimeLineID latest_tli;
511 : 7 : int n;
512 : 7 : List *tles;
513 : 7 : XLogRecPtr unsummarized_lsn = InvalidXLogRecPtr;
514 : 7 : TimeLineID unsummarized_tli = 0;
515 : 7 : bool should_make_exact = false;
516 : 7 : List *existing_summaries;
517 : 7 : ListCell *lc;
518 : 7 : bool am_wal_summarizer = AmWalSummarizerProcess();
519 : :
520 : : /* If not summarizing WAL, do nothing. */
521 [ + - ]: 7 : if (!summarize_wal)
522 : 7 : return InvalidXLogRecPtr;
523 : :
524 : : /*
525 : : * If we are not the WAL summarizer process, then we normally just want to
526 : : * read the values from shared memory. However, as an exception, if shared
527 : : * memory hasn't been initialized yet, then we need to do that so that we
528 : : * can read legal values and not remove any WAL too early.
529 : : */
530 [ # # ]: 0 : if (!am_wal_summarizer)
531 : : {
532 : 0 : LWLockAcquire(WALSummarizerLock, LW_SHARED);
533 : :
534 [ # # ]: 0 : if (WalSummarizerCtl->initialized)
535 : : {
536 : 0 : unsummarized_lsn = WalSummarizerCtl->summarized_lsn;
537 [ # # ]: 0 : if (tli != NULL)
538 : 0 : *tli = WalSummarizerCtl->summarized_tli;
539 [ # # ]: 0 : if (lsn_is_exact != NULL)
540 : 0 : *lsn_is_exact = WalSummarizerCtl->lsn_is_exact;
541 : 0 : LWLockRelease(WALSummarizerLock);
542 : 0 : return unsummarized_lsn;
543 : : }
544 : :
545 : 0 : LWLockRelease(WALSummarizerLock);
546 : 0 : }
547 : :
548 : : /*
549 : : * Find the oldest timeline on which WAL still exists, and the earliest
550 : : * segment for which it exists.
551 : : *
552 : : * Note that we do this every time the WAL summarizer process restarts or
553 : : * recovers from an error, in case the contents of pg_wal have changed
554 : : * under us e.g. if some files were removed, either manually - which
555 : : * shouldn't really happen, but might - or by postgres itself, if
556 : : * summarize_wal was turned off and then back on again.
557 : : */
558 : 0 : (void) GetLatestLSN(&latest_tli);
559 : 0 : tles = readTimeLineHistory(latest_tli);
560 [ # # ]: 0 : for (n = list_length(tles) - 1; n >= 0; --n)
561 : : {
562 : 0 : TimeLineHistoryEntry *tle = list_nth(tles, n);
563 : 0 : XLogSegNo oldest_segno;
564 : :
565 : 0 : oldest_segno = XLogGetOldestSegno(tle->tli);
566 [ # # ]: 0 : if (oldest_segno != 0)
567 : : {
568 : : /* Compute oldest LSN that still exists on disk. */
569 : 0 : XLogSegNoOffsetToRecPtr(oldest_segno, 0, wal_segment_size,
570 : : unsummarized_lsn);
571 : :
572 : 0 : unsummarized_tli = tle->tli;
573 : 0 : break;
574 : : }
575 [ # # # ]: 0 : }
576 : :
577 : : /*
578 : : * Don't try to summarize anything older than the end LSN of the newest
579 : : * summary file that exists for this timeline.
580 : : */
581 : 0 : existing_summaries =
582 : 0 : GetWalSummaries(unsummarized_tli,
583 : : InvalidXLogRecPtr, InvalidXLogRecPtr);
584 [ # # # # : 0 : foreach(lc, existing_summaries)
# # ]
585 : : {
586 : 0 : WalSummaryFile *ws = lfirst(lc);
587 : :
588 [ # # ]: 0 : if (ws->end_lsn > unsummarized_lsn)
589 : : {
590 : 0 : unsummarized_lsn = ws->end_lsn;
591 : 0 : should_make_exact = true;
592 : 0 : }
593 : 0 : }
594 : :
595 : : /* It really should not be possible for us to find no WAL. */
596 [ # # ]: 0 : if (unsummarized_tli == 0)
597 [ # # # # ]: 0 : ereport(ERROR,
598 : : errcode(ERRCODE_INTERNAL_ERROR),
599 : : errmsg_internal("no WAL found on timeline %u", latest_tli));
600 : :
601 : : /*
602 : : * If we're the WAL summarizer, we always want to store the values we just
603 : : * computed into shared memory, because those are the values we're going
604 : : * to use to drive our operation, and so they are the authoritative
605 : : * values. Otherwise, we only store values into shared memory if shared
606 : : * memory is uninitialized. Our values are not canonical in such a case,
607 : : * but it's better to have something than nothing, to guide WAL retention.
608 : : */
609 : 0 : LWLockAcquire(WALSummarizerLock, LW_EXCLUSIVE);
610 [ # # # # ]: 0 : if (am_wal_summarizer || !WalSummarizerCtl->initialized)
611 : : {
612 : 0 : WalSummarizerCtl->initialized = true;
613 : 0 : WalSummarizerCtl->summarized_lsn = unsummarized_lsn;
614 : 0 : WalSummarizerCtl->summarized_tli = unsummarized_tli;
615 : 0 : WalSummarizerCtl->lsn_is_exact = should_make_exact;
616 : 0 : WalSummarizerCtl->pending_lsn = unsummarized_lsn;
617 : 0 : }
618 : : else
619 : 0 : unsummarized_lsn = WalSummarizerCtl->summarized_lsn;
620 : :
621 : : /* Also return the to the caller as required. */
622 [ # # ]: 0 : if (tli != NULL)
623 : 0 : *tli = WalSummarizerCtl->summarized_tli;
624 [ # # ]: 0 : if (lsn_is_exact != NULL)
625 : 0 : *lsn_is_exact = WalSummarizerCtl->lsn_is_exact;
626 : 0 : LWLockRelease(WALSummarizerLock);
627 : :
628 : 0 : return unsummarized_lsn;
629 : 7 : }
630 : :
631 : : /*
632 : : * Wake up the WAL summarizer process.
633 : : *
634 : : * This might not work, because there's no guarantee that the WAL summarizer
635 : : * process was successfully started, and it also might have started but
636 : : * subsequently terminated. So, under normal circumstances, this will get the
637 : : * latch set, but there's no guarantee.
638 : : */
639 : : void
640 : 7 : WakeupWalSummarizer(void)
641 : : {
642 : 7 : ProcNumber pgprocno;
643 : :
644 [ + - ]: 7 : if (WalSummarizerCtl == NULL)
645 : 0 : return;
646 : :
647 : 7 : LWLockAcquire(WALSummarizerLock, LW_SHARED);
648 : 7 : pgprocno = WalSummarizerCtl->summarizer_pgprocno;
649 : 7 : LWLockRelease(WALSummarizerLock);
650 : :
651 [ + - ]: 7 : if (pgprocno != INVALID_PROC_NUMBER)
652 : 0 : SetLatch(&GetPGProcByNumber(pgprocno)->procLatch);
653 [ - + ]: 7 : }
654 : :
655 : : /*
656 : : * Wait until WAL summarization reaches the given LSN, but time out with an
657 : : * error if the summarizer seems to be stick.
658 : : *
659 : : * Returns immediately if summarize_wal is turned off while we wait. Caller
660 : : * is expected to handle this case, if necessary.
661 : : */
662 : : void
663 : 0 : WaitForWalSummarization(XLogRecPtr lsn)
664 : : {
665 : 0 : TimestampTz initial_time,
666 : : cycle_time,
667 : : current_time;
668 : 0 : XLogRecPtr prior_pending_lsn = InvalidXLogRecPtr;
669 : 0 : int deadcycles = 0;
670 : :
671 : 0 : initial_time = cycle_time = GetCurrentTimestamp();
672 : :
673 : 0 : while (1)
674 : : {
675 : 0 : long timeout_in_ms = 10000;
676 : 0 : XLogRecPtr summarized_lsn;
677 : 0 : XLogRecPtr pending_lsn;
678 : :
679 [ # # ]: 0 : CHECK_FOR_INTERRUPTS();
680 : :
681 : : /* If WAL summarization is disabled while we're waiting, give up. */
682 [ # # ]: 0 : if (!summarize_wal)
683 : 0 : return;
684 : :
685 : : /*
686 : : * If the LSN summarized on disk has reached the target value, stop.
687 : : */
688 : 0 : LWLockAcquire(WALSummarizerLock, LW_SHARED);
689 : 0 : summarized_lsn = WalSummarizerCtl->summarized_lsn;
690 : 0 : pending_lsn = WalSummarizerCtl->pending_lsn;
691 : 0 : LWLockRelease(WALSummarizerLock);
692 : :
693 : : /* If WAL summarization has progressed sufficiently, stop waiting. */
694 [ # # ]: 0 : if (summarized_lsn >= lsn)
695 : 0 : break;
696 : :
697 : : /* Recheck current time. */
698 : 0 : current_time = GetCurrentTimestamp();
699 : :
700 : : /* Have we finished the current cycle of waiting? */
701 : 0 : if (TimestampDifferenceMilliseconds(cycle_time,
702 [ # # # # ]: 0 : current_time) >= timeout_in_ms)
703 : : {
704 : 0 : long elapsed_seconds;
705 : :
706 : : /* Begin new wait cycle. */
707 : 0 : cycle_time = TimestampTzPlusMilliseconds(cycle_time,
708 : : timeout_in_ms);
709 : :
710 : : /*
711 : : * Keep track of the number of cycles during which there has been
712 : : * no progression of pending_lsn. If pending_lsn is not advancing,
713 : : * that means that not only are no new files appearing on disk,
714 : : * but we're not even incorporating new records into the in-memory
715 : : * state.
716 : : */
717 [ # # ]: 0 : if (pending_lsn > prior_pending_lsn)
718 : : {
719 : 0 : prior_pending_lsn = pending_lsn;
720 : 0 : deadcycles = 0;
721 : 0 : }
722 : : else
723 : 0 : ++deadcycles;
724 : :
725 : : /*
726 : : * If we've managed to wait for an entire minute without the WAL
727 : : * summarizer absorbing a single WAL record, error out; probably
728 : : * something is wrong.
729 : : *
730 : : * We could consider also erroring out if the summarizer is taking
731 : : * too long to catch up, but it's not clear what rate of progress
732 : : * would be acceptable and what would be too slow. So instead, we
733 : : * just try to error out in the case where there's no progress at
734 : : * all. That seems likely to catch a reasonable number of the
735 : : * things that can go wrong in practice (e.g. the summarizer
736 : : * process is completely hung, say because somebody hooked up a
737 : : * debugger to it or something) without giving up too quickly when
738 : : * the system is just slow.
739 : : */
740 [ # # ]: 0 : if (deadcycles >= 6)
741 [ # # # # ]: 0 : ereport(ERROR,
742 : : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
743 : : errmsg("WAL summarization is not progressing"),
744 : : errdetail("Summarization is needed through %X/%08X, but is stuck at %X/%08X on disk and %X/%08X in memory.",
745 : : LSN_FORMAT_ARGS(lsn),
746 : : LSN_FORMAT_ARGS(summarized_lsn),
747 : : LSN_FORMAT_ARGS(pending_lsn))));
748 : :
749 : :
750 : : /*
751 : : * Otherwise, just let the user know what's happening.
752 : : */
753 : 0 : elapsed_seconds =
754 : 0 : TimestampDifferenceMilliseconds(initial_time,
755 : 0 : current_time) / 1000;
756 [ # # # # ]: 0 : ereport(WARNING,
757 : : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
758 : : errmsg_plural("still waiting for WAL summarization through %X/%08X after %ld second",
759 : : "still waiting for WAL summarization through %X/%08X after %ld seconds",
760 : : elapsed_seconds,
761 : : LSN_FORMAT_ARGS(lsn),
762 : : elapsed_seconds),
763 : : errdetail("Summarization has reached %X/%08X on disk and %X/%08X in memory.",
764 : : LSN_FORMAT_ARGS(summarized_lsn),
765 : : LSN_FORMAT_ARGS(pending_lsn))));
766 : 0 : }
767 : :
768 : : /*
769 : : * Align the wait time to prevent drift. This doesn't really matter,
770 : : * but we'd like the warnings about how long we've been waiting to say
771 : : * 10 seconds, 20 seconds, 30 seconds, 40 seconds ... without ever
772 : : * drifting to something that is not a multiple of ten.
773 : : */
774 : 0 : timeout_in_ms -=
775 : 0 : TimestampDifferenceMilliseconds(cycle_time, current_time);
776 : :
777 : : /* Wait and see. */
778 : 0 : ConditionVariableTimedSleep(&WalSummarizerCtl->summary_file_cv,
779 : 0 : timeout_in_ms,
780 : : WAIT_EVENT_WAL_SUMMARY_READY);
781 [ # # # ]: 0 : }
782 : :
783 : 0 : ConditionVariableCancelSleep();
784 [ # # ]: 0 : }
785 : :
786 : : /*
787 : : * On exit, update shared memory to make it clear that we're no longer
788 : : * running.
789 : : */
790 : : static void
791 : 0 : WalSummarizerShutdown(int code, Datum arg)
792 : : {
793 : 0 : LWLockAcquire(WALSummarizerLock, LW_EXCLUSIVE);
794 : 0 : WalSummarizerCtl->summarizer_pgprocno = INVALID_PROC_NUMBER;
795 : 0 : LWLockRelease(WALSummarizerLock);
796 : 0 : }
797 : :
798 : : /*
799 : : * Get the latest LSN that is eligible to be summarized, and set *tli to the
800 : : * corresponding timeline.
801 : : */
802 : : static XLogRecPtr
803 : 0 : GetLatestLSN(TimeLineID *tli)
804 : : {
805 [ # # ]: 0 : if (!RecoveryInProgress())
806 : : {
807 : : /* Don't summarize WAL before it's flushed. */
808 : 0 : return GetFlushRecPtr(tli);
809 : : }
810 : : else
811 : : {
812 : 0 : XLogRecPtr flush_lsn;
813 : 0 : TimeLineID flush_tli;
814 : 0 : XLogRecPtr replay_lsn;
815 : 0 : TimeLineID replay_tli;
816 : 0 : TimeLineID insert_tli;
817 : :
818 : : /*
819 : : * After the insert TLI has been set and before the control file has
820 : : * been updated to show the DB in production, RecoveryInProgress()
821 : : * will return true, because it's not yet safe for all backends to
822 : : * begin writing WAL. However, replay has already ceased, so from our
823 : : * point of view, recovery is already over. We should summarize up to
824 : : * where replay stopped and then prepare to resume at the start of the
825 : : * insert timeline.
826 : : */
827 [ # # ]: 0 : if ((insert_tli = GetWALInsertionTimeLineIfSet()) != 0)
828 : : {
829 : 0 : *tli = insert_tli;
830 : 0 : return GetXLogReplayRecPtr(NULL);
831 : : }
832 : :
833 : : /*
834 : : * What we really want to know is how much WAL has been flushed to
835 : : * disk, but the only flush position available is the one provided by
836 : : * the walreceiver, which may not be running, because this could be
837 : : * crash recovery or recovery via restore_command. So use either the
838 : : * WAL receiver's flush position or the replay position, whichever is
839 : : * further ahead, on the theory that if the WAL has been replayed then
840 : : * it must also have been flushed to disk.
841 : : */
842 : 0 : flush_lsn = GetWalRcvFlushRecPtr(NULL, &flush_tli);
843 : 0 : replay_lsn = GetXLogReplayRecPtr(&replay_tli);
844 [ # # ]: 0 : if (flush_lsn > replay_lsn)
845 : : {
846 : 0 : *tli = flush_tli;
847 : 0 : return flush_lsn;
848 : : }
849 : : else
850 : : {
851 : 0 : *tli = replay_tli;
852 : 0 : return replay_lsn;
853 : : }
854 : 0 : }
855 : 0 : }
856 : :
857 : : /*
858 : : * Interrupt handler for main loop of WAL summarizer process.
859 : : */
860 : : static void
861 : 0 : ProcessWalSummarizerInterrupts(void)
862 : : {
863 [ # # ]: 0 : if (ProcSignalBarrierPending)
864 : 0 : ProcessProcSignalBarrier();
865 : :
866 [ # # ]: 0 : if (ConfigReloadPending)
867 : : {
868 : 0 : ConfigReloadPending = false;
869 : 0 : ProcessConfigFile(PGC_SIGHUP);
870 : 0 : }
871 : :
872 [ # # ]: 0 : if (ShutdownRequestPending || !summarize_wal)
873 : : {
874 [ # # # # ]: 0 : ereport(DEBUG1,
875 : : errmsg_internal("WAL summarizer shutting down"));
876 : 0 : proc_exit(0);
877 : : }
878 : :
879 : : /* Perform logging of memory contexts of this process */
880 [ # # ]: 0 : if (LogMemoryContextPending)
881 : 0 : ProcessLogMemoryContextInterrupt();
882 : 0 : }
883 : :
884 : : /*
885 : : * Summarize a range of WAL records on a single timeline.
886 : : *
887 : : * 'tli' is the timeline to be summarized.
888 : : *
889 : : * 'start_lsn' is the point at which we should start summarizing. If this
890 : : * value comes from the end LSN of the previous record as returned by the
891 : : * xlogreader machinery, 'exact' should be true; otherwise, 'exact' should
892 : : * be false, and this function will search forward for the start of a valid
893 : : * WAL record.
894 : : *
895 : : * 'switch_lsn' is the point at which we should switch to a later timeline,
896 : : * if we're summarizing a historic timeline.
897 : : *
898 : : * 'maximum_lsn' identifies the point beyond which we can't count on being
899 : : * able to read any more WAL. It should be the switch point when reading a
900 : : * historic timeline, or the most-recently-measured end of WAL when reading
901 : : * the current timeline.
902 : : *
903 : : * The return value is the LSN at which the WAL summary actually ends. Most
904 : : * often, a summary file ends because we notice that a checkpoint has
905 : : * occurred and reach the redo pointer of that checkpoint, but sometimes
906 : : * we stop for other reasons, such as a timeline switch.
907 : : */
908 : : static XLogRecPtr
909 : 0 : SummarizeWAL(TimeLineID tli, XLogRecPtr start_lsn, bool exact,
910 : : XLogRecPtr switch_lsn, XLogRecPtr maximum_lsn)
911 : : {
912 : 0 : SummarizerReadLocalXLogPrivate *private_data;
913 : 0 : XLogReaderState *xlogreader;
914 : 0 : XLogRecPtr summary_start_lsn;
915 : 0 : XLogRecPtr summary_end_lsn = switch_lsn;
916 : 0 : char temp_path[MAXPGPATH];
917 : 0 : char final_path[MAXPGPATH];
918 : 0 : WalSummaryIO io;
919 : 0 : BlockRefTable *brtab = CreateEmptyBlockRefTable();
920 : 0 : bool fast_forward = true;
921 : :
922 : : /* Initialize private data for xlogreader. */
923 : 0 : private_data = palloc0_object(SummarizerReadLocalXLogPrivate);
924 : 0 : private_data->tli = tli;
925 : 0 : private_data->historic = XLogRecPtrIsValid(switch_lsn);
926 : 0 : private_data->read_upto = maximum_lsn;
927 : :
928 : : /* Create xlogreader. */
929 : 0 : xlogreader = XLogReaderAllocate(wal_segment_size, NULL,
930 : 0 : XL_ROUTINE(.page_read = &summarizer_read_local_xlog_page,
931 : : .segment_open = &wal_segment_open,
932 : : .segment_close = &wal_segment_close),
933 : 0 : private_data);
934 [ # # ]: 0 : if (xlogreader == NULL)
935 [ # # # # ]: 0 : ereport(ERROR,
936 : : (errcode(ERRCODE_OUT_OF_MEMORY),
937 : : errmsg("out of memory"),
938 : : errdetail("Failed while allocating a WAL reading processor.")));
939 : :
940 : : /*
941 : : * When exact = false, we're starting from an arbitrary point in the WAL
942 : : * and must search forward for the start of the next record.
943 : : *
944 : : * When exact = true, start_lsn should be either the LSN where a record
945 : : * begins, or the LSN of a page where the page header is immediately
946 : : * followed by the start of a new record. XLogBeginRead should tolerate
947 : : * either case.
948 : : *
949 : : * We need to allow for both cases because the behavior of xlogreader
950 : : * varies. When a record spans two or more xlog pages, the ending LSN
951 : : * reported by xlogreader will be the starting LSN of the following
952 : : * record, but when an xlog page boundary falls between two records, the
953 : : * end LSN for the first will be reported as the first byte of the
954 : : * following page. We can't know until we read that page how large the
955 : : * header will be, but we'll have to skip over it to find the next record.
956 : : */
957 [ # # ]: 0 : if (exact)
958 : : {
959 : : /*
960 : : * Even if start_lsn is the beginning of a page rather than the
961 : : * beginning of the first record on that page, we should still use it
962 : : * as the start LSN for the summary file. That's because we detect
963 : : * missing summary files by looking for cases where the end LSN of one
964 : : * file is less than the start LSN of the next file. When only a page
965 : : * header is skipped, nothing has been missed.
966 : : */
967 : 0 : XLogBeginRead(xlogreader, start_lsn);
968 : 0 : summary_start_lsn = start_lsn;
969 : 0 : }
970 : : else
971 : : {
972 : 0 : summary_start_lsn = XLogFindNextRecord(xlogreader, start_lsn);
973 [ # # ]: 0 : if (!XLogRecPtrIsValid(summary_start_lsn))
974 : : {
975 : : /*
976 : : * If we hit end-of-WAL while trying to find the next valid
977 : : * record, we must be on a historic timeline that has no valid
978 : : * records that begin after start_lsn and before end of WAL.
979 : : */
980 [ # # ]: 0 : if (private_data->end_of_wal)
981 : : {
982 [ # # # # ]: 0 : ereport(DEBUG1,
983 : : errmsg_internal("could not read WAL from timeline %u at %X/%08X: end of WAL at %X/%08X",
984 : : tli,
985 : : LSN_FORMAT_ARGS(start_lsn),
986 : : LSN_FORMAT_ARGS(private_data->read_upto)));
987 : :
988 : : /*
989 : : * The timeline ends at or after start_lsn, without containing
990 : : * any records. Thus, we must make sure the main loop does not
991 : : * iterate. If start_lsn is the end of the timeline, then we
992 : : * won't actually emit an empty summary file, but otherwise,
993 : : * we must, to capture the fact that the LSN range in question
994 : : * contains no interesting WAL records.
995 : : */
996 : 0 : summary_start_lsn = start_lsn;
997 : 0 : summary_end_lsn = private_data->read_upto;
998 : 0 : switch_lsn = xlogreader->EndRecPtr;
999 : 0 : }
1000 : : else
1001 [ # # # # ]: 0 : ereport(ERROR,
1002 : : errmsg("could not find a valid record after %X/%08X",
1003 : : LSN_FORMAT_ARGS(start_lsn)));
1004 : 0 : }
1005 : :
1006 : : /* We shouldn't go backward. */
1007 [ # # ]: 0 : Assert(summary_start_lsn >= start_lsn);
1008 : : }
1009 : :
1010 : : /*
1011 : : * Main loop: read xlog records one by one.
1012 : : */
1013 : 0 : while (1)
1014 : : {
1015 : 0 : int block_id;
1016 : 0 : char *errormsg;
1017 : 0 : XLogRecord *record;
1018 : 0 : uint8 rmid;
1019 : :
1020 : 0 : ProcessWalSummarizerInterrupts();
1021 : :
1022 : : /* We shouldn't go backward. */
1023 [ # # ]: 0 : Assert(summary_start_lsn <= xlogreader->EndRecPtr);
1024 : :
1025 : : /* Now read the next record. */
1026 : 0 : record = XLogReadRecord(xlogreader, &errormsg);
1027 [ # # ]: 0 : if (record == NULL)
1028 : : {
1029 [ # # ]: 0 : if (private_data->end_of_wal)
1030 : : {
1031 : : /*
1032 : : * This timeline must be historic and must end before we were
1033 : : * able to read a complete record.
1034 : : */
1035 [ # # # # ]: 0 : ereport(DEBUG1,
1036 : : errmsg_internal("could not read WAL from timeline %u at %X/%08X: end of WAL at %X/%08X",
1037 : : tli,
1038 : : LSN_FORMAT_ARGS(xlogreader->EndRecPtr),
1039 : : LSN_FORMAT_ARGS(private_data->read_upto)));
1040 : : /* Summary ends at end of WAL. */
1041 : 0 : summary_end_lsn = private_data->read_upto;
1042 : 0 : break;
1043 : : }
1044 [ # # ]: 0 : if (errormsg)
1045 [ # # # # ]: 0 : ereport(ERROR,
1046 : : (errcode_for_file_access(),
1047 : : errmsg("could not read WAL from timeline %u at %X/%08X: %s",
1048 : : tli, LSN_FORMAT_ARGS(xlogreader->EndRecPtr),
1049 : : errormsg)));
1050 : : else
1051 [ # # # # ]: 0 : ereport(ERROR,
1052 : : (errcode_for_file_access(),
1053 : : errmsg("could not read WAL from timeline %u at %X/%08X",
1054 : : tli, LSN_FORMAT_ARGS(xlogreader->EndRecPtr))));
1055 : 0 : }
1056 : :
1057 : : /* We shouldn't go backward. */
1058 [ # # ]: 0 : Assert(summary_start_lsn <= xlogreader->EndRecPtr);
1059 : :
1060 [ # # # # ]: 0 : if (XLogRecPtrIsValid(switch_lsn) &&
1061 : 0 : xlogreader->ReadRecPtr >= switch_lsn)
1062 : : {
1063 : : /*
1064 : : * Whoops! We've read a record that *starts* after the switch LSN,
1065 : : * contrary to our goal of reading only until we hit the first
1066 : : * record that ends at or after the switch LSN. Pretend we didn't
1067 : : * read it after all by bailing out of this loop right here,
1068 : : * before we do anything with this record.
1069 : : *
1070 : : * This can happen because the last record before the switch LSN
1071 : : * might be continued across multiple pages, and then we might
1072 : : * come to a page with XLP_FIRST_IS_OVERWRITE_CONTRECORD set. In
1073 : : * that case, the record that was continued across multiple pages
1074 : : * is incomplete and will be disregarded, and the read will
1075 : : * restart from the beginning of the page that is flagged
1076 : : * XLP_FIRST_IS_OVERWRITE_CONTRECORD.
1077 : : *
1078 : : * If this case occurs, we can fairly say that the current summary
1079 : : * file ends at the switch LSN exactly. The first record on the
1080 : : * page marked XLP_FIRST_IS_OVERWRITE_CONTRECORD will be
1081 : : * discovered when generating the next summary file.
1082 : : */
1083 : 0 : summary_end_lsn = switch_lsn;
1084 : 0 : break;
1085 : : }
1086 : :
1087 : : /*
1088 : : * Certain types of records require special handling. Redo points and
1089 : : * shutdown checkpoints trigger creation of new summary files and can
1090 : : * also cause us to enter or exit "fast forward" mode. Other types of
1091 : : * records can require special updates to the block reference table.
1092 : : */
1093 : 0 : rmid = XLogRecGetRmid(xlogreader);
1094 [ # # ]: 0 : if (rmid == RM_XLOG_ID)
1095 : : {
1096 : 0 : bool new_fast_forward;
1097 : :
1098 : : /*
1099 : : * If we've already processed some WAL records when we hit a redo
1100 : : * point or shutdown checkpoint, then we stop summarization before
1101 : : * including this record in the current file, so that it will be
1102 : : * the first record in the next file.
1103 : : *
1104 : : * When we hit one of those record types as the first record in a
1105 : : * file, we adjust our notion of whether we're fast-forwarding.
1106 : : * Any WAL generated with wal_level=minimal must be skipped
1107 : : * without actually generating any summary file, because an
1108 : : * incremental backup that crosses such WAL would be unsafe.
1109 : : */
1110 [ # # ]: 0 : if (SummarizeXlogRecord(xlogreader, &new_fast_forward))
1111 : : {
1112 [ # # ]: 0 : if (xlogreader->ReadRecPtr > summary_start_lsn)
1113 : : {
1114 : 0 : summary_end_lsn = xlogreader->ReadRecPtr;
1115 : 0 : break;
1116 : : }
1117 : : else
1118 : 0 : fast_forward = new_fast_forward;
1119 : 0 : }
1120 [ # # ]: 0 : }
1121 [ # # ]: 0 : else if (!fast_forward)
1122 : : {
1123 : : /*
1124 : : * This switch handles record types that require extra updates to
1125 : : * the contents of the block reference table.
1126 : : */
1127 [ # # # # ]: 0 : switch (rmid)
1128 : : {
1129 : : case RM_DBASE_ID:
1130 : 0 : SummarizeDbaseRecord(xlogreader, brtab);
1131 : 0 : break;
1132 : : case RM_SMGR_ID:
1133 : 0 : SummarizeSmgrRecord(xlogreader, brtab);
1134 : 0 : break;
1135 : : case RM_XACT_ID:
1136 : 0 : SummarizeXactRecord(xlogreader, brtab);
1137 : 0 : break;
1138 : : }
1139 : 0 : }
1140 : :
1141 : : /*
1142 : : * If we're in fast-forward mode, we don't really need to do anything.
1143 : : * Otherwise, feed block references from xlog record to block
1144 : : * reference table.
1145 : : */
1146 [ # # ]: 0 : if (!fast_forward)
1147 : : {
1148 [ # # ]: 0 : for (block_id = 0; block_id <= XLogRecMaxBlockId(xlogreader);
1149 : 0 : block_id++)
1150 : : {
1151 : 0 : RelFileLocator rlocator;
1152 : 0 : ForkNumber forknum;
1153 : 0 : BlockNumber blocknum;
1154 : :
1155 [ # # ]: 0 : if (!XLogRecGetBlockTagExtended(xlogreader, block_id, &rlocator,
1156 : : &forknum, &blocknum, NULL))
1157 : 0 : continue;
1158 : :
1159 : : /*
1160 : : * As we do elsewhere, ignore the FSM fork, because it's not
1161 : : * fully WAL-logged.
1162 : : */
1163 [ # # ]: 0 : if (forknum != FSM_FORKNUM)
1164 : 0 : BlockRefTableMarkBlockModified(brtab, &rlocator, forknum,
1165 : 0 : blocknum);
1166 [ # # ]: 0 : }
1167 : 0 : }
1168 : :
1169 : : /* Update our notion of where this summary file ends. */
1170 : 0 : summary_end_lsn = xlogreader->EndRecPtr;
1171 : :
1172 : : /* Also update shared memory. */
1173 : 0 : LWLockAcquire(WALSummarizerLock, LW_EXCLUSIVE);
1174 [ # # ]: 0 : Assert(summary_end_lsn >= WalSummarizerCtl->summarized_lsn);
1175 : 0 : WalSummarizerCtl->pending_lsn = summary_end_lsn;
1176 : 0 : LWLockRelease(WALSummarizerLock);
1177 : :
1178 : : /*
1179 : : * If we have a switch LSN and have reached it, stop before reading
1180 : : * the next record.
1181 : : */
1182 [ # # # # ]: 0 : if (XLogRecPtrIsValid(switch_lsn) &&
1183 : 0 : xlogreader->EndRecPtr >= switch_lsn)
1184 : 0 : break;
1185 [ # # ]: 0 : }
1186 : :
1187 : : /* Destroy xlogreader. */
1188 : 0 : pfree(xlogreader->private_data);
1189 : 0 : XLogReaderFree(xlogreader);
1190 : :
1191 : : /*
1192 : : * If a timeline switch occurs, we may fail to make any progress at all
1193 : : * before exiting the loop above. If that happens, we don't write a WAL
1194 : : * summary file at all. We can also skip writing a file if we're in
1195 : : * fast-forward mode.
1196 : : */
1197 [ # # # # ]: 0 : if (summary_end_lsn > summary_start_lsn && !fast_forward)
1198 : : {
1199 : : /* Generate temporary and final path name. */
1200 : 0 : snprintf(temp_path, MAXPGPATH,
1201 : : XLOGDIR "/summaries/temp.summary");
1202 : 0 : snprintf(final_path, MAXPGPATH,
1203 : : XLOGDIR "/summaries/%08X%08X%08X%08X%08X.summary",
1204 : 0 : tli,
1205 : 0 : LSN_FORMAT_ARGS(summary_start_lsn),
1206 : 0 : LSN_FORMAT_ARGS(summary_end_lsn));
1207 : :
1208 : : /* Open the temporary file for writing. */
1209 : 0 : io.filepos = 0;
1210 : 0 : io.file = PathNameOpenFile(temp_path, O_WRONLY | O_CREAT | O_TRUNC);
1211 [ # # ]: 0 : if (io.file < 0)
1212 [ # # # # ]: 0 : ereport(ERROR,
1213 : : (errcode_for_file_access(),
1214 : : errmsg("could not create file \"%s\": %m", temp_path)));
1215 : :
1216 : : /* Write the data. */
1217 : 0 : WriteBlockRefTable(brtab, WriteWalSummary, &io);
1218 : :
1219 : : /* Close temporary file and shut down xlogreader. */
1220 : 0 : FileClose(io.file);
1221 : :
1222 : : /* Tell the user what we did. */
1223 [ # # # # ]: 0 : ereport(DEBUG1,
1224 : : errmsg_internal("summarized WAL on TLI %u from %X/%08X to %X/%08X",
1225 : : tli,
1226 : : LSN_FORMAT_ARGS(summary_start_lsn),
1227 : : LSN_FORMAT_ARGS(summary_end_lsn)));
1228 : :
1229 : : /* Durably rename the new summary into place. */
1230 : 0 : durable_rename(temp_path, final_path, ERROR);
1231 : 0 : }
1232 : :
1233 : : /* If we skipped a non-zero amount of WAL, log a debug message. */
1234 [ # # # # ]: 0 : if (summary_end_lsn > summary_start_lsn && fast_forward)
1235 [ # # # # ]: 0 : ereport(DEBUG1,
1236 : : errmsg_internal("skipped summarizing WAL on TLI %u from %X/%08X to %X/%08X",
1237 : : tli,
1238 : : LSN_FORMAT_ARGS(summary_start_lsn),
1239 : : LSN_FORMAT_ARGS(summary_end_lsn)));
1240 : :
1241 : 0 : return summary_end_lsn;
1242 : 0 : }
1243 : :
1244 : : /*
1245 : : * Special handling for WAL records with RM_DBASE_ID.
1246 : : */
1247 : : static void
1248 : 0 : SummarizeDbaseRecord(XLogReaderState *xlogreader, BlockRefTable *brtab)
1249 : : {
1250 : 0 : uint8 info = XLogRecGetInfo(xlogreader) & ~XLR_INFO_MASK;
1251 : :
1252 : : /*
1253 : : * We use relfilenode zero for a given database OID and tablespace OID to
1254 : : * indicate that all relations with that pair of IDs have been recreated
1255 : : * if they exist at all. Effectively, we're setting a limit block of 0 for
1256 : : * all such relfilenodes.
1257 : : *
1258 : : * Technically, this special handling is only needed in the case of
1259 : : * XLOG_DBASE_CREATE_FILE_COPY, because that can create a whole bunch of
1260 : : * relation files in a directory without logging anything specific to each
1261 : : * one. If we didn't mark the whole DB OID/TS OID combination in some way,
1262 : : * then a tablespace that was dropped after the reference backup and
1263 : : * recreated using the FILE_COPY method prior to the incremental backup
1264 : : * would look just like one that was never touched at all, which would be
1265 : : * catastrophic.
1266 : : *
1267 : : * But it seems best to adopt this treatment for all records that drop or
1268 : : * create a DB OID/TS OID combination. That's similar to how we treat the
1269 : : * limit block for individual relations, and it's an extra layer of safety
1270 : : * here. We can never lose data by marking more stuff as needing to be
1271 : : * backed up in full.
1272 : : */
1273 [ # # ]: 0 : if (info == XLOG_DBASE_CREATE_FILE_COPY)
1274 : : {
1275 : 0 : xl_dbase_create_file_copy_rec *xlrec;
1276 : 0 : RelFileLocator rlocator;
1277 : :
1278 : 0 : xlrec =
1279 : 0 : (xl_dbase_create_file_copy_rec *) XLogRecGetData(xlogreader);
1280 : 0 : rlocator.spcOid = xlrec->tablespace_id;
1281 : 0 : rlocator.dbOid = xlrec->db_id;
1282 : 0 : rlocator.relNumber = 0;
1283 : 0 : BlockRefTableSetLimitBlock(brtab, &rlocator, MAIN_FORKNUM, 0);
1284 : 0 : }
1285 [ # # ]: 0 : else if (info == XLOG_DBASE_CREATE_WAL_LOG)
1286 : : {
1287 : 0 : xl_dbase_create_wal_log_rec *xlrec;
1288 : 0 : RelFileLocator rlocator;
1289 : :
1290 : 0 : xlrec = (xl_dbase_create_wal_log_rec *) XLogRecGetData(xlogreader);
1291 : 0 : rlocator.spcOid = xlrec->tablespace_id;
1292 : 0 : rlocator.dbOid = xlrec->db_id;
1293 : 0 : rlocator.relNumber = 0;
1294 : 0 : BlockRefTableSetLimitBlock(brtab, &rlocator, MAIN_FORKNUM, 0);
1295 : 0 : }
1296 [ # # ]: 0 : else if (info == XLOG_DBASE_DROP)
1297 : : {
1298 : 0 : xl_dbase_drop_rec *xlrec;
1299 : 0 : RelFileLocator rlocator;
1300 : 0 : int i;
1301 : :
1302 : 0 : xlrec = (xl_dbase_drop_rec *) XLogRecGetData(xlogreader);
1303 : 0 : rlocator.dbOid = xlrec->db_id;
1304 : 0 : rlocator.relNumber = 0;
1305 [ # # ]: 0 : for (i = 0; i < xlrec->ntablespaces; ++i)
1306 : : {
1307 : 0 : rlocator.spcOid = xlrec->tablespace_ids[i];
1308 : 0 : BlockRefTableSetLimitBlock(brtab, &rlocator, MAIN_FORKNUM, 0);
1309 : 0 : }
1310 : 0 : }
1311 : 0 : }
1312 : :
1313 : : /*
1314 : : * Special handling for WAL records with RM_SMGR_ID.
1315 : : */
1316 : : static void
1317 : 0 : SummarizeSmgrRecord(XLogReaderState *xlogreader, BlockRefTable *brtab)
1318 : : {
1319 : 0 : uint8 info = XLogRecGetInfo(xlogreader) & ~XLR_INFO_MASK;
1320 : :
1321 [ # # ]: 0 : if (info == XLOG_SMGR_CREATE)
1322 : : {
1323 : 0 : xl_smgr_create *xlrec;
1324 : :
1325 : : /*
1326 : : * If a new relation fork is created on disk, there is no point
1327 : : * tracking anything about which blocks have been modified, because
1328 : : * the whole thing will be new. Hence, set the limit block for this
1329 : : * fork to 0.
1330 : : *
1331 : : * Ignore the FSM fork, which is not fully WAL-logged.
1332 : : */
1333 : 0 : xlrec = (xl_smgr_create *) XLogRecGetData(xlogreader);
1334 : :
1335 [ # # ]: 0 : if (xlrec->forkNum != FSM_FORKNUM)
1336 : 0 : BlockRefTableSetLimitBlock(brtab, &xlrec->rlocator,
1337 : 0 : xlrec->forkNum, 0);
1338 : 0 : }
1339 [ # # ]: 0 : else if (info == XLOG_SMGR_TRUNCATE)
1340 : : {
1341 : 0 : xl_smgr_truncate *xlrec;
1342 : :
1343 : 0 : xlrec = (xl_smgr_truncate *) XLogRecGetData(xlogreader);
1344 : :
1345 : : /*
1346 : : * If a relation fork is truncated on disk, there is no point in
1347 : : * tracking anything about block modifications beyond the truncation
1348 : : * point.
1349 : : *
1350 : : * We ignore SMGR_TRUNCATE_FSM here because the FSM isn't fully
1351 : : * WAL-logged and thus we can't track modified blocks for it anyway.
1352 : : */
1353 [ # # ]: 0 : if ((xlrec->flags & SMGR_TRUNCATE_HEAP) != 0)
1354 : 0 : BlockRefTableSetLimitBlock(brtab, &xlrec->rlocator,
1355 : 0 : MAIN_FORKNUM, xlrec->blkno);
1356 [ # # ]: 0 : if ((xlrec->flags & SMGR_TRUNCATE_VM) != 0)
1357 : 0 : BlockRefTableSetLimitBlock(brtab, &xlrec->rlocator,
1358 : 0 : VISIBILITYMAP_FORKNUM, xlrec->blkno);
1359 : 0 : }
1360 : 0 : }
1361 : :
1362 : : /*
1363 : : * Special handling for WAL records with RM_XACT_ID.
1364 : : */
1365 : : static void
1366 : 0 : SummarizeXactRecord(XLogReaderState *xlogreader, BlockRefTable *brtab)
1367 : : {
1368 : 0 : uint8 info = XLogRecGetInfo(xlogreader) & ~XLR_INFO_MASK;
1369 : 0 : uint8 xact_info = info & XLOG_XACT_OPMASK;
1370 : :
1371 [ # # # # ]: 0 : if (xact_info == XLOG_XACT_COMMIT ||
1372 : 0 : xact_info == XLOG_XACT_COMMIT_PREPARED)
1373 : : {
1374 : 0 : xl_xact_commit *xlrec = (xl_xact_commit *) XLogRecGetData(xlogreader);
1375 : 0 : xl_xact_parsed_commit parsed;
1376 : 0 : int i;
1377 : :
1378 : : /*
1379 : : * Don't track modified blocks for any relations that were removed on
1380 : : * commit.
1381 : : */
1382 : 0 : ParseCommitRecord(XLogRecGetInfo(xlogreader), xlrec, &parsed);
1383 [ # # ]: 0 : for (i = 0; i < parsed.nrels; ++i)
1384 : : {
1385 : 0 : ForkNumber forknum;
1386 : :
1387 [ # # ]: 0 : for (forknum = 0; forknum <= MAX_FORKNUM; ++forknum)
1388 [ # # ]: 0 : if (forknum != FSM_FORKNUM)
1389 : 0 : BlockRefTableSetLimitBlock(brtab, &parsed.xlocators[i],
1390 : 0 : forknum, 0);
1391 : 0 : }
1392 : 0 : }
1393 [ # # # # ]: 0 : else if (xact_info == XLOG_XACT_ABORT ||
1394 : 0 : xact_info == XLOG_XACT_ABORT_PREPARED)
1395 : : {
1396 : 0 : xl_xact_abort *xlrec = (xl_xact_abort *) XLogRecGetData(xlogreader);
1397 : 0 : xl_xact_parsed_abort parsed;
1398 : 0 : int i;
1399 : :
1400 : : /*
1401 : : * Don't track modified blocks for any relations that were removed on
1402 : : * abort.
1403 : : */
1404 : 0 : ParseAbortRecord(XLogRecGetInfo(xlogreader), xlrec, &parsed);
1405 [ # # ]: 0 : for (i = 0; i < parsed.nrels; ++i)
1406 : : {
1407 : 0 : ForkNumber forknum;
1408 : :
1409 [ # # ]: 0 : for (forknum = 0; forknum <= MAX_FORKNUM; ++forknum)
1410 [ # # ]: 0 : if (forknum != FSM_FORKNUM)
1411 : 0 : BlockRefTableSetLimitBlock(brtab, &parsed.xlocators[i],
1412 : 0 : forknum, 0);
1413 : 0 : }
1414 : 0 : }
1415 : 0 : }
1416 : :
1417 : : /*
1418 : : * Special handling for WAL records with RM_XLOG_ID.
1419 : : *
1420 : : * The return value is true if WAL summarization should stop before this
1421 : : * record and false otherwise. When the return value is true,
1422 : : * *new_fast_forward indicates whether future processing should be done
1423 : : * in fast forward mode (i.e. read WAL without emitting summaries) or not.
1424 : : */
1425 : : static bool
1426 : 0 : SummarizeXlogRecord(XLogReaderState *xlogreader, bool *new_fast_forward)
1427 : : {
1428 : 0 : uint8 info = XLogRecGetInfo(xlogreader) & ~XLR_INFO_MASK;
1429 : 0 : int record_wal_level;
1430 : :
1431 [ # # ]: 0 : if (info == XLOG_CHECKPOINT_REDO)
1432 : : {
1433 : : /* Payload is wal_level at the time record was written. */
1434 : 0 : memcpy(&record_wal_level, XLogRecGetData(xlogreader), sizeof(int));
1435 : 0 : }
1436 [ # # ]: 0 : else if (info == XLOG_CHECKPOINT_SHUTDOWN)
1437 : : {
1438 : 0 : CheckPoint rec_ckpt;
1439 : :
1440 : : /* Extract wal_level at time record was written from payload. */
1441 : 0 : memcpy(&rec_ckpt, XLogRecGetData(xlogreader), sizeof(CheckPoint));
1442 : 0 : record_wal_level = rec_ckpt.wal_level;
1443 : 0 : }
1444 [ # # ]: 0 : else if (info == XLOG_PARAMETER_CHANGE)
1445 : : {
1446 : 0 : xl_parameter_change xlrec;
1447 : :
1448 : : /* Extract wal_level at time record was written from payload. */
1449 : 0 : memcpy(&xlrec, XLogRecGetData(xlogreader),
1450 : : sizeof(xl_parameter_change));
1451 : 0 : record_wal_level = xlrec.wal_level;
1452 : 0 : }
1453 [ # # ]: 0 : else if (info == XLOG_END_OF_RECOVERY)
1454 : : {
1455 : 0 : xl_end_of_recovery xlrec;
1456 : :
1457 : : /* Extract wal_level at time record was written from payload. */
1458 : 0 : memcpy(&xlrec, XLogRecGetData(xlogreader), sizeof(xl_end_of_recovery));
1459 : 0 : record_wal_level = xlrec.wal_level;
1460 : 0 : }
1461 : : else
1462 : : {
1463 : : /* No special handling required. Return false. */
1464 : 0 : return false;
1465 : : }
1466 : :
1467 : : /*
1468 : : * Redo can only begin at an XLOG_CHECKPOINT_REDO or
1469 : : * XLOG_CHECKPOINT_SHUTDOWN record, so we want WAL summarization to begin
1470 : : * at those points. Hence, when those records are encountered, return
1471 : : * true, so that we stop just before summarizing either of those records.
1472 : : *
1473 : : * We also reach here if we just saw XLOG_END_OF_RECOVERY or
1474 : : * XLOG_PARAMETER_CHANGE. These are not places where recovery can start,
1475 : : * but they're still relevant here. A new timeline can begin with
1476 : : * XLOG_END_OF_RECOVERY, so we need to confirm the WAL level at that
1477 : : * point; and a restart can provoke XLOG_PARAMETER_CHANGE after an
1478 : : * intervening change to postgresql.conf, which might force us to stop
1479 : : * summarizing.
1480 : : */
1481 : 0 : *new_fast_forward = (record_wal_level == WAL_LEVEL_MINIMAL);
1482 : 0 : return true;
1483 : 0 : }
1484 : :
1485 : : /*
1486 : : * Similar to read_local_xlog_page, but limited to read from one particular
1487 : : * timeline. If the end of WAL is reached, it will wait for more if reading
1488 : : * from the current timeline, or give up if reading from a historic timeline.
1489 : : * In the latter case, it will also set private_data->end_of_wal = true.
1490 : : *
1491 : : * Caller must set private_data->tli to the TLI of interest,
1492 : : * private_data->read_upto to the lowest LSN that is not known to be safe
1493 : : * to read on that timeline, and private_data->historic to true if and only
1494 : : * if the timeline is not the current timeline. This function will update
1495 : : * private_data->read_upto and private_data->historic if more WAL appears
1496 : : * on the current timeline or if the current timeline becomes historic.
1497 : : */
1498 : : static int
1499 : 0 : summarizer_read_local_xlog_page(XLogReaderState *state,
1500 : : XLogRecPtr targetPagePtr, int reqLen,
1501 : : XLogRecPtr targetRecPtr, char *cur_page)
1502 : : {
1503 : 0 : int count;
1504 : 0 : WALReadError errinfo;
1505 : 0 : SummarizerReadLocalXLogPrivate *private_data;
1506 : :
1507 : 0 : ProcessWalSummarizerInterrupts();
1508 : :
1509 : 0 : private_data = (SummarizerReadLocalXLogPrivate *)
1510 : 0 : state->private_data;
1511 : :
1512 : 0 : while (1)
1513 : : {
1514 [ # # ]: 0 : if (targetPagePtr + XLOG_BLCKSZ <= private_data->read_upto)
1515 : : {
1516 : : /*
1517 : : * more than one block available; read only that block, have
1518 : : * caller come back if they need more.
1519 : : */
1520 : 0 : count = XLOG_BLCKSZ;
1521 : 0 : break;
1522 : : }
1523 [ # # ]: 0 : else if (targetPagePtr + reqLen > private_data->read_upto)
1524 : : {
1525 : : /* We don't seem to have enough data. */
1526 [ # # ]: 0 : if (private_data->historic)
1527 : : {
1528 : : /*
1529 : : * This is a historic timeline, so there will never be any
1530 : : * more data than we have currently.
1531 : : */
1532 : 0 : private_data->end_of_wal = true;
1533 : 0 : return -1;
1534 : : }
1535 : : else
1536 : : {
1537 : 0 : XLogRecPtr latest_lsn;
1538 : 0 : TimeLineID latest_tli;
1539 : :
1540 : : /*
1541 : : * This is - or at least was up until very recently - the
1542 : : * current timeline, so more data might show up. Delay here
1543 : : * so we don't tight-loop.
1544 : : */
1545 : 0 : ProcessWalSummarizerInterrupts();
1546 : 0 : summarizer_wait_for_wal();
1547 : :
1548 : : /* Recheck end-of-WAL. */
1549 : 0 : latest_lsn = GetLatestLSN(&latest_tli);
1550 [ # # ]: 0 : if (private_data->tli == latest_tli)
1551 : : {
1552 : : /* Still the current timeline, update max LSN. */
1553 [ # # ]: 0 : Assert(latest_lsn >= private_data->read_upto);
1554 : 0 : private_data->read_upto = latest_lsn;
1555 : 0 : }
1556 : : else
1557 : : {
1558 : 0 : List *tles = readTimeLineHistory(latest_tli);
1559 : 0 : XLogRecPtr switchpoint;
1560 : :
1561 : : /*
1562 : : * The timeline we're scanning is no longer the latest
1563 : : * one. Figure out when it ended.
1564 : : */
1565 : 0 : private_data->historic = true;
1566 : 0 : switchpoint = tliSwitchPoint(private_data->tli, tles,
1567 : : NULL);
1568 : :
1569 : : /*
1570 : : * Allow reads up to exactly the switch point.
1571 : : *
1572 : : * It's possible that this will cause read_upto to move
1573 : : * backwards, because we might have been promoted before
1574 : : * reaching the end of the previous timeline. In that
1575 : : * case, the next loop iteration will likely conclude that
1576 : : * we've reached end of WAL.
1577 : : */
1578 : 0 : private_data->read_upto = switchpoint;
1579 : :
1580 : : /* Debugging output. */
1581 [ # # # # ]: 0 : ereport(DEBUG1,
1582 : : errmsg_internal("timeline %u became historic, can read up to %X/%08X",
1583 : : private_data->tli, LSN_FORMAT_ARGS(private_data->read_upto)));
1584 : 0 : }
1585 : :
1586 : : /* Go around and try again. */
1587 : 0 : }
1588 : 0 : }
1589 : : else
1590 : : {
1591 : : /* enough bytes available to satisfy the request */
1592 : 0 : count = private_data->read_upto - targetPagePtr;
1593 : 0 : break;
1594 : : }
1595 : : }
1596 : :
1597 [ # # # # ]: 0 : if (!WALRead(state, cur_page, targetPagePtr, count,
1598 : 0 : private_data->tli, &errinfo))
1599 : 0 : WALReadRaiseError(&errinfo);
1600 : :
1601 : : /* Track that we read a page, for sleep time calculation. */
1602 : 0 : ++pages_read_since_last_sleep;
1603 : :
1604 : : /* number of valid bytes in the buffer */
1605 : 0 : return count;
1606 : 0 : }
1607 : :
1608 : : /*
1609 : : * Sleep for long enough that we believe it's likely that more WAL will
1610 : : * be available afterwards.
1611 : : */
1612 : : static void
1613 : 0 : summarizer_wait_for_wal(void)
1614 : : {
1615 [ # # ]: 0 : if (pages_read_since_last_sleep == 0)
1616 : : {
1617 : : /*
1618 : : * No pages were read since the last sleep, so double the sleep time,
1619 : : * but not beyond the maximum allowable value.
1620 : : */
1621 [ # # ]: 0 : sleep_quanta = Min(sleep_quanta * 2, MAX_SLEEP_QUANTA);
1622 : 0 : }
1623 [ # # ]: 0 : else if (pages_read_since_last_sleep > 1)
1624 : : {
1625 : : /*
1626 : : * Multiple pages were read since the last sleep, so reduce the sleep
1627 : : * time.
1628 : : *
1629 : : * A large burst of activity should be able to quickly reduce the
1630 : : * sleep time to the minimum, but we don't want a handful of extra WAL
1631 : : * records to provoke a strong reaction. We choose to reduce the sleep
1632 : : * time by 1 quantum for each page read beyond the first, which is a
1633 : : * fairly arbitrary way of trying to be reactive without overreacting.
1634 : : */
1635 [ # # ]: 0 : if (pages_read_since_last_sleep > sleep_quanta - 1)
1636 : 0 : sleep_quanta = 1;
1637 : : else
1638 : 0 : sleep_quanta -= pages_read_since_last_sleep;
1639 : 0 : }
1640 : :
1641 : : /* Report pending statistics to the cumulative stats system. */
1642 : 0 : pgstat_report_wal(false);
1643 : :
1644 : : /* OK, now sleep. */
1645 : 0 : (void) WaitLatch(MyLatch,
1646 : : WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
1647 : 0 : sleep_quanta * MS_PER_SLEEP_QUANTUM,
1648 : : WAIT_EVENT_WAL_SUMMARIZER_WAL);
1649 : 0 : ResetLatch(MyLatch);
1650 : :
1651 : : /* Reset count of pages read. */
1652 : 0 : pages_read_since_last_sleep = 0;
1653 : 0 : }
1654 : :
1655 : : /*
1656 : : * Remove WAL summaries whose mtimes are older than wal_summary_keep_time.
1657 : : */
1658 : : static void
1659 : 0 : MaybeRemoveOldWalSummaries(void)
1660 : : {
1661 : 0 : XLogRecPtr redo_pointer = GetRedoRecPtr();
1662 : 0 : List *wslist;
1663 : 0 : time_t cutoff_time;
1664 : :
1665 : : /* If WAL summary removal is disabled, don't do anything. */
1666 [ # # ]: 0 : if (wal_summary_keep_time == 0)
1667 : 0 : return;
1668 : :
1669 : : /*
1670 : : * If the redo pointer has not advanced, don't do anything.
1671 : : *
1672 : : * This has the effect that we only try to remove old WAL summary files
1673 : : * once per checkpoint cycle.
1674 : : */
1675 [ # # ]: 0 : if (redo_pointer == redo_pointer_at_last_summary_removal)
1676 : 0 : return;
1677 : 0 : redo_pointer_at_last_summary_removal = redo_pointer;
1678 : :
1679 : : /*
1680 : : * Files should only be removed if the last modification time precedes the
1681 : : * cutoff time we compute here.
1682 : : */
1683 : 0 : cutoff_time = time(NULL) - wal_summary_keep_time * SECS_PER_MINUTE;
1684 : :
1685 : : /* Get all the summaries that currently exist. */
1686 : 0 : wslist = GetWalSummaries(0, InvalidXLogRecPtr, InvalidXLogRecPtr);
1687 : :
1688 : : /* Loop until all summaries have been considered for removal. */
1689 [ # # ]: 0 : while (wslist != NIL)
1690 : : {
1691 : 0 : ListCell *lc;
1692 : 0 : XLogSegNo oldest_segno;
1693 : 0 : XLogRecPtr oldest_lsn = InvalidXLogRecPtr;
1694 : 0 : TimeLineID selected_tli;
1695 : :
1696 : 0 : ProcessWalSummarizerInterrupts();
1697 : :
1698 : : /*
1699 : : * Pick a timeline for which some summary files still exist on disk,
1700 : : * and find the oldest LSN that still exists on disk for that
1701 : : * timeline.
1702 : : */
1703 : 0 : selected_tli = ((WalSummaryFile *) linitial(wslist))->tli;
1704 : 0 : oldest_segno = XLogGetOldestSegno(selected_tli);
1705 [ # # ]: 0 : if (oldest_segno != 0)
1706 : 0 : XLogSegNoOffsetToRecPtr(oldest_segno, 0, wal_segment_size,
1707 : : oldest_lsn);
1708 : :
1709 : :
1710 : : /* Consider each WAL file on the selected timeline in turn. */
1711 [ # # # # : 0 : foreach(lc, wslist)
# # ]
1712 : : {
1713 : 0 : WalSummaryFile *ws = lfirst(lc);
1714 : :
1715 : 0 : ProcessWalSummarizerInterrupts();
1716 : :
1717 : : /* If it's not on this timeline, it's not time to consider it. */
1718 [ # # ]: 0 : if (selected_tli != ws->tli)
1719 : 0 : continue;
1720 : :
1721 : : /*
1722 : : * If the WAL doesn't exist any more, we can remove it if the file
1723 : : * modification time is old enough.
1724 : : */
1725 [ # # # # ]: 0 : if (!XLogRecPtrIsValid(oldest_lsn) || ws->end_lsn <= oldest_lsn)
1726 : 0 : RemoveWalSummaryIfOlderThan(ws, cutoff_time);
1727 : :
1728 : : /*
1729 : : * Whether we removed the file or not, we need not consider it
1730 : : * again.
1731 : : */
1732 : 0 : wslist = foreach_delete_current(wslist, lc);
1733 : 0 : pfree(ws);
1734 [ # # ]: 0 : }
1735 : 0 : }
1736 : 0 : }
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