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backend_status.c
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1 /* ----------
2  * backend_status.c
3  * Backend status reporting infrastructure.
4  *
5  * Copyright (c) 2001-2023, PostgreSQL Global Development Group
6  *
7  *
8  * IDENTIFICATION
9  * src/backend/utils/activity/backend_status.c
10  * ----------
11  */
12 #include "postgres.h"
13 
14 #include "access/xact.h"
15 #include "libpq/libpq.h"
16 #include "miscadmin.h"
17 #include "pg_trace.h"
18 #include "pgstat.h"
19 #include "port/atomics.h" /* for memory barriers */
20 #include "storage/ipc.h"
21 #include "storage/proc.h" /* for MyProc */
22 #include "storage/sinvaladt.h"
23 #include "utils/ascii.h"
24 #include "utils/backend_status.h"
25 #include "utils/guc.h" /* for application_name */
26 #include "utils/memutils.h"
27 
28 
29 /* ----------
30  * Total number of backends including auxiliary
31  *
32  * We reserve a slot for each possible BackendId, plus one for each
33  * possible auxiliary process type. (This scheme assumes there is not
34  * more than one of any auxiliary process type at a time.) MaxBackends
35  * includes autovacuum workers and background workers as well.
36  * ----------
37  */
38 #define NumBackendStatSlots (MaxBackends + NUM_AUXPROCTYPES)
39 
40 
41 /* ----------
42  * GUC parameters
43  * ----------
44  */
47 
48 
49 /* exposed so that backend_progress.c can access it */
51 
52 
54 static char *BackendAppnameBuffer = NULL;
55 static char *BackendClientHostnameBuffer = NULL;
56 static char *BackendActivityBuffer = NULL;
58 #ifdef USE_SSL
59 static PgBackendSSLStatus *BackendSslStatusBuffer = NULL;
60 #endif
61 #ifdef ENABLE_GSS
62 static PgBackendGSSStatus *BackendGssStatusBuffer = NULL;
63 #endif
64 
65 
66 /* Status for backends including auxiliary */
68 
69 /* Total number of backends including auxiliary */
70 static int localNumBackends = 0;
71 
73 
74 
75 static void pgstat_beshutdown_hook(int code, Datum arg);
76 static void pgstat_read_current_status(void);
77 static void pgstat_setup_backend_status_context(void);
78 
79 
80 /*
81  * Report shared-memory space needed by CreateSharedBackendStatus.
82  */
83 Size
85 {
86  Size size;
87 
88  /* BackendStatusArray: */
90  /* BackendAppnameBuffer: */
91  size = add_size(size,
93  /* BackendClientHostnameBuffer: */
94  size = add_size(size,
96  /* BackendActivityBuffer: */
97  size = add_size(size,
99 #ifdef USE_SSL
100  /* BackendSslStatusBuffer: */
101  size = add_size(size,
103 #endif
104 #ifdef ENABLE_GSS
105  /* BackendGssStatusBuffer: */
106  size = add_size(size,
108 #endif
109  return size;
110 }
111 
112 /*
113  * Initialize the shared status array and several string buffers
114  * during postmaster startup.
115  */
116 void
118 {
119  Size size;
120  bool found;
121  int i;
122  char *buffer;
123 
124  /* Create or attach to the shared array */
127  ShmemInitStruct("Backend Status Array", size, &found);
128 
129  if (!found)
130  {
131  /*
132  * We're the first - initialize.
133  */
134  MemSet(BackendStatusArray, 0, size);
135  }
136 
137  /* Create or attach to the shared appname buffer */
139  BackendAppnameBuffer = (char *)
140  ShmemInitStruct("Backend Application Name Buffer", size, &found);
141 
142  if (!found)
143  {
144  MemSet(BackendAppnameBuffer, 0, size);
145 
146  /* Initialize st_appname pointers. */
147  buffer = BackendAppnameBuffer;
148  for (i = 0; i < NumBackendStatSlots; i++)
149  {
150  BackendStatusArray[i].st_appname = buffer;
151  buffer += NAMEDATALEN;
152  }
153  }
154 
155  /* Create or attach to the shared client hostname buffer */
157  BackendClientHostnameBuffer = (char *)
158  ShmemInitStruct("Backend Client Host Name Buffer", size, &found);
159 
160  if (!found)
161  {
163 
164  /* Initialize st_clienthostname pointers. */
166  for (i = 0; i < NumBackendStatSlots; i++)
167  {
169  buffer += NAMEDATALEN;
170  }
171  }
172 
173  /* Create or attach to the shared activity buffer */
176  BackendActivityBuffer = (char *)
177  ShmemInitStruct("Backend Activity Buffer",
179  &found);
180 
181  if (!found)
182  {
184 
185  /* Initialize st_activity pointers. */
186  buffer = BackendActivityBuffer;
187  for (i = 0; i < NumBackendStatSlots; i++)
188  {
191  }
192  }
193 
194 #ifdef USE_SSL
195  /* Create or attach to the shared SSL status buffer */
197  BackendSslStatusBuffer = (PgBackendSSLStatus *)
198  ShmemInitStruct("Backend SSL Status Buffer", size, &found);
199 
200  if (!found)
201  {
202  PgBackendSSLStatus *ptr;
203 
204  MemSet(BackendSslStatusBuffer, 0, size);
205 
206  /* Initialize st_sslstatus pointers. */
207  ptr = BackendSslStatusBuffer;
208  for (i = 0; i < NumBackendStatSlots; i++)
209  {
211  ptr++;
212  }
213  }
214 #endif
215 
216 #ifdef ENABLE_GSS
217  /* Create or attach to the shared GSSAPI status buffer */
219  BackendGssStatusBuffer = (PgBackendGSSStatus *)
220  ShmemInitStruct("Backend GSS Status Buffer", size, &found);
221 
222  if (!found)
223  {
224  PgBackendGSSStatus *ptr;
225 
226  MemSet(BackendGssStatusBuffer, 0, size);
227 
228  /* Initialize st_gssstatus pointers. */
229  ptr = BackendGssStatusBuffer;
230  for (i = 0; i < NumBackendStatSlots; i++)
231  {
233  ptr++;
234  }
235  }
236 #endif
237 }
238 
239 /*
240  * Initialize pgstats backend activity state, and set up our on-proc-exit
241  * hook. Called from InitPostgres and AuxiliaryProcessMain. For auxiliary
242  * process, MyBackendId is invalid. Otherwise, MyBackendId must be set, but we
243  * must not have started any transaction yet (since the exit hook must run
244  * after the last transaction exit).
245  *
246  * NOTE: MyDatabaseId isn't set yet; so the shutdown hook has to be careful.
247  */
248 void
250 {
251  /* Initialize MyBEEntry */
253  {
256  }
257  else
258  {
259  /* Must be an auxiliary process */
261 
262  /*
263  * Assign the MyBEEntry for an auxiliary process. Since it doesn't
264  * have a BackendId, the slot is statically allocated based on the
265  * auxiliary process type (MyAuxProcType). Backends use slots indexed
266  * in the range from 1 to MaxBackends (inclusive), so we use
267  * MaxBackends + AuxBackendType + 1 as the index of the slot for an
268  * auxiliary process.
269  */
271  }
272 
273  /* Set up a process-exit hook to clean up */
275 }
276 
277 
278 /* ----------
279  * pgstat_bestart() -
280  *
281  * Initialize this backend's entry in the PgBackendStatus array.
282  * Called from InitPostgres.
283  *
284  * Apart from auxiliary processes, MyBackendId, MyDatabaseId,
285  * session userid, and application_name must be set for a
286  * backend (hence, this cannot be combined with pgstat_beinit).
287  * Note also that we must be inside a transaction if this isn't an aux
288  * process, as we may need to do encoding conversion on some strings.
289  * ----------
290  */
291 void
293 {
294  volatile PgBackendStatus *vbeentry = MyBEEntry;
295  PgBackendStatus lbeentry;
296 #ifdef USE_SSL
297  PgBackendSSLStatus lsslstatus;
298 #endif
299 #ifdef ENABLE_GSS
300  PgBackendGSSStatus lgssstatus;
301 #endif
302 
303  /* pgstats state must be initialized from pgstat_beinit() */
304  Assert(vbeentry != NULL);
305 
306  /*
307  * To minimize the time spent modifying the PgBackendStatus entry, and
308  * avoid risk of errors inside the critical section, we first copy the
309  * shared-memory struct to a local variable, then modify the data in the
310  * local variable, then copy the local variable back to shared memory.
311  * Only the last step has to be inside the critical section.
312  *
313  * Most of the data we copy from shared memory is just going to be
314  * overwritten, but the struct's not so large that it's worth the
315  * maintenance hassle to copy only the needful fields.
316  */
317  memcpy(&lbeentry,
318  unvolatize(PgBackendStatus *, vbeentry),
319  sizeof(PgBackendStatus));
320 
321  /* These structs can just start from zeroes each time, though */
322 #ifdef USE_SSL
323  memset(&lsslstatus, 0, sizeof(lsslstatus));
324 #endif
325 #ifdef ENABLE_GSS
326  memset(&lgssstatus, 0, sizeof(lgssstatus));
327 #endif
328 
329  /*
330  * Now fill in all the fields of lbeentry, except for strings that are
331  * out-of-line data. Those have to be handled separately, below.
332  */
333  lbeentry.st_procpid = MyProcPid;
334  lbeentry.st_backendType = MyBackendType;
336  lbeentry.st_activity_start_timestamp = 0;
337  lbeentry.st_state_start_timestamp = 0;
338  lbeentry.st_xact_start_timestamp = 0;
339  lbeentry.st_databaseid = MyDatabaseId;
340 
341  /* We have userid for client-backends, wal-sender and bgworker processes */
342  if (lbeentry.st_backendType == B_BACKEND
343  || lbeentry.st_backendType == B_WAL_SENDER
344  || lbeentry.st_backendType == B_BG_WORKER)
345  lbeentry.st_userid = GetSessionUserId();
346  else
347  lbeentry.st_userid = InvalidOid;
348 
349  /*
350  * We may not have a MyProcPort (eg, if this is the autovacuum process).
351  * If so, use all-zeroes client address, which is dealt with specially in
352  * pg_stat_get_backend_client_addr and pg_stat_get_backend_client_port.
353  */
354  if (MyProcPort)
355  memcpy(&lbeentry.st_clientaddr, &MyProcPort->raddr,
356  sizeof(lbeentry.st_clientaddr));
357  else
358  MemSet(&lbeentry.st_clientaddr, 0, sizeof(lbeentry.st_clientaddr));
359 
360 #ifdef USE_SSL
362  {
363  lbeentry.st_ssl = true;
370  }
371  else
372  {
373  lbeentry.st_ssl = false;
374  }
375 #else
376  lbeentry.st_ssl = false;
377 #endif
378 
379 #ifdef ENABLE_GSS
380  if (MyProcPort && MyProcPort->gss != NULL)
381  {
382  const char *princ = be_gssapi_get_princ(MyProcPort);
383 
384  lbeentry.st_gss = true;
385  lgssstatus.gss_auth = be_gssapi_get_auth(MyProcPort);
386  lgssstatus.gss_enc = be_gssapi_get_enc(MyProcPort);
388  if (princ)
389  strlcpy(lgssstatus.gss_princ, princ, NAMEDATALEN);
390  }
391  else
392  {
393  lbeentry.st_gss = false;
394  }
395 #else
396  lbeentry.st_gss = false;
397 #endif
398 
399  lbeentry.st_state = STATE_UNDEFINED;
402  lbeentry.st_query_id = UINT64CONST(0);
403 
404  /*
405  * we don't zero st_progress_param here to save cycles; nobody should
406  * examine it until st_progress_command has been set to something other
407  * than PROGRESS_COMMAND_INVALID
408  */
409 
410  /*
411  * We're ready to enter the critical section that fills the shared-memory
412  * status entry. We follow the protocol of bumping st_changecount before
413  * and after; and make sure it's even afterwards. We use a volatile
414  * pointer here to ensure the compiler doesn't try to get cute.
415  */
416  PGSTAT_BEGIN_WRITE_ACTIVITY(vbeentry);
417 
418  /* make sure we'll memcpy the same st_changecount back */
419  lbeentry.st_changecount = vbeentry->st_changecount;
420 
421  memcpy(unvolatize(PgBackendStatus *, vbeentry),
422  &lbeentry,
423  sizeof(PgBackendStatus));
424 
425  /*
426  * We can write the out-of-line strings and structs using the pointers
427  * that are in lbeentry; this saves some de-volatilizing messiness.
428  */
429  lbeentry.st_appname[0] = '\0';
432  NAMEDATALEN);
433  else
434  lbeentry.st_clienthostname[0] = '\0';
435  lbeentry.st_activity_raw[0] = '\0';
436  /* Also make sure the last byte in each string area is always 0 */
437  lbeentry.st_appname[NAMEDATALEN - 1] = '\0';
438  lbeentry.st_clienthostname[NAMEDATALEN - 1] = '\0';
440 
441 #ifdef USE_SSL
442  memcpy(lbeentry.st_sslstatus, &lsslstatus, sizeof(PgBackendSSLStatus));
443 #endif
444 #ifdef ENABLE_GSS
445  memcpy(lbeentry.st_gssstatus, &lgssstatus, sizeof(PgBackendGSSStatus));
446 #endif
447 
448  PGSTAT_END_WRITE_ACTIVITY(vbeentry);
449 
450  /* Update app name to current GUC setting */
451  if (application_name)
453 }
454 
455 /*
456  * Clear out our entry in the PgBackendStatus array.
457  */
458 static void
460 {
461  volatile PgBackendStatus *beentry = MyBEEntry;
462 
463  /*
464  * Clear my status entry, following the protocol of bumping st_changecount
465  * before and after. We use a volatile pointer here to ensure the
466  * compiler doesn't try to get cute.
467  */
469 
470  beentry->st_procpid = 0; /* mark invalid */
471 
472  PGSTAT_END_WRITE_ACTIVITY(beentry);
473 
474  /* so that functions can check if backend_status.c is up via MyBEEntry */
475  MyBEEntry = NULL;
476 }
477 
478 /*
479  * Discard any data collected in the current transaction. Any subsequent
480  * request will cause new snapshots to be read.
481  *
482  * This is also invoked during transaction commit or abort to discard the
483  * no-longer-wanted snapshot.
484  */
485 void
487 {
488  /* Release memory, if any was allocated */
490  {
493  }
494 
495  /* Reset variables */
497  localNumBackends = 0;
498 }
499 
500 static void
502 {
505  "Backend Status Snapshot",
507 }
508 
509 
510 /* ----------
511  * pgstat_report_activity() -
512  *
513  * Called from tcop/postgres.c to report what the backend is actually doing
514  * (but note cmd_str can be NULL for certain cases).
515  *
516  * All updates of the status entry follow the protocol of bumping
517  * st_changecount before and after. We use a volatile pointer here to
518  * ensure the compiler doesn't try to get cute.
519  * ----------
520  */
521 void
523 {
524  volatile PgBackendStatus *beentry = MyBEEntry;
525  TimestampTz start_timestamp;
526  TimestampTz current_timestamp;
527  int len = 0;
528 
529  TRACE_POSTGRESQL_STATEMENT_STATUS(cmd_str);
530 
531  if (!beentry)
532  return;
533 
535  {
536  if (beentry->st_state != STATE_DISABLED)
537  {
538  volatile PGPROC *proc = MyProc;
539 
540  /*
541  * track_activities is disabled, but we last reported a
542  * non-disabled state. As our final update, change the state and
543  * clear fields we will not be updating anymore.
544  */
546  beentry->st_state = STATE_DISABLED;
547  beentry->st_state_start_timestamp = 0;
548  beentry->st_activity_raw[0] = '\0';
549  beentry->st_activity_start_timestamp = 0;
550  /* st_xact_start_timestamp and wait_event_info are also disabled */
551  beentry->st_xact_start_timestamp = 0;
552  beentry->st_query_id = UINT64CONST(0);
553  proc->wait_event_info = 0;
554  PGSTAT_END_WRITE_ACTIVITY(beentry);
555  }
556  return;
557  }
558 
559  /*
560  * To minimize the time spent modifying the entry, and avoid risk of
561  * errors inside the critical section, fetch all the needed data first.
562  */
563  start_timestamp = GetCurrentStatementStartTimestamp();
564  if (cmd_str != NULL)
565  {
566  /*
567  * Compute length of to-be-stored string unaware of multi-byte
568  * characters. For speed reasons that'll get corrected on read, rather
569  * than computed every write.
570  */
571  len = Min(strlen(cmd_str), pgstat_track_activity_query_size - 1);
572  }
573  current_timestamp = GetCurrentTimestamp();
574 
575  /*
576  * If the state has changed from "active" or "idle in transaction",
577  * calculate the duration.
578  */
579  if ((beentry->st_state == STATE_RUNNING ||
580  beentry->st_state == STATE_FASTPATH ||
581  beentry->st_state == STATE_IDLEINTRANSACTION ||
583  state != beentry->st_state)
584  {
585  long secs;
586  int usecs;
587 
589  current_timestamp,
590  &secs, &usecs);
591 
592  if (beentry->st_state == STATE_RUNNING ||
593  beentry->st_state == STATE_FASTPATH)
594  pgstat_count_conn_active_time((PgStat_Counter) secs * 1000000 + usecs);
595  else
596  pgstat_count_conn_txn_idle_time((PgStat_Counter) secs * 1000000 + usecs);
597  }
598 
599  /*
600  * Now update the status entry
601  */
603 
604  beentry->st_state = state;
605  beentry->st_state_start_timestamp = current_timestamp;
606 
607  /*
608  * If a new query is started, we reset the query identifier as it'll only
609  * be known after parse analysis, to avoid reporting last query's
610  * identifier.
611  */
612  if (state == STATE_RUNNING)
613  beentry->st_query_id = UINT64CONST(0);
614 
615  if (cmd_str != NULL)
616  {
617  memcpy((char *) beentry->st_activity_raw, cmd_str, len);
618  beentry->st_activity_raw[len] = '\0';
619  beentry->st_activity_start_timestamp = start_timestamp;
620  }
621 
622  PGSTAT_END_WRITE_ACTIVITY(beentry);
623 }
624 
625 /* --------
626  * pgstat_report_query_id() -
627  *
628  * Called to update top-level query identifier.
629  * --------
630  */
631 void
632 pgstat_report_query_id(uint64 query_id, bool force)
633 {
634  volatile PgBackendStatus *beentry = MyBEEntry;
635 
636  /*
637  * if track_activities is disabled, st_query_id should already have been
638  * reset
639  */
640  if (!beentry || !pgstat_track_activities)
641  return;
642 
643  /*
644  * We only report the top-level query identifiers. The stored query_id is
645  * reset when a backend calls pgstat_report_activity(STATE_RUNNING), or
646  * with an explicit call to this function using the force flag. If the
647  * saved query identifier is not zero it means that it's not a top-level
648  * command, so ignore the one provided unless it's an explicit call to
649  * reset the identifier.
650  */
651  if (beentry->st_query_id != 0 && !force)
652  return;
653 
654  /*
655  * Update my status entry, following the protocol of bumping
656  * st_changecount before and after. We use a volatile pointer here to
657  * ensure the compiler doesn't try to get cute.
658  */
660  beentry->st_query_id = query_id;
661  PGSTAT_END_WRITE_ACTIVITY(beentry);
662 }
663 
664 
665 /* ----------
666  * pgstat_report_appname() -
667  *
668  * Called to update our application name.
669  * ----------
670  */
671 void
672 pgstat_report_appname(const char *appname)
673 {
674  volatile PgBackendStatus *beentry = MyBEEntry;
675  int len;
676 
677  if (!beentry)
678  return;
679 
680  /* This should be unnecessary if GUC did its job, but be safe */
681  len = pg_mbcliplen(appname, strlen(appname), NAMEDATALEN - 1);
682 
683  /*
684  * Update my status entry, following the protocol of bumping
685  * st_changecount before and after. We use a volatile pointer here to
686  * ensure the compiler doesn't try to get cute.
687  */
689 
690  memcpy((char *) beentry->st_appname, appname, len);
691  beentry->st_appname[len] = '\0';
692 
693  PGSTAT_END_WRITE_ACTIVITY(beentry);
694 }
695 
696 /*
697  * Report current transaction start timestamp as the specified value.
698  * Zero means there is no active transaction.
699  */
700 void
702 {
703  volatile PgBackendStatus *beentry = MyBEEntry;
704 
705  if (!pgstat_track_activities || !beentry)
706  return;
707 
708  /*
709  * Update my status entry, following the protocol of bumping
710  * st_changecount before and after. We use a volatile pointer here to
711  * ensure the compiler doesn't try to get cute.
712  */
714 
715  beentry->st_xact_start_timestamp = tstamp;
716 
717  PGSTAT_END_WRITE_ACTIVITY(beentry);
718 }
719 
720 /* ----------
721  * pgstat_read_current_status() -
722  *
723  * Copy the current contents of the PgBackendStatus array to local memory,
724  * if not already done in this transaction.
725  * ----------
726  */
727 static void
729 {
730  volatile PgBackendStatus *beentry;
731  LocalPgBackendStatus *localtable;
732  LocalPgBackendStatus *localentry;
733  char *localappname,
734  *localclienthostname,
735  *localactivity;
736 #ifdef USE_SSL
737  PgBackendSSLStatus *localsslstatus;
738 #endif
739 #ifdef ENABLE_GSS
740  PgBackendGSSStatus *localgssstatus;
741 #endif
742  int i;
743 
745  return; /* already done */
746 
748 
749  /*
750  * Allocate storage for local copy of state data. We can presume that
751  * none of these requests overflow size_t, because we already calculated
752  * the same values using mul_size during shmem setup. However, with
753  * probably-silly values of pgstat_track_activity_query_size and
754  * max_connections, the localactivity buffer could exceed 1GB, so use
755  * "huge" allocation for that one.
756  */
757  localtable = (LocalPgBackendStatus *)
760  localappname = (char *)
763  localclienthostname = (char *)
766  localactivity = (char *)
769 #ifdef USE_SSL
770  localsslstatus = (PgBackendSSLStatus *)
773 #endif
774 #ifdef ENABLE_GSS
775  localgssstatus = (PgBackendGSSStatus *)
778 #endif
779 
780  localNumBackends = 0;
781 
782  beentry = BackendStatusArray;
783  localentry = localtable;
784  for (i = 1; i <= NumBackendStatSlots; i++)
785  {
786  /*
787  * Follow the protocol of retrying if st_changecount changes while we
788  * copy the entry, or if it's odd. (The check for odd is needed to
789  * cover the case where we are able to completely copy the entry while
790  * the source backend is between increment steps.) We use a volatile
791  * pointer here to ensure the compiler doesn't try to get cute.
792  */
793  for (;;)
794  {
795  int before_changecount;
796  int after_changecount;
797 
798  pgstat_begin_read_activity(beentry, before_changecount);
799 
800  localentry->backendStatus.st_procpid = beentry->st_procpid;
801  /* Skip all the data-copying work if entry is not in use */
802  if (localentry->backendStatus.st_procpid > 0)
803  {
804  memcpy(&localentry->backendStatus, unvolatize(PgBackendStatus *, beentry), sizeof(PgBackendStatus));
805 
806  /*
807  * For each PgBackendStatus field that is a pointer, copy the
808  * pointed-to data, then adjust the local copy of the pointer
809  * field to point at the local copy of the data.
810  *
811  * strcpy is safe even if the string is modified concurrently,
812  * because there's always a \0 at the end of the buffer.
813  */
814  strcpy(localappname, (char *) beentry->st_appname);
815  localentry->backendStatus.st_appname = localappname;
816  strcpy(localclienthostname, (char *) beentry->st_clienthostname);
817  localentry->backendStatus.st_clienthostname = localclienthostname;
818  strcpy(localactivity, (char *) beentry->st_activity_raw);
819  localentry->backendStatus.st_activity_raw = localactivity;
820 #ifdef USE_SSL
821  if (beentry->st_ssl)
822  {
823  memcpy(localsslstatus, beentry->st_sslstatus, sizeof(PgBackendSSLStatus));
824  localentry->backendStatus.st_sslstatus = localsslstatus;
825  }
826 #endif
827 #ifdef ENABLE_GSS
828  if (beentry->st_gss)
829  {
830  memcpy(localgssstatus, beentry->st_gssstatus, sizeof(PgBackendGSSStatus));
831  localentry->backendStatus.st_gssstatus = localgssstatus;
832  }
833 #endif
834  }
835 
836  pgstat_end_read_activity(beentry, after_changecount);
837 
838  if (pgstat_read_activity_complete(before_changecount,
839  after_changecount))
840  break;
841 
842  /* Make sure we can break out of loop if stuck... */
844  }
845 
846  /* Only valid entries get included into the local array */
847  if (localentry->backendStatus.st_procpid > 0)
848  {
849  /*
850  * The BackendStatusArray index is exactly the BackendId of the
851  * source backend. Note that this means localBackendStatusTable
852  * is in order by backend_id. pgstat_fetch_stat_beentry() depends
853  * on that.
854  */
855  localentry->backend_id = i;
857  &localentry->backend_xid,
858  &localentry->backend_xmin,
859  &localentry->backend_subxact_count,
860  &localentry->backend_subxact_overflowed);
861 
862  localentry++;
863  localappname += NAMEDATALEN;
864  localclienthostname += NAMEDATALEN;
865  localactivity += pgstat_track_activity_query_size;
866 #ifdef USE_SSL
867  localsslstatus++;
868 #endif
869 #ifdef ENABLE_GSS
870  localgssstatus++;
871 #endif
873  }
874 
875  beentry++;
876  }
877 
878  /* Set the pointer only after completion of a valid table */
879  localBackendStatusTable = localtable;
880 }
881 
882 
883 /* ----------
884  * pgstat_get_backend_current_activity() -
885  *
886  * Return a string representing the current activity of the backend with
887  * the specified PID. This looks directly at the BackendStatusArray,
888  * and so will provide current information regardless of the age of our
889  * transaction's snapshot of the status array.
890  *
891  * It is the caller's responsibility to invoke this only for backends whose
892  * state is expected to remain stable while the result is in use. The
893  * only current use is in deadlock reporting, where we can expect that
894  * the target backend is blocked on a lock. (There are corner cases
895  * where the target's wait could get aborted while we are looking at it,
896  * but the very worst consequence is to return a pointer to a string
897  * that's been changed, so we won't worry too much.)
898  *
899  * Note: return strings for special cases match pg_stat_get_backend_activity.
900  * ----------
901  */
902 const char *
903 pgstat_get_backend_current_activity(int pid, bool checkUser)
904 {
905  PgBackendStatus *beentry;
906  int i;
907 
908  beentry = BackendStatusArray;
909  for (i = 1; i <= MaxBackends; i++)
910  {
911  /*
912  * Although we expect the target backend's entry to be stable, that
913  * doesn't imply that anyone else's is. To avoid identifying the
914  * wrong backend, while we check for a match to the desired PID we
915  * must follow the protocol of retrying if st_changecount changes
916  * while we examine the entry, or if it's odd. (This might be
917  * unnecessary, since fetching or storing an int is almost certainly
918  * atomic, but let's play it safe.) We use a volatile pointer here to
919  * ensure the compiler doesn't try to get cute.
920  */
921  volatile PgBackendStatus *vbeentry = beentry;
922  bool found;
923 
924  for (;;)
925  {
926  int before_changecount;
927  int after_changecount;
928 
929  pgstat_begin_read_activity(vbeentry, before_changecount);
930 
931  found = (vbeentry->st_procpid == pid);
932 
933  pgstat_end_read_activity(vbeentry, after_changecount);
934 
935  if (pgstat_read_activity_complete(before_changecount,
936  after_changecount))
937  break;
938 
939  /* Make sure we can break out of loop if stuck... */
941  }
942 
943  if (found)
944  {
945  /* Now it is safe to use the non-volatile pointer */
946  if (checkUser && !superuser() && beentry->st_userid != GetUserId())
947  return "<insufficient privilege>";
948  else if (*(beentry->st_activity_raw) == '\0')
949  return "<command string not enabled>";
950  else
951  {
952  /* this'll leak a bit of memory, but that seems acceptable */
953  return pgstat_clip_activity(beentry->st_activity_raw);
954  }
955  }
956 
957  beentry++;
958  }
959 
960  /* If we get here, caller is in error ... */
961  return "<backend information not available>";
962 }
963 
964 /* ----------
965  * pgstat_get_crashed_backend_activity() -
966  *
967  * Return a string representing the current activity of the backend with
968  * the specified PID. Like the function above, but reads shared memory with
969  * the expectation that it may be corrupt. On success, copy the string
970  * into the "buffer" argument and return that pointer. On failure,
971  * return NULL.
972  *
973  * This function is only intended to be used by the postmaster to report the
974  * query that crashed a backend. In particular, no attempt is made to
975  * follow the correct concurrency protocol when accessing the
976  * BackendStatusArray. But that's OK, in the worst case we'll return a
977  * corrupted message. We also must take care not to trip on ereport(ERROR).
978  * ----------
979  */
980 const char *
981 pgstat_get_crashed_backend_activity(int pid, char *buffer, int buflen)
982 {
983  volatile PgBackendStatus *beentry;
984  int i;
985 
986  beentry = BackendStatusArray;
987 
988  /*
989  * We probably shouldn't get here before shared memory has been set up,
990  * but be safe.
991  */
992  if (beentry == NULL || BackendActivityBuffer == NULL)
993  return NULL;
994 
995  for (i = 1; i <= MaxBackends; i++)
996  {
997  if (beentry->st_procpid == pid)
998  {
999  /* Read pointer just once, so it can't change after validation */
1000  const char *activity = beentry->st_activity_raw;
1001  const char *activity_last;
1002 
1003  /*
1004  * We mustn't access activity string before we verify that it
1005  * falls within the BackendActivityBuffer. To make sure that the
1006  * entire string including its ending is contained within the
1007  * buffer, subtract one activity length from the buffer size.
1008  */
1011 
1012  if (activity < BackendActivityBuffer ||
1013  activity > activity_last)
1014  return NULL;
1015 
1016  /* If no string available, no point in a report */
1017  if (activity[0] == '\0')
1018  return NULL;
1019 
1020  /*
1021  * Copy only ASCII-safe characters so we don't run into encoding
1022  * problems when reporting the message; and be sure not to run off
1023  * the end of memory. As only ASCII characters are reported, it
1024  * doesn't seem necessary to perform multibyte aware clipping.
1025  */
1026  ascii_safe_strlcpy(buffer, activity,
1028 
1029  return buffer;
1030  }
1031 
1032  beentry++;
1033  }
1034 
1035  /* PID not found */
1036  return NULL;
1037 }
1038 
1039 /* ----------
1040  * pgstat_get_my_query_id() -
1041  *
1042  * Return current backend's query identifier.
1043  */
1044 uint64
1046 {
1047  if (!MyBEEntry)
1048  return 0;
1049 
1050  /*
1051  * There's no need for a lock around pgstat_begin_read_activity /
1052  * pgstat_end_read_activity here as it's only called from
1053  * pg_stat_get_activity which is already protected, or from the same
1054  * backend which means that there won't be concurrent writes.
1055  */
1056  return MyBEEntry->st_query_id;
1057 }
1058 
1059 /* ----------
1060  * cmp_lbestatus
1061  *
1062  * Comparison function for bsearch() on an array of LocalPgBackendStatus.
1063  * The backend_id field is used to compare the arguments.
1064  * ----------
1065  */
1066 static int
1067 cmp_lbestatus(const void *a, const void *b)
1068 {
1069  const LocalPgBackendStatus *lbestatus1 = (const LocalPgBackendStatus *) a;
1070  const LocalPgBackendStatus *lbestatus2 = (const LocalPgBackendStatus *) b;
1071 
1072  return lbestatus1->backend_id - lbestatus2->backend_id;
1073 }
1074 
1075 /* ----------
1076  * pgstat_fetch_stat_beentry() -
1077  *
1078  * Support function for the SQL-callable pgstat* functions. Returns
1079  * our local copy of the current-activity entry for one backend,
1080  * or NULL if the given beid doesn't identify any known session.
1081  *
1082  * The beid argument is the BackendId of the desired session
1083  * (note that this is unlike pgstat_fetch_stat_local_beentry()).
1084  *
1085  * NB: caller is responsible for a check if the user is permitted to see
1086  * this info (especially the querystring).
1087  * ----------
1088  */
1091 {
1093  LocalPgBackendStatus *ret;
1094 
1096 
1097  /*
1098  * Since the localBackendStatusTable is in order by backend_id, we can use
1099  * bsearch() to search it efficiently.
1100  */
1101  key.backend_id = beid;
1102  ret = (LocalPgBackendStatus *) bsearch(&key, localBackendStatusTable,
1104  sizeof(LocalPgBackendStatus),
1105  cmp_lbestatus);
1106  if (ret)
1107  return &ret->backendStatus;
1108 
1109  return NULL;
1110 }
1111 
1112 
1113 /* ----------
1114  * pgstat_fetch_stat_local_beentry() -
1115  *
1116  * Like pgstat_fetch_stat_beentry() but with locally computed additions (like
1117  * xid and xmin values of the backend)
1118  *
1119  * The beid argument is a 1-based index in the localBackendStatusTable
1120  * (note that this is unlike pgstat_fetch_stat_beentry()).
1121  * Returns NULL if the argument is out of range (no current caller does that).
1122  *
1123  * NB: caller is responsible for a check if the user is permitted to see
1124  * this info (especially the querystring).
1125  * ----------
1126  */
1129 {
1131 
1132  if (beid < 1 || beid > localNumBackends)
1133  return NULL;
1134 
1135  return &localBackendStatusTable[beid - 1];
1136 }
1137 
1138 
1139 /* ----------
1140  * pgstat_fetch_stat_numbackends() -
1141  *
1142  * Support function for the SQL-callable pgstat* functions. Returns
1143  * the number of sessions known in the localBackendStatusTable, i.e.
1144  * the maximum 1-based index to pass to pgstat_fetch_stat_local_beentry().
1145  * ----------
1146  */
1147 int
1149 {
1151 
1152  return localNumBackends;
1153 }
1154 
1155 /*
1156  * Convert a potentially unsafely truncated activity string (see
1157  * PgBackendStatus.st_activity_raw's documentation) into a correctly truncated
1158  * one.
1159  *
1160  * The returned string is allocated in the caller's memory context and may be
1161  * freed.
1162  */
1163 char *
1164 pgstat_clip_activity(const char *raw_activity)
1165 {
1166  char *activity;
1167  int rawlen;
1168  int cliplen;
1169 
1170  /*
1171  * Some callers, like pgstat_get_backend_current_activity(), do not
1172  * guarantee that the buffer isn't concurrently modified. We try to take
1173  * care that the buffer is always terminated by a NUL byte regardless, but
1174  * let's still be paranoid about the string's length. In those cases the
1175  * underlying buffer is guaranteed to be pgstat_track_activity_query_size
1176  * large.
1177  */
1178  activity = pnstrdup(raw_activity, pgstat_track_activity_query_size - 1);
1179 
1180  /* now double-guaranteed to be NUL terminated */
1181  rawlen = strlen(activity);
1182 
1183  /*
1184  * All supported server-encodings make it possible to determine the length
1185  * of a multi-byte character from its first byte (this is not the case for
1186  * client encodings, see GB18030). As st_activity is always stored using
1187  * server encoding, this allows us to perform multi-byte aware truncation,
1188  * even if the string earlier was truncated in the middle of a multi-byte
1189  * character.
1190  */
1191  cliplen = pg_mbcliplen(activity, rawlen,
1193 
1194  activity[cliplen] = '\0';
1195 
1196  return activity;
1197 }
void ascii_safe_strlcpy(char *dest, const char *src, size_t destsiz)
Definition: ascii.c:174
AuxProcType MyAuxProcType
Definition: auxprocess.c:45
void TimestampDifference(TimestampTz start_time, TimestampTz stop_time, long *secs, int *microsecs)
Definition: timestamp.c:1659
TimestampTz GetCurrentTimestamp(void)
Definition: timestamp.c:1583
@ PROGRESS_COMMAND_INVALID
#define NumBackendStatSlots
int pgstat_fetch_stat_numbackends(void)
PgBackendStatus * MyBEEntry
uint64 pgstat_get_my_query_id(void)
void pgstat_clear_backend_activity_snapshot(void)
static LocalPgBackendStatus * localBackendStatusTable
static int localNumBackends
static void pgstat_beshutdown_hook(int code, Datum arg)
const char * pgstat_get_backend_current_activity(int pid, bool checkUser)
static char * BackendClientHostnameBuffer
static int cmp_lbestatus(const void *a, const void *b)
bool pgstat_track_activities
static MemoryContext backendStatusSnapContext
void CreateSharedBackendStatus(void)
static char * BackendActivityBuffer
LocalPgBackendStatus * pgstat_fetch_stat_local_beentry(int beid)
static void pgstat_setup_backend_status_context(void)
void pgstat_report_query_id(uint64 query_id, bool force)
static char * BackendAppnameBuffer
PgBackendStatus * pgstat_fetch_stat_beentry(BackendId beid)
void pgstat_report_activity(BackendState state, const char *cmd_str)
void pgstat_report_xact_timestamp(TimestampTz tstamp)
const char * pgstat_get_crashed_backend_activity(int pid, char *buffer, int buflen)
static PgBackendStatus * BackendStatusArray
void pgstat_beinit(void)
Size BackendStatusShmemSize(void)
void pgstat_report_appname(const char *appname)
static Size BackendActivityBufferSize
static void pgstat_read_current_status(void)
int pgstat_track_activity_query_size
void pgstat_bestart(void)
char * pgstat_clip_activity(const char *raw_activity)
BackendState
@ STATE_UNDEFINED
@ STATE_IDLEINTRANSACTION_ABORTED
@ STATE_IDLEINTRANSACTION
@ STATE_DISABLED
@ STATE_FASTPATH
@ STATE_RUNNING
#define pgstat_read_activity_complete(before_changecount, after_changecount)
#define PGSTAT_END_WRITE_ACTIVITY(beentry)
#define PGSTAT_BEGIN_WRITE_ACTIVITY(beentry)
#define pgstat_end_read_activity(beentry, after_changecount)
#define pgstat_begin_read_activity(beentry, before_changecount)
int BackendId
Definition: backendid.h:21
#define InvalidBackendId
Definition: backendid.h:23
bool be_gssapi_get_auth(Port *port)
bool be_gssapi_get_enc(Port *port)
const char * be_gssapi_get_princ(Port *port)
bool be_gssapi_get_delegation(Port *port)
const char * be_tls_get_version(Port *port)
int be_tls_get_cipher_bits(Port *port)
void be_tls_get_peer_serial(Port *port, char *ptr, size_t len)
void be_tls_get_peer_issuer_name(Port *port, char *ptr, size_t len)
const char * be_tls_get_cipher(Port *port)
void be_tls_get_peer_subject_name(Port *port, char *ptr, size_t len)
#define Min(x, y)
Definition: c.h:988
#define unvolatize(underlying_type, expr)
Definition: c.h:1252
#define MemSet(start, val, len)
Definition: c.h:1004
size_t Size
Definition: c.h:589
int64 TimestampTz
Definition: timestamp.h:39
int MyProcPid
Definition: globals.c:44
BackendId MyBackendId
Definition: globals.c:85
int MaxBackends
Definition: globals.c:140
TimestampTz MyStartTimestamp
Definition: globals.c:46
struct Port * MyProcPort
Definition: globals.c:47
Oid MyDatabaseId
Definition: globals.c:89
char * application_name
Definition: guc_tables.c:535
void on_shmem_exit(pg_on_exit_callback function, Datum arg)
Definition: ipc.c:361
int b
Definition: isn.c:70
int a
Definition: isn.c:69
int i
Definition: isn.c:73
Assert(fmt[strlen(fmt) - 1] !='\n')
int pg_mbcliplen(const char *mbstr, int len, int limit)
Definition: mbutils.c:1084
static int cliplen(const char *str, int len, int limit)
Definition: mbutils.c:1151
char * pnstrdup(const char *in, Size len)
Definition: mcxt.c:1655
MemoryContext TopMemoryContext
Definition: mcxt.c:141
void * MemoryContextAlloc(MemoryContext context, Size size)
Definition: mcxt.c:1021
void * MemoryContextAllocHuge(MemoryContext context, Size size)
Definition: mcxt.c:1586
void MemoryContextDelete(MemoryContext context)
Definition: mcxt.c:403
#define AllocSetContextCreate
Definition: memutils.h:129
#define ALLOCSET_SMALL_SIZES
Definition: memutils.h:163
#define CHECK_FOR_INTERRUPTS()
Definition: miscadmin.h:121
@ B_WAL_SENDER
Definition: miscadmin.h:340
@ B_BG_WORKER
Definition: miscadmin.h:333
@ B_BACKEND
Definition: miscadmin.h:332
@ NotAnAuxProcess
Definition: miscadmin.h:439
Oid GetUserId(void)
Definition: miscinit.c:510
Oid GetSessionUserId(void)
Definition: miscinit.c:544
BackendType MyBackendType
Definition: miscinit.c:63
void * arg
#define NAMEDATALEN
const void size_t len
#define pgstat_count_conn_txn_idle_time(n)
Definition: pgstat.h:556
#define pgstat_count_conn_active_time(n)
Definition: pgstat.h:554
int64 PgStat_Counter
Definition: pgstat.h:89
size_t strlcpy(char *dst, const char *src, size_t siz)
Definition: strlcpy.c:45
uintptr_t Datum
Definition: postgres.h:64
#define InvalidOid
Definition: postgres_ext.h:36
Size add_size(Size s1, Size s2)
Definition: shmem.c:502
void * ShmemInitStruct(const char *name, Size size, bool *foundPtr)
Definition: shmem.c:396
Size mul_size(Size s1, Size s2)
Definition: shmem.c:519
void BackendIdGetTransactionIds(int backendID, TransactionId *xid, TransactionId *xmin, int *nsubxid, bool *overflowed)
Definition: sinvaladt.c:412
PGPROC * MyProc
Definition: proc.c:66
TransactionId backend_xid
PgBackendStatus backendStatus
TransactionId backend_xmin
Definition: proc.h:162
uint32 wait_event_info
Definition: proc.h:270
char gss_princ[NAMEDATALEN]
char ssl_version[NAMEDATALEN]
char ssl_cipher[NAMEDATALEN]
char ssl_client_dn[NAMEDATALEN]
char ssl_client_serial[NAMEDATALEN]
char ssl_issuer_dn[NAMEDATALEN]
BackendType st_backendType
TimestampTz st_state_start_timestamp
TimestampTz st_proc_start_timestamp
PgBackendGSSStatus * st_gssstatus
BackendState st_state
TimestampTz st_activity_start_timestamp
ProgressCommandType st_progress_command
SockAddr st_clientaddr
PgBackendSSLStatus * st_sslstatus
TimestampTz st_xact_start_timestamp
char * st_clienthostname
Oid st_progress_command_target
bool ssl_in_use
Definition: libpq-be.h:217
char * remote_hostname
Definition: libpq-be.h:154
void * gss
Definition: libpq-be.h:211
SockAddr raddr
Definition: libpq-be.h:152
Definition: regguts.h:323
bool superuser(void)
Definition: superuser.c:46
TimestampTz GetCurrentStatementStartTimestamp(void)
Definition: xact.c:864