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Add background worker type
Add bgw_type field to background worker structure. It is intended to be set to the same value for all workers of the same type, so they can be grouped in pg_stat_activity, for example. The backend_type column in pg_stat_activity now shows bgw_type for a background worker. The ps listing also no longer calls out that a process is a background worker but just show the bgw_type. That way, being a background worker is more of an implementation detail now that is not shown to the user. However, most log messages still refer to 'background worker "%s"'; otherwise constructing sensible and translatable log messages would become tricky. Reviewed-by: Michael Paquier <michael.paquier@gmail.com> Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
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10 files changed

+89
-16
lines changed

10 files changed

+89
-16
lines changed

‎contrib/pg_prewarm/autoprewarm.c

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -800,7 +800,8 @@ apw_start_master_worker(void)
800800
worker.bgw_start_time = BgWorkerStart_ConsistentState;
801801
strcpy(worker.bgw_library_name, "pg_prewarm");
802802
strcpy(worker.bgw_function_name, "autoprewarm_main");
803-
strcpy(worker.bgw_name, "autoprewarm");
803+
strcpy(worker.bgw_name, "autoprewarm master");
804+
strcpy(worker.bgw_type, "autoprewarm master");
804805

805806
if (process_shared_preload_libraries_in_progress)
806807
{
@@ -840,7 +841,8 @@ apw_start_database_worker(void)
840841
worker.bgw_start_time = BgWorkerStart_ConsistentState;
841842
strcpy(worker.bgw_library_name, "pg_prewarm");
842843
strcpy(worker.bgw_function_name, "autoprewarm_database_main");
843-
strcpy(worker.bgw_name, "autoprewarm");
844+
strcpy(worker.bgw_name, "autoprewarm worker");
845+
strcpy(worker.bgw_type, "autoprewarm worker");
844846

845847
/* must set notify PID to wait for shutdown */
846848
worker.bgw_notify_pid = MyProcPid;

‎doc/src/sgml/bgworker.sgml

Lines changed: 9 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -51,6 +51,7 @@ typedef void (*bgworker_main_type)(Datum main_arg);
5151
typedef struct BackgroundWorker
5252
{
5353
char bgw_name[BGW_MAXLEN];
54+
char bgw_type[BGW_MAXLEN];
5455
int bgw_flags;
5556
BgWorkerStartTime bgw_start_time;
5657
int bgw_restart_time; /* in seconds, or BGW_NEVER_RESTART */
@@ -64,8 +65,14 @@ typedef struct BackgroundWorker
6465
</para>
6566

6667
<para>
67-
<structfield>bgw_name</> is a string to be used in log messages, process
68-
listings and similar contexts.
68+
<structfield>bgw_name</> and <structfield>bgw_type</structfield> are
69+
strings to be used in log messages, process listings and similar contexts.
70+
<structfield>bgw_type</structfield> should be the same for all background
71+
workers of the same type, so that it is possible to group such workers in a
72+
process listing, for example. <structfield>bgw_name</structfield> on the
73+
other hand can contain additional information about the specific process.
74+
(Typically, the string for <structfield>bgw_name</structfield> will contain
75+
the type somehow, but that is not strictly required.)
6976
</para>
7077

7178
<para>

‎src/backend/access/transam/parallel.c

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -467,6 +467,7 @@ LaunchParallelWorkers(ParallelContext *pcxt)
467467
memset(&worker, 0, sizeof(worker));
468468
snprintf(worker.bgw_name, BGW_MAXLEN, "parallel worker for PID %d",
469469
MyProcPid);
470+
snprintf(worker.bgw_type, BGW_MAXLEN, "parallel worker");
470471
worker.bgw_flags =
471472
BGWORKER_SHMEM_ACCESS | BGWORKER_BACKEND_DATABASE_CONNECTION
472473
| BGWORKER_CLASS_PARALLEL;

‎src/backend/postmaster/bgworker.c

Lines changed: 47 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -344,6 +344,8 @@ BackgroundWorkerStateChange(void)
344344
*/
345345
ascii_safe_strlcpy(rw->rw_worker.bgw_name,
346346
slot->worker.bgw_name, BGW_MAXLEN);
347+
ascii_safe_strlcpy(rw->rw_worker.bgw_type,
348+
slot->worker.bgw_type, BGW_MAXLEN);
347349
ascii_safe_strlcpy(rw->rw_worker.bgw_library_name,
348350
slot->worker.bgw_library_name, BGW_MAXLEN);
349351
ascii_safe_strlcpy(rw->rw_worker.bgw_function_name,
@@ -630,6 +632,12 @@ SanityCheckBackgroundWorker(BackgroundWorker *worker, int elevel)
630632
return false;
631633
}
632634

635+
/*
636+
* If bgw_type is not filled in, use bgw_name.
637+
*/
638+
if (strcmp(worker->bgw_type, "") == 0)
639+
strcpy(worker->bgw_type, worker->bgw_name);
640+
633641
return true;
634642
}
635643

@@ -671,7 +679,7 @@ bgworker_die(SIGNAL_ARGS)
671679
ereport(FATAL,
672680
(errcode(ERRCODE_ADMIN_SHUTDOWN),
673681
errmsg("terminating background worker \"%s\" due to administrator command",
674-
MyBgworkerEntry->bgw_name)));
682+
MyBgworkerEntry->bgw_type)));
675683
}
676684

677685
/*
@@ -700,7 +708,6 @@ void
700708
StartBackgroundWorker(void)
701709
{
702710
sigjmp_buf local_sigjmp_buf;
703-
char buf[MAXPGPATH];
704711
BackgroundWorker *worker = MyBgworkerEntry;
705712
bgworker_main_type entrypt;
706713

@@ -710,8 +717,7 @@ StartBackgroundWorker(void)
710717
IsBackgroundWorker = true;
711718

712719
/* Identify myself via ps */
713-
snprintf(buf, MAXPGPATH, "bgworker: %s", worker->bgw_name);
714-
init_ps_display(buf, "", "", "");
720+
init_ps_display(worker->bgw_name, "", "", "");
715721

716722
/*
717723
* If we're not supposed to have shared memory access, then detach from
@@ -1233,3 +1239,40 @@ LookupBackgroundWorkerFunction(const char *libraryname, const char *funcname)
12331239
return (bgworker_main_type)
12341240
load_external_function(libraryname, funcname, true, NULL);
12351241
}
1242+
1243+
/*
1244+
* Given a PID, get the bgw_type of the background worker. Returns NULL if
1245+
* not a valid background worker.
1246+
*
1247+
* The return value is in static memory belonging to this function, so it has
1248+
* to be used before calling this function again. This is so that the caller
1249+
* doesn't have to worry about the background worker locking protocol.
1250+
*/
1251+
const char *
1252+
GetBackgroundWorkerTypeByPid(pid_t pid)
1253+
{
1254+
int slotno;
1255+
bool found = false;
1256+
static char result[BGW_MAXLEN];
1257+
1258+
LWLockAcquire(BackgroundWorkerLock, LW_SHARED);
1259+
1260+
for (slotno = 0; slotno < BackgroundWorkerData->total_slots; slotno++)
1261+
{
1262+
BackgroundWorkerSlot *slot = &BackgroundWorkerData->slot[slotno];
1263+
1264+
if (slot->pid > 0 && slot->pid == pid)
1265+
{
1266+
strcpy(result, slot->worker.bgw_type);
1267+
found = true;
1268+
break;
1269+
}
1270+
}
1271+
1272+
LWLockRelease(BackgroundWorkerLock);
1273+
1274+
if (!found)
1275+
return NULL;
1276+
1277+
return result;
1278+
}

‎src/backend/postmaster/postmaster.c

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -3117,8 +3117,9 @@ CleanupBackgroundWorker(int pid,
31173117
exitstatus = 0;
31183118
#endif
31193119

3120-
snprintf(namebuf, MAXPGPATH, "%s: %s", _("worker process"),
3121-
rw->rw_worker.bgw_name);
3120+
snprintf(namebuf, MAXPGPATH, _("background worker \"%s\""),
3121+
rw->rw_worker.bgw_type);
3122+
31223123

31233124
if (!EXIT_STATUS_0(exitstatus))
31243125
{

‎src/backend/replication/logical/launcher.c

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -422,6 +422,7 @@ logicalrep_worker_launch(Oid dbid, Oid subid, const char *subname, Oid userid,
422422
else
423423
snprintf(bgw.bgw_name, BGW_MAXLEN,
424424
"logical replication worker for subscription %u", subid);
425+
snprintf(bgw.bgw_type, BGW_MAXLEN, "logical replication worker");
425426

426427
bgw.bgw_restart_time = BGW_NEVER_RESTART;
427428
bgw.bgw_notify_pid = MyProcPid;
@@ -775,6 +776,8 @@ ApplyLauncherRegister(void)
775776
snprintf(bgw.bgw_function_name, BGW_MAXLEN, "ApplyLauncherMain");
776777
snprintf(bgw.bgw_name, BGW_MAXLEN,
777778
"logical replication launcher");
779+
snprintf(bgw.bgw_type, BGW_MAXLEN,
780+
"logical replication launcher");
778781
bgw.bgw_restart_time = 5;
779782
bgw.bgw_notify_pid = 0;
780783
bgw.bgw_main_arg = (Datum) 0;

‎src/backend/utils/adt/pgstatfuncs.c

Lines changed: 14 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -21,6 +21,7 @@
2121
#include "funcapi.h"
2222
#include "miscadmin.h"
2323
#include "pgstat.h"
24+
#include "postmaster/bgworker_internals.h"
2425
#include "postmaster/postmaster.h"
2526
#include "storage/proc.h"
2627
#include "storage/procarray.h"
@@ -823,8 +824,19 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
823824
}
824825
}
825826
/* Add backend type */
826-
values[17] =
827-
CStringGetTextDatum(pgstat_get_backend_desc(beentry->st_backendType));
827+
if (beentry->st_backendType == B_BG_WORKER)
828+
{
829+
const char *bgw_type;
830+
831+
bgw_type = GetBackgroundWorkerTypeByPid(beentry->st_procpid);
832+
if (bgw_type)
833+
values[17] = CStringGetTextDatum(bgw_type);
834+
else
835+
nulls[17] = true;
836+
}
837+
else
838+
values[17] =
839+
CStringGetTextDatum(pgstat_get_backend_desc(beentry->st_backendType));
828840
}
829841
else
830842
{

‎src/include/postmaster/bgworker.h

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -88,6 +88,7 @@ typedef enum
8888
typedef struct BackgroundWorker
8989
{
9090
char bgw_name[BGW_MAXLEN];
91+
char bgw_type[BGW_MAXLEN];
9192
int bgw_flags;
9293
BgWorkerStartTime bgw_start_time;
9394
int bgw_restart_time; /* in seconds, or BGW_NEVER_RESTART */
@@ -122,6 +123,7 @@ extern BgwHandleStatus GetBackgroundWorkerPid(BackgroundWorkerHandle *handle,
122123
extern BgwHandleStatus WaitForBackgroundWorkerStartup(BackgroundWorkerHandle *handle, pid_t *pid);
123124
extern BgwHandleStatus
124125
WaitForBackgroundWorkerShutdown(BackgroundWorkerHandle *);
126+
extern const char *GetBackgroundWorkerTypeByPid(pid_t pid);
125127

126128
/* Terminate a bgworker */
127129
extern void TerminateBackgroundWorker(BackgroundWorkerHandle *handle);

‎src/test/modules/test_shm_mq/setup.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -219,7 +219,7 @@ setup_background_workers(int nworkers, dsm_segment *seg)
219219
worker.bgw_restart_time = BGW_NEVER_RESTART;
220220
sprintf(worker.bgw_library_name, "test_shm_mq");
221221
sprintf(worker.bgw_function_name, "test_shm_mq_main");
222-
snprintf(worker.bgw_name, BGW_MAXLEN, "test_shm_mq");
222+
snprintf(worker.bgw_type, BGW_MAXLEN, "test_shm_mq");
223223
worker.bgw_main_arg = UInt32GetDatum(dsm_segment_handle(seg));
224224
/* set bgw_notify_pid, so we can detect if the worker stops */
225225
worker.bgw_notify_pid = MyProcPid;

‎src/test/modules/worker_spi/worker_spi.c

Lines changed: 5 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -111,7 +111,7 @@ initialize_worker_spi(worktable *table)
111111
StartTransactionCommand();
112112
SPI_connect();
113113
PushActiveSnapshot(GetTransactionSnapshot());
114-
pgstat_report_activity(STATE_RUNNING, "initializing spi_worker schema");
114+
pgstat_report_activity(STATE_RUNNING, "initializing worker_spi schema");
115115

116116
/* XXX could we use CREATE SCHEMA IF NOT EXISTS? */
117117
initStringInfo(&buf);
@@ -359,7 +359,8 @@ _PG_init(void)
359359
*/
360360
for (i = 1; i <= worker_spi_total_workers; i++)
361361
{
362-
snprintf(worker.bgw_name, BGW_MAXLEN, "worker %d", i);
362+
snprintf(worker.bgw_name, BGW_MAXLEN, "worker_spi worker %d", i);
363+
snprintf(worker.bgw_type, BGW_MAXLEN, "worker_spi");
363364
worker.bgw_main_arg = Int32GetDatum(i);
364365

365366
RegisterBackgroundWorker(&worker);
@@ -385,7 +386,8 @@ worker_spi_launch(PG_FUNCTION_ARGS)
385386
worker.bgw_restart_time = BGW_NEVER_RESTART;
386387
sprintf(worker.bgw_library_name, "worker_spi");
387388
sprintf(worker.bgw_function_name, "worker_spi_main");
388-
snprintf(worker.bgw_name, BGW_MAXLEN, "worker %d", i);
389+
snprintf(worker.bgw_name, BGW_MAXLEN, "worker_spi worker %d", i);
390+
snprintf(worker.bgw_type, BGW_MAXLEN, "worker_spi");
389391
worker.bgw_main_arg = Int32GetDatum(i);
390392
/* set bgw_notify_pid so that we can use WaitForBackgroundWorkerStartup */
391393
worker.bgw_notify_pid = MyProcPid;

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