From 6bc8ef0b7f1f1df3998745a66e1790e27424aa0c Mon Sep 17 00:00:00 2001 From: Robert Haas Date: Thu, 4 Jul 2013 11:24:24 -0400 Subject: [PATCH] Add new GUC, max_worker_processes, limiting number of bgworkers. In 9.3, there's no particular limit on the number of bgworkers; instead, we just count up the number that are actually registered, and use that to set MaxBackends. However, that approach causes problems for Hot Standby, which needs both MaxBackends and the size of the lock table to be the same on the standby as on the master, yet it may not be desirable to run the same bgworkers in both places. 9.3 handles that by failing to notice the problem, which will probably work fine in nearly all cases anyway, but is not theoretically sound. A further problem with simply counting the number of registered workers is that new workers can't be registered without a postmaster restart. This is inconvenient for administrators, since bouncing the postmaster causes an interruption of service. Moreover, there are a number of applications for background processes where, by necessity, the background process must be started on the fly (e.g. parallel query). While this patch doesn't actually make it possible to register new background workers after startup time, it's a necessary prerequisite. Patch by me. Review by Michael Paquier. --- doc/src/sgml/bgworker.sgml | 5 ++ doc/src/sgml/config.sgml | 19 +++++++ src/backend/access/rmgrdesc/xlogdesc.c | 3 +- src/backend/access/transam/xlog.c | 8 +++ src/backend/postmaster/postmaster.c | 54 +++---------------- src/backend/storage/lmgr/proc.c | 6 +-- src/backend/utils/init/globals.c | 1 + src/backend/utils/init/postinit.c | 2 +- src/backend/utils/misc/guc.c | 28 ++++++++-- src/backend/utils/misc/postgresql.conf.sample | 1 + src/bin/pg_controldata/pg_controldata.c | 2 + src/bin/pg_resetxlog/pg_resetxlog.c | 2 + src/include/access/xlog_internal.h | 3 +- src/include/catalog/pg_control.h | 1 + src/include/miscadmin.h | 1 + 15 files changed, 77 insertions(+), 59 deletions(-) diff --git a/doc/src/sgml/bgworker.sgml b/doc/src/sgml/bgworker.sgml index b0dde7564d..f7126388af 100644 --- a/doc/src/sgml/bgworker.sgml +++ b/doc/src/sgml/bgworker.sgml @@ -146,4 +146,9 @@ typedef struct BackgroundWorker The worker_spi contrib module contains a working example, which demonstrates some useful techniques. + + + The maximum number of registered background workers is limited by + . + diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 437dbb7711..9126bc37cb 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -1595,6 +1595,25 @@ include 'filename' + + + max_worker_processes (integer) + + max_worker_processes configuration parameter + + + + Sets the maximum number of background processes that the system + can support. This parameter can only be set at server start. + + + + When running a standby server, you must set this parameter to the + same or higher value than on the master server. Otherwise, queries + will not be allowed in the standby server. + + + diff --git a/src/backend/access/rmgrdesc/xlogdesc.c b/src/backend/access/rmgrdesc/xlogdesc.c index 12370521d4..1b36f9a88a 100644 --- a/src/backend/access/rmgrdesc/xlogdesc.c +++ b/src/backend/access/rmgrdesc/xlogdesc.c @@ -117,8 +117,9 @@ xlog_desc(StringInfo buf, uint8 xl_info, char *rec) } } - appendStringInfo(buf, "parameter change: max_connections=%d max_prepared_xacts=%d max_locks_per_xact=%d wal_level=%s", + appendStringInfo(buf, "parameter change: max_connections=%d max_worker_processes=%d max_prepared_xacts=%d max_locks_per_xact=%d wal_level=%s", xlrec.MaxConnections, + xlrec.max_worker_processes, xlrec.max_prepared_xacts, xlrec.max_locks_per_xact, wal_level_str); diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 0ce661bf9f..4220859c8a 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -4134,6 +4134,7 @@ BootStrapXLOG(void) /* Set important parameter values for use when replaying WAL */ ControlFile->MaxConnections = MaxConnections; + ControlFile->max_worker_processes = max_worker_processes; ControlFile->max_prepared_xacts = max_prepared_xacts; ControlFile->max_locks_per_xact = max_locks_per_xact; ControlFile->wal_level = wal_level; @@ -4841,6 +4842,9 @@ CheckRequiredParameterValues(void) RecoveryRequiresIntParameter("max_connections", MaxConnections, ControlFile->MaxConnections); + RecoveryRequiresIntParameter("max_worker_processes", + max_worker_processes, + ControlFile->max_worker_processes); RecoveryRequiresIntParameter("max_prepared_transactions", max_prepared_xacts, ControlFile->max_prepared_xacts); @@ -7770,6 +7774,7 @@ XLogReportParameters(void) { if (wal_level != ControlFile->wal_level || MaxConnections != ControlFile->MaxConnections || + max_worker_processes != ControlFile->max_worker_processes || max_prepared_xacts != ControlFile->max_prepared_xacts || max_locks_per_xact != ControlFile->max_locks_per_xact) { @@ -7786,6 +7791,7 @@ XLogReportParameters(void) xl_parameter_change xlrec; xlrec.MaxConnections = MaxConnections; + xlrec.max_worker_processes = max_worker_processes; xlrec.max_prepared_xacts = max_prepared_xacts; xlrec.max_locks_per_xact = max_locks_per_xact; xlrec.wal_level = wal_level; @@ -7799,6 +7805,7 @@ XLogReportParameters(void) } ControlFile->MaxConnections = MaxConnections; + ControlFile->max_worker_processes = max_worker_processes; ControlFile->max_prepared_xacts = max_prepared_xacts; ControlFile->max_locks_per_xact = max_locks_per_xact; ControlFile->wal_level = wal_level; @@ -8184,6 +8191,7 @@ xlog_redo(XLogRecPtr lsn, XLogRecord *record) LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); ControlFile->MaxConnections = xlrec.MaxConnections; + ControlFile->max_worker_processes = xlrec.max_worker_processes; ControlFile->max_prepared_xacts = xlrec.max_prepared_xacts; ControlFile->max_locks_per_xact = xlrec.max_locks_per_xact; ControlFile->wal_level = xlrec.wal_level; diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c index 15fd4c90ea..e3b32cbe08 100644 --- a/src/backend/postmaster/postmaster.c +++ b/src/backend/postmaster/postmaster.c @@ -402,7 +402,6 @@ static void reaper(SIGNAL_ARGS); static void sigusr1_handler(SIGNAL_ARGS); static void startup_die(SIGNAL_ARGS); static void dummy_handler(SIGNAL_ARGS); -static int GetNumRegisteredBackgroundWorkers(int flags); static void StartupPacketTimeoutHandler(void); static void CleanupBackend(int pid, int exitstatus); static bool CleanupBackgroundWorker(int pid, int exitstatus); @@ -5212,7 +5211,7 @@ int MaxLivePostmasterChildren(void) { return 2 * (MaxConnections + autovacuum_max_workers + 1 + - GetNumRegisteredBackgroundWorkers(0)); + max_worker_processes); } /* @@ -5226,7 +5225,6 @@ RegisterBackgroundWorker(BackgroundWorker *worker) { RegisteredBgWorker *rw; int namelen = strlen(worker->bgw_name); - static int maxworkers; static int numworkers = 0; #ifdef EXEC_BACKEND @@ -5238,11 +5236,6 @@ RegisterBackgroundWorker(BackgroundWorker *worker) static int BackgroundWorkerCookie = 1; #endif - /* initialize upper limit on first call */ - if (numworkers == 0) - maxworkers = MAX_BACKENDS - - (MaxConnections + autovacuum_max_workers + 1); - if (!IsUnderPostmaster) ereport(LOG, (errmsg("registering background worker: %s", worker->bgw_name))); @@ -5298,17 +5291,17 @@ RegisterBackgroundWorker(BackgroundWorker *worker) /* * Enforce maximum number of workers. Note this is overly restrictive: we * could allow more non-shmem-connected workers, because these don't count - * towards the MAX_BACKENDS limit elsewhere. This doesn't really matter - * for practical purposes; several million processes would need to run on - * a single server. + * towards the MAX_BACKENDS limit elsewhere. For now, it doesn't seem + * important to relax this restriction. */ - if (++numworkers > maxworkers) + if (++numworkers > max_worker_processes) { ereport(LOG, (errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED), errmsg("too many background workers"), errdetail("Up to %d background workers can be registered with the current settings.", - maxworkers))); + max_worker_processes), + errhint("Consider increasing the configuration parameter \"max_worker_processes\"."))); return; } @@ -5589,41 +5582,6 @@ do_start_bgworker(void) proc_exit(0); } -/* - * Return the number of background workers registered that have at least - * one of the passed flag bits set. - */ -static int -GetNumRegisteredBackgroundWorkers(int flags) -{ - slist_iter iter; - int count = 0; - - slist_foreach(iter, &BackgroundWorkerList) - { - RegisteredBgWorker *rw; - - rw = slist_container(RegisteredBgWorker, rw_lnode, iter.cur); - - if (flags != 0 && - !(rw->rw_worker.bgw_flags & flags)) - continue; - - count++; - } - - return count; -} - -/* - * Return the number of bgworkers that need to have PGPROC entries. - */ -int -GetNumShmemAttachedBgworkers(void) -{ - return GetNumRegisteredBackgroundWorkers(BGWORKER_SHMEM_ACCESS); -} - #ifdef EXEC_BACKEND static pid_t bgworker_forkexec(int cookie) diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c index 6d72a637f7..25bd528566 100644 --- a/src/backend/storage/lmgr/proc.c +++ b/src/backend/storage/lmgr/proc.c @@ -140,10 +140,8 @@ ProcGlobalSemas(void) * running out when trying to start another backend is a common failure. * So, now we grab enough semaphores to support the desired max number * of backends immediately at initialization --- if the sysadmin has set - * MaxConnections or autovacuum_max_workers higher than his kernel will - * support, he'll find out sooner rather than later. (The number of - * background worker processes registered by loadable modules is also taken - * into consideration.) + * MaxConnections, max_worker_processes, or autovacuum_max_workers higher + * than his kernel will support, he'll find out sooner rather than later. * * Another reason for creating semaphores here is that the semaphore * implementation typically requires us to create semaphores in the diff --git a/src/backend/utils/init/globals.c b/src/backend/utils/init/globals.c index 9f51929191..33efb3c3cc 100644 --- a/src/backend/utils/init/globals.c +++ b/src/backend/utils/init/globals.c @@ -109,6 +109,7 @@ int maintenance_work_mem = 16384; */ int NBuffers = 1000; int MaxConnections = 90; +int max_worker_processes = 8; int MaxBackends = 0; int VacuumCostPageHit = 1; /* GUC parameters for vacuum */ diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c index 127f9273e8..2c7f0f1764 100644 --- a/src/backend/utils/init/postinit.c +++ b/src/backend/utils/init/postinit.c @@ -436,7 +436,7 @@ InitializeMaxBackends(void) /* the extra unit accounts for the autovacuum launcher */ MaxBackends = MaxConnections + autovacuum_max_workers + 1 + - GetNumShmemAttachedBgworkers(); + + max_worker_processes; /* internal error because the values were all checked previously */ if (MaxBackends > MAX_BACKENDS) diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c index 3a7653698d..d6200616de 100644 --- a/src/backend/utils/misc/guc.c +++ b/src/backend/utils/misc/guc.c @@ -190,6 +190,7 @@ static const char *show_tcp_keepalives_idle(void); static const char *show_tcp_keepalives_interval(void); static const char *show_tcp_keepalives_count(void); static bool check_maxconnections(int *newval, void **extra, GucSource source); +static bool check_max_worker_processes(int *newval, void **extra, GucSource source); static bool check_autovacuum_max_workers(int *newval, void **extra, GucSource source); static bool check_effective_io_concurrency(int *newval, void **extra, GucSource source); static void assign_effective_io_concurrency(int newval, void *extra); @@ -2158,6 +2159,18 @@ static struct config_int ConfigureNamesInt[] = check_effective_io_concurrency, assign_effective_io_concurrency, NULL }, + { + {"max_worker_processes", + PGC_POSTMASTER, + RESOURCES_ASYNCHRONOUS, + gettext_noop("Maximum number of concurrent worker processes."), + NULL, + }, + &max_worker_processes, + 8, 1, MAX_BACKENDS, + check_max_worker_processes, NULL, NULL + }, + { {"log_rotation_age", PGC_SIGHUP, LOGGING_WHERE, gettext_noop("Automatic log file rotation will occur after N minutes."), @@ -8667,8 +8680,8 @@ show_tcp_keepalives_count(void) static bool check_maxconnections(int *newval, void **extra, GucSource source) { - if (*newval + GetNumShmemAttachedBgworkers() + autovacuum_max_workers + 1 > - MAX_BACKENDS) + if (*newval + autovacuum_max_workers + 1 + + max_worker_processes > MAX_BACKENDS) return false; return true; } @@ -8676,8 +8689,15 @@ check_maxconnections(int *newval, void **extra, GucSource source) static bool check_autovacuum_max_workers(int *newval, void **extra, GucSource source) { - if (MaxConnections + *newval + 1 + GetNumShmemAttachedBgworkers() > - MAX_BACKENDS) + if (MaxConnections + *newval + 1 + max_worker_processes > MAX_BACKENDS) + return false; + return true; +} + +static bool +check_max_worker_processes(int *newval, void **extra, GucSource source) +{ + if (MaxConnections + autovacuum_max_workers + 1 + *newval > MAX_BACKENDS) return false; return true; } diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample index 0d7249f4db..d69a02be87 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -152,6 +152,7 @@ # - Asynchronous Behavior - #effective_io_concurrency = 1 # 1-1000; 0 disables prefetching +#max_worker_processes = 8 #------------------------------------------------------------------------------ diff --git a/src/bin/pg_controldata/pg_controldata.c b/src/bin/pg_controldata/pg_controldata.c index a790f99cb5..fde483a616 100644 --- a/src/bin/pg_controldata/pg_controldata.c +++ b/src/bin/pg_controldata/pg_controldata.c @@ -260,6 +260,8 @@ main(int argc, char *argv[]) wal_level_str(ControlFile.wal_level)); printf(_("Current max_connections setting: %d\n"), ControlFile.MaxConnections); + printf(_("Current max_worker_processes setting: %d\n"), + ControlFile.max_worker_processes); printf(_("Current max_prepared_xacts setting: %d\n"), ControlFile.max_prepared_xacts); printf(_("Current max_locks_per_xact setting: %d\n"), diff --git a/src/bin/pg_resetxlog/pg_resetxlog.c b/src/bin/pg_resetxlog/pg_resetxlog.c index 6d3e9f5439..465905c850 100644 --- a/src/bin/pg_resetxlog/pg_resetxlog.c +++ b/src/bin/pg_resetxlog/pg_resetxlog.c @@ -518,6 +518,7 @@ GuessControlValues(void) ControlFile.wal_level = WAL_LEVEL_MINIMAL; ControlFile.MaxConnections = 100; + ControlFile.max_worker_processes = 8; ControlFile.max_prepared_xacts = 0; ControlFile.max_locks_per_xact = 64; @@ -664,6 +665,7 @@ RewriteControlFile(void) */ ControlFile.wal_level = WAL_LEVEL_MINIMAL; ControlFile.MaxConnections = 100; + ControlFile.max_worker_processes = 8; ControlFile.max_prepared_xacts = 0; ControlFile.max_locks_per_xact = 64; diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index ee12d1a110..c3e173106f 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -55,7 +55,7 @@ typedef struct BkpBlock /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD075 /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD076 /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { @@ -205,6 +205,7 @@ typedef XLogLongPageHeaderData *XLogLongPageHeader; typedef struct xl_parameter_change { int MaxConnections; + int max_worker_processes; int max_prepared_xacts; int max_locks_per_xact; int wal_level; diff --git a/src/include/catalog/pg_control.h b/src/include/catalog/pg_control.h index 0e297610d8..637221e634 100644 --- a/src/include/catalog/pg_control.h +++ b/src/include/catalog/pg_control.h @@ -172,6 +172,7 @@ typedef struct ControlFileData */ int wal_level; int MaxConnections; + int max_worker_processes; int max_prepared_xacts; int max_locks_per_xact; diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h index be3add95dc..48985b370f 100644 --- a/src/include/miscadmin.h +++ b/src/include/miscadmin.h @@ -141,6 +141,7 @@ extern PGDLLIMPORT char *DataDir; extern PGDLLIMPORT int NBuffers; extern int MaxBackends; extern int MaxConnections; +extern int max_worker_processes; extern PGDLLIMPORT int MyProcPid; extern PGDLLIMPORT pg_time_t MyStartTime;