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Allow changing autovacuum_max_workers without restarting.

Browse Source 
This commit introduces a new parameter named
autovacuum_worker_slots that controls how many autovacuum worker
slots to reserve during server startup.  Modifying this new
parameter's value does require a server restart, but it should
typically be set to the upper bound of what you might realistically
need to set autovacuum_max_workers.  With that new parameter in
place, autovacuum_max_workers can now be changed with a SIGHUP
(e.g., pg_ctl reload).

If autovacuum_max_workers is set higher than
autovacuum_worker_slots, a WARNING is emitted, and the server will
only start up to autovacuum_worker_slots workers at a given time.
If autovacuum_max_workers is set to a value less than the number of
currently-running autovacuum workers, the existing workers will
continue running, but no new workers will be started until the
number of running autovacuum workers drops below
autovacuum_max_workers.

Reviewed-by: Sami Imseih, Justin Pryzby, Robert Haas, Andres Freund, Yogesh Sharma
Discussion: https://postgr.es/m/20240410212344.GA1824549%40nathanxps13
This commit is contained in:
Nathan Bossart
2025-01-06 15:01:22 -06:00
parent 5e68f61192
commit c758119e5b
11 changed files with 117 additions and 31 deletions
Download Patch File Download Diff File Expand all files Collapse all files

82
src/backend/postmaster/autovacuum.c
View File

@@ -115,6 +115,7 @@
* GUC parameters
*/
bool autovacuum_start_daemon = false;
int autovacuum_worker_slots;
int autovacuum_max_workers;
int autovacuum_work_mem = -1;
int autovacuum_naptime;
@@ -210,7 +211,7 @@ typedef struct autovac_table
/*-------------
* This struct holds information about a single worker's whereabouts. We keep
* an array of these in shared memory, sized according to
* autovacuum_max_workers.
* autovacuum_worker_slots.
*
* wi_links entry into free list or running list
* wi_dboid OID of the database this worker is supposed to work on
@@ -291,7 +292,7 @@ typedef struct
{
sig_atomic_t av_signal[AutoVacNumSignals];
pid_t av_launcherpid;
dlist_head av_freeWorkers;
dclist_head av_freeWorkers;
dlist_head av_runningWorkers;
WorkerInfo av_startingWorker;
AutoVacuumWorkItem av_workItems[NUM_WORKITEMS];
@@ -349,6 +350,8 @@ static void autovac_report_activity(autovac_table *tab);
static void autovac_report_workitem(AutoVacuumWorkItem *workitem,
const char *nspname, const char *relname);
static void avl_sigusr2_handler(SIGNAL_ARGS);
static bool av_worker_available(void);
static void check_av_worker_gucs(void);
@@ -577,8 +580,7 @@ AutoVacLauncherMain(char *startup_data, size_t startup_data_len)
* wakening conditions.
*/
launcher_determine_sleep(!dlist_is_empty(&AutoVacuumShmem->av_freeWorkers),
false, &nap);
launcher_determine_sleep(av_worker_available(), false, &nap);
/*
* Wait until naptime expires or we get some type of signal (all the
@@ -638,7 +640,7 @@ AutoVacLauncherMain(char *startup_data, size_t startup_data_len)
current_time = GetCurrentTimestamp();
LWLockAcquire(AutovacuumLock, LW_SHARED);
can_launch = !dlist_is_empty(&AutoVacuumShmem->av_freeWorkers);
can_launch = av_worker_available();
if (AutoVacuumShmem->av_startingWorker != NULL)
{
@@ -681,8 +683,8 @@ AutoVacLauncherMain(char *startup_data, size_t startup_data_len)
worker->wi_sharedrel = false;
worker->wi_proc = NULL;
worker->wi_launchtime = 0;
dlist_push_head(&AutoVacuumShmem->av_freeWorkers,
&worker->wi_links);
dclist_push_head(&AutoVacuumShmem->av_freeWorkers,
&worker->wi_links);
AutoVacuumShmem->av_startingWorker = NULL;
ereport(WARNING,
errmsg("autovacuum worker took too long to start; canceled"));
@@ -747,6 +749,8 @@ HandleAutoVacLauncherInterrupts(void)
if (ConfigReloadPending)
{
int autovacuum_max_workers_prev = autovacuum_max_workers;
ConfigReloadPending = false;
ProcessConfigFile(PGC_SIGHUP);
@@ -754,6 +758,14 @@ HandleAutoVacLauncherInterrupts(void)
if (!AutoVacuumingActive())
AutoVacLauncherShutdown();
/*
* If autovacuum_max_workers changed, emit a WARNING if
* autovacuum_worker_slots < autovacuum_max_workers. If it didn't
* change, skip this to avoid too many repeated log messages.
*/
if (autovacuum_max_workers_prev != autovacuum_max_workers)
check_av_worker_gucs();
/* rebuild the list in case the naptime changed */
rebuild_database_list(InvalidOid);
}
@@ -1089,7 +1101,7 @@ do_start_worker(void)
/* return quickly when there are no free workers */
LWLockAcquire(AutovacuumLock, LW_SHARED);
if (dlist_is_empty(&AutoVacuumShmem->av_freeWorkers))
if (!av_worker_available())
{
LWLockRelease(AutovacuumLock);
return InvalidOid;
@@ -1242,7 +1254,7 @@ do_start_worker(void)
* Get a worker entry from the freelist. We checked above, so there
* really should be a free slot.
*/
wptr = dlist_pop_head_node(&AutoVacuumShmem->av_freeWorkers);
wptr = dclist_pop_head_node(&AutoVacuumShmem->av_freeWorkers);
worker = dlist_container(WorkerInfoData, wi_links, wptr);
worker->wi_dboid = avdb->adw_datid;
@@ -1615,8 +1627,8 @@ FreeWorkerInfo(int code, Datum arg)
MyWorkerInfo->wi_proc = NULL;
MyWorkerInfo->wi_launchtime = 0;
pg_atomic_clear_flag(&MyWorkerInfo->wi_dobalance);
dlist_push_head(&AutoVacuumShmem->av_freeWorkers,
&MyWorkerInfo->wi_links);
dclist_push_head(&AutoVacuumShmem->av_freeWorkers,
&MyWorkerInfo->wi_links);
/* not mine anymore */
MyWorkerInfo = NULL;
@@ -3248,10 +3260,14 @@ AutoVacuumRequestWork(AutoVacuumWorkItemType type, Oid relationId,
void
autovac_init(void)
{
if (autovacuum_start_daemon && !pgstat_track_counts)
if (!autovacuum_start_daemon)
return;
else if (!pgstat_track_counts)
ereport(WARNING,
(errmsg("autovacuum not started because of misconfiguration"),
errhint("Enable the \"track_counts\" option.")));
else
check_av_worker_gucs();
}
/*
@@ -3268,7 +3284,7 @@ AutoVacuumShmemSize(void)
*/
size = sizeof(AutoVacuumShmemStruct);
size = MAXALIGN(size);
size = add_size(size, mul_size(autovacuum_max_workers,
size = add_size(size, mul_size(autovacuum_worker_slots,
sizeof(WorkerInfoData)));
return size;
}
@@ -3295,7 +3311,7 @@ AutoVacuumShmemInit(void)
Assert(!found);
AutoVacuumShmem->av_launcherpid = 0;
dlist_init(&AutoVacuumShmem->av_freeWorkers);
dclist_init(&AutoVacuumShmem->av_freeWorkers);
dlist_init(&AutoVacuumShmem->av_runningWorkers);
AutoVacuumShmem->av_startingWorker = NULL;
memset(AutoVacuumShmem->av_workItems, 0,
@@ -3305,10 +3321,10 @@ AutoVacuumShmemInit(void)
MAXALIGN(sizeof(AutoVacuumShmemStruct)));
/* initialize the WorkerInfo free list */
for (i = 0; i < autovacuum_max_workers; i++)
for (i = 0; i < autovacuum_worker_slots; i++)
{
dlist_push_head(&AutoVacuumShmem->av_freeWorkers,
&worker[i].wi_links);
dclist_push_head(&AutoVacuumShmem->av_freeWorkers,
&worker[i].wi_links);
pg_atomic_init_flag(&worker[i].wi_dobalance);
}
@@ -3344,3 +3360,35 @@ check_autovacuum_work_mem(int *newval, void **extra, GucSource source)
return true;
}
/*
* Returns whether there is a free autovacuum worker slot available.
*/
static bool
av_worker_available(void)
{
int free_slots;
int reserved_slots;
free_slots = dclist_count(&AutoVacuumShmem->av_freeWorkers);
reserved_slots = autovacuum_worker_slots - autovacuum_max_workers;
reserved_slots = Max(0, reserved_slots);
return free_slots > reserved_slots;
}
/*
* Emits a WARNING if autovacuum_worker_slots < autovacuum_max_workers.
*/
static void
check_av_worker_gucs(void)
{
if (autovacuum_worker_slots < autovacuum_max_workers)
ereport(WARNING,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("\"autovacuum_max_workers\" (%d) should be less than or equal to \"autovacuum_worker_slots\" (%d)",
autovacuum_max_workers, autovacuum_worker_slots),
errdetail("The server will only start up to \"autovacuum_worker_slots\" (%d) autovacuum workers at a given time.",
autovacuum_worker_slots)));
}

4
src/backend/postmaster/pmchild.c
View File

@@ -8,7 +8,7 @@
* child process is allocated a PMChild struct from a fixed pool of structs.
* The size of the pool is determined by various settings that configure how
* many worker processes and backend connections are allowed, i.e.
* autovacuum_max_workers, max_worker_processes, max_wal_senders, and
* autovacuum_worker_slots, max_worker_processes, max_wal_senders, and
* max_connections.
*
* Dead-end backends are handled slightly differently. There is no limit
@@ -99,7 +99,7 @@ InitPostmasterChildSlots(void)
*/
pmchild_pools[B_BACKEND].size = 2 * (MaxConnections + max_wal_senders);
pmchild_pools[B_AUTOVAC_WORKER].size = autovacuum_max_workers;
pmchild_pools[B_AUTOVAC_WORKER].size = autovacuum_worker_slots;
pmchild_pools[B_BG_WORKER].size = max_worker_processes;
/*