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Feb 4, 2025
Merged

Store GUC variables in local process memory to avoid IPC shenanigans #86

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6 changes: 3 additions & 3 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -158,9 +158,9 @@ If `pg_wait_sampling.sample_cpu` is set to true then processes that are not
waiting on anything are also sampled. The wait event columns for such processes
will be NULL.

These GUCs are allowed to be changed by superuser. Also, they are placed into
shared memory. Thus, they could be changed from any backend and affects worker
runtime.
Values of these GUC variables can be changed only in config file or with ALTER SYSTEM.
Then you need to reload server's configuration (such as with pg_reload_conf function)
for changes to take effect.

See
[PostgreSQL documentation](http://www.postgresql.org/docs/devel/static/monitoring-stats.html#WAIT-EVENT-TABLE)
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30 changes: 17 additions & 13 deletions collector.c
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Expand Up @@ -16,6 +16,7 @@
#include "funcapi.h"
#include "miscadmin.h"
#include "postmaster/bgworker.h"
#include "postmaster/interrupt.h"
#include "storage/ipc.h"
#include "storage/procarray.h"
#include "storage/procsignal.h"
Expand Down Expand Up @@ -151,7 +152,7 @@ probe_waits(History *observations, HTAB *profile_hash,
TimestampTz ts = GetCurrentTimestamp();

/* Realloc waits history if needed */
newSize = pgws_collector_hdr->historySize;
newSize = pgws_historySize;
if (observations->count != newSize)
realloc_history(observations, newSize);

Expand All @@ -170,7 +171,7 @@ probe_waits(History *observations, HTAB *profile_hash,
item.pid = proc->pid;
item.wait_event_info = proc->wait_event_info;

if (pgws_collector_hdr->profileQueries)
if (pgws_profileQueries)
item.queryId = pgws_proc_queryids[i];
else
item.queryId = 0;
Expand Down Expand Up @@ -289,7 +290,7 @@ make_profile_hash()
hash_ctl.hash = tag_hash;
hash_ctl.hcxt = TopMemoryContext;

if (pgws_collector_hdr->profileQueries)
if (pgws_profileQueries)
hash_ctl.keysize = offsetof(ProfileItem, count);
else
hash_ctl.keysize = offsetof(ProfileItem, queryId);
Expand Down Expand Up @@ -346,6 +347,7 @@ pgws_collector_main(Datum main_arg)
* partitipate to the ProcSignal infrastructure.
*/
pqsignal(SIGTERM, handle_sigterm);
pqsignal(SIGHUP, SignalHandlerForConfigReload);
pqsignal(SIGUSR1, procsignal_sigusr1_handler);
BackgroundWorkerUnblockSignals();
InitPostgresCompat(NULL, InvalidOid, NULL, InvalidOid, 0, NULL);
Expand All @@ -361,7 +363,7 @@ pgws_collector_main(Datum main_arg)
collector_context = AllocSetContextCreate(TopMemoryContext,
"pg_wait_sampling context", ALLOCSET_DEFAULT_SIZES);
old_context = MemoryContextSwitchTo(collector_context);
alloc_history(&observations, pgws_collector_hdr->historySize);
alloc_history(&observations, pgws_historySize);
MemoryContextSwitchTo(old_context);

ereport(LOG, (errmsg("pg_wait_sampling collector started")));
Expand All @@ -375,29 +377,31 @@ pgws_collector_main(Datum main_arg)
shm_mq_handle *mqh;
int64 history_diff,
profile_diff;
int history_period,
profile_period;
bool write_history,
write_profile;

/* We need an explicit call for at least ProcSignal notifications. */
CHECK_FOR_INTERRUPTS();

if (ConfigReloadPending)
{
ConfigReloadPending = false;
ProcessConfigFile(PGC_SIGHUP);
}

/* Wait calculate time to next sample for history or profile */
current_ts = GetCurrentTimestamp();

history_diff = millisecs_diff(history_ts, current_ts);
profile_diff = millisecs_diff(profile_ts, current_ts);
history_period = pgws_collector_hdr->historyPeriod;
profile_period = pgws_collector_hdr->profilePeriod;

write_history = (history_diff >= (int64)history_period);
write_profile = (profile_diff >= (int64)profile_period);
write_history = (history_diff >= (int64)pgws_historyPeriod);
write_profile = (profile_diff >= (int64)pgws_profilePeriod);

if (write_history || write_profile)
{
probe_waits(&observations, profile_hash,
write_history, write_profile, pgws_collector_hdr->profilePid);
write_history, write_profile, pgws_profilePid);

if (write_history)
{
Expand All @@ -421,8 +425,8 @@ pgws_collector_main(Datum main_arg)
* shared memory.
*/
rc = WaitLatch(&MyProc->procLatch, WL_LATCH_SET | WL_TIMEOUT | WL_POSTMASTER_DEATH,
Min(history_period - (int)history_diff,
profile_period - (int)profile_diff), PG_WAIT_EXTENSION);
Min(pgws_historyPeriod - (int)history_diff,
pgws_historyPeriod - (int)profile_diff), PG_WAIT_EXTENSION);

if (rc & WL_POSTMASTER_DEATH)
proc_exit(1);
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14 changes: 0 additions & 14 deletions compat.h
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Expand Up @@ -51,18 +51,4 @@ InitPostgresCompat(const char *in_dbname, Oid dboid,
#endif
}

static inline void
get_guc_variables_compat(struct config_generic ***vars, int *num_vars)
{
Assert(vars != NULL);
Assert(num_vars != NULL);

#if PG_VERSION_NUM >= 160000
*vars = get_guc_variables(num_vars);
#else
*vars = get_guc_variables();
*num_vars = GetNumConfigOptions();
#endif
}

#endif
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