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pgstat: Bring up pgstat in BaseInit() to fix uninitialized use of pgstat by AV.

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Previously pgstat_initialize() was called in InitPostgres() and
AuxiliaryProcessMain(). As it turns out there was at least one case where we
reported stats before pgstat_initialize() was called, see
AutoVacWorkerMain()'s intentionally early call to pgstat_report_autovac().

This turns out to not be a problem with the current pgstat implementation as
pgstat_initialize() only registers a shutdown callback. But in the shared
memory based stats implementation we are working towards pgstat_initialize()
has to do more work.

After b406478b87 BaseInit() is a central place where initialization shared by
normal backends and auxiliary backends can be put. Obviously BaseInit() is
called before InitPostgres() registers ShutdownPostgres. Previously
ShutdownPostgres was the first before_shmem_exit callback, now that's commonly
pgstats. That should be fine.

Previously pgstat_initialize() was not called in bootstrap mode, but there
does not appear to be a need for that. It's now done unconditionally.

To detect future issues like this, assertions are added to a few places
verifying that the pgstat subsystem is initialized and not yet shut down.

Author: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/20210405092914.mmxqe7j56lsjfsej@alap3.anarazel.de
Discussion: https://postgr.es/m/20210802164124.ufo5buo4apl6yuvs@alap3.anarazel.de
This commit is contained in:
Andres Freund
2021-08-06 18:54:39 -07:00
parent 5c056b0c25
commit ee3f8d3d3a
3 changed files with 65 additions and 13 deletions
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23
src/backend/utils/init/postinit.c
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@ -517,6 +517,14 @@ BaseInit(void)
*/
DebugFileOpen();
/*
* Initialize statistics reporting. This needs to happen early to ensure
* that pgstat's shutdown callback runs after the shutdown callbacks of
* all subsystems that can produce stats (like e.g. transaction commits
* can).
*/
pgstat_initialize();
/* Do local initialization of file, storage and buffer managers */
InitFileAccess();
InitSync();
@ -646,10 +654,6 @@ InitPostgres(const char *in_dbname, Oid dboid, const char *username,
/* Initialize portal manager */
EnablePortalManager();
/* Initialize stats collection --- must happen before first xact */
if (!bootstrap)
pgstat_initialize();
/* Initialize status reporting */
if (!bootstrap)
pgstat_beinit();
@ -662,11 +666,12 @@ InitPostgres(const char *in_dbname, Oid dboid, const char *username,
/*
* Set up process-exit callback to do pre-shutdown cleanup. This is the
* first before_shmem_exit callback we register; thus, this will be the
* last thing we do before low-level modules like the buffer manager begin
* to close down. We need to have this in place before we begin our first
* transaction --- if we fail during the initialization transaction, as is
* entirely possible, we need the AbortTransaction call to clean up.
* one of the first before_shmem_exit callbacks we register; thus, this
* will be one the last things we do before low-level modules like the
* buffer manager begin to close down. We need to have this in place
* before we begin our first transaction --- if we fail during the
* initialization transaction, as is entirely possible, we need the
* AbortTransaction call to clean up.
*/
before_shmem_exit(ShutdownPostgres, 0);