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Fix an assertion failure in Citus maintenance daemon that can happen in very slow systems (#8158) 

Fixes #5808.

DESCRIPTION: Fixes an assertion failure in Citus maintenance daemon that
can happen in very slow systems.

Try running `make -C src/test/regress/ check-multi-1-vg` - while the
tests will exit with code 2 at least %50 of the times in the very early
stages of the test suite by producing a core-dump on main, it won't be
the case on this branch, at least based on my trials :)
pull/8176/head
Onur Tirtir 2025-09-04 15:13:57 +03:00 committed by GitHub
parent 2834fa26c9
commit 0c658b73fc
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1 changed files with 23 additions and 5 deletions
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24
src/backend/distributed/utils/maintenanced.c
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@ -1040,13 +1040,31 @@ MaintenanceDaemonShmemExit(int code, Datum arg)
if (myDbData != NULL)
{
/*
* Confirm that I am still the registered maintenance daemon before exiting.
* Once the maintenance daemon fails (e.g., due to an error in the main loop),
* both Postgres tries to restart the failed daemon and Citus attempt to start
* a new one. In that case, the one started by Citus ends up here.
*
* As the maintenance daemon that Citus tried to start, we might see the entry
* for the daemon restarted by Postgres if the system was so slow that it
* took a long time for us to be re-scheduled to call MaintenanceDaemonShmemExit(),
* e.g., under valgrind testing.
*
* In that case, we should unregister ourself only if we are still the registered
* maintenance daemon.
*/
Assert(myDbData->workerPid == MyProcPid);
if (myDbData->workerPid == MyProcPid)
{
myDbData->daemonStarted = false;
myDbData->workerPid = 0;
}
else
{
ereport(LOG, (errmsg(
"maintenance daemon for database %u has already been replaced by "
"Postgres, skipping to unregister this maintenance daemon",
databaseOid)));
}
}
LWLockRelease(&MaintenanceDaemonControl->lock);
}