Re: TRAP: FailedAssertion("tabstat->trans == trans", File: "pgstat_relation.c", Line: 508

At Tue, 19 Apr 2022 10:55:26 -0700, Andres Freund <andres(at)anarazel(dot)de> wrote in
> Hi,
>
> On 2022-04-19 10:36:24 -0700, Andres Freund wrote:
> > On 2022-04-19 13:50:25 +0200, Erik Rijkers wrote:
> > > The 12th run of statbug.sh crashed and gave a corefile.
> >
> > I ran through quite a few iterations by now, without reproducing :(
> >
> > I guess there's some timing issue and you're hitting on your system
> > due to the slower disks.
>
> Ah. I found the issue. The new pgstat_report_stat(true) call in
> LogicalRepApplyLoop()'s "timeout" section doesn't check if we're in a
> transaction. And the transactional stats code doesn't handle that (never
> has).
>
> I think all that's needed is a if (IsTransactionState()) around that
> pgstat_report_stat().

if (!IsTransactinoState()) ?

> It might be possible to put an assertion into pgstat_report_stat(), but
> I need to look at the process exit code to see if it is.

Inserting a sleep in pgoutput_commit_txn reproduced this. Crashes with
the same stack trace with the similar variable state.

diff --git a/src/backend/replication/pgoutput/pgoutput.c b/src/backend/replication/pgoutput/pgoutput.c
index b197bfd565..def4d751d3 100644
--- a/src/backend/replication/pgoutput/pgoutput.c
+++ b/src/backend/replication/pgoutput/pgoutput.c
@@ -568,6 +568,7 @@ pgoutput_commit_txn(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
return;
}

+ sleep(2);
OutputPluginPrepareWrite(ctx, true);
logicalrep_write_commit(ctx->out, txn, commit_lsn);
OutputPluginWrite(ctx, true);

The following actuall works for this.

diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index 4171371296..f4e5359513 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -2882,10 +2882,11 @@ LogicalRepApplyLoop(XLogRecPtr last_received)
send_feedback(last_received, requestReply, requestReply);

/*
- * Force reporting to ensure long idle periods don't lead to
- * arbitrarily delayed stats.
+ * Force reporting to ensure long out-of-transaction idle periods
+ * don't lead to arbitrarily delayed stats.
*/
- pgstat_report_stat(true);
+ if (!IsTransactionState())
+ pgstat_report_stat(true);
}
}

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center