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

At Tue, 19 Apr 2022 10:55:26 -0700, Andres Freund <andres@anarazel.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