On 20/11/2020 02:38, Andres Freund wrote:
I locally, on a heavily modified branch (AIO support), started to get
consistent failures in this test. I *suspect*, but am not sure, that
it's the test's fault, not the fault of modifications.
As far as I can tell, after the pg_rewind call, there's no guarantee
that node_c has fully caught up to the 'in A, after C was promoted'
insertion on node a. Thus at the check_query() I sometimes get just 'in
A, before promotion' back.
After adding a wait that problem seems to be fixed. Here's what I did
diff --git i/src/bin/pg_rewind/t/007_standby_source.pl
w/src/bin/pg_rewind/t/007_standby_source.pl
index f6abcc2d987..48898bef2f5 100644
--- i/src/bin/pg_rewind/t/007_standby_source.pl
+++ w/src/bin/pg_rewind/t/007_standby_source.pl
@@ -88,6 +88,7 @@ $node_c->safe_psql('postgres', "checkpoint");
# - you need to rewind.
$node_a->safe_psql('postgres',
"INSERT INTO tbl1 VALUES ('in A, after C was promoted')");
+$lsn = $node_a->lsn('insert');
# Also insert a new row in the standby, which won't be present in the
# old primary.
@@ -142,6 +143,8 @@ $node_primary = $node_c;
# Run some checks to verify that C has been successfully rewound,
# and connected back to follow B.
+$node_b->wait_for_catchup('node_c', 'replay', $lsn);
+
check_query(
'SELECT * FROM tbl1',
qq(in A
Yes, I was able to reproduced that by inserting a strategic sleep in the
test and pausing replication by attaching gdb to the walsender process.
Pushed a fix similar to your patch, but I put the wait_for_catchup()
before running pg_rewind. The point of inserting the 'in A, after C was
promoted' row is that it's present in B when pg_rewind runs.
Thanks!
- Heikki
