Обсуждение: Isn't wait_for_catchup slightly broken?

While trying to make sense of some recent buildfarm failures,
I happened to notice that the default query issued by
the TAP sub wait_for_catchup looks like

SELECT pg_current_wal_lsn() <= replay_lsn AND state = 'streaming' FROM pg_catalog.pg_stat_replication WHERE
application_name= '<whatever>'; 

ISTM there are two things wrong with this:

1. Since pg_current_wal_lsn() is re-evaluated each time, we're
effectively setting a moving target for the standby to reach.
Admittedly we're not going to be issuing any new DML while
waiting in wait_for_catchup, but background activity such as
autovacuum could be creating new WAL.  Thus, the test is likely
to wait longer than it needs to.  In the worst case, we'd never
catch up until the primary server has been totally quiescent
for awhile.

2. Aside from being slower than necessary, this also makes the
test squishy and formally incorrect, because the standby might
get the opportunity to replay more WAL than the test intends.

So I think we need to fix it to capture the target WAL position
at the start, as I've done in the attached patch.  In principle
this might make things a bit slower because of the extra
transaction required, but I don't notice any above-the-noise
difference on my own workstation.

Another thing that is bothering me a bit is that a number of the
callers use $node->lsn('insert') as the target.  This also seems
rather dubious, because that could be ahead of what's been written
out.  These callers are just taking it on faith that something will
eventually cause that extra WAL to get written out (and become
available to the standby).  Again, that seems to make the test
slower than it need be, with a worst-case scenario being that it
eventually times out.  Admittedly this is unlikely to be a big
problem unless some background op issues an abortive transaction
at just the wrong time.  Nonetheless, I wonder if we shouldn't
standardize on "thou shalt use the write position", because I
don't think the other alternatives have anything to recommend them.
I've not addressed that below, though I did tweak the comment about
that parameter.

Thoughts?

            regards, tom lane

diff --git a/src/test/perl/PostgreSQL/Test/Cluster.pm b/src/test/perl/PostgreSQL/Test/Cluster.pm
index e18f27276c..fb6cc39db4 100644
--- a/src/test/perl/PostgreSQL/Test/Cluster.pm
+++ b/src/test/perl/PostgreSQL/Test/Cluster.pm
@@ -2509,8 +2509,10 @@ poll_query_until timeout.

 Requires that the 'postgres' db exists and is accessible.

-target_lsn may be any arbitrary lsn, but is typically $primary_node->lsn('insert').
-If omitted, pg_current_wal_lsn() is used.
+The default value of target_lsn is $node->lsn('write'), which ensures
+that the standby has caught up to what has been committed on the primary.
+Another plausible choice is $node->lsn('insert'), which ensures that
+preceding executed-but-not-committed WAL has been replayed as well.

 This is not a test. It die()s on failure.

@@ -2531,23 +2533,18 @@ sub wait_for_catchup
     {
         $standby_name = $standby_name->name;
     }
-    my $lsn_expr;
-    if (defined($target_lsn))
+    if (!defined($target_lsn))
     {
-        $lsn_expr = "'$target_lsn'";
-    }
-    else
-    {
-        $lsn_expr = 'pg_current_wal_lsn()';
+        $target_lsn = $self->lsn('write');
     }
     print "Waiting for replication conn "
       . $standby_name . "'s "
       . $mode
       . "_lsn to pass "
-      . $lsn_expr . " on "
+      . $target_lsn . " on "
       . $self->name . "\n";
     my $query =
-      qq[SELECT $lsn_expr <= ${mode}_lsn AND state = 'streaming' FROM pg_catalog.pg_stat_replication WHERE
application_name= '$standby_name';]; 
+      qq[SELECT '$target_lsn' <= ${mode}_lsn AND state = 'streaming' FROM pg_catalog.pg_stat_replication WHERE
application_name= '$standby_name';]; 
     $self->poll_query_until('postgres', $query)
       or croak "timed out waiting for catchup";
     print "done\n";

On Mon, Jan 10, 2022 at 02:31:38PM -0500, Tom Lane wrote:
> 
> So I think we need to fix it to capture the target WAL position
> at the start, as I've done in the attached patch.

+1, it looks sensible to me.

> In principle
> this might make things a bit slower because of the extra
> transaction required, but I don't notice any above-the-noise
> difference on my own workstation.

I'm wondering if the environments where this extra transaction could make
a noticeable difference are also environments where doing that extra
transaction can save some iteration(s), which would be at least as costly.

I wrote:
> Another thing that is bothering me a bit is that a number of the
> callers use $node->lsn('insert') as the target.  This also seems
> rather dubious, because that could be ahead of what's been written
> out.  These callers are just taking it on faith that something will
> eventually cause that extra WAL to get written out (and become
> available to the standby).  Again, that seems to make the test
> slower than it need be, with a worst-case scenario being that it
> eventually times out.  Admittedly this is unlikely to be a big
> problem unless some background op issues an abortive transaction
> at just the wrong time.  Nonetheless, I wonder if we shouldn't
> standardize on "thou shalt use the write position", because I
> don't think the other alternatives have anything to recommend them.

Here's a version that makes sure that callers specify a write position not
an insert position.  I also simplified the callers wherever it turned
out that they could just use the default parameters.

            regards, tom lane

diff --git a/src/bin/pg_basebackup/t/020_pg_receivewal.pl b/src/bin/pg_basebackup/t/020_pg_receivewal.pl
index b616c0ccf1..98dbdab595 100644
--- a/src/bin/pg_basebackup/t/020_pg_receivewal.pl
+++ b/src/bin/pg_basebackup/t/020_pg_receivewal.pl
@@ -290,7 +290,7 @@ $standby->psql(
     "CREATE_REPLICATION_SLOT $archive_slot PHYSICAL (RESERVE_WAL)",
     replication => 1);
 # Wait for standby catchup
-$primary->wait_for_catchup($standby, 'replay', $primary->lsn('write'));
+$primary->wait_for_catchup($standby);
 # Get a walfilename from before the promotion to make sure it is archived
 # after promotion
 my $standby_slot = $standby->slot($archive_slot);
diff --git a/src/bin/pg_rewind/t/007_standby_source.pl b/src/bin/pg_rewind/t/007_standby_source.pl
index 62254344f6..239b510c1a 100644
--- a/src/bin/pg_rewind/t/007_standby_source.pl
+++ b/src/bin/pg_rewind/t/007_standby_source.pl
@@ -74,7 +74,7 @@ $node_a->safe_psql('postgres',
     "INSERT INTO tbl1 values ('in A, before promotion')");
 $node_a->safe_psql('postgres', 'CHECKPOINT');

-my $lsn = $node_a->lsn('insert');
+my $lsn = $node_a->lsn('write');
 $node_a->wait_for_catchup('node_b', 'write', $lsn);
 $node_b->wait_for_catchup('node_c', 'write', $lsn);

@@ -93,8 +93,7 @@ $node_a->safe_psql('postgres',
     "INSERT INTO tbl1 VALUES ('in A, after C was promoted')");

 # make sure it's replicated to B before we continue
-$lsn = $node_a->lsn('insert');
-$node_a->wait_for_catchup('node_b', 'replay', $lsn);
+$node_a->wait_for_catchup('node_b');

 # Also insert a new row in the standby, which won't be present in the
 # old primary.
@@ -161,7 +160,7 @@ in A, after C was promoted
 $node_a->safe_psql('postgres',
     "INSERT INTO tbl1 values ('in A, after rewind')");

-$lsn = $node_a->lsn('insert');
+$lsn = $node_a->lsn('write');
 $node_b->wait_for_catchup('node_c', 'replay', $lsn);

 check_query(
diff --git a/src/bin/pg_rewind/t/008_min_recovery_point.pl b/src/bin/pg_rewind/t/008_min_recovery_point.pl
index 9ad7e6b62b..8240229230 100644
--- a/src/bin/pg_rewind/t/008_min_recovery_point.pl
+++ b/src/bin/pg_rewind/t/008_min_recovery_point.pl
@@ -69,8 +69,7 @@ $node_3->init_from_backup($node_1, $backup_name, has_streaming => 1);
 $node_3->start;

 # Wait until node 3 has connected and caught up
-my $lsn = $node_1->lsn('insert');
-$node_1->wait_for_catchup('node_3', 'replay', $lsn);
+$node_1->wait_for_catchup('node_3');

 #
 # Swap the roles of node_1 and node_3, so that node_1 follows node_3.
@@ -106,8 +105,7 @@ $node_2->restart();
 #

 # make sure node_1 is full caught up with node_3 first
-$lsn = $node_3->lsn('insert');
-$node_3->wait_for_catchup('node_1', 'replay', $lsn);
+$node_3->wait_for_catchup('node_1');

 $node_1->promote;
 # Force a checkpoint after promotion, like earlier.
diff --git a/src/test/perl/PostgreSQL/Test/Cluster.pm b/src/test/perl/PostgreSQL/Test/Cluster.pm
index e18f27276c..eceb8b2d8b 100644
--- a/src/test/perl/PostgreSQL/Test/Cluster.pm
+++ b/src/test/perl/PostgreSQL/Test/Cluster.pm
@@ -2509,8 +2509,11 @@ poll_query_until timeout.

 Requires that the 'postgres' db exists and is accessible.

-target_lsn may be any arbitrary lsn, but is typically $primary_node->lsn('insert').
-If omitted, pg_current_wal_lsn() is used.
+The default value of target_lsn is $node->lsn('write'), which ensures
+that the standby has caught up to what has been committed on the primary.
+If you pass an explicit value of target_lsn, it should almost always be
+the primary's write LSN; so this parameter is seldom needed except when
+querying some intermediate replication node rather than the primary.

 This is not a test. It die()s on failure.

@@ -2531,23 +2534,18 @@ sub wait_for_catchup
     {
         $standby_name = $standby_name->name;
     }
-    my $lsn_expr;
-    if (defined($target_lsn))
+    if (!defined($target_lsn))
     {
-        $lsn_expr = "'$target_lsn'";
-    }
-    else
-    {
-        $lsn_expr = 'pg_current_wal_lsn()';
+        $target_lsn = $self->lsn('write');
     }
     print "Waiting for replication conn "
       . $standby_name . "'s "
       . $mode
       . "_lsn to pass "
-      . $lsn_expr . " on "
+      . $target_lsn . " on "
       . $self->name . "\n";
     my $query =
-      qq[SELECT $lsn_expr <= ${mode}_lsn AND state = 'streaming' FROM pg_catalog.pg_stat_replication WHERE
application_name= '$standby_name';]; 
+      qq[SELECT '$target_lsn' <= ${mode}_lsn AND state = 'streaming' FROM pg_catalog.pg_stat_replication WHERE
application_name= '$standby_name';]; 
     $self->poll_query_until('postgres', $query)
       or croak "timed out waiting for catchup";
     print "done\n";
diff --git a/src/test/recovery/t/001_stream_rep.pl b/src/test/recovery/t/001_stream_rep.pl
index fb8f66878a..ca760c7210 100644
--- a/src/test/recovery/t/001_stream_rep.pl
+++ b/src/test/recovery/t/001_stream_rep.pl
@@ -47,10 +47,9 @@ $node_primary->safe_psql('postgres',
     "CREATE TABLE tab_int AS SELECT generate_series(1,1002) AS a");

 # Wait for standbys to catch up
-$node_primary->wait_for_catchup($node_standby_1, 'replay',
-    $node_primary->lsn('insert'));
-$node_standby_1->wait_for_catchup($node_standby_2, 'replay',
-    $node_standby_1->lsn('replay'));
+my $primary_lsn = $node_primary->lsn('write');
+$node_primary->wait_for_catchup($node_standby_1, 'replay', $primary_lsn);
+$node_standby_1->wait_for_catchup($node_standby_2, 'replay', $primary_lsn);

 my $result =
   $node_standby_1->safe_psql('postgres', "SELECT count(*) FROM tab_int");
@@ -67,10 +66,9 @@ $node_primary->safe_psql('postgres',
     "CREATE SEQUENCE seq1; SELECT nextval('seq1')");

 # Wait for standbys to catch up
-$node_primary->wait_for_catchup($node_standby_1, 'replay',
-    $node_primary->lsn('insert'));
-$node_standby_1->wait_for_catchup($node_standby_2, 'replay',
-    $node_standby_1->lsn('replay'));
+$primary_lsn = $node_primary->lsn('write');
+$node_primary->wait_for_catchup($node_standby_1, 'replay', $primary_lsn);
+$node_standby_1->wait_for_catchup($node_standby_2, 'replay', $primary_lsn);

 $result = $node_standby_1->safe_psql('postgres', "SELECT * FROM seq1");
 print "standby 1: $result\n";
@@ -374,10 +372,10 @@ sub replay_check
     my $newval = $node_primary->safe_psql('postgres',
         'INSERT INTO replayed(val) SELECT coalesce(max(val),0) + 1 AS newval FROM replayed RETURNING val'
     );
-    $node_primary->wait_for_catchup($node_standby_1, 'replay',
-        $node_primary->lsn('insert'));
-    $node_standby_1->wait_for_catchup($node_standby_2, 'replay',
-        $node_standby_1->lsn('replay'));
+    my $primary_lsn = $node_primary->lsn('write');
+    $node_primary->wait_for_catchup($node_standby_1, 'replay', $primary_lsn);
+    $node_standby_1->wait_for_catchup($node_standby_2, 'replay', $primary_lsn);
+
     $node_standby_1->safe_psql('postgres',
         qq[SELECT 1 FROM replayed WHERE val = $newval])
       or die "standby_1 didn't replay primary value $newval";
@@ -481,8 +479,7 @@ $node_standby_1->stop;
 my $newval = $node_primary->safe_psql('postgres',
     'INSERT INTO replayed(val) SELECT coalesce(max(val),0) + 1 AS newval FROM replayed RETURNING val'
 );
-$node_primary->wait_for_catchup($node_standby_2, 'replay',
-    $node_primary->lsn('insert'));
+$node_primary->wait_for_catchup($node_standby_2);
 my $is_replayed = $node_standby_2->safe_psql('postgres',
     qq[SELECT 1 FROM replayed WHERE val = $newval]);
 is($is_replayed, qq(1), "standby_2 didn't replay primary value $newval");
diff --git a/src/test/recovery/t/004_timeline_switch.pl b/src/test/recovery/t/004_timeline_switch.pl
index 333d37b0a4..05b7931668 100644
--- a/src/test/recovery/t/004_timeline_switch.pl
+++ b/src/test/recovery/t/004_timeline_switch.pl
@@ -38,8 +38,7 @@ $node_primary->safe_psql('postgres',
     "CREATE TABLE tab_int AS SELECT generate_series(1,1000) AS a");

 # Wait until standby has replayed enough data on standby 1
-$node_primary->wait_for_catchup($node_standby_1, 'replay',
-    $node_primary->lsn('write'));
+$node_primary->wait_for_catchup($node_standby_1);

 # Stop and remove primary
 $node_primary->teardown_node;
@@ -64,8 +63,7 @@ $node_standby_2->restart;
 # to ensure that the timeline switch has been done.
 $node_standby_1->safe_psql('postgres',
     "INSERT INTO tab_int VALUES (generate_series(1001,2000))");
-$node_standby_1->wait_for_catchup($node_standby_2, 'replay',
-    $node_standby_1->lsn('write'));
+$node_standby_1->wait_for_catchup($node_standby_2);

 my $result =
   $node_standby_2->safe_psql('postgres', "SELECT count(*) FROM tab_int");
@@ -103,8 +101,7 @@ $node_primary_2->promote;
 $node_standby_3->start;
 $node_primary_2->safe_psql('postgres',
     "CREATE TABLE tab_int AS SELECT 1 AS a");
-$node_primary_2->wait_for_catchup($node_standby_3, 'replay',
-    $node_primary_2->lsn('write'));
+$node_primary_2->wait_for_catchup($node_standby_3);

 my $result_2 =
   $node_standby_3->safe_psql('postgres', "SELECT count(*) FROM tab_int");
diff --git a/src/test/recovery/t/010_logical_decoding_timelines.pl
b/src/test/recovery/t/010_logical_decoding_timelines.pl
index 648695928d..672cd74f3b 100644
--- a/src/test/recovery/t/010_logical_decoding_timelines.pl
+++ b/src/test/recovery/t/010_logical_decoding_timelines.pl
@@ -88,8 +88,7 @@ $node_replica->start;
 # db and associated slot.
 is($node_primary->psql('postgres', 'DROP DATABASE dropme'),
     0, 'dropped DB with logical slot OK on primary');
-$node_primary->wait_for_catchup($node_replica, 'replay',
-    $node_primary->lsn('insert'));
+$node_primary->wait_for_catchup($node_replica);
 is( $node_replica->safe_psql(
         'postgres', q[SELECT 1 FROM pg_database WHERE datname = 'dropme']),
     '',
diff --git a/src/test/recovery/t/012_subtransactions.pl b/src/test/recovery/t/012_subtransactions.pl
index 150455b1be..2a558b2301 100644
--- a/src/test/recovery/t/012_subtransactions.pl
+++ b/src/test/recovery/t/012_subtransactions.pl
@@ -103,8 +103,7 @@ $node_primary->psql(
     BEGIN;
     SELECT hs_subxids(127);
     COMMIT;");
-$node_primary->wait_for_catchup($node_standby, 'replay',
-    $node_primary->lsn('insert'));
+$node_primary->wait_for_catchup($node_standby);
 $node_standby->psql(
     'postgres',
     "SELECT coalesce(sum(id),-1) FROM t_012_tbl",
@@ -150,8 +149,7 @@ $node_primary->psql(
     BEGIN;
     SELECT hs_subxids(127);
     PREPARE TRANSACTION 'xact_012_1';");
-$node_primary->wait_for_catchup($node_standby, 'replay',
-    $node_primary->lsn('insert'));
+$node_primary->wait_for_catchup($node_standby);
 $node_standby->psql(
     'postgres',
     "SELECT coalesce(sum(id),-1) FROM t_012_tbl",
@@ -187,8 +185,7 @@ $node_primary->psql(
     BEGIN;
     SELECT hs_subxids(201);
     PREPARE TRANSACTION 'xact_012_1';");
-$node_primary->wait_for_catchup($node_standby, 'replay',
-    $node_primary->lsn('insert'));
+$node_primary->wait_for_catchup($node_standby);
 $node_standby->psql(
     'postgres',
     "SELECT coalesce(sum(id),-1) FROM t_012_tbl",
diff --git a/src/test/recovery/t/015_promotion_pages.pl b/src/test/recovery/t/015_promotion_pages.pl
index c4f9e5e0ce..65443df5fe 100644
--- a/src/test/recovery/t/015_promotion_pages.pl
+++ b/src/test/recovery/t/015_promotion_pages.pl
@@ -44,7 +44,7 @@ $alpha->safe_psql('postgres', 'checkpoint');
 # problematic WAL records.
 $alpha->safe_psql('postgres', 'vacuum verbose test1');
 # Wait for last record to have been replayed on the standby.
-$alpha->wait_for_catchup($bravo, 'replay', $alpha->lsn('insert'));
+$alpha->wait_for_catchup($bravo);

 # Now force a checkpoint on the standby. This seems unnecessary but for "some"
 # reason, the previous checkpoint on the primary does not reflect on the standby
@@ -60,7 +60,7 @@ $alpha->safe_psql('postgres',
 $alpha->safe_psql('postgres', 'truncate test2');

 # Wait again for all records to be replayed.
-$alpha->wait_for_catchup($bravo, 'replay', $alpha->lsn('insert'));
+$alpha->wait_for_catchup($bravo);

 # Do the promotion, which reinitializes minRecoveryPoint in the control
 # file so as WAL is replayed up to the end.
diff --git a/src/test/recovery/t/016_min_consistency.pl b/src/test/recovery/t/016_min_consistency.pl
index 22e553510b..86fd6f5546 100644
--- a/src/test/recovery/t/016_min_consistency.pl
+++ b/src/test/recovery/t/016_min_consistency.pl
@@ -78,7 +78,7 @@ $primary->safe_psql('postgres', 'CHECKPOINT;');
 $primary->safe_psql('postgres', 'UPDATE test1 SET a = a + 1;');

 # Wait for last record to have been replayed on the standby.
-$primary->wait_for_catchup($standby, 'replay', $primary->lsn('insert'));
+$primary->wait_for_catchup($standby);

 # Fill in the standby's shared buffers with the data filled in
 # previously.
@@ -99,7 +99,7 @@ my $relfilenode = $primary->safe_psql('postgres',
     "SELECT pg_relation_filepath('test1'::regclass);");

 # Wait for last record to have been replayed on the standby.
-$primary->wait_for_catchup($standby, 'replay', $primary->lsn('insert'));
+$primary->wait_for_catchup($standby);

 # Issue a restart point on the standby now, which makes the checkpointer
 # update minRecoveryPoint.
diff --git a/src/test/recovery/t/019_replslot_limit.pl b/src/test/recovery/t/019_replslot_limit.pl
index 606399bb6f..47cfbdd646 100644
--- a/src/test/recovery/t/019_replslot_limit.pl
+++ b/src/test/recovery/t/019_replslot_limit.pl
@@ -49,8 +49,7 @@ $node_standby->append_conf('postgresql.conf', "primary_slot_name = 'rep1'");
 $node_standby->start;

 # Wait until standby has replayed enough data
-my $start_lsn = $node_primary->lsn('write');
-$node_primary->wait_for_catchup($node_standby, 'replay', $start_lsn);
+$node_primary->wait_for_catchup($node_standby);

 # Stop standby
 $node_standby->stop;
@@ -84,8 +83,7 @@ is($result, "reserved|t", 'check that slot is working');
 # The standby can reconnect to primary
 $node_standby->start;

-$start_lsn = $node_primary->lsn('write');
-$node_primary->wait_for_catchup($node_standby, 'replay', $start_lsn);
+$node_primary->wait_for_catchup($node_standby);

 $node_standby->stop;

@@ -115,8 +113,7 @@ is($result, "reserved",

 # The standby can reconnect to primary
 $node_standby->start;
-$start_lsn = $node_primary->lsn('write');
-$node_primary->wait_for_catchup($node_standby, 'replay', $start_lsn);
+$node_primary->wait_for_catchup($node_standby);
 $node_standby->stop;

 # wal_keep_size overrides max_slot_wal_keep_size
@@ -135,8 +132,7 @@ $result = $node_primary->safe_psql('postgres',

 # The standby can reconnect to primary
 $node_standby->start;
-$start_lsn = $node_primary->lsn('write');
-$node_primary->wait_for_catchup($node_standby, 'replay', $start_lsn);
+$node_primary->wait_for_catchup($node_standby);
 $node_standby->stop;

 # Advance WAL again without checkpoint, reducing remain by 6 MB.
@@ -163,8 +159,7 @@ is($result, "unreserved|t",
 # The standby still can connect to primary before a checkpoint
 $node_standby->start;

-$start_lsn = $node_primary->lsn('write');
-$node_primary->wait_for_catchup($node_standby, 'replay', $start_lsn);
+$node_primary->wait_for_catchup($node_standby);

 $node_standby->stop;

@@ -334,7 +329,7 @@ $node_standby3->init_from_backup($node_primary3, $backup_name,
     has_streaming => 1);
 $node_standby3->append_conf('postgresql.conf', "primary_slot_name = 'rep3'");
 $node_standby3->start;
-$node_primary3->wait_for_catchup($node_standby3->name, 'replay');
+$node_primary3->wait_for_catchup($node_standby3->name);
 my $senderpid = $node_primary3->safe_psql('postgres',
     "SELECT pid FROM pg_stat_activity WHERE backend_type = 'walsender'");
 like($senderpid, qr/^[0-9]+$/, "have walsender pid $senderpid");
diff --git a/src/test/recovery/t/021_row_visibility.pl b/src/test/recovery/t/021_row_visibility.pl
index 4a62e47722..1ceb032750 100644
--- a/src/test/recovery/t/021_row_visibility.pl
+++ b/src/test/recovery/t/021_row_visibility.pl
@@ -76,8 +76,7 @@ ok( send_query_and_wait(
 #
 $node_primary->psql('postgres',
     "INSERT INTO test_visibility VALUES ('first insert')");
-$node_primary->wait_for_catchup($node_standby, 'replay',
-    $node_primary->lsn('insert'));
+$node_primary->wait_for_catchup($node_standby);

 ok( send_query_and_wait(
         \%psql_standby,
@@ -98,8 +97,7 @@ UPDATE test_visibility SET data = 'first update' RETURNING data;
     'UPDATE');

 $node_primary->psql('postgres', "SELECT txid_current();");  # ensure WAL flush
-$node_primary->wait_for_catchup($node_standby, 'replay',
-    $node_primary->lsn('insert'));
+$node_primary->wait_for_catchup($node_standby);

 ok( send_query_and_wait(
         \%psql_standby,
@@ -112,8 +110,7 @@ ok( send_query_and_wait(
 #
 ok(send_query_and_wait(\%psql_primary, q[COMMIT;], qr/^COMMIT$/m), 'COMMIT');

-$node_primary->wait_for_catchup($node_standby, 'replay',
-    $node_primary->lsn('insert'));
+$node_primary->wait_for_catchup($node_standby);

 ok( send_query_and_wait(
         \%psql_standby,
@@ -142,8 +139,7 @@ PREPARE TRANSACTION 'will_abort';
         qr/^PREPARE TRANSACTION$/m),
     'prepared will_abort');

-$node_primary->wait_for_catchup($node_standby, 'replay',
-    $node_primary->lsn('insert'));
+$node_primary->wait_for_catchup($node_standby);

 ok( send_query_and_wait(
         \%psql_standby,
@@ -154,8 +150,7 @@ ok( send_query_and_wait(
 # For some variation, finish prepared xacts via separate connections
 $node_primary->safe_psql('postgres', "COMMIT PREPARED 'will_commit';");
 $node_primary->safe_psql('postgres', "ROLLBACK PREPARED 'will_abort';");
-$node_primary->wait_for_catchup($node_standby, 'replay',
-    $node_primary->lsn('insert'));
+$node_primary->wait_for_catchup($node_standby);

 ok( send_query_and_wait(
         \%psql_standby,
diff --git a/src/test/recovery/t/025_stuck_on_old_timeline.pl b/src/test/recovery/t/025_stuck_on_old_timeline.pl
index 7997eecdd3..dc48f909c4 100644
--- a/src/test/recovery/t/025_stuck_on_old_timeline.pl
+++ b/src/test/recovery/t/025_stuck_on_old_timeline.pl
@@ -101,8 +101,7 @@ $node_cascade->start;
 $node_standby->safe_psql('postgres', "CREATE TABLE tab_int AS SELECT 1 AS a");

 # Wait for the replication to catch up
-$node_standby->wait_for_catchup($node_cascade, 'replay',
-    $node_standby->lsn('insert'));
+$node_standby->wait_for_catchup($node_cascade);

 # Check that cascading standby has the new content
 my $result =

Hi,

On Sat, Jan 15, 2022 at 05:58:02PM -0500, Tom Lane wrote:
> 
> Here's a version that makes sure that callers specify a write position not
> an insert position.  I also simplified the callers wherever it turned
> out that they could just use the default parameters.

LGTM, and passes make check-world on my machine.

Julien Rouhaud <rjuju123@gmail.com> writes:
> On Sat, Jan 15, 2022 at 05:58:02PM -0500, Tom Lane wrote:
>> Here's a version that makes sure that callers specify a write position not
>> an insert position.  I also simplified the callers wherever it turned
>> out that they could just use the default parameters.

> LGTM, and passes make check-world on my machine.

Pushed, thanks for reviewing.

            regards, tom lane