In tests, await an LSN no later than the recovery target.

Otherwise, the test fails with "Timed out while waiting for standby to
catch up".  This happened rarely, perhaps only when autovacuum wrote WAL
between our choosing the recovery target and choosing the LSN to await.
Commit b26f7fa6ae2b4e5d64525b3d5bc66a0ddccd9e24 fixed one case of this.
Fix two more.  Back-patch to 9.6, which introduced the affected test.

Discussion: https://postgr.es/m/20180101055227.GA2952815@rfd.leadboat.com

diff --git a/src/test/recovery/t/003_recovery_targets.pl b/src/test/recovery/t/003_recovery_targets.pl
index cc7c04b6cb937633710b733a798916dd44ddec65..824fa4da529f5e71b1418d936c2eca3b8491b676 100644 (file)
--- a/src/test/recovery/t/003_recovery_targets.pl
+++ b/src/test/recovery/t/003_recovery_targets.pl
@@ -5,8 +5,9 @@ use PostgresNode;
 use TestLib;
 use Test::More tests => 9;
 
-# Create and test a standby from given backup, with a certain
-# recovery target.
+# Create and test a standby from given backup, with a certain recovery target.
+# Choose $until_lsn later than the transaction commit that causes the row
+# count to reach $num_rows, yet not later than the recovery target.
 sub test_recovery_standby
 {
        my $test_name       = shift;
@@ -70,9 +71,9 @@ my ($lsn2, $recovery_txid) = split /\|/, $ret;
 # More data, with recovery target timestamp
 $node_master->safe_psql('postgres',
        "INSERT INTO tab_int VALUES (generate_series(2001,3000))");
-$ret =
-  $node_master->safe_psql('postgres', "SELECT pg_current_wal_lsn(), now();");
-my ($lsn3, $recovery_time) = split /\|/, $ret;
+my $lsn3 =
+  $node_master->safe_psql('postgres', "SELECT pg_current_wal_lsn();");
+my $recovery_time = $node_master->safe_psql('postgres', "SELECT now()");
 
 # Even more data, this time with a recovery target name
 $node_master->safe_psql('postgres',
@@ -86,10 +87,8 @@ $node_master->safe_psql('postgres',
 # And now for a recovery target LSN
 $node_master->safe_psql('postgres',
        "INSERT INTO tab_int VALUES (generate_series(4001,5000))");
-my $recovery_lsn =
+my $lsn5 = my $recovery_lsn =
   $node_master->safe_psql('postgres', "SELECT pg_current_wal_lsn()");
-my $lsn5 =
-  $node_master->safe_psql('postgres', "SELECT pg_current_wal_lsn();");
 
 $node_master->safe_psql('postgres',
        "INSERT INTO tab_int VALUES (generate_series(5001,6000))");