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pg_createsubscriber: Remove failover replication slots on subscriber

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After running pg_createsubscriber, these replication slots have no use
on subscriber, so drop them.

Author: Euler Taveira <euler.taveira@enterprisedb.com>
Reviewed-by: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Discussion: https://www.postgresql.org/message-id/776c5cac-5ef5-4001-b1bc-5b698bc0c62a%40app.fastmail.com
This commit is contained in:
Peter Eisentraut 2024-06-17 12:12:49 +02:00
parent b963913826
commit 81d20fbf7a
3 changed files with 76 additions and 2 deletions
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9
doc/src/sgml/ref/pg_createsubscriber.sgml
View file

@ -482,6 +482,15 @@ PostgreSQL documentation
</para>
</step>
<step>
<para>
If the standby server contains <link
linkend="logicaldecoding-replication-slots-synchronization">failover
replication slots</link>, they cannot be synchronized anymore, so drop
them.
</para>
</step>
<step>
<para>
Update the system identifier on the target server. The

49
src/bin/pg_basebackup/pg_createsubscriber.c
View file

@ -85,6 +85,7 @@ static void setup_recovery(const struct LogicalRepInfo *dbinfo, const char *data
const char *lsn);
static void drop_primary_replication_slot(struct LogicalRepInfo *dbinfo,
const char *slotname);
static void drop_failover_replication_slots(struct LogicalRepInfo *dbinfo);
static char *create_logical_replication_slot(PGconn *conn,
struct LogicalRepInfo *dbinfo);
static void drop_replication_slot(PGconn *conn, struct LogicalRepInfo *dbinfo,
@ -1137,6 +1138,49 @@ drop_primary_replication_slot(struct LogicalRepInfo *dbinfo, const char *slotnam
}
}
/*
* Drop failover replication slots on subscriber. After the transformation,
* they have no use.
*
* XXX We do not fail here. Instead, we provide a warning so the user can drop
* them later.
*/
static void
drop_failover_replication_slots(struct LogicalRepInfo *dbinfo)
{
PGconn *conn;
PGresult *res;
conn = connect_database(dbinfo[0].subconninfo, false);
if (conn != NULL)
{
/* Get failover replication slot names */
res = PQexec(conn,
"SELECT slot_name FROM pg_catalog.pg_replication_slots WHERE failover");
if (PQresultStatus(res) == PGRES_TUPLES_OK)
{
/* Remove failover replication slots from subscriber */
for (int i = 0; i < PQntuples(res); i++)
drop_replication_slot(conn, &dbinfo[0], PQgetvalue(res, i, 0));
}
else
{
pg_log_warning("could not obtain failover replication slot information: %s",
PQresultErrorMessage(res));
pg_log_warning_hint("Drop the failover replication slots on subscriber soon to avoid retention of WAL files.");
}
PQclear(res);
disconnect_database(conn, false);
}
else
{
pg_log_warning("could not drop failover replication slot");
pg_log_warning_hint("Drop the failover replication slots on subscriber soon to avoid retention of WAL files.");
}
}
/*
* Create a logical replication slot and returns a LSN.
*
@ -1268,7 +1312,7 @@ start_standby_server(const struct CreateSubscriberOptions *opt, bool restricted_
PQExpBuffer pg_ctl_cmd = createPQExpBuffer();
int rc;
appendPQExpBuffer(pg_ctl_cmd, "\"%s\" start -D \"%s\" -s",
appendPQExpBuffer(pg_ctl_cmd, "\"%s\" start -D \"%s\" -s -o \"-c sync_replication_slots=off\"",
pg_ctl_path, subscriber_dir);
if (restricted_access)
{
@ -2065,6 +2109,9 @@ main(int argc, char **argv)
/* Remove primary_slot_name if it exists on primary */
drop_primary_replication_slot(dbinfo, primary_slot_name);
/* Remove failover replication slots if they exist on subscriber */
drop_failover_replication_slots(dbinfo);
/* Stop the subscriber */
pg_log_info("stopping the subscriber");
stop_standby_server(subscriber_dir);

20
src/bin/pg_basebackup/t/040_pg_createsubscriber.pl
View file

@ -88,6 +88,7 @@ command_fails(
# Set up node P as primary
my $node_p = PostgreSQL::Test::Cluster->new('node_p');
my $pconnstr = $node_p->connstr;
$node_p->init(allows_streaming => 'logical');
$node_p->start;
@ -122,6 +123,8 @@ $node_s->init_from_backup($node_p, 'backup_1', has_streaming => 1);
$node_s->append_conf(
'postgresql.conf', qq[
primary_slot_name = '$slotname'
primary_conninfo = '$pconnstr dbname=postgres'
hot_standby_feedback = on
]);
$node_s->set_standby_mode();
$node_s->start;
@ -260,6 +263,16 @@ max_worker_processes = 8
# Restore default settings on both servers
$node_p->restart;
# Create failover slot to test its removal
my $fslotname = 'failover_slot';
$node_p->safe_psql('pg1',
"SELECT pg_create_logical_replication_slot('$fslotname', 'pgoutput', false, false, true)");
$node_s->start;
$node_s->safe_psql('postgres', "SELECT pg_sync_replication_slots()");
my $result = $node_s->safe_psql('postgres', "SELECT slot_name FROM pg_replication_slots WHERE slot_name = '$fslotname' AND synced AND NOT temporary");
is($result, 'failover_slot', 'failover slot is synced');
$node_s->stop;
# dry run mode on node S
command_ok(
[
@ -318,7 +331,7 @@ command_ok(
'run pg_createsubscriber on node S');
# Confirm the physical replication slot has been removed
my $result = $node_p->safe_psql('pg1',
$result = $node_p->safe_psql('pg1',
"SELECT count(*) FROM pg_replication_slots WHERE slot_name = '$slotname'"
);
is($result, qq(0),
@ -343,6 +356,11 @@ my @subnames = split("\n", $result);
$node_s->wait_for_subscription_sync($node_p, $subnames[0]);
$node_s->wait_for_subscription_sync($node_p, $subnames[1]);
# Confirm the failover slot has been removed
$result = $node_s->safe_psql('pg1',
"SELECT count(*) FROM pg_replication_slots WHERE slot_name = '$fslotname'");
is($result, qq(0), 'failover slot was removed');
# Check result on database pg1
$result = $node_s->safe_psql('pg1', 'SELECT * FROM tbl1');
is( $result, qq(first row