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repmgrd: optionally disconnect WAL receivers during failover

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This is intended to ensure that all nodes have a constant LSN while
making the failover decision.

This feature is experimental and needs to be explicitly enabled with the
configuration file option "standby_disconnect_on_failover".

Note enabling this option will result in a delay in the failover decision
until the WAL receiver is disconnected on all nodes.
This commit is contained in:
Ian Barwick
2019-03-01 18:20:44 +09:00
committed by Ian Barwick
parent dd04ebb809
commit 1615353f48
16 changed files with 404 additions and 17 deletions
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121
sysutils.c
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@@ -17,6 +17,8 @@
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <signal.h>
#include "repmgr.h"
static bool _local_command(const char *command, PQExpBufferData *outputbuf, bool simple, int *return_value);
@@ -176,3 +178,122 @@ remote_command(const char *host, const char *user, const char *command, const ch
return true;
}
pid_t
disable_wal_receiver(PGconn *conn)
{
char buf[MAXLEN];
int wal_retrieve_retry_interval;
pid_t wal_receiver_pid = UNKNOWN_PID;
if (is_superuser_connection(conn, NULL) == false)
{
log_error(_("superuser connection required"));
return UNKNOWN_PID;
}
get_pg_setting(conn, "wal_retrieve_retry_interval", buf);
// XXX handle error
wal_retrieve_retry_interval = atoi(buf);
if (wal_retrieve_retry_interval < WALRECEIVER_DISABLE_TIMEOUT_VALUE)
{
alter_system_int(conn, "wal_retrieve_retry_interval", wal_retrieve_retry_interval + WALRECEIVER_DISABLE_TIMEOUT_VALUE);
pg_reload_conf(conn);
}
wal_receiver_pid = (pid_t)get_wal_receiver_pid(conn);
if (wal_receiver_pid == UNKNOWN_PID)
{
log_warning(_("unable to retrieve walreceiver PID"));
return UNKNOWN_PID;
}
if (wal_receiver_pid == 0)
{
log_warning(_("walreceiver not running"));
}
else
{
int kill_ret;
int i, j;
int max_retries = 2;
for (i = 0; i < max_retries; i++)
{
/* why 5? */
sleep(5);
log_notice(_("killing walreceiver with PID %i"), (int)wal_receiver_pid);
kill((int)wal_receiver_pid, SIGTERM);
for (j = 0; j < 30; j++)
{
kill_ret = kill(wal_receiver_pid, 0);
if (kill_ret != 0)
{
log_info("killed");
break;
}
sleep(1);
}
/* */
sleep(1);
wal_receiver_pid = (pid_t)get_wal_receiver_pid(conn);
if (wal_receiver_pid == UNKNOWN_PID || wal_receiver_pid == 0)
break;
}
}
return wal_receiver_pid;
}
pid_t
enable_wal_receiver(PGconn *conn)
{
char buf[MAXLEN];
int wal_retrieve_retry_interval;
pid_t wal_receiver_pid = UNKNOWN_PID;
if (is_superuser_connection(conn, NULL) == false)
{
log_error(_("superuser connection required"));
return UNKNOWN_PID;
}
get_pg_setting(conn, "wal_retrieve_retry_interval", buf);
// XXX handle error
wal_retrieve_retry_interval = atoi(buf);
if (wal_retrieve_retry_interval > WALRECEIVER_DISABLE_TIMEOUT_VALUE)
{
int new_wal_retrieve_retry_interval = wal_retrieve_retry_interval - WALRECEIVER_DISABLE_TIMEOUT_VALUE;
log_notice(_("setting \"wal_retrieve_retry_interval\" to %i ms"),
new_wal_retrieve_retry_interval);
// XXX handle error
alter_system_int(conn,
"wal_retrieve_retry_interval",
new_wal_retrieve_retry_interval);
pg_reload_conf(conn);
}
else
{
// XXX add threshold sanity check
log_info(_("\"wal_retrieve_retry_interval\" is %i, not changing"),
wal_retrieve_retry_interval);
}
// XXX get wal receiver PID
return wal_receiver_pid;
}