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node rejoin: handle unclean shutdown in Pg13

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From PostgreSQL 13, pg_rewind will automatically handle an unclean
shutdown itself, so as long as --force-rewind was provided, so there
is no need to fail with an error.

Note that pg_rewind handles the unclean shutdown by starting PostgreSQL
in single user mode, which it does before performing any checks as
to whether a rewind is actually necessary.

However pg_rewind doesn't take into account the possible presence
of a standby.signal file, so we remove that and recreate it after
pg_rewind was executed.
This commit is contained in:
Ian Barwick
2020-10-13 10:18:29 +09:00
parent d62743ddf4
commit 5f986bc981
7 changed files with 163 additions and 58 deletions
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83
repmgr-action-node.c
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@@ -2494,6 +2494,8 @@ do_node_rejoin(void)
DBState db_state;
PGPing status;
bool is_shutdown = true;
int server_version_num = UNKNOWN_SERVER_VERSION_NUM;
bool hide_standby_signal = true;
PQExpBufferData command;
PQExpBufferData command_output;
@@ -2538,6 +2540,21 @@ do_node_rejoin(void)
exit(ERR_REJOIN_FAIL);
}
/*
* Server version number required to determine whether pg_rewind will run
* crash recovery (Pg 13 and later).
*/
server_version_num = get_pg_version(config_file_options.data_directory, NULL);
if (server_version_num == UNKNOWN_SERVER_VERSION_NUM)
{
/* This is very unlikely to happen */
log_error(_("unable to determine database version"));
exit(ERR_BAD_CONFIG);
}
log_verbose(LOG_DEBUG, "server version number is: %i", server_version_num);
/* check if cleanly shut down */
if (db_state != DB_SHUTDOWNED && db_state != DB_SHUTDOWNED_IN_RECOVERY)
{
@@ -2545,15 +2562,41 @@ do_node_rejoin(void)
{
log_error(_("database is still shutting down"));
}
else if (server_version_num >= 130000 && runtime_options.force_rewind_used == true)
{
log_warning(_("database is not shut down cleanly"));
log_detail(_("--force-rewind provided, pg_rewind will automatically perform recovery"));
/*
* If pg_rewind is executed, the first change it will make
* is to start the server in single user mode, which will fail
* in the presence of "standby.signal", so we'll "hide" it
* (actually delete and recreate).
*/
hide_standby_signal = true;
}
else
{
/*
* If the database was not shut down cleanly, it *might* rejoin correctly
* after starting up and recovering, but better to ensure the database
* can recover before trying anything else.
*/
log_error(_("database is not shut down cleanly"));
if (runtime_options.force_rewind_used == true)
if (server_version_num >= 130000)
{
log_detail(_("pg_rewind will not be able to run"));
log_hint(_("provide --force-rewind to run recovery"));
}
log_hint(_("database should be restarted then shut down cleanly after crash recovery completes"));
else
{
if (runtime_options.force_rewind_used == true)
{
log_detail(_("pg_rewind will not be able to run"));
}
log_hint(_("database should be restarted then shut down cleanly after crash recovery completes"));
}
exit(ERR_REJOIN_FAIL);
}
}
@@ -2757,6 +2800,30 @@ do_node_rejoin(void)
log_detail(_("pg_rewind command is \"%s\""),
command.data);
/*
* In Pg13 and later, pg_rewind will attempt to start up a server which
* was not cleanly shut down in single user mode. This will fail if
* "standby.signal" is present. We'll remove it and restore it after
* pg_rewind runs.
*/
if (hide_standby_signal == true)
{
char standby_signal_file_path[MAXPGPATH] = "";
log_notice(_("temporarily removing \"standby.signal\""));
log_detail(_("this is required so pg_rewind can fix the unclean shutdown"));
make_standby_signal_path(standby_signal_file_path);
if (unlink(standby_signal_file_path) < 0 && errno != ENOENT)
{
log_error(_("unable to remove \"standby.signal\" file in data directory \"%s\""),
standby_signal_file_path);
log_detail("%s", strerror(errno));
exit(ERR_REJOIN_FAIL);
}
}
initPQExpBuffer(&command_output);
ret = local_command(command.data,
@@ -2764,6 +2831,16 @@ do_node_rejoin(void)
termPQExpBuffer(&command);
if (hide_standby_signal == true)
{
/*
* Restore standby.signal if we previously removed it, regardless
* of whether the pg_rewind operation failed.
*/
log_notice(_("recreating \"standby.signal\""));
write_standby_signal();
}
if (ret == false)
{
log_error(_("unable to execute pg_rewind"));