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MXS-2036 Redirect slaves with stopped SQL threads

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This is somewhat questionable, as the slaves won't be able to really
replicate from the new master. However, not doing this causes the wrong
master to be selected after failover unless the new master has a majority
of slaves under it.
This commit is contained in:
Esa Korhonen 2018-09-04 16:48:49 +03:00
parent 087272c3e4
commit ad71655a36
1 changed files with 72 additions and 51 deletions
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123
server/modules/monitor/mariadbmon/mariadbmon.cc
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@ -80,12 +80,6 @@ enum mysql_server_version
MYSQL_SERVER_VERSION_51
};
enum print_repl_warnings_t
{
WARNINGS_ON,
WARNINGS_OFF
};
static void monitorMain(void *);
static void *startMonitor(MXS_MONITOR *, const MXS_CONFIG_PARAMETER*);
static void stopMonitor(MXS_MONITOR *);
@ -152,6 +146,10 @@ static const char CN_MASTER_FAILURE_TIMEOUT[] = "master_failure_timeout";
static const char CN_REPLICATION_USER[] = "replication_user";
static const char CN_REPLICATION_PASSWORD[] = "replication_password";
static const char NOT_A_SLAVE[] = "it is not a slave or a query failed.";
static const char NO_BINLOG[] = "its binary log is disabled.";
static const char NO_SLAVE_SQL[] = "its slave SQL thread is not running.";
/** Default failover timeout */
#define DEFAULT_FAILOVER_TIMEOUT "90"
@ -3477,10 +3475,10 @@ bool mon_process_failover(MYSQL_MONITOR* monitor, uint32_t failover_timeout, boo
static MySqlServerInfo* update_slave_info(MYSQL_MONITOR* mon, MXS_MONITORED_SERVER* server)
{
MySqlServerInfo* info = get_server_info(mon, server);
if (info->slave_status.slave_sql_running &&
update_replication_settings(server, info) &&
if (update_replication_settings(server, info) &&
update_gtids(mon, server, info) &&
do_show_slave_status(mon, info, server))
do_show_slave_status(mon, info, server) &&
info->slave_status.master_server_id >= 0)
{
return info;
}
@ -3492,40 +3490,30 @@ static MySqlServerInfo* update_slave_info(MYSQL_MONITOR* mon, MXS_MONITORED_SERV
*
* @param server Server to check
* @param server_info Server info
* @param print_on Print warnings or not
* @return True if log_bin is on
*/
static bool check_replication_settings(const MXS_MONITORED_SERVER* server, MySqlServerInfo* server_info,
print_repl_warnings_t print_warnings = WARNINGS_ON)
static bool check_replication_settings(const MXS_MONITORED_SERVER* server, MySqlServerInfo* server_info)
{
bool rval = true;
const char* servername = server->server->unique_name;
if (server_info->rpl_settings.log_bin == false)
{
if (print_warnings == WARNINGS_ON)
{
const char NO_BINLOG[] =
"Slave '%s' has binary log disabled and is not a valid promotion candidate.";
MXS_WARNING(NO_BINLOG, servername);
}
rval = false;
}
else if (print_warnings == WARNINGS_ON)
if (server_info->rpl_settings.gtid_strict_mode == false)
{
if (server_info->rpl_settings.gtid_strict_mode == false)
{
const char NO_STRICT[] =
"Slave '%s' has gtid_strict_mode disabled. Enabling this setting is recommended. "
"For more information, see https://mariadb.com/kb/en/library/gtid/#gtid_strict_mode";
MXS_WARNING(NO_STRICT, servername);
}
if (server_info->rpl_settings.log_slave_updates == false)
{
const char NO_SLAVE_UPDATES[] =
"Slave '%s' has log_slave_updates disabled. It is a valid candidate but replication "
"will break for lagging slaves if '%s' is promoted.";
MXS_WARNING(NO_SLAVE_UPDATES, servername, servername);
}
const char NO_STRICT[] =
"Slave '%s' has gtid_strict_mode disabled. Enabling this setting is recommended. "
"For more information, see https://mariadb.com/kb/en/library/gtid/#gtid_strict_mode";
MXS_WARNING(NO_STRICT, servername);
}
if (server_info->rpl_settings.log_slave_updates == false)
{
const char NO_SLAVE_UPDATES[] =
"Slave '%s' has log_slave_updates disabled. It is a valid candidate but replication "
"will break for lagging slaves if '%s' is promoted.";
MXS_WARNING(NO_SLAVE_UPDATES, servername, servername);
}
return rval;
}
@ -3541,13 +3529,26 @@ static bool check_replication_settings(const MXS_MONITORED_SERVER* server, MySql
bool switchover_check_preferred_master(MYSQL_MONITOR* mon, MXS_MONITORED_SERVER* preferred, json_t** err_out)
{
ss_dassert(preferred);
bool rval = true;
bool rval = false;
const char NOT_VALID[] = "The requested server '%s' is not a valid promotion candidate because %s";
const char* name = preferred->server->unique_name;
MySqlServerInfo* preferred_info = update_slave_info(mon, preferred);
if (preferred_info == NULL || !check_replication_settings(preferred, preferred_info))
if (preferred_info == NULL)
{
PRINT_MXS_JSON_ERROR(err_out, "The requested server '%s' is not a valid promotion candidate.",
preferred->server->unique_name);
rval = false;
PRINT_MXS_JSON_ERROR(err_out, NOT_VALID, name, NOT_A_SLAVE);
}
else if (!check_replication_settings(preferred, preferred_info))
{
PRINT_MXS_JSON_ERROR(err_out, NOT_VALID, name, NO_BINLOG);
}
else if (!preferred_info->slave_status.slave_sql_running)
{
PRINT_MXS_JSON_ERROR(err_out, NOT_VALID, name, NO_SLAVE_SQL);
}
else
{
rval = true;
}
return rval;
}
@ -3612,22 +3613,42 @@ MXS_MONITORED_SERVER* select_new_master(MYSQL_MONITOR* mon, ServerVector* slaves
for (MXS_MONITORED_SERVER *cand = mon->monitor->monitored_servers; cand; cand = cand->next)
{
// If a server cannot be connected to, it won't be considered for promotion or redirected.
// Do not worry about the exclusion list yet, querying the excluded servers is ok.
MySqlServerInfo* cand_info = update_slave_info(mon, cand);
// If master is replicating from external master, it is updated but not added to array.
if (cand_info && cand != mon->master)
if (SERVER_IS_DOWN(cand->server))
{
slaves_out->push_back(cand);
// Check that server is not in the exclusion list while still being a valid choice.
if (server_is_excluded(mon, cand) && check_replication_settings(cand, cand_info, WARNINGS_OFF))
continue;
}
const char* name = cand->server->unique_name;
// Do not worry about the exclusion list yet, querying the excluded servers is ok.
// If master is replicating from external master, it is updated but not added to array.
const char WONT_PROMOTE[] = "'%s' cannot be promoted because %s";
MySqlServerInfo* cand_info = update_slave_info(mon, cand);
if (cand_info == NULL)
{
if (cand != mon->master)
{
valid_but_excluded.push_back(cand);
const char CANNOT_SELECT[] = "Promotion candidate '%s' is excluded from new "
"master selection.";
MXS_INFO(CANNOT_SELECT, cand->server->unique_name);
MXS_WARNING(WONT_PROMOTE, name, NOT_A_SLAVE);
}
else if (check_replication_settings(cand, cand_info))
}
else
{
slaves_out->push_back(cand); // Will be redirected.
if (!check_replication_settings(cand, cand_info))
{
MXS_WARNING(WONT_PROMOTE, name, NO_BINLOG);
}
else if (!cand_info->slave_status.slave_sql_running)
{
MXS_WARNING(WONT_PROMOTE, name, NO_SLAVE_SQL);
}
else if (server_is_excluded(mon, cand))
{
// Server is in the exclusion list but is otherwise a valid choice.
valid_but_excluded.push_back(cand);
MXS_WARNING(WONT_PROMOTE, name, "it is excluded.");
}
else
{
// Server is ok for new master.
// If no new master yet, accept any valid candidate. Otherwise check.
if (current_best == NULL || is_candidate_better(current_best_info, cand_info))
{
@ -3658,7 +3679,7 @@ MXS_MONITORED_SERVER* select_new_master(MYSQL_MONITOR* mon, ServerVector* slaves
if (current_best == NULL)
{
const char EXCLUDED_ONLY_CAND[] = "Server '%s' is a viable choice for new master, "
"but cannot be selected as it's excluded.";
"but cannot be selected as it's excluded.";
MXS_WARNING(EXCLUDED_ONLY_CAND, excluded_name);
break;
}