44a57dbefd
This is possible if read_only is turned ON on the master and there is no alternative master to swap to.
1745 lines
66 KiB
C++
1745 lines
66 KiB
C++
/*
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* Copyright (c) 2018 MariaDB Corporation Ab
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*
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* Use of this software is governed by the Business Source License included
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* in the LICENSE.TXT file and at www.mariadb.com/bsl11.
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*
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* Change Date: 2022-01-01
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*
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* On the date above, in accordance with the Business Source License, use
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* of this software will be governed by version 2 or later of the General
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* Public License.
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*/
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#include "mariadbmon.hh"
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#include <inttypes.h>
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#include <sstream>
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#include <maxscale/clock.h>
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#include <maxscale/mysql_utils.h>
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#include <maxscale/utils.hh>
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using std::string;
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using maxscale::string_printf;
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static const char RE_ENABLE_FMT[] = "To re-enable automatic %s, manually set '%s' to 'true' "
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"for monitor '%s' via MaxAdmin or the REST API, or restart MaxScale.";
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static void print_redirect_errors(MariaDBServer* first_server, const ServerArray& servers,
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json_t** err_out);
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/**
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* Run a manual switchover, promoting a new master server and demoting the existing master.
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*
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* @param promotion_server The server which should be promoted. If null, monitor will autoselect.
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* @param demotion_server The server which should be demoted. Can be null for autoselect, in which case
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* monitor will select the cluster master server. Otherwise must be a valid master server or a relay.
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* @param error_out Error output
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* @return True, if switchover was performed successfully
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*/
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bool MariaDBMonitor::manual_switchover(SERVER* promotion_server, SERVER* demotion_server, json_t** error_out)
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{
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/* The server parameters may be null, in which case the monitor will autoselect.
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*
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* Manual commands (as well as automatic ones) are ran at the end of a normal monitor loop,
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* so server states can be assumed to be up-to-date.
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*/
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bool switchover_done = false;
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MariaDBServer* promotion_target = NULL;
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MariaDBServer* demotion_target = NULL;
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auto ok_to_switch = switchover_prepare(promotion_server, demotion_server, Log::ON,
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&promotion_target, &demotion_target,
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error_out);
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if (ok_to_switch)
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{
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switchover_done = do_switchover(demotion_target, promotion_target, error_out);
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if (switchover_done)
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{
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MXS_NOTICE("Switchover '%s' -> '%s' performed.",
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demotion_target->name(), promotion_target->name());
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}
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else
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{
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string msg = string_printf("Switchover %s -> %s failed",
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demotion_target->name(), promotion_target->name());
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bool failover_setting = config_get_bool(m_monitor->parameters, CN_AUTO_FAILOVER);
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if (failover_setting)
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{
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disable_setting(CN_AUTO_FAILOVER);
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msg += ", automatic failover has been disabled";
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}
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msg += ".";
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PRINT_MXS_JSON_ERROR(error_out, "%s", msg.c_str());
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}
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}
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else
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{
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PRINT_MXS_JSON_ERROR(error_out, "Switchover cancelled.");
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}
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return switchover_done;
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}
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bool MariaDBMonitor::manual_failover(json_t** output)
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{
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bool failover_done = false;
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MariaDBServer* promotion_target = NULL;
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MariaDBServer* demotion_target = NULL;
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bool ok_to_failover = failover_prepare(Log::ON, &promotion_target, &demotion_target, output);
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if (ok_to_failover)
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{
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failover_done = do_failover(promotion_target, demotion_target, output);
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if (failover_done)
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{
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MXS_NOTICE("Failover '%s' -> '%s' performed.",
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demotion_target->name(), promotion_target->name());
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}
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else
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{
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PRINT_MXS_JSON_ERROR(output, "Failover '%s' -> '%s' failed.",
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demotion_target->name(), promotion_target->name());
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}
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}
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else
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{
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PRINT_MXS_JSON_ERROR(output, "Failover cancelled.");
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}
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return failover_done;
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}
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bool MariaDBMonitor::manual_rejoin(SERVER* rejoin_server, json_t** output)
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{
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bool rval = false;
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if (cluster_can_be_joined())
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{
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const char* rejoin_serv_name = rejoin_server->name;
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MXS_MONITORED_SERVER* mon_slave_cand = mon_get_monitored_server(m_monitor, rejoin_server);
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if (mon_slave_cand)
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{
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MariaDBServer* slave_cand = get_server_info(mon_slave_cand);
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if (server_is_rejoin_suspect(slave_cand, output))
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{
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if (m_master->update_gtids())
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{
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string no_rejoin_reason;
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if (slave_cand->can_replicate_from(m_master, &no_rejoin_reason))
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{
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ServerArray joinable_server;
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joinable_server.push_back(slave_cand);
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if (do_rejoin(joinable_server, output) == 1)
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{
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rval = true;
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MXS_NOTICE("Rejoin performed.");
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}
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else
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{
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PRINT_MXS_JSON_ERROR(output, "Rejoin attempted but failed.");
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}
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}
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else
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{
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PRINT_MXS_JSON_ERROR(output, "Server '%s' cannot replicate from cluster master '%s': "
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"%s.", rejoin_serv_name, m_master->name(),
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no_rejoin_reason.c_str());
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}
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}
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else
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{
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PRINT_MXS_JSON_ERROR(output, "Cluster master '%s' gtid info could not be updated.",
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m_master->name());
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}
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} // server_is_rejoin_suspect has added any error messages to the output, no need to print here
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}
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else
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{
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PRINT_MXS_JSON_ERROR(output, "The given server '%s' is not monitored by this monitor.",
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rejoin_serv_name);
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}
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}
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else
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{
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const char BAD_CLUSTER[] = "The server cluster of monitor '%s' is not in a state valid for joining. "
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"Either it has no master or its gtid domain is unknown.";
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PRINT_MXS_JSON_ERROR(output, BAD_CLUSTER, m_monitor->name);
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}
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return rval;
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}
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/**
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* Generate a CHANGE MASTER TO-query.
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*
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* @param master_host Master hostname/address
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* @param master_port Master port
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* @return Generated query
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*/
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string MariaDBMonitor::generate_change_master_cmd(const string& master_host, int master_port)
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{
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std::stringstream change_cmd;
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change_cmd << "CHANGE MASTER TO MASTER_HOST = '" << master_host << "', ";
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change_cmd << "MASTER_PORT = " << master_port << ", ";
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change_cmd << "MASTER_USE_GTID = current_pos, ";
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change_cmd << "MASTER_USER = '" << m_replication_user << "', ";
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const char MASTER_PW[] = "MASTER_PASSWORD = '";
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const char END[] = "';";
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#if defined(SS_DEBUG)
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std::stringstream change_cmd_nopw;
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change_cmd_nopw << change_cmd.str();
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change_cmd_nopw << MASTER_PW << "******" << END;;
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MXS_DEBUG("Change master command is '%s'.", change_cmd_nopw.str().c_str());
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#endif
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change_cmd << MASTER_PW << m_replication_password << END;
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return change_cmd.str();
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}
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/**
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* Redirects slaves to replicate from another master server.
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*
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* @param new_master The replication master
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* @param slaves An array of slaves
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* @param redirected_slaves A vector where to insert successfully redirected slaves.
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* @return The number of slaves successfully redirected.
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*/
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int MariaDBMonitor::redirect_slaves(MariaDBServer* new_master, const ServerArray& slaves,
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ServerArray* redirected_slaves)
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{
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ss_dassert(redirected_slaves != NULL);
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MXS_NOTICE("Redirecting slaves to new master.");
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string change_cmd = generate_change_master_cmd(new_master->m_server_base->server->address,
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new_master->m_server_base->server->port);
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int successes = 0;
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for (auto iter = slaves.begin(); iter != slaves.end(); iter++)
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{
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if ((*iter)->redirect_one_slave(change_cmd))
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{
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successes++;
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redirected_slaves->push_back(*iter);
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}
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}
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return successes;
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}
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/**
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* Set the new master to replicate from the cluster external master.
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*
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* @param new_master The server being promoted
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* @param err_out Error output
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* @return True if new master accepted commands
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*/
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bool MariaDBMonitor::start_external_replication(MariaDBServer* new_master, json_t** err_out)
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{
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bool rval = false;
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MYSQL* new_master_conn = new_master->m_server_base->con;
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string change_cmd = generate_change_master_cmd(m_external_master_host, m_external_master_port);
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if (mxs_mysql_query(new_master_conn, change_cmd.c_str()) == 0 &&
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mxs_mysql_query(new_master_conn, "START SLAVE;") == 0)
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{
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MXS_NOTICE("New master starting replication from external master %s:%d.",
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m_external_master_host.c_str(), m_external_master_port);
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rval = true;
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}
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else
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{
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PRINT_MXS_JSON_ERROR(err_out, "Could not start replication from external master: '%s'.",
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mysql_error(new_master_conn));
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}
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return rval;
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}
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/**
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* Starts a new slave connection on a server. Should be used on a demoted master server.
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*
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* @param old_master The server which will start replication
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* @param new_master Replication target
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* @return True if commands were accepted. This does not guarantee that replication proceeds
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* successfully.
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*/
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bool MariaDBMonitor::switchover_start_slave(MariaDBServer* old_master, MariaDBServer* new_master)
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{
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bool rval = false;
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MYSQL* old_master_con = old_master->m_server_base->con;
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SERVER* new_master_server = new_master->m_server_base->server;
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string change_cmd = generate_change_master_cmd(new_master_server->address, new_master_server->port);
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if (mxs_mysql_query(old_master_con, change_cmd.c_str()) == 0 &&
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mxs_mysql_query(old_master_con, "START SLAVE;") == 0)
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{
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MXS_NOTICE("Old master '%s' starting replication from '%s'.",
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old_master->name(), new_master->name());
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rval = true;
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}
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else
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{
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MXS_ERROR("Old master '%s' could not start replication: '%s'.",
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old_master->name(), mysql_error(old_master_con));
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}
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return rval;
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}
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/**
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* (Re)join given servers to the cluster. The servers in the array are assumed to be joinable.
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* Usually the list is created by get_joinable_servers().
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*
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* @param joinable_servers Which servers to rejoin
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* @param output Error output. Can be null.
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* @return The number of servers successfully rejoined
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*/
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uint32_t MariaDBMonitor::do_rejoin(const ServerArray& joinable_servers, json_t** output)
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{
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SERVER* master_server = m_master->m_server_base->server;
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const char* master_name = master_server->name;
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uint32_t servers_joined = 0;
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if (!joinable_servers.empty())
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{
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string change_cmd = generate_change_master_cmd(master_server->address, master_server->port);
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for (auto iter = joinable_servers.begin(); iter != joinable_servers.end(); iter++)
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{
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MariaDBServer* joinable = *iter;
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const char* name = joinable->name();
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bool op_success = false;
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if (joinable->m_slave_status.empty())
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{
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if (!m_demote_sql_file.empty() && !joinable->run_sql_from_file(m_demote_sql_file, output))
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{
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PRINT_MXS_JSON_ERROR(output, "%s execution failed when attempting to rejoin server '%s'.",
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CN_DEMOTION_SQL_FILE, joinable->name());
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}
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else
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{
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MXS_NOTICE("Directing standalone server '%s' to replicate from '%s'.", name, master_name);
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op_success = joinable->join_cluster(change_cmd);
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}
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}
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else
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{
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MXS_NOTICE("Server '%s' is replicating from a server other than '%s', "
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"redirecting it to '%s'.", name, master_name, master_name);
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op_success = joinable->redirect_one_slave(change_cmd);
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}
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if (op_success)
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{
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servers_joined++;
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m_cluster_modified = true;
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}
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}
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}
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return servers_joined;
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}
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/**
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* Check if the cluster is a valid rejoin target.
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*
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* @return True if master and gtid domain are known
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*/
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bool MariaDBMonitor::cluster_can_be_joined()
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{
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return (m_master != NULL && m_master->is_master() && m_master_gtid_domain != GTID_DOMAIN_UNKNOWN);
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}
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/**
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* Scan the servers in the cluster and add (re)joinable servers to an array.
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*
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* @param mon Cluster monitor
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* @param output Array to save results to. Each element is a valid (re)joinable server according
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* to latest data.
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* @return False, if there were possible rejoinable servers but communications error to master server
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* prevented final checks.
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*/
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bool MariaDBMonitor::get_joinable_servers(ServerArray* output)
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{
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ss_dassert(output);
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// Whether a join operation should be attempted or not depends on several criteria. Start with the ones
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// easiest to test. Go though all slaves and construct a preliminary list.
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ServerArray suspects;
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for (auto iter = m_servers.begin(); iter != m_servers.end(); iter++)
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{
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if (server_is_rejoin_suspect(*iter, NULL))
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{
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suspects.push_back(*iter);
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}
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}
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// Update Gtid of master for better info.
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bool comm_ok = true;
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if (!suspects.empty())
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{
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if (m_master->update_gtids())
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{
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for (size_t i = 0; i < suspects.size(); i++)
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{
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string rejoin_err_msg;
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if (suspects[i]->can_replicate_from(m_master, &rejoin_err_msg))
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{
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output->push_back(suspects[i]);
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}
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else if (m_warn_cannot_rejoin)
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{
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// Print a message explaining why an auto-rejoin is not done. Suppress printing.
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MXS_WARNING("Automatic rejoin was not attempted on server '%s' even though it is a "
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"valid candidate. Will keep retrying with this message suppressed for all "
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"servers. Errors: \n%s",
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suspects[i]->name(), rejoin_err_msg.c_str());
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m_warn_cannot_rejoin = false;
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}
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}
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}
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else
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{
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comm_ok = false;
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}
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}
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else
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{
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m_warn_cannot_rejoin = true;
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}
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return comm_ok;
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}
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/**
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* Checks if a server is a possible rejoin candidate. A true result from this function is not yet sufficient
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* criteria and another call to can_replicate_from() should be made.
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*
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* @param rejoin_cand Server to check
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* @param output Error output. If NULL, no error is printed to log.
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* @return True, if server is a rejoin suspect.
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*/
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bool MariaDBMonitor::server_is_rejoin_suspect(MariaDBServer* rejoin_cand, json_t** output)
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{
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bool is_suspect = false;
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if (rejoin_cand->is_usable() && !rejoin_cand->is_master())
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{
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// Has no slave connection, yet is not a master.
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if (rejoin_cand->m_slave_status.empty())
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{
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is_suspect = true;
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}
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// Or has existing slave connection ...
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else if (rejoin_cand->m_slave_status.size() == 1)
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{
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SlaveStatus* slave_status = &rejoin_cand->m_slave_status[0];
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// which is connected to master but it's the wrong one
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if (slave_status->slave_io_running == SlaveStatus::SLAVE_IO_YES &&
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slave_status->master_server_id != m_master->m_server_id)
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{
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is_suspect = true;
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}
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// or is disconnected but master host or port is wrong.
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else if (slave_status->slave_io_running == SlaveStatus::SLAVE_IO_CONNECTING &&
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slave_status->slave_sql_running &&
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(slave_status->master_host != m_master->m_server_base->server->address ||
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slave_status->master_port != m_master->m_server_base->server->port))
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{
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is_suspect = true;
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}
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}
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if (output != NULL && !is_suspect)
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{
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/* User has requested a manual rejoin but with a server which has multiple slave connections or
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* is already connected or trying to connect to the correct master. TODO: Slave IO stopped is
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* not yet handled perfectly. */
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if (rejoin_cand->m_slave_status.size() > 1)
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{
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const char MULTI_SLAVE[] = "Server '%s' has multiple slave connections, cannot rejoin.";
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PRINT_MXS_JSON_ERROR(output, MULTI_SLAVE, rejoin_cand->name());
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}
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else
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{
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const char CONNECTED[] = "Server '%s' is already connected or trying to connect to the "
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"correct master server.";
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PRINT_MXS_JSON_ERROR(output, CONNECTED, rejoin_cand->name());
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}
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}
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}
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else if (output != NULL)
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{
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PRINT_MXS_JSON_ERROR(output, "Server '%s' is master or not running.", rejoin_cand->name());
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}
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return is_suspect;
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}
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/**
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* Performs switchover for a simple topology (1 master, N slaves, no intermediate masters). If an
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* intermediate step fails, the cluster may be left without a master and manual intervention is
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* required to fix things.
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*
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* @param demotion_target Server to demote
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* @param promotion_target Server to promote
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* @param err_out json object for error printing. Can be NULL.
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* @return True if successful. If false, replication may be broken.
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*/
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bool MariaDBMonitor::do_switchover(MariaDBServer* demotion_target, MariaDBServer* promotion_target,
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json_t** err_out)
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{
|
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ss_dassert(demotion_target && promotion_target);
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|
|
// Total time limit on how long this operation may take. Checked and modified after significant steps are
|
|
// completed.
|
|
int seconds_remaining = m_switchover_timeout;
|
|
time_t start_time = time(NULL);
|
|
|
|
// Step 1: Save all slaves except promotion target to an array.
|
|
// Try to redirect even disconnected slaves.
|
|
// TODO: 'switchover_wait_slaves_catchup' needs to be smarter and not bother with such slaves.
|
|
ServerArray redirectable_slaves = get_redirectables(promotion_target, demotion_target);
|
|
|
|
bool rval = false;
|
|
// Step 2: Set read-only to on, flush logs, update master gtid:s
|
|
if (switchover_demote_master(demotion_target, err_out))
|
|
{
|
|
m_cluster_modified = true;
|
|
bool catchup_and_promote_success = false;
|
|
time_t step2_time = time(NULL);
|
|
seconds_remaining -= difftime(step2_time, start_time);
|
|
|
|
// Step 3: Wait for the slaves (including promotion target) to catch up with master.
|
|
ServerArray catchup_slaves = redirectable_slaves;
|
|
catchup_slaves.push_back(promotion_target);
|
|
if (switchover_wait_slaves_catchup(catchup_slaves, demotion_target->m_gtid_binlog_pos,
|
|
seconds_remaining, err_out))
|
|
{
|
|
time_t step3_time = time(NULL);
|
|
int seconds_step3 = difftime(step3_time, step2_time);
|
|
MXS_DEBUG("Switchover: slave catchup took %d seconds.", seconds_step3);
|
|
seconds_remaining -= seconds_step3;
|
|
|
|
// Step 4: On new master STOP and RESET SLAVE, set read-only to off.
|
|
if (promote_new_master(promotion_target, err_out))
|
|
{
|
|
catchup_and_promote_success = true;
|
|
m_next_master = promotion_target;
|
|
|
|
// Step 5: Redirect slaves and start replication on old master.
|
|
ServerArray redirected_slaves;
|
|
bool start_ok = switchover_start_slave(demotion_target, promotion_target);
|
|
if (start_ok)
|
|
{
|
|
redirected_slaves.push_back(demotion_target);
|
|
}
|
|
int redirects = redirect_slaves(promotion_target, redirectable_slaves, &redirected_slaves);
|
|
|
|
bool success = redirectable_slaves.empty() ? start_ok : start_ok || redirects > 0;
|
|
if (success)
|
|
{
|
|
time_t step5_time = time(NULL);
|
|
seconds_remaining -= difftime(step5_time, step3_time);
|
|
|
|
// Step 6: Finally, add an event to the new master to advance gtid and wait for the slaves
|
|
// to receive it. If using external replication, skip this step. Come up with an
|
|
// alternative later.
|
|
if (m_external_master_port != PORT_UNKNOWN)
|
|
{
|
|
MXS_WARNING("Replicating from external master, skipping final check.");
|
|
rval = true;
|
|
}
|
|
else if (wait_cluster_stabilization(promotion_target, redirected_slaves,
|
|
seconds_remaining))
|
|
{
|
|
rval = true;
|
|
time_t step6_time = time(NULL);
|
|
int seconds_step6 = difftime(step6_time, step5_time);
|
|
seconds_remaining -= seconds_step6;
|
|
MXS_DEBUG("Switchover: slave replication confirmation took %d seconds with "
|
|
"%d seconds to spare.", seconds_step6, seconds_remaining);
|
|
}
|
|
}
|
|
else
|
|
{
|
|
print_redirect_errors(demotion_target, redirectable_slaves, err_out);
|
|
}
|
|
}
|
|
}
|
|
|
|
if (!catchup_and_promote_success)
|
|
{
|
|
// Step 3 or 4 failed, try to undo step 2.
|
|
const char QUERY_UNDO[] = "SET GLOBAL read_only=0;";
|
|
if (mxs_mysql_query(demotion_target->m_server_base->con, QUERY_UNDO) == 0)
|
|
{
|
|
PRINT_MXS_JSON_ERROR(err_out, "read_only disabled on server %s.", demotion_target->name());
|
|
}
|
|
else
|
|
{
|
|
PRINT_MXS_JSON_ERROR(err_out, "Could not disable read_only on server %s: '%s'.",
|
|
demotion_target->name(),
|
|
mysql_error(demotion_target->m_server_base->con));
|
|
}
|
|
|
|
// Try to reactivate external replication if any.
|
|
if (m_external_master_port != PORT_UNKNOWN)
|
|
{
|
|
start_external_replication(promotion_target, err_out);
|
|
}
|
|
}
|
|
}
|
|
return rval;
|
|
}
|
|
|
|
/**
|
|
* Performs failover for a simple topology (1 master, N slaves, no intermediate masters).
|
|
*
|
|
* @param demotion_target Server to demote
|
|
* @param promotion_target Server to promote
|
|
* @param err_out Error output
|
|
* @return True if successful
|
|
*/
|
|
bool MariaDBMonitor::do_failover(MariaDBServer* promotion_target, MariaDBServer* demotion_target,
|
|
json_t** error_out)
|
|
{
|
|
// Total time limit on how long this operation may take. Checked and modified after significant steps are
|
|
// completed.
|
|
int seconds_remaining = m_failover_timeout;
|
|
time_t start_time = time(NULL);
|
|
// Step 1: Populate a vector with all slaves not the selected master.
|
|
ServerArray redirectable_slaves = get_redirectables(promotion_target, demotion_target);
|
|
|
|
time_t step1_time = time(NULL);
|
|
seconds_remaining -= difftime(step1_time, start_time);
|
|
|
|
bool rval = false;
|
|
// Step 2: Wait until relay log consumed.
|
|
if (promotion_target->failover_wait_relay_log(seconds_remaining, error_out))
|
|
{
|
|
time_t step2_time = time(NULL);
|
|
int seconds_step2 = difftime(step2_time, step1_time);
|
|
MXS_DEBUG("Failover: relay log processing took %d seconds.", seconds_step2);
|
|
seconds_remaining -= seconds_step2;
|
|
|
|
// Step 3: Stop and reset slave, set read-only to 0.
|
|
if (promote_new_master(promotion_target, error_out))
|
|
{
|
|
m_next_master = promotion_target;
|
|
m_cluster_modified = true;
|
|
// Step 4: Redirect slaves.
|
|
ServerArray redirected_slaves;
|
|
int redirects = redirect_slaves(promotion_target, redirectable_slaves, &redirected_slaves);
|
|
bool success = redirectable_slaves.empty() ? true : redirects > 0;
|
|
if (success)
|
|
{
|
|
time_t step4_time = time(NULL);
|
|
seconds_remaining -= difftime(step4_time, step2_time);
|
|
|
|
// Step 5: Finally, add an event to the new master to advance gtid and wait for the slaves
|
|
// to receive it. seconds_remaining can be 0 or less at this point. Even in such a case
|
|
// wait_cluster_stabilization() may succeed if replication is fast enough. If using external
|
|
// replication, skip this step. Come up with an alternative later.
|
|
if (m_external_master_port != PORT_UNKNOWN)
|
|
{
|
|
MXS_WARNING("Replicating from external master, skipping final check.");
|
|
rval = true;
|
|
}
|
|
else if (redirected_slaves.empty())
|
|
{
|
|
// No slaves to check. Assume success.
|
|
rval = true;
|
|
MXS_DEBUG("Failover: no slaves to redirect, skipping stabilization check.");
|
|
}
|
|
else if (wait_cluster_stabilization(promotion_target, redirected_slaves, seconds_remaining))
|
|
{
|
|
rval = true;
|
|
time_t step5_time = time(NULL);
|
|
int seconds_step5 = difftime(step5_time, step4_time);
|
|
seconds_remaining -= seconds_step5;
|
|
MXS_DEBUG("Failover: slave replication confirmation took %d seconds with "
|
|
"%d seconds to spare.", seconds_step5, seconds_remaining);
|
|
}
|
|
}
|
|
else
|
|
{
|
|
print_redirect_errors(NULL, redirectable_slaves, error_out);
|
|
}
|
|
}
|
|
}
|
|
|
|
return rval;
|
|
}
|
|
|
|
/**
|
|
* Demotes the current master server, preparing it for replicating from another server. This step can take a
|
|
* while if long writes are running on the server.
|
|
*
|
|
* @param current_master Server to demote
|
|
* @param info Current master info. Will be written to. TODO: Remove need for this.
|
|
* @param err_out json object for error printing. Can be NULL.
|
|
* @return True if successful.
|
|
*/
|
|
bool MariaDBMonitor::switchover_demote_master(MariaDBServer* current_master, json_t** err_out)
|
|
{
|
|
MXS_NOTICE("Demoting server '%s'.", current_master->name());
|
|
bool success = false;
|
|
bool query_error = false;
|
|
MYSQL* conn = current_master->m_server_base->con;
|
|
const char* query = ""; // The next query to execute. Used also for error printing.
|
|
// The presence of an external master changes several things.
|
|
const bool external_master = server_is_slave_of_ext_master(current_master->m_server_base->server);
|
|
|
|
if (external_master)
|
|
{
|
|
// First need to stop slave. read_only is probably on already, although not certain.
|
|
query = "STOP SLAVE;";
|
|
query_error = (mxs_mysql_query(conn, query) != 0);
|
|
if (!query_error)
|
|
{
|
|
query = "RESET SLAVE ALL;";
|
|
query_error = (mxs_mysql_query(conn, query) != 0);
|
|
}
|
|
}
|
|
|
|
bool error_fetched = false;
|
|
string error_desc;
|
|
if (!query_error)
|
|
{
|
|
query = "SET GLOBAL read_only=1;";
|
|
query_error = (mxs_mysql_query(conn, query) != 0);
|
|
if (!query_error)
|
|
{
|
|
// If have external master, no writes are allowed so skip this step. It's not essential, just
|
|
// adds one to gtid.
|
|
if (!external_master)
|
|
{
|
|
query = "FLUSH TABLES;";
|
|
query_error = (mxs_mysql_query(conn, query) != 0);
|
|
}
|
|
|
|
if (!query_error)
|
|
{
|
|
query = "FLUSH LOGS;";
|
|
query_error = (mxs_mysql_query(conn, query) != 0);
|
|
if (!query_error)
|
|
{
|
|
query = "";
|
|
if (current_master->update_gtids())
|
|
{
|
|
success = true;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (!success)
|
|
{
|
|
// Somehow, a step after "SET read_only" failed. Try to set read_only back to 0. It may not
|
|
// work since the connection is likely broken.
|
|
error_desc = mysql_error(conn); // Read connection error before next step.
|
|
error_fetched = true;
|
|
mxs_mysql_query(conn, "SET GLOBAL read_only=0;");
|
|
}
|
|
}
|
|
}
|
|
|
|
if (query_error && !error_fetched)
|
|
{
|
|
error_desc = mysql_error(conn);
|
|
}
|
|
|
|
if (!success)
|
|
{
|
|
if (query_error)
|
|
{
|
|
if (error_desc.empty())
|
|
{
|
|
const char UNKNOWN_ERROR[] = "Demotion failed due to an unknown error when executing "
|
|
"a query. Query: '%s'.";
|
|
PRINT_MXS_JSON_ERROR(err_out, UNKNOWN_ERROR, query);
|
|
}
|
|
else
|
|
{
|
|
const char KNOWN_ERROR[] = "Demotion failed due to a query error: '%s'. Query: '%s'.";
|
|
PRINT_MXS_JSON_ERROR(err_out, KNOWN_ERROR, error_desc.c_str(), query);
|
|
}
|
|
}
|
|
else
|
|
{
|
|
const char * const GTID_ERROR = "Demotion failed due to an error in updating gtid:s. "
|
|
"Check log for more details.";
|
|
PRINT_MXS_JSON_ERROR(err_out, GTID_ERROR);
|
|
}
|
|
}
|
|
else if (!m_demote_sql_file.empty() && !current_master->run_sql_from_file(m_demote_sql_file, err_out))
|
|
{
|
|
PRINT_MXS_JSON_ERROR(err_out, "%s execution failed when demoting server '%s'.",
|
|
CN_DEMOTION_SQL_FILE, current_master->name());
|
|
success = false;
|
|
}
|
|
|
|
return success;
|
|
}
|
|
|
|
/**
|
|
* Wait until slave replication catches up with the master gtid for all slaves in the vector.
|
|
*
|
|
* @param slave Slaves to wait on
|
|
* @param gtid Which gtid must be reached
|
|
* @param total_timeout Maximum wait time in seconds
|
|
* @param err_out json object for error printing. Can be NULL.
|
|
* @return True, if target gtid was reached within allotted time for all servers
|
|
*/
|
|
bool MariaDBMonitor::switchover_wait_slaves_catchup(const ServerArray& slaves, const GtidList& gtid,
|
|
int total_timeout, json_t** err_out)
|
|
{
|
|
bool success = true;
|
|
int seconds_remaining = total_timeout;
|
|
|
|
for (auto iter = slaves.begin(); iter != slaves.end() && success; iter++)
|
|
{
|
|
if (seconds_remaining <= 0)
|
|
{
|
|
success = false;
|
|
}
|
|
else
|
|
{
|
|
time_t begin = time(NULL);
|
|
MariaDBServer* slave_server = *iter;
|
|
if (slave_server->wait_until_gtid(gtid, seconds_remaining, err_out))
|
|
{
|
|
seconds_remaining -= difftime(time(NULL), begin);
|
|
}
|
|
else
|
|
{
|
|
success = false;
|
|
}
|
|
}
|
|
}
|
|
return success;
|
|
}
|
|
|
|
/**
|
|
* Send an event to new master and wait for slaves to get the event.
|
|
*
|
|
* @param new_master Where to send the event
|
|
* @param slaves Servers to monitor
|
|
* @param seconds_remaining How long can we wait
|
|
* @return True, if at least one slave got the new event within the time limit
|
|
*/
|
|
bool MariaDBMonitor::wait_cluster_stabilization(MariaDBServer* new_master, const ServerArray& slaves,
|
|
int seconds_remaining)
|
|
{
|
|
ss_dassert(!slaves.empty());
|
|
bool rval = false;
|
|
time_t begin = time(NULL);
|
|
|
|
if (mxs_mysql_query(new_master->m_server_base->con, "FLUSH TABLES;") == 0 &&
|
|
new_master->update_gtids())
|
|
{
|
|
int query_fails = 0;
|
|
int repl_fails = 0;
|
|
int successes = 0;
|
|
const GtidList& target = new_master->m_gtid_current_pos;
|
|
ServerArray wait_list = slaves; // Check all the servers in the list
|
|
bool first_round = true;
|
|
bool time_is_up = false;
|
|
|
|
while (!wait_list.empty() && !time_is_up)
|
|
{
|
|
if (!first_round)
|
|
{
|
|
std::this_thread::sleep_for(std::chrono::milliseconds(500));
|
|
}
|
|
|
|
// Erasing elements from an array, so iterate from last to first
|
|
int i = wait_list.size() - 1;
|
|
while (i >= 0)
|
|
{
|
|
MariaDBServer* slave = wait_list[i];
|
|
if (slave->update_gtids() && slave->do_show_slave_status() && !slave->m_slave_status.empty())
|
|
{
|
|
if (!slave->m_slave_status[0].last_error.empty())
|
|
{
|
|
// IO or SQL error on slave, replication is a fail
|
|
MXS_WARNING("Slave '%s' cannot start replication: '%s'.", slave->name(),
|
|
slave->m_slave_status[0].last_error.c_str());
|
|
wait_list.erase(wait_list.begin() + i);
|
|
repl_fails++;
|
|
}
|
|
else if (GtidList::events_ahead(target, slave->m_gtid_current_pos,
|
|
GtidList::MISSING_DOMAIN_IGNORE) == 0)
|
|
{
|
|
// This slave has reached the same gtid as master, remove from list
|
|
wait_list.erase(wait_list.begin() + i);
|
|
successes++;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
wait_list.erase(wait_list.begin() + i);
|
|
query_fails++;
|
|
}
|
|
i--;
|
|
}
|
|
|
|
first_round = false; // Sleep at start of next iteration
|
|
if (difftime(time(NULL), begin) >= seconds_remaining)
|
|
{
|
|
time_is_up = true;
|
|
}
|
|
}
|
|
|
|
auto fails = repl_fails + query_fails + wait_list.size();
|
|
if (fails > 0)
|
|
{
|
|
const char MSG[] = "Replication from the new master could not be confirmed for %lu slaves. "
|
|
"%d encountered an I/O or SQL error, %d failed to reply and %lu did not "
|
|
"advance in Gtid until time ran out.";
|
|
MXS_WARNING(MSG, fails, repl_fails, query_fails, wait_list.size());
|
|
}
|
|
rval = (successes > 0);
|
|
}
|
|
else
|
|
{
|
|
MXS_ERROR("Could not confirm replication after switchover/failover because query to "
|
|
"the new master failed.");
|
|
}
|
|
return rval;
|
|
}
|
|
|
|
/**
|
|
* Check that the given slave is a valid promotion candidate.
|
|
*
|
|
* @param preferred Preferred new master
|
|
* @param err_out Json object for error printing. Can be NULL.
|
|
* @return True, if given slave is a valid promotion candidate.
|
|
*/
|
|
bool MariaDBMonitor::switchover_check_preferred_master(MariaDBServer* preferred, json_t** err_out)
|
|
{
|
|
ss_dassert(preferred);
|
|
bool rval = true;
|
|
if (!preferred->update_slave_info() || !preferred->check_replication_settings())
|
|
{
|
|
PRINT_MXS_JSON_ERROR(err_out, "The requested server '%s' is not a valid promotion candidate.",
|
|
preferred->name());
|
|
rval = false;
|
|
}
|
|
return rval;
|
|
}
|
|
|
|
/**
|
|
* Prepares a server for the replication master role.
|
|
*
|
|
* @param new_master The new master server
|
|
* @param err_out json object for error printing. Can be NULL.
|
|
* @return True if successful
|
|
*/
|
|
bool MariaDBMonitor::promote_new_master(MariaDBServer* new_master, json_t** err_out)
|
|
{
|
|
bool success = false;
|
|
MYSQL* new_master_conn = new_master->m_server_base->con;
|
|
MXS_NOTICE("Promoting server '%s' to master.", new_master->name());
|
|
const char* query = "STOP SLAVE;";
|
|
if (mxs_mysql_query(new_master_conn, query) == 0)
|
|
{
|
|
query = "RESET SLAVE ALL;";
|
|
if (mxs_mysql_query(new_master_conn, query) == 0)
|
|
{
|
|
query = "SET GLOBAL read_only=0;";
|
|
if (mxs_mysql_query(new_master_conn, query) == 0)
|
|
{
|
|
success = true;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (!success)
|
|
{
|
|
PRINT_MXS_JSON_ERROR(err_out, "Promotion failed: '%s'. Query: '%s'.",
|
|
mysql_error(new_master_conn), query);
|
|
}
|
|
else
|
|
{
|
|
// Promotion commands ran successfully, run promotion sql script file before external replication.
|
|
if (!m_promote_sql_file.empty() && !new_master->run_sql_from_file(m_promote_sql_file, err_out))
|
|
{
|
|
PRINT_MXS_JSON_ERROR(err_out, "%s execution failed when promoting server '%s'.",
|
|
CN_PROMOTION_SQL_FILE, new_master->name());
|
|
success = false;
|
|
}
|
|
// If the previous master was a slave to an external master, start the equivalent slave connection on
|
|
// the new master. Success of replication is not checked.
|
|
else if (m_external_master_port != PORT_UNKNOWN && !start_external_replication(new_master, err_out))
|
|
{
|
|
success = false;
|
|
}
|
|
}
|
|
|
|
return success;
|
|
}
|
|
|
|
MariaDBServer* MariaDBMonitor::select_promotion_target(MariaDBServer* demotion_target,
|
|
ClusterOperation op, Log log_mode,
|
|
json_t** error_out)
|
|
{
|
|
/* Select a new master candidate. Selects the one with the latest event in relay log.
|
|
* If multiple slaves have same number of events, select the one with most processed events. */
|
|
|
|
if (!demotion_target->m_node.children.empty())
|
|
{
|
|
if (log_mode == Log::ON)
|
|
{
|
|
MXS_NOTICE("Selecting a server to promote and replace '%s'. Candidates are: %s.",
|
|
demotion_target->name(),
|
|
monitored_servers_to_string(demotion_target->m_node.children).c_str());
|
|
}
|
|
}
|
|
else
|
|
{
|
|
PRINT_ERROR_IF(log_mode, error_out, "'%s' does not have any slaves to promote.",
|
|
demotion_target->name());
|
|
return NULL;
|
|
}
|
|
|
|
// Servers that cannot be selected because of exclusion, but seem otherwise ok.
|
|
ServerArray valid_but_excluded;
|
|
|
|
string all_reasons;
|
|
DelimitedPrinter printer("\n");
|
|
// The valid promotion candidates are the slaves replicating directly from the demotion target.
|
|
ServerArray candidates;
|
|
for (MariaDBServer* cand : demotion_target->m_node.children)
|
|
{
|
|
string reason;
|
|
if (!cand->can_be_promoted(op, demotion_target, &reason))
|
|
{
|
|
string msg = string_printf("'%s' cannot be selected because %s", cand->name(), reason.c_str());
|
|
printer.cat(all_reasons, msg);
|
|
}
|
|
else if (server_is_excluded(cand))
|
|
{
|
|
valid_but_excluded.push_back(cand);
|
|
string msg = string_printf("'%s' cannot be selected because it is excluded.", cand->name());
|
|
printer.cat(all_reasons, msg);
|
|
}
|
|
else
|
|
{
|
|
candidates.push_back(cand);
|
|
}
|
|
}
|
|
|
|
MariaDBServer* current_best = NULL;
|
|
if (candidates.empty())
|
|
{
|
|
PRINT_ERROR_IF(log_mode, error_out, "No suitable promotion candidate found:\n%s", all_reasons.c_str());
|
|
}
|
|
else
|
|
{
|
|
current_best = candidates.front();
|
|
candidates.erase(candidates.begin());
|
|
if (!all_reasons.empty() && log_mode == Log::ON)
|
|
{
|
|
MXS_WARNING("Some servers were disqualified for promotion:\n%s", all_reasons.c_str());
|
|
}
|
|
}
|
|
|
|
// Check which candidate is best
|
|
string current_best_reason;
|
|
for (MariaDBServer* cand : candidates)
|
|
{
|
|
if (is_candidate_better(cand, current_best, m_master_gtid_domain, ¤t_best_reason))
|
|
{
|
|
// Select the server for promotion, for now.
|
|
current_best = cand;
|
|
}
|
|
}
|
|
|
|
// Check if any of the excluded servers would be better than the best candidate. Only print one item.
|
|
if (log_mode == Log::ON)
|
|
{
|
|
for (MariaDBServer* excluded_info : valid_but_excluded)
|
|
{
|
|
const char* excluded_name = excluded_info->name();
|
|
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.";
|
|
MXS_WARNING(EXCLUDED_ONLY_CAND, excluded_name);
|
|
break;
|
|
}
|
|
else if (is_candidate_better(excluded_info, current_best, m_master_gtid_domain))
|
|
{
|
|
// Print a warning if this server is actually a better candidate than the previous best.
|
|
const char EXCLUDED_CAND[] = "Server '%s' is superior to current best candidate '%s', "
|
|
"but cannot be selected as it's excluded. This may lead to "
|
|
"loss of data if '%s' is ahead of other servers.";
|
|
MXS_WARNING(EXCLUDED_CAND, excluded_name, current_best->name(), excluded_name);
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (current_best && log_mode == Log::ON)
|
|
{
|
|
// If there was a specific reason this server was selected, print it now. If the first candidate
|
|
// was chosen (likely all servers were equally good), do not print.
|
|
string msg = string_printf("Selected '%s'", current_best->name());
|
|
msg += current_best_reason.empty() ? "." : (" because " + current_best_reason);
|
|
MXS_NOTICE("%s", msg.c_str());
|
|
}
|
|
return current_best;
|
|
}
|
|
|
|
/**
|
|
* Is the server in the excluded list
|
|
*
|
|
* @param server Server to test
|
|
* @return True if server is in the excluded-list of the monitor.
|
|
*/
|
|
bool MariaDBMonitor::server_is_excluded(const MariaDBServer* server)
|
|
{
|
|
for (auto iter = m_excluded_servers.begin(); iter != m_excluded_servers.end(); iter++)
|
|
{
|
|
if (*iter == server)
|
|
{
|
|
return true;
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/**
|
|
* Is the candidate a better choice for master than the previous best?
|
|
*
|
|
* @param candidate_info Server info of new candidate
|
|
* @param current_best_info Server info of current best choice
|
|
* @param gtid_domain Which domain to compare
|
|
* @param reason_out Why is the candidate better than current_best
|
|
* @return True if candidate is better
|
|
*/
|
|
bool MariaDBMonitor::is_candidate_better(const MariaDBServer* candidate, const MariaDBServer* current_best,
|
|
uint32_t gtid_domain, std::string* reason_out)
|
|
{
|
|
string reason;
|
|
bool is_better = false;
|
|
uint64_t cand_io = candidate->m_slave_status[0].gtid_io_pos.get_gtid(gtid_domain).m_sequence;
|
|
uint64_t curr_io = current_best->m_slave_status[0].gtid_io_pos.get_gtid(gtid_domain).m_sequence;
|
|
// A slave with a later event in relay log is always preferred.
|
|
if (cand_io > curr_io)
|
|
{
|
|
is_better = true;
|
|
reason = "it has received more events.";
|
|
}
|
|
// If io sequences are identical ...
|
|
else if (cand_io == curr_io)
|
|
{
|
|
uint64_t cand_processed = candidate->m_gtid_current_pos.get_gtid(gtid_domain).m_sequence;
|
|
uint64_t curr_processed = current_best->m_gtid_current_pos.get_gtid(gtid_domain).m_sequence;
|
|
// ... the slave with more events processed wins.
|
|
if (cand_processed > curr_processed)
|
|
{
|
|
is_better = true;
|
|
reason = "it has processed more events.";
|
|
}
|
|
// If gtid positions are identical ...
|
|
else if (cand_processed == curr_processed)
|
|
{
|
|
bool cand_updates = candidate->m_rpl_settings.log_slave_updates;
|
|
bool curr_updates = current_best->m_rpl_settings.log_slave_updates;
|
|
// ... prefer a slave with log_slave_updates.
|
|
if (cand_updates && !curr_updates)
|
|
{
|
|
is_better = true;
|
|
reason = "it has 'log_slave_updates' on.";
|
|
}
|
|
// If both have log_slave_updates on ...
|
|
else if (cand_updates && curr_updates)
|
|
{
|
|
bool cand_disk_ok = !server_is_disk_space_exhausted(candidate->m_server_base->server);
|
|
bool curr_disk_ok = !server_is_disk_space_exhausted(current_best->m_server_base->server);
|
|
// ... prefer a slave without disk space issues.
|
|
if (cand_disk_ok && !curr_disk_ok)
|
|
{
|
|
is_better = true;
|
|
reason = "it is not low on disk space.";
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
if (reason_out && is_better)
|
|
{
|
|
*reason_out = reason;
|
|
}
|
|
return is_better;
|
|
}
|
|
|
|
/**
|
|
* Check cluster and parameters for suitability to failover. Also writes found servers to output pointers.
|
|
*
|
|
* @param log_mode Logging mode
|
|
* @param promotion_target_out Output for promotion target
|
|
* @param demotion_target_out Output for demotion target
|
|
* @param error_out Error output
|
|
* @return True if cluster is suitable and failover may proceed
|
|
*/
|
|
bool MariaDBMonitor::failover_prepare(Log log_mode,
|
|
MariaDBServer** promotion_target_out,
|
|
MariaDBServer** demotion_target_out,
|
|
json_t** error_out)
|
|
{
|
|
// This function resembles 'switchover_prepare', but does not yet support manual selection.
|
|
const auto op = ClusterOperation::FAILOVER;
|
|
// Check that the cluster has a non-functional master server and that one of the slaves of
|
|
// that master can be promoted. TODO: add support for demoting a relay server.
|
|
MariaDBServer* demotion_target = NULL;
|
|
// Autoselect current master as demotion target.
|
|
string demotion_msg;
|
|
if (m_master == NULL)
|
|
{
|
|
const char msg[] = "Can not select a demotion target for failover: cluster does not have a master.";
|
|
PRINT_ERROR_IF(log_mode, error_out, msg);
|
|
}
|
|
else if (!m_master->can_be_demoted_failover(&demotion_msg))
|
|
{
|
|
const char msg[] = "Can not select '%s' as a demotion target for failover because %s";
|
|
PRINT_ERROR_IF(log_mode, error_out, msg, m_master->name(), demotion_msg.c_str());
|
|
}
|
|
else
|
|
{
|
|
demotion_target = m_master;
|
|
}
|
|
|
|
MariaDBServer* promotion_target = NULL;
|
|
if (demotion_target)
|
|
{
|
|
// Autoselect best server for promotion.
|
|
MariaDBServer* promotion_candidate = select_promotion_target(demotion_target, op,
|
|
log_mode, error_out);
|
|
if (promotion_candidate)
|
|
{
|
|
promotion_target = promotion_candidate;
|
|
}
|
|
else
|
|
{
|
|
PRINT_ERROR_IF(log_mode, error_out, "Could not autoselect promotion target for failover.");
|
|
}
|
|
}
|
|
|
|
bool gtid_ok = false;
|
|
if (demotion_target)
|
|
{
|
|
gtid_ok = check_gtid_replication(log_mode, demotion_target, error_out);
|
|
}
|
|
|
|
if (promotion_target && demotion_target && gtid_ok)
|
|
{
|
|
*promotion_target_out = promotion_target;
|
|
*demotion_target_out = demotion_target;
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/**
|
|
* @brief Process possible failover event
|
|
*
|
|
* If a master failure has occurred and MaxScale is configured with failover functionality, this fuction
|
|
* executes failover to select and promote a new master server. This function should be called immediately
|
|
* after @c mon_process_state_changes. If an error occurs, this method disables automatic failover.
|
|
*/
|
|
void MariaDBMonitor::handle_auto_failover()
|
|
{
|
|
string cluster_issues;
|
|
// TODO: Only check this when topology has changed.
|
|
if (!cluster_supports_failover(&cluster_issues))
|
|
{
|
|
const char PROBLEMS[] = "The backend cluster does not support failover due to the following "
|
|
"reason(s):\n"
|
|
"%s\n\n"
|
|
"Automatic failover has been disabled. It should only be enabled after the "
|
|
"above issues have been resolved.";
|
|
string p1 = string_printf(PROBLEMS, cluster_issues.c_str());
|
|
string p2 = string_printf(RE_ENABLE_FMT, "failover", CN_AUTO_FAILOVER, m_monitor->name);
|
|
string total_msg = p1 + " " + p2;
|
|
MXS_ERROR("%s", total_msg.c_str());
|
|
m_auto_failover = false;
|
|
disable_setting(CN_AUTO_FAILOVER);
|
|
return;
|
|
}
|
|
|
|
if (m_master && m_master->is_master())
|
|
{
|
|
// Certainly no need for a failover.
|
|
return;
|
|
}
|
|
|
|
// If master seems to be down, check if slaves are receiving events.
|
|
if (m_verify_master_failure && m_master && m_master->is_down() && slave_receiving_events())
|
|
{
|
|
MXS_INFO("Master failure not yet confirmed by slaves, delaying failover.");
|
|
return;
|
|
}
|
|
|
|
MariaDBServer* failed_master = NULL;
|
|
for (auto iter = m_servers.begin(); iter != m_servers.end(); iter++)
|
|
{
|
|
MariaDBServer* server = *iter;
|
|
MXS_MONITORED_SERVER* mon_server = server->m_server_base;
|
|
if (mon_server->new_event && mon_server->server->last_event == MASTER_DOWN_EVENT)
|
|
{
|
|
if (mon_server->server->active_event)
|
|
{
|
|
// MaxScale was active when the event took place
|
|
failed_master = server;
|
|
}
|
|
else
|
|
{
|
|
/* If a master_down event was triggered when this MaxScale was passive, we need to execute
|
|
* the failover script again if no new masters have appeared. */
|
|
int64_t timeout = MXS_SEC_TO_CLOCK(m_failover_timeout);
|
|
int64_t t = mxs_clock() - mon_server->server->triggered_at;
|
|
|
|
if (t > timeout)
|
|
{
|
|
MXS_WARNING("Failover of server '%s' did not take place within %u seconds, "
|
|
"failover needs to be re-triggered", server->name(), m_failover_timeout);
|
|
failed_master = server;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
if (failed_master)
|
|
{
|
|
if (m_failcount > 1 && failed_master->m_server_base->mon_err_count == 1)
|
|
{
|
|
MXS_WARNING("Master has failed. If master status does not change in %d monitor passes, failover "
|
|
"begins.", m_failcount - 1);
|
|
}
|
|
else if (failed_master->m_server_base->mon_err_count >= m_failcount)
|
|
{
|
|
// Failover is required, but first we should check if preconditions are met.
|
|
MariaDBServer* promotion_target = NULL;
|
|
MariaDBServer* demotion_target = NULL;
|
|
Log log_mode = m_warn_failover_precond ? Log::ON : Log::OFF;
|
|
if (failover_prepare(log_mode, &promotion_target, &demotion_target, NULL))
|
|
{
|
|
m_warn_failover_precond = true;
|
|
MXS_NOTICE("Performing automatic failover to replace failed master '%s'.",
|
|
failed_master->name());
|
|
failed_master->m_server_base->new_event = false;
|
|
if (!do_failover(promotion_target, demotion_target, NULL))
|
|
{
|
|
report_and_disable("failover", CN_AUTO_FAILOVER, &m_auto_failover);
|
|
}
|
|
}
|
|
else
|
|
{
|
|
// Failover was not attempted because of errors, however these errors are not permanent.
|
|
// Servers were not modified, so it's ok to try this again.
|
|
if (m_warn_failover_precond)
|
|
{
|
|
MXS_WARNING("Not performing automatic failover. Will keep retrying with this message "
|
|
"suppressed.");
|
|
m_warn_failover_precond = false;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
else
|
|
{
|
|
m_warn_failover_precond = true;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Is the topology such that failover is supported, even if not required just yet?
|
|
*
|
|
* @param reasons_out Why failover is not supported
|
|
* @return True if cluster supports failover
|
|
*/
|
|
bool MariaDBMonitor::cluster_supports_failover(string* reasons_out)
|
|
{
|
|
bool rval = true;
|
|
string separator;
|
|
// Currently, only simple topologies are supported. No Relay Masters or multiple slave connections.
|
|
// Gtid-replication is required, and a server version which supports it.
|
|
for (MariaDBServer* server : m_servers)
|
|
{
|
|
// Need to accept unknown versions here. Otherwise servers which are down when the monitor starts
|
|
// would deactivate failover.
|
|
if (server->m_version != MariaDBServer::version::UNKNOWN &&
|
|
server->m_version != MariaDBServer::version::MARIADB_100)
|
|
{
|
|
*reasons_out += separator + string_printf("The version of server '%s' is not supported. Failover "
|
|
"requires MariaDB 10.X.", server->name());
|
|
separator = "\n";
|
|
rval = false;
|
|
}
|
|
|
|
if (server->is_slave() && !server->m_slave_status.empty())
|
|
{
|
|
if (server->m_slave_status.size() > 1)
|
|
{
|
|
*reasons_out += separator +
|
|
string_printf("Server '%s' is replicating or attempting to replicate from "
|
|
"multiple masters.", server->name());
|
|
separator = "\n";
|
|
rval = false;
|
|
}
|
|
if (!server->uses_gtid())
|
|
{
|
|
*reasons_out += separator +
|
|
string_printf("Server '%s' is not using gtid-replication.", server->name());
|
|
separator = "\n";
|
|
rval = false;
|
|
}
|
|
}
|
|
|
|
if (server->is_relay_master())
|
|
{
|
|
*reasons_out += separator +
|
|
string_printf("Server '%s' is a relay master. Only topologies with one replication "
|
|
"layer are supported.", server->name());
|
|
separator = "\n";
|
|
rval = false;
|
|
}
|
|
}
|
|
return rval;
|
|
}
|
|
|
|
/**
|
|
* Check if a slave is receiving events from master.
|
|
*
|
|
* @return True, if a slave has an event more recent than master_failure_timeout.
|
|
*/
|
|
bool MariaDBMonitor::slave_receiving_events()
|
|
{
|
|
ss_dassert(m_master);
|
|
bool received_event = false;
|
|
int64_t master_id = m_master->m_server_base->server->node_id;
|
|
|
|
for (auto iter = m_servers.begin(); iter != m_servers.end(); iter++)
|
|
{
|
|
MariaDBServer* server = *iter;
|
|
if (!server->m_slave_status.empty() &&
|
|
server->m_slave_status[0].slave_io_running == SlaveStatus::SLAVE_IO_YES &&
|
|
server->m_slave_status[0].master_server_id == master_id &&
|
|
difftime(time(NULL), server->m_latest_event) < m_master_failure_timeout)
|
|
{
|
|
/**
|
|
* The slave is still connected to the correct master and has received events. This means that
|
|
* while MaxScale can't connect to the master, it's probably still alive.
|
|
*/
|
|
received_event = true;
|
|
break;
|
|
}
|
|
}
|
|
return received_event;
|
|
}
|
|
|
|
/**
|
|
* Print a redirect error to logs. If err_out exists, generate a combined error message by querying all
|
|
* the server parameters for connection errors and append these errors to err_out.
|
|
*
|
|
* @param demotion_target If not NULL, this is the first server to query.
|
|
* @param redirectable_slaves Other servers to query for errors.
|
|
* @param err_out If not null, the error output object.
|
|
*/
|
|
static void print_redirect_errors(MariaDBServer* first_server, const ServerArray& servers,
|
|
json_t** err_out)
|
|
{
|
|
// Individual server errors have already been printed to the log.
|
|
// For JSON, gather the errors again.
|
|
const char* const MSG = "Could not redirect any slaves to the new master.";
|
|
MXS_ERROR(MSG);
|
|
if (err_out)
|
|
{
|
|
ServerArray failed_slaves;
|
|
if (first_server)
|
|
{
|
|
failed_slaves.push_back(first_server);
|
|
}
|
|
for (auto iter = servers.begin(); iter != servers.end(); iter++)
|
|
{
|
|
failed_slaves.push_back(*iter);
|
|
}
|
|
|
|
string combined_error = get_connection_errors(failed_slaves);
|
|
*err_out = mxs_json_error_append(*err_out, "%s Errors: %s.", MSG, combined_error.c_str());
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Check cluster and parameters for suitability to switchover. Also writes found servers to output pointers.
|
|
*
|
|
* @param promotion_server The server which should be promoted. If null, monitor will autoselect.
|
|
* @param demotion_server The server which should be demoted. Can be null for autoselect.
|
|
* @param log_mode Logging mode
|
|
* @param promotion_target_out Output for promotion target
|
|
* @param demotion_target_out Output for demotion target
|
|
* @param error_out Error output
|
|
* @return True if cluster is suitable and server parameters were valid
|
|
*/
|
|
bool MariaDBMonitor::switchover_prepare(SERVER* promotion_server, SERVER* demotion_server,
|
|
Log log_mode,
|
|
MariaDBServer** promotion_target_out,
|
|
MariaDBServer** demotion_target_out,
|
|
json_t** error_out)
|
|
{
|
|
const auto op = ClusterOperation::SWITCHOVER;
|
|
// Check that both servers are ok if specified, or autoselect them. Demotion target must be checked
|
|
// first since the promotion target depends on it.
|
|
ss_dassert(promotion_target_out && demotion_target_out &&
|
|
!*promotion_target_out && !*demotion_target_out);
|
|
const char NO_SERVER[] = "Server '%s' is not a member of monitor '%s'.";
|
|
|
|
MariaDBServer* demotion_target = NULL;
|
|
string demotion_msg;
|
|
if (demotion_server)
|
|
{
|
|
// Manual select.
|
|
MariaDBServer* demotion_candidate = get_server(demotion_server);
|
|
if (demotion_candidate == NULL)
|
|
{
|
|
PRINT_ERROR_IF(log_mode, error_out, NO_SERVER, demotion_server->name, m_monitor->name);
|
|
}
|
|
else if (!demotion_candidate->can_be_demoted_switchover(&demotion_msg))
|
|
{
|
|
PRINT_ERROR_IF(log_mode, error_out, "'%s' is not a valid demotion target for switchover: %s",
|
|
demotion_candidate->name(), demotion_msg.c_str());
|
|
}
|
|
else
|
|
{
|
|
demotion_target = demotion_candidate;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
// Autoselect current master as demotion target.
|
|
if (m_master == NULL)
|
|
{
|
|
const char msg[] = "Can not autoselect a demotion target for switchover: cluster does "
|
|
"not have a master.";
|
|
PRINT_ERROR_IF(log_mode, error_out, msg);
|
|
}
|
|
else if (!m_master->can_be_demoted_switchover(&demotion_msg))
|
|
{
|
|
const char msg[] = "Can not autoselect '%s' as a demotion target for switchover because %s";
|
|
PRINT_ERROR_IF(log_mode, error_out, msg, m_master->name(), demotion_msg.c_str());
|
|
}
|
|
else
|
|
{
|
|
demotion_target = m_master;
|
|
}
|
|
}
|
|
|
|
MariaDBServer* promotion_target = NULL;
|
|
if (demotion_target)
|
|
{
|
|
string promotion_msg;
|
|
if (promotion_server)
|
|
{
|
|
// Manual select.
|
|
MariaDBServer* promotion_candidate = get_server(promotion_server);
|
|
if (promotion_candidate == NULL)
|
|
{
|
|
PRINT_ERROR_IF(log_mode, error_out, NO_SERVER, promotion_server->name, m_monitor->name);
|
|
}
|
|
else if (!promotion_candidate->can_be_promoted(op, demotion_target, &promotion_msg))
|
|
{
|
|
const char msg[] = "'%s' is not a valid promotion target for switchover because %s";
|
|
PRINT_ERROR_IF(log_mode, error_out, msg, promotion_candidate->name(), promotion_msg.c_str());
|
|
}
|
|
else
|
|
{
|
|
promotion_target = promotion_candidate;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
// Autoselect. More involved than the autoselecting the demotion target.
|
|
MariaDBServer* promotion_candidate = select_promotion_target(demotion_target, op,
|
|
log_mode, error_out);
|
|
if (promotion_candidate)
|
|
{
|
|
promotion_target = promotion_candidate;
|
|
}
|
|
else
|
|
{
|
|
PRINT_ERROR_IF(log_mode, error_out, "Could not autoselect promotion target for switchover.");
|
|
}
|
|
}
|
|
}
|
|
|
|
bool gtid_ok = false;
|
|
if (demotion_target)
|
|
{
|
|
gtid_ok = check_gtid_replication(log_mode, demotion_target, error_out);
|
|
}
|
|
|
|
if (promotion_target && demotion_target && gtid_ok)
|
|
{
|
|
*demotion_target_out = demotion_target;
|
|
*promotion_target_out = promotion_target;
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
void MariaDBMonitor::enforce_read_only_on_slaves()
|
|
{
|
|
const char QUERY[] = "SET GLOBAL read_only=1;";
|
|
for (auto iter = m_servers.begin(); iter != m_servers.end(); iter++)
|
|
{
|
|
MariaDBServer* server = *iter;
|
|
if (server->is_slave() && !server->is_read_only() &&
|
|
(server->m_version != MariaDBServer::version::BINLOG_ROUTER))
|
|
{
|
|
MYSQL* conn = server->m_server_base->con;
|
|
if (mxs_mysql_query(conn, QUERY) == 0)
|
|
{
|
|
MXS_NOTICE("read_only set to ON on server '%s'.", server->name());
|
|
}
|
|
else
|
|
{
|
|
MXS_ERROR("Setting read_only on server '%s' failed: '%s.", server->name(), mysql_error(conn));
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
void MariaDBMonitor::set_low_disk_slaves_maintenance()
|
|
{
|
|
// Only set pure slave and standalone servers to maintenance.
|
|
for (MariaDBServer* server : m_servers)
|
|
{
|
|
if (server->has_status(SERVER_DISK_SPACE_EXHAUSTED) && server->is_usable() &&
|
|
!server->is_master() && !server->is_relay_master())
|
|
{
|
|
server->set_status(SERVER_MAINT);
|
|
m_cluster_modified = true;
|
|
}
|
|
}
|
|
}
|
|
|
|
void MariaDBMonitor::handle_low_disk_space_master()
|
|
{
|
|
if (m_master && m_master->is_master() && m_master->is_low_on_disk_space())
|
|
{
|
|
if (m_warn_switchover_precond)
|
|
{
|
|
MXS_WARNING("Master server '%s' is low on disk space. Attempting to switch it with a slave.",
|
|
m_master->name());
|
|
}
|
|
|
|
// Looks like the master should be swapped out. Before trying it, check if there is even
|
|
// a likely valid slave to swap to.
|
|
MariaDBServer* demotion_target = NULL;
|
|
MariaDBServer* promotion_target = NULL;
|
|
Log log_mode = m_warn_switchover_precond ? Log::ON : Log::OFF;
|
|
auto ok_to_switch = switchover_prepare(NULL, m_master->m_server_base->server, log_mode,
|
|
&promotion_target, &demotion_target,
|
|
NULL);
|
|
if (ok_to_switch)
|
|
{
|
|
m_warn_switchover_precond = true;
|
|
bool switched = do_switchover(demotion_target, promotion_target, NULL);
|
|
if (switched)
|
|
{
|
|
MXS_NOTICE("Switchover %s -> %s performed.",
|
|
demotion_target->name(), promotion_target->name());
|
|
}
|
|
else
|
|
{
|
|
report_and_disable("switchover", CN_SWITCHOVER_ON_LOW_DISK_SPACE,
|
|
&m_switchover_on_low_disk_space);
|
|
}
|
|
}
|
|
else
|
|
{
|
|
// Switchover was not attempted because of errors, however these errors are not permanent.
|
|
// Servers were not modified, so it's ok to try this again.
|
|
if (m_warn_switchover_precond)
|
|
{
|
|
MXS_WARNING("Not performing automatic switchover. Will keep retrying with this message "
|
|
"suppressed.");
|
|
m_warn_switchover_precond = false;
|
|
}
|
|
}
|
|
}
|
|
else
|
|
{
|
|
m_warn_switchover_precond = true;
|
|
}
|
|
}
|
|
|
|
void MariaDBMonitor::report_and_disable(const string& operation, const string& setting_name,
|
|
bool* setting_var)
|
|
{
|
|
string p1 = string_printf("Automatic %s failed, disabling automatic %s.", operation.c_str(),
|
|
operation.c_str());
|
|
string p2 = string_printf(RE_ENABLE_FMT, operation.c_str(), setting_name.c_str(), m_monitor->name);
|
|
string error_msg = p1 + " " + p2;
|
|
MXS_ERROR("%s", error_msg.c_str());
|
|
*setting_var = false;
|
|
disable_setting(setting_name.c_str());
|
|
}
|
|
|
|
/**
|
|
* Check that the slaves to demotion target are using gtid replication and that the gtid domain of the
|
|
* cluster is defined. Only the slave connections to the demotion target are checked.
|
|
*
|
|
* @param log_mode Logging mode
|
|
* @param demotion_target The server whose slaves should be checked
|
|
* @param error_out Error output
|
|
* @return True if gtid is used
|
|
*/
|
|
bool MariaDBMonitor::check_gtid_replication(Log log_mode,
|
|
const MariaDBServer* demotion_target,
|
|
json_t** error_out)
|
|
{
|
|
bool gtid_domain_ok = false;
|
|
if (m_master_gtid_domain == GTID_DOMAIN_UNKNOWN)
|
|
{
|
|
PRINT_ERROR_IF(log_mode, error_out,
|
|
"Cluster gtid domain is unknown. This is usually caused by the cluster never "
|
|
"having a master server while MaxScale was running.");
|
|
}
|
|
else
|
|
{
|
|
gtid_domain_ok = true;
|
|
}
|
|
|
|
// Check that all slaves are using gtid-replication.
|
|
bool gtid_ok = true;
|
|
for (MariaDBServer* server : demotion_target->m_node.children)
|
|
{
|
|
auto sstatus = server->slave_connection_status(demotion_target);
|
|
if (sstatus && sstatus->gtid_io_pos.empty())
|
|
{
|
|
PRINT_ERROR_IF(log_mode, error_out,
|
|
"The slave connection '%s' -> '%s' is not using gtid replication.",
|
|
server->name(), demotion_target->name());
|
|
gtid_ok = false;
|
|
}
|
|
}
|
|
|
|
return gtid_domain_ok && gtid_ok;
|
|
}
|
|
|
|
/**
|
|
* List slaves which should be redirected to the new master.
|
|
*
|
|
* @param promotion_target The server which will be promoted
|
|
* @param demotion_target The server which will be demoted
|
|
* @return A list of slaves to redirect
|
|
*/
|
|
ServerArray MariaDBMonitor::get_redirectables(const MariaDBServer* promotion_target,
|
|
const MariaDBServer* demotion_target)
|
|
{
|
|
ServerArray redirectable_slaves;
|
|
for (MariaDBServer* slave : demotion_target->m_node.children)
|
|
{
|
|
if (slave != promotion_target)
|
|
{
|
|
auto sstatus = slave->slave_connection_status(demotion_target);
|
|
if (sstatus && !sstatus->gtid_io_pos.empty())
|
|
{
|
|
redirectable_slaves.push_back(slave);
|
|
}
|
|
}
|
|
}
|
|
return redirectable_slaves;
|
|
}
|