1818 lines
70 KiB
C++
1818 lines
70 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 <set>
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#include <sstream>
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#include <maxbase/stopwatch.hh>
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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 std::unique_ptr;
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using maxscale::string_printf;
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using maxbase::StopWatch;
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using maxbase::Duration;
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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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const char NO_SERVER[] = "Server '%s' is not monitored by '%s'.";
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const char FAILOVER_OK[] = "Failover '%s' -> '%s' performed.";
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const char FAILOVER_FAIL[] = "Failover '%s' -> '%s' failed.";
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const char SWITCHOVER_OK[] = "Switchover '%s' -> '%s' performed.";
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const char SWITCHOVER_FAIL[] = "Switchover %s -> %s failed";
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static void print_redirect_errors(MariaDBServer* first_server,
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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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auto op = switchover_prepare(promotion_server, demotion_server, Log::ON, error_out);
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if (op)
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{
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switchover_done = switchover_perform(*op);
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if (switchover_done)
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{
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MXS_NOTICE(SWITCHOVER_OK, op->demotion_target->name(), op->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_FAIL,
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op->demotion_target->name(), op->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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auto op = failover_prepare(Log::ON, output);
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if (op)
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{
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failover_done = failover_perform(*op);
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if (failover_done)
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{
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MXS_NOTICE(FAILOVER_OK, op->demotion_target->name(), op->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_FAIL,
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op->demotion_target->name(), op->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,
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"Server '%s' cannot replicate from cluster master '%s': "
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"%s.",
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rejoin_serv_name,
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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,
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"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,
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"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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* Reset replication of the cluster. Removes all slave connections and deletes binlogs. Then resets the
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* gtid sequence of the cluster to 0 and directs all servers to replicate from the given master.
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*
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* @param master_server Server to use as master
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* @param error_out Error output
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* @return True if operation was successful
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*/
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bool MariaDBMonitor::manual_reset_replication(SERVER* master_server, json_t** error_out)
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{
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// This command is a hail-mary type, so no need to be that careful. Users are only supposed to run this
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// when replication is broken and they know the cluster is in sync.
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// If a master has been given, use that as the master. Otherwise autoselect.
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MariaDBServer* new_master = NULL;
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if (master_server)
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{
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MariaDBServer* new_master_cand = get_server(master_server);
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if (new_master_cand == NULL)
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{
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PRINT_MXS_JSON_ERROR(error_out, NO_SERVER, master_server->name, m_monitor->name);
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}
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else if (!new_master_cand->is_usable())
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{
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PRINT_MXS_JSON_ERROR(error_out,
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"Server '%s' is down or in maintenance and cannot be used as master.",
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new_master_cand->name());
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}
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else
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{
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new_master = new_master_cand;
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}
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}
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else
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{
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const char BAD_MASTER[] = "Could not autoselect new master for replication reset because %s";
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if (m_master == NULL)
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{
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PRINT_MXS_JSON_ERROR(error_out, BAD_MASTER, "the cluster has no master.");
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}
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else if (!m_master->is_usable())
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{
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PRINT_MXS_JSON_ERROR(error_out, BAD_MASTER, "the master is down or in maintenance.");
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}
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else
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{
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new_master = m_master;
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}
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}
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bool rval = false;
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if (new_master)
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{
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bool error = false;
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// Step 1: Gather the list of affected servers. If any operation on the servers fails,
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// the reset fails as well.
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ServerArray targets;
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for (MariaDBServer* server : m_servers)
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{
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if (server->is_usable())
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{
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targets.push_back(server);
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}
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}
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// The 'targets'-array cannot be empty, at least 'new_master' is there.
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MXB_NOTICE("Reseting replication on the following servers: %s. '%s' will be the new master.",
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monitored_servers_to_string(targets).c_str(), new_master->name());
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// Helper function for running a command on all servers in the list.
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auto exec_cmd_on_array = [&error](const ServerArray& targets, const string& query,
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json_t** error_out) {
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if (!error)
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{
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for (MariaDBServer* server : targets)
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{
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string error_msg;
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if (!server->execute_cmd(query, &error_msg))
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{
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error = true;
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PRINT_MXS_JSON_ERROR(error_out, "%s", error_msg.c_str());
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break;
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}
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}
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}
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};
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// Step 2: Stop and reset all slave connections, even external ones.
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for (MariaDBServer* server : targets)
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{
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if (!server->reset_all_slave_conns(error_out))
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{
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error = true;
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break;
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}
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}
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// In theory, this is wrong if there are no slaves. Cluster is modified soon anyway.
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m_cluster_modified = true;
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// Step 3: Set read_only and disable events.
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exec_cmd_on_array(targets, "SET GLOBAL read_only=1;", error_out);
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if (!error)
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{
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MXB_NOTICE("read_only set on affected servers.");
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if (m_handle_event_scheduler)
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{
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for (MariaDBServer* server : targets)
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{
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if (!server->disable_events(MariaDBServer::BinlogMode::BINLOG_OFF, error_out))
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{
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error = true;
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break;
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}
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}
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}
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}
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// Step 4: delete binary logs.
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exec_cmd_on_array(targets, "RESET MASTER;", error_out);
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if (!error)
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{
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MXB_NOTICE("Binary logs deleted (RESET MASTER) on affected servers.");
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}
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// Step 5: Set gtid_slave_pos on all servers. This is also sets gtid_current_pos since binary logs
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// have been deleted.
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if (!error)
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{
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string slave_pos = string_printf("%" PRIi64 "-%" PRIi64 "-0",
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new_master->m_gtid_domain_id, new_master->m_server_id);
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string set_slave_pos = string_printf("SET GLOBAL gtid_slave_pos='%s';", slave_pos.c_str());
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exec_cmd_on_array(targets, set_slave_pos, error_out);
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if (!error)
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{
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MXB_NOTICE("gtid_slave_pos set to '%s' on affected servers.", slave_pos.c_str());
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}
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}
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if (!error)
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{
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// Step 6: Enable writing and events on new master.
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string error_msg;
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if (new_master->execute_cmd("SET GLOBAL read_only=0;", &error_msg))
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{
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m_next_master = new_master;
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if (!new_master->enable_events(error_out))
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{
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error = true;
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}
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}
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else
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{
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error = true;
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PRINT_MXS_JSON_ERROR(error_out,
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"Could not enable writes on '%s': %s",
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new_master->name(), error_msg.c_str());
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}
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if (m_next_master == new_master)
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{
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// Step 7: Set all slaves to replicate from the master. Perform this step even if enabling
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// events failed.
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// The following commands are only sent to slaves.
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auto location = std::find(targets.begin(), targets.end(), new_master);
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targets.erase(location);
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// TODO: the following call does stop slave & reset slave again. Fix this later, although it
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// doesn't cause error.
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ServerArray dummy;
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if ((size_t)redirect_slaves(new_master, targets, &dummy) == targets.size())
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{
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// TODO: Properly check check slave IO/SQL threads.
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MXS_NOTICE("All slaves redirected successfully.");
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}
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else
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{
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error = true;
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PRINT_MXS_JSON_ERROR(error_out,
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"Some servers were not redirected to '%s'.", new_master->name());
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}
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}
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}
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if (error)
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{
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PRINT_MXS_JSON_ERROR(error_out, "Replication reset failed or succeeded only partially. "
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"Server cluster may be in an invalid state for replication.");
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}
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rval = !error;
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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,
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const ServerArray& slaves,
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ServerArray* redirected_slaves)
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{
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mxb_assert(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 (MariaDBServer* slave : slaves)
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{
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if (slave->redirect_one_slave(change_cmd))
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{
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successes++;
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redirected_slaves->push_back(slave);
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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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* Redirect slaves to replicate from the promotion target.
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*
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* @param op Operation descriptor
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* @param slaves An array of slaves to redirect
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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_ex(ClusterOperation& op, const ServerArray& slaves,
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ServerArray* redirected_slaves)
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{
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mxb_assert(redirected_slaves != NULL);
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if (slaves.empty())
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{
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// This is ok, nothing to do.
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return 0;
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}
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string slave_names = monitored_servers_to_string(slaves);
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MXS_NOTICE("Redirecting %s to replicate from %s instead of %s.",
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slave_names.c_str(), op.promotion_target->name(), op.demotion_target->name());
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int successes = 0;
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for (MariaDBServer* redirectable : slaves)
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{
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if (redirectable->redirect_existing_slave_conn(op))
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{
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successes++;
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redirected_slaves->push_back(redirectable);
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}
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}
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if (size_t(successes) == slaves.size())
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{
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MXS_NOTICE("All redirects successful.");
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}
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else
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{
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MXS_WARNING("%lu out of %lu redirects failed.", slaves.size() - successes, slaves.size());
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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(),
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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,
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"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;
|
|
SERVER* new_master_server = new_master->m_server_base->server;
|
|
|
|
string change_cmd = generate_change_master_cmd(new_master_server->address, new_master_server->port);
|
|
if (mxs_mysql_query(old_master_con, change_cmd.c_str()) == 0
|
|
&& mxs_mysql_query(old_master_con, "START SLAVE;") == 0)
|
|
{
|
|
MXS_NOTICE("Old master '%s' starting replication from '%s'.",
|
|
old_master->name(),
|
|
new_master->name());
|
|
rval = true;
|
|
}
|
|
else
|
|
{
|
|
MXS_ERROR("Old master '%s' could not start replication: '%s'.",
|
|
old_master->name(),
|
|
mysql_error(old_master_con));
|
|
}
|
|
return rval;
|
|
}
|
|
|
|
/**
|
|
* (Re)join given servers to the cluster. The servers in the array are assumed to be joinable.
|
|
* Usually the list is created by get_joinable_servers().
|
|
*
|
|
* @param joinable_servers Which servers to rejoin
|
|
* @param output Error output. Can be null.
|
|
* @return The number of servers successfully rejoined
|
|
*/
|
|
uint32_t MariaDBMonitor::do_rejoin(const ServerArray& joinable_servers, json_t** output)
|
|
{
|
|
SERVER* master_server = m_master->m_server_base->server;
|
|
const char* master_name = master_server->name;
|
|
uint32_t servers_joined = 0;
|
|
if (!joinable_servers.empty())
|
|
{
|
|
string change_cmd = generate_change_master_cmd(master_server->address, master_server->port);
|
|
for (MariaDBServer* joinable : joinable_servers)
|
|
{
|
|
const char* name = joinable->name();
|
|
bool op_success = false;
|
|
|
|
if (joinable->m_slave_status.empty())
|
|
{
|
|
if (!m_demote_sql_file.empty() && !joinable->run_sql_from_file(m_demote_sql_file, output))
|
|
{
|
|
PRINT_MXS_JSON_ERROR(output,
|
|
"%s execution failed when attempting to rejoin server '%s'.",
|
|
CN_DEMOTION_SQL_FILE,
|
|
joinable->name());
|
|
}
|
|
else
|
|
{
|
|
MXS_NOTICE("Directing standalone server '%s' to replicate from '%s'.", name, master_name);
|
|
op_success = joinable->join_cluster(change_cmd, m_handle_event_scheduler);
|
|
}
|
|
}
|
|
else
|
|
{
|
|
MXS_NOTICE("Server '%s' is replicating from a server other than '%s', "
|
|
"redirecting it to '%s'.",
|
|
name,
|
|
master_name,
|
|
master_name);
|
|
op_success = joinable->redirect_one_slave(change_cmd);
|
|
}
|
|
|
|
if (op_success)
|
|
{
|
|
servers_joined++;
|
|
m_cluster_modified = true;
|
|
}
|
|
}
|
|
}
|
|
return servers_joined;
|
|
}
|
|
|
|
/**
|
|
* Check if the cluster is a valid rejoin target.
|
|
*
|
|
* @return True if master and gtid domain are known
|
|
*/
|
|
bool MariaDBMonitor::cluster_can_be_joined()
|
|
{
|
|
return m_master != NULL && m_master->is_master() && m_master_gtid_domain != GTID_DOMAIN_UNKNOWN;
|
|
}
|
|
|
|
/**
|
|
* Scan the servers in the cluster and add (re)joinable servers to an array.
|
|
*
|
|
* @param mon Cluster monitor
|
|
* @param output Array to save results to. Each element is a valid (re)joinable server according
|
|
* to latest data.
|
|
* @return False, if there were possible rejoinable servers but communications error to master server
|
|
* prevented final checks.
|
|
*/
|
|
bool MariaDBMonitor::get_joinable_servers(ServerArray* output)
|
|
{
|
|
mxb_assert(output);
|
|
|
|
// Whether a join operation should be attempted or not depends on several criteria. Start with the ones
|
|
// easiest to test. Go though all slaves and construct a preliminary list.
|
|
ServerArray suspects;
|
|
for (MariaDBServer* server : m_servers)
|
|
{
|
|
if (server_is_rejoin_suspect(server, NULL))
|
|
{
|
|
suspects.push_back(server);
|
|
}
|
|
}
|
|
|
|
// Update Gtid of master for better info.
|
|
bool comm_ok = true;
|
|
if (!suspects.empty())
|
|
{
|
|
if (m_master->update_gtids())
|
|
{
|
|
for (size_t i = 0; i < suspects.size(); i++)
|
|
{
|
|
string rejoin_err_msg;
|
|
if (suspects[i]->can_replicate_from(m_master, &rejoin_err_msg))
|
|
{
|
|
output->push_back(suspects[i]);
|
|
}
|
|
else if (m_warn_cannot_rejoin)
|
|
{
|
|
// Print a message explaining why an auto-rejoin is not done. Suppress printing.
|
|
MXS_WARNING("Automatic rejoin was not attempted on server '%s' even though it is a "
|
|
"valid candidate. Will keep retrying with this message suppressed for all "
|
|
"servers. Errors: \n%s",
|
|
suspects[i]->name(),
|
|
rejoin_err_msg.c_str());
|
|
m_warn_cannot_rejoin = false;
|
|
}
|
|
}
|
|
}
|
|
else
|
|
{
|
|
comm_ok = false;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
m_warn_cannot_rejoin = true;
|
|
}
|
|
return comm_ok;
|
|
}
|
|
|
|
/**
|
|
* Checks if a server is a possible rejoin candidate. A true result from this function is not yet sufficient
|
|
* criteria and another call to can_replicate_from() should be made.
|
|
*
|
|
* @param rejoin_cand Server to check
|
|
* @param output Error output. If NULL, no error is printed to log.
|
|
* @return True, if server is a rejoin suspect.
|
|
*/
|
|
bool MariaDBMonitor::server_is_rejoin_suspect(MariaDBServer* rejoin_cand, json_t** output)
|
|
{
|
|
bool is_suspect = false;
|
|
if (rejoin_cand->is_usable() && !rejoin_cand->is_master())
|
|
{
|
|
// Has no slave connection, yet is not a master.
|
|
if (rejoin_cand->m_slave_status.empty())
|
|
{
|
|
is_suspect = true;
|
|
}
|
|
// Or has existing slave connection ...
|
|
else if (rejoin_cand->m_slave_status.size() == 1)
|
|
{
|
|
SlaveStatus* slave_status = &rejoin_cand->m_slave_status[0];
|
|
// which is connected to master but it's the wrong one
|
|
if (slave_status->slave_io_running == SlaveStatus::SLAVE_IO_YES
|
|
&& slave_status->master_server_id != m_master->m_server_id)
|
|
{
|
|
is_suspect = true;
|
|
}
|
|
// or is disconnected but master host or port is wrong.
|
|
else if (slave_status->slave_io_running == SlaveStatus::SLAVE_IO_CONNECTING
|
|
&& slave_status->slave_sql_running
|
|
&& (slave_status->master_host != m_master->m_server_base->server->address
|
|
|| slave_status->master_port != m_master->m_server_base->server->port))
|
|
{
|
|
is_suspect = true;
|
|
}
|
|
}
|
|
|
|
if (output != NULL && !is_suspect)
|
|
{
|
|
/* User has requested a manual rejoin but with a server which has multiple slave connections or
|
|
* is already connected or trying to connect to the correct master. TODO: Slave IO stopped is
|
|
* not yet handled perfectly. */
|
|
if (rejoin_cand->m_slave_status.size() > 1)
|
|
{
|
|
const char MULTI_SLAVE[] = "Server '%s' has multiple slave connections, cannot rejoin.";
|
|
PRINT_MXS_JSON_ERROR(output, MULTI_SLAVE, rejoin_cand->name());
|
|
}
|
|
else
|
|
{
|
|
const char CONNECTED[] = "Server '%s' is already connected or trying to connect to the "
|
|
"correct master server.";
|
|
PRINT_MXS_JSON_ERROR(output, CONNECTED, rejoin_cand->name());
|
|
}
|
|
}
|
|
}
|
|
else if (output != NULL)
|
|
{
|
|
PRINT_MXS_JSON_ERROR(output, "Server '%s' is master or not running.", rejoin_cand->name());
|
|
}
|
|
return is_suspect;
|
|
}
|
|
|
|
/**
|
|
* Performs switchover for a simple topology (1 master, N slaves, no intermediate masters). If an
|
|
* intermediate step fails, the cluster may be left without a master and manual intervention is
|
|
* required to fix things.
|
|
*
|
|
* @param op Operation descriptor
|
|
* @return True if successful. If false, replication may be broken.
|
|
*/
|
|
bool MariaDBMonitor::switchover_perform(ClusterOperation& op)
|
|
{
|
|
MariaDBServer* const promotion_target = op.promotion_target;
|
|
MariaDBServer* const demotion_target = op.demotion_target;
|
|
json_t** const error_out = op.error_out;
|
|
mxb_assert(promotion_target && demotion_target);
|
|
|
|
// 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 gtid:s.
|
|
if (demotion_target->demote(op))
|
|
{
|
|
m_cluster_modified = true;
|
|
bool catchup_and_promote_success = false;
|
|
StopWatch timer;
|
|
// Step 3: Wait for the promotion target to catch up with the demotion target. Disregard the other
|
|
// slaves of the promotion target to avoid needless waiting.
|
|
// The gtid:s of the demotion target were updated at the end of demotion.
|
|
if (promotion_target->catchup_to_master(op))
|
|
{
|
|
MXS_INFO("Switchover: Catchup took %.1f seconds.", timer.lap().secs());
|
|
// Step 4: On new master: remove slave connections, set read-only to OFF etc.
|
|
if (promotion_target->promote(op))
|
|
{
|
|
// Point of no return. Even if following steps fail, do not try to undo.
|
|
// Switchover considered at least partially successful.
|
|
catchup_and_promote_success = true;
|
|
rval = true;
|
|
if (op.demotion_target_is_master)
|
|
{
|
|
// Force a master swap on next tick.
|
|
m_next_master = promotion_target;
|
|
}
|
|
|
|
timer.restart();
|
|
// 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);
|
|
}
|
|
op.time_remaining -= timer.lap();
|
|
|
|
int redirects = redirect_slaves_ex(op, redirectable_slaves, &redirected_slaves);
|
|
|
|
bool success = redirectable_slaves.empty() ? start_ok : start_ok || redirects > 0;
|
|
if (success)
|
|
{
|
|
timer.restart();
|
|
// Step 6: Finally, check that slaves are replicating.
|
|
wait_cluster_stabilization(op, redirected_slaves);
|
|
auto step6_duration = timer.lap();
|
|
MXS_INFO("Switchover: slave replication confirmation took %.1f seconds with "
|
|
"%.1f seconds to spare.",
|
|
step6_duration.secs(), op.time_remaining.secs());
|
|
}
|
|
}
|
|
}
|
|
|
|
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(error_out, "read_only disabled on server %s.", demotion_target->name());
|
|
}
|
|
else
|
|
{
|
|
PRINT_MXS_JSON_ERROR(error_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, error_out);
|
|
}
|
|
}
|
|
}
|
|
return rval;
|
|
}
|
|
|
|
/**
|
|
* Performs failover for a simple topology (1 master, N slaves, no intermediate masters).
|
|
*
|
|
* @param op Operation descriptor
|
|
* @return True if successful
|
|
*/
|
|
bool MariaDBMonitor::failover_perform(ClusterOperation& op)
|
|
{
|
|
mxb_assert(op.promotion_target && op.demotion_target);
|
|
MariaDBServer* const promotion_target = op.promotion_target;
|
|
|
|
// Step 1: Populate a vector with all slaves not the selected master.
|
|
ServerArray redirectable_slaves = get_redirectables(promotion_target, op.demotion_target);
|
|
|
|
bool rval = false;
|
|
// Step 2: Stop and reset slave, set read-only to OFF.
|
|
if (promotion_target->promote(op))
|
|
{
|
|
// Point of no return. Even if following steps fail, do not try to undo. Failover considered
|
|
// at least partially successful.
|
|
rval = true;
|
|
m_cluster_modified = true;
|
|
if (op.demotion_target_is_master)
|
|
{
|
|
// Force a master swap on next tick.
|
|
m_next_master = promotion_target;
|
|
}
|
|
|
|
// Step 3: Redirect slaves.
|
|
ServerArray redirected_slaves;
|
|
redirect_slaves_ex(op, redirectable_slaves, &redirected_slaves);
|
|
if (!redirected_slaves.empty())
|
|
{
|
|
StopWatch timer;
|
|
/* Step 4: Finally, check that slaves are connected to the new master. Even if
|
|
* time is out at this point, wait_cluster_stabilization() will check the slaves
|
|
* once so that latest status is printed. */
|
|
wait_cluster_stabilization(op, redirected_slaves);
|
|
MXS_INFO("Failover: slave replication confirmation took %.1f seconds with "
|
|
"%.1f seconds to spare.",
|
|
timer.lap().secs(), op.time_remaining.secs());
|
|
}
|
|
}
|
|
return rval;
|
|
}
|
|
|
|
/**
|
|
* Check that the given slaves are connected and replicating from the new master. Only checks
|
|
* the SLAVE STATUS of the slaves.
|
|
*
|
|
* @param op Operation descriptor
|
|
* @param redirected_slaves Slaves to check
|
|
*/
|
|
void MariaDBMonitor::wait_cluster_stabilization(ClusterOperation& op, const ServerArray& redirected_slaves)
|
|
{
|
|
if (redirected_slaves.empty())
|
|
{
|
|
// No need to check anything or print messages.
|
|
return;
|
|
}
|
|
|
|
StopWatch timer;
|
|
const MariaDBServer* new_master = op.promotion_target;
|
|
// Check all the servers in the list. Using a set because erasing from container.
|
|
std::set<MariaDBServer*> unconfirmed(redirected_slaves.begin(), redirected_slaves.end());
|
|
ServerArray successes;
|
|
ServerArray repl_fails;
|
|
ServerArray query_fails;
|
|
bool time_is_up = false; // Try at least once, even if time is up.
|
|
|
|
while (!unconfirmed.empty() && !time_is_up)
|
|
{
|
|
auto iter = unconfirmed.begin();
|
|
while (iter != unconfirmed.end())
|
|
{
|
|
MariaDBServer* slave = *iter;
|
|
if (slave->do_show_slave_status())
|
|
{
|
|
auto slave_conn = slave->slave_connection_status_host_port(new_master);
|
|
if (slave_conn == NULL)
|
|
{
|
|
// Highly unlikely. Maybe someone just removed the slave connection after it was created.
|
|
MXS_WARNING("%s does not have a slave connection to %s although one should have "
|
|
"been created.",
|
|
slave->name(), new_master->name());
|
|
repl_fails.push_back(*iter);
|
|
iter = unconfirmed.erase(iter);
|
|
}
|
|
else if (slave_conn->slave_io_running == SlaveStatus::SLAVE_IO_YES
|
|
&& slave_conn->slave_sql_running == true)
|
|
{
|
|
// This slave has connected to master and replication seems to be ok.
|
|
successes.push_back(*iter);
|
|
iter = unconfirmed.erase(iter);
|
|
}
|
|
else if (slave_conn->slave_io_running == SlaveStatus::SLAVE_IO_NO)
|
|
{
|
|
// IO error on slave
|
|
MXS_WARNING("%s cannot start replication because of IO thread error: '%s'.",
|
|
slave_conn->to_short_string(slave->name()).c_str(),
|
|
slave_conn->last_error.c_str());
|
|
repl_fails.push_back(*iter);
|
|
iter = unconfirmed.erase(iter);
|
|
}
|
|
else if (slave_conn->slave_sql_running == false)
|
|
{
|
|
// SQL error on slave
|
|
MXS_WARNING("%s cannot start replication because of SQL thread error: '%s'.",
|
|
slave_conn->to_short_string(slave->name()).c_str(),
|
|
slave_conn->last_error.c_str());
|
|
repl_fails.push_back(*iter);
|
|
iter = unconfirmed.erase(iter);
|
|
}
|
|
else
|
|
{
|
|
// Slave IO is still connecting, must wait.
|
|
++iter;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
query_fails.push_back(*iter);
|
|
iter = unconfirmed.erase(iter);
|
|
}
|
|
}
|
|
|
|
op.time_remaining -= timer.lap();
|
|
if (!unconfirmed.empty())
|
|
{
|
|
if (op.time_remaining.secs() > 0)
|
|
{
|
|
double standard_sleep = 0.5; // In seconds.
|
|
// If we have unconfirmed slaves and have time remaining, sleep a bit and try again.
|
|
/* TODO: This sleep is kinda pointless, because whether or not replication begins,
|
|
* all operations for failover/switchover are complete. The sleep is only required to
|
|
* get correct messages to the user. Think about removing it, or shortening the maximum
|
|
* time of this function. */
|
|
Duration sleep_time = (op.time_remaining.secs() > standard_sleep) ?
|
|
Duration(standard_sleep) : op.time_remaining;
|
|
std::this_thread::sleep_for(sleep_time);
|
|
}
|
|
else
|
|
{
|
|
// Have undecided slaves and is out of time.
|
|
time_is_up = true;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (successes.size() == redirected_slaves.size())
|
|
{
|
|
// Complete success.
|
|
MXS_NOTICE("All redirected slaves successfully started replication from %s.", new_master->name());
|
|
}
|
|
else
|
|
{
|
|
if (!successes.empty())
|
|
{
|
|
MXS_NOTICE("%s successfully started replication from %s.",
|
|
monitored_servers_to_string(successes).c_str(), new_master->name());
|
|
}
|
|
// Something went wrong.
|
|
auto fails = query_fails.size() + repl_fails.size() + unconfirmed.size();
|
|
const char MSG[] = "%lu slaves did not start replicating from %s. "
|
|
"%lu encountered an I/O or SQL error, %lu failed to reply and %lu did not "
|
|
"connect to %s within the time limit.";
|
|
MXS_WARNING(MSG, fails, new_master->name(), repl_fails.size(), query_fails.size(),
|
|
unconfirmed.size(), new_master->name());
|
|
}
|
|
op.time_remaining -= timer.lap();
|
|
}
|
|
|
|
/**
|
|
* Select a promotion target for failover/switchover. Looks at the slaves of 'demotion_target' and selects
|
|
* the server with the most up-do-date event or, if events are equal, the one with the best settings and
|
|
* status.
|
|
*
|
|
* @param demotion_target The former master server/relay
|
|
* @param op Switchover or failover
|
|
* @param log_mode Print log or operate silently
|
|
* @param error_out Error output
|
|
* @return The selected promotion target or NULL if no valid candidates
|
|
*/
|
|
MariaDBServer* MariaDBMonitor::select_promotion_target(MariaDBServer* demotion_target,
|
|
OperationType 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);
|
|
// Print some warnings about the candidate server.
|
|
if (log_mode == Log::ON)
|
|
{
|
|
cand->warn_replication_settings();
|
|
}
|
|
}
|
|
}
|
|
|
|
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;
|
|
int64_t gtid_domain = m_master_gtid_domain;
|
|
for (MariaDBServer* cand : candidates)
|
|
{
|
|
if (is_candidate_better(cand, current_best, demotion_target, 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 : valid_but_excluded)
|
|
{
|
|
const char* excluded_name = excluded->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, current_best, demotion_target, 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 (MariaDBServer* excluded : m_excluded_servers)
|
|
{
|
|
if (excluded == 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 demotion_target Server which will be demoted
|
|
* @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,
|
|
const MariaDBServer* demotion_target,
|
|
uint32_t gtid_domain,
|
|
std::string* reason_out)
|
|
{
|
|
const SlaveStatus* cand_slave_conn = candidate->slave_connection_status(demotion_target);
|
|
const SlaveStatus* curr_best_slave_conn = current_best->slave_connection_status(demotion_target);
|
|
mxb_assert(cand_slave_conn && curr_best_slave_conn);
|
|
|
|
uint64_t cand_io = cand_slave_conn->gtid_io_pos.get_gtid(gtid_domain).m_sequence;
|
|
uint64_t curr_io = curr_best_slave_conn->gtid_io_pos.get_gtid(gtid_domain).m_sequence;
|
|
string reason;
|
|
bool is_better = false;
|
|
// 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 error_out Error output
|
|
* @return Operation object if cluster is suitable and failover may proceed, or NULL on error
|
|
*/
|
|
unique_ptr<ClusterOperation> MariaDBMonitor::failover_prepare(Log log_mode, json_t** error_out)
|
|
{
|
|
// This function resembles 'switchover_prepare', but does not yet support manual selection.
|
|
|
|
// 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, OperationType::FAILOVER,
|
|
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);
|
|
}
|
|
|
|
unique_ptr<ClusterOperation> rval;
|
|
if (promotion_target && demotion_target && gtid_ok)
|
|
{
|
|
const SlaveStatus* slave_conn = promotion_target->slave_connection_status(demotion_target);
|
|
mxb_assert(slave_conn);
|
|
uint64_t events = promotion_target->relay_log_events(*slave_conn);
|
|
if (events > 0)
|
|
{
|
|
// The relay log of the promotion target is not yet clear. This is not really an error,
|
|
// but should be communicated to the user in the case of manual failover. For automatic
|
|
// failover, it's best to just try again during the next monitor iteration. The difference
|
|
// to a typical prepare-fail is that the relay log status should be logged
|
|
// repeatedly since it is likely to change continuously.
|
|
if (error_out || log_mode == Log::ON)
|
|
{
|
|
const char unproc_fmt[] =
|
|
"The relay log of '%s' has %" PRIu64
|
|
" unprocessed events (Gtid_IO_Pos: %s, Gtid_Current_Pos: %s).";
|
|
string unproc_events = string_printf(unproc_fmt, promotion_target->name(), events,
|
|
slave_conn->gtid_io_pos.to_string().c_str(),
|
|
promotion_target->m_gtid_current_pos.to_string().c_str());
|
|
if (error_out)
|
|
{
|
|
/* Print a bit more helpful error for the user, goes to log too.
|
|
* This should be a very rare occurrence: either the dba managed to start failover
|
|
* really fast, or the relay log is massive. In the latter case it's ok
|
|
* that the monitor does not do the waiting since there is no telling how long
|
|
* the wait will be. */
|
|
const char wait_relay_log[] =
|
|
"%s To avoid data loss, failover should be postponed until "
|
|
"the log has been processed. Please try again later.";
|
|
string error_msg = string_printf(wait_relay_log, unproc_events.c_str());
|
|
PRINT_MXS_JSON_ERROR(error_out, "%s", error_msg.c_str());
|
|
}
|
|
else if (log_mode == Log::ON)
|
|
{
|
|
// For automatic failover the message is more typical. TODO: Think if this message should
|
|
// be logged more often.
|
|
MXS_WARNING("%s To avoid data loss, failover is postponed until the log "
|
|
"has been processed.", unproc_events.c_str());
|
|
}
|
|
}
|
|
}
|
|
else
|
|
{
|
|
// The Duration ctor taking a double interprets is as seconds.
|
|
auto time_limit = maxbase::Duration((double)m_failover_timeout);
|
|
rval.reset(new ClusterOperation(OperationType::FAILOVER,
|
|
promotion_target, demotion_target,
|
|
demotion_target == m_master, m_handle_event_scheduler,
|
|
m_promote_sql_file, m_demote_sql_file,
|
|
m_replication_user, m_replication_password,
|
|
error_out, time_limit));
|
|
}
|
|
}
|
|
return rval;
|
|
}
|
|
|
|
/**
|
|
* @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()
|
|
{
|
|
if (m_master == NULL || m_master->is_running())
|
|
{
|
|
// No need for failover. This also applies if master is in maintenance, because that is a user
|
|
// problem.
|
|
m_warn_master_down = true;
|
|
m_warn_failover_precond = true;
|
|
return;
|
|
}
|
|
|
|
int master_down_count = m_master->m_server_base->mon_err_count;
|
|
const MariaDBServer* connected_slave = NULL;
|
|
Duration event_age;
|
|
Duration delay_time;
|
|
|
|
if (m_failcount > 1 && m_warn_master_down)
|
|
{
|
|
int monitor_passes = m_failcount - master_down_count;
|
|
MXS_WARNING("Master has failed. If master status does not change in %d monitor passes, failover "
|
|
"begins.",
|
|
(monitor_passes > 1) ? monitor_passes : 1);
|
|
m_warn_master_down = false;
|
|
}
|
|
// If master seems to be down, check if slaves are receiving events.
|
|
else if (m_verify_master_failure
|
|
&& (connected_slave = slave_receiving_events(m_master, &event_age, &delay_time)) != NULL)
|
|
{
|
|
MXS_NOTICE("Slave %s is still connected to %s and received a new gtid or heartbeat event %.1f "
|
|
"seconds ago. Delaying failover for at least %.1f seconds.",
|
|
connected_slave->name(), m_master->name(), event_age.secs(), delay_time.secs());
|
|
}
|
|
else if (master_down_count >= m_failcount)
|
|
{
|
|
// Failover is required, but first we should check if preconditions are met.
|
|
Log log_mode = m_warn_failover_precond ? Log::ON : Log::OFF;
|
|
auto op = failover_prepare(log_mode, NULL);
|
|
if (op)
|
|
{
|
|
m_warn_failover_precond = true;
|
|
MXS_NOTICE("Performing automatic failover to replace failed master '%s'.", m_master->name());
|
|
if (failover_perform(*op))
|
|
{
|
|
MXS_NOTICE(FAILOVER_OK, op->demotion_target->name(), op->promotion_target->name());
|
|
}
|
|
else
|
|
{
|
|
MXS_ERROR(FAILOVER_FAIL, op->demotion_target->name(), op->promotion_target->name());
|
|
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 most error messages "
|
|
"suppressed.");
|
|
m_warn_failover_precond = false;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Is the topology such that failover and switchover are supported, even if not required just yet?
|
|
* Print errors and disable the settings if this is not the case.
|
|
*/
|
|
void MariaDBMonitor::check_cluster_operations_support()
|
|
{
|
|
bool supported = true;
|
|
DelimitedPrinter printer("\n");
|
|
string all_reasons;
|
|
// 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)
|
|
{
|
|
supported = false;
|
|
auto reason = string_printf("The version of server %s is not supported. Failover/switchover "
|
|
"requires MariaDB 10.X.",
|
|
server->name());
|
|
printer.cat(all_reasons, reason);
|
|
}
|
|
|
|
if (server->is_slave() && !server->m_slave_status.empty())
|
|
{
|
|
for (const auto& slave_conn : server->m_slave_status)
|
|
{
|
|
if (slave_conn.gtid_io_pos.empty())
|
|
{
|
|
supported = false;
|
|
auto reason = string_printf("%s is not using gtid-replication.",
|
|
slave_conn.to_short_string(server->name()).c_str());
|
|
printer.cat(all_reasons, reason);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
if (!supported)
|
|
{
|
|
const char PROBLEMS[] =
|
|
"The backend cluster does not support failover/switchover due to the following reason(s):\n"
|
|
"%s\n"
|
|
"Automatic failover/switchover has been disabled. They should only be enabled "
|
|
"after the above issues have been resolved.";
|
|
string p1 = string_printf(PROBLEMS, all_reasons.c_str());
|
|
string p2 = string_printf(RE_ENABLE_FMT, "failover", CN_AUTO_FAILOVER, m_monitor->name);
|
|
string p3 = string_printf(RE_ENABLE_FMT, "switchover", CN_SWITCHOVER_ON_LOW_DISK_SPACE,
|
|
m_monitor->name);
|
|
string total_msg = p1 + " " + p2 + " " + p3;
|
|
MXS_ERROR("%s", total_msg.c_str());
|
|
|
|
if (m_auto_failover)
|
|
{
|
|
m_auto_failover = false;
|
|
disable_setting(CN_AUTO_FAILOVER);
|
|
}
|
|
if (m_switchover_on_low_disk_space)
|
|
{
|
|
m_switchover_on_low_disk_space = false;
|
|
disable_setting(CN_SWITCHOVER_ON_LOW_DISK_SPACE);
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Check if a slave is receiving events from master. Returns the first slave that is both
|
|
* connected (or not realized the disconnect yet) and has an event more recent than
|
|
* master_failure_timeout. The age of the event is written in 'event_age_out'.
|
|
*
|
|
* @param demotion_target The server whose slaves should be checked
|
|
* @param event_age_out Output for event age
|
|
* @return The first connected slave or NULL if none found
|
|
*/
|
|
const MariaDBServer* MariaDBMonitor::slave_receiving_events(const MariaDBServer* demotion_target,
|
|
Duration* event_age_out, Duration* delay_out)
|
|
{
|
|
Duration event_timeout(static_cast<double>(m_master_failure_timeout));
|
|
auto current_time = maxbase::Clock::now();
|
|
maxbase::Clock::time_point recent_event_time = current_time - event_timeout;
|
|
|
|
const MariaDBServer* connected_slave = NULL;
|
|
for (MariaDBServer* slave : demotion_target->m_node.children)
|
|
{
|
|
const SlaveStatus* slave_conn = NULL;
|
|
if (slave->is_running()
|
|
&& (slave_conn = slave->slave_connection_status(demotion_target)) != NULL
|
|
&& slave_conn->slave_io_running == SlaveStatus::SLAVE_IO_YES
|
|
&& slave_conn->last_data_time >= recent_event_time)
|
|
{
|
|
// 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.
|
|
connected_slave = slave;
|
|
auto latest_event_age = current_time - slave_conn->last_data_time;
|
|
*event_age_out = latest_event_age;
|
|
*delay_out = event_timeout - latest_event_age;
|
|
break;
|
|
}
|
|
}
|
|
return connected_slave;
|
|
}
|
|
|
|
/**
|
|
* 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 error_out Error output
|
|
* @return Operation object if cluster is suitable and switchover may proceed, or NULL on error
|
|
*/
|
|
unique_ptr<ClusterOperation> MariaDBMonitor::switchover_prepare(SERVER* promotion_server,
|
|
SERVER* demotion_server,
|
|
Log log_mode,
|
|
json_t** error_out)
|
|
{
|
|
// Check that both servers are ok if specified, or autoselect them. Demotion target must be checked
|
|
// first since the promotion target depends on it.
|
|
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;
|
|
}
|
|
}
|
|
|
|
const auto op_type = OperationType::SWITCHOVER;
|
|
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_type, 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_type,
|
|
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);
|
|
}
|
|
|
|
unique_ptr<ClusterOperation> rval;
|
|
if (promotion_target && demotion_target && gtid_ok)
|
|
{
|
|
maxbase::Duration time_limit((double)m_switchover_timeout);
|
|
rval.reset(new ClusterOperation(op_type,
|
|
promotion_target, demotion_target,
|
|
demotion_target == m_master, m_handle_event_scheduler,
|
|
m_promote_sql_file, m_demote_sql_file,
|
|
m_replication_user, m_replication_password,
|
|
error_out, time_limit));
|
|
}
|
|
return rval;
|
|
}
|
|
|
|
void MariaDBMonitor::enforce_read_only_on_slaves()
|
|
{
|
|
const char QUERY[] = "SET GLOBAL read_only=1;";
|
|
for (MariaDBServer* server : m_servers)
|
|
{
|
|
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.
|
|
Log log_mode = m_warn_switchover_precond ? Log::ON : Log::OFF;
|
|
auto op = switchover_prepare(NULL, m_master->m_server_base->server, log_mode, NULL);
|
|
if (op)
|
|
{
|
|
m_warn_switchover_precond = true;
|
|
bool switched = switchover_perform(*op);
|
|
if (switched)
|
|
{
|
|
MXS_NOTICE(SWITCHOVER_OK, op->demotion_target->name(), op->promotion_target->name());
|
|
}
|
|
else
|
|
{
|
|
MXS_ERROR(SWITCHOVER_FAIL, op->demotion_target->name(), op->promotion_target->name());
|
|
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->is_usable() && 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;
|
|
}
|