/* * Copyright (c) 2018 MariaDB Corporation Ab * * Use of this software is governed by the Business Source License included * in the LICENSE.TXT file and at www.mariadb.com/bsl11. * * Change Date: 2022-01-01 * * On the date above, in accordance with the Business Source License, use * of this software will be governed by version 2 or later of the General * Public License. */ #include "mariadbmon.hh" #include #include #include #include using std::string; using maxscale::string_printf; static void print_redirect_errors(MariaDBServer* first_server, const ServerArray& servers, json_t** err_out); bool MariaDBMonitor::manual_switchover(SERVER* new_master, SERVER* current_master, json_t** error_out) { /* It's possible for either current_master, or both new_master & current_master to be NULL, which means * autoselect. Only autoselecting new_master is not possible. Autoselection will happen at the actual * switchover function. */ MariaDBServer *found_new_master = NULL, *found_curr_master = NULL; auto ok_to_switch = switchover_check(new_master, current_master, &found_new_master, &found_curr_master, error_out); bool rval = false; if (ok_to_switch) { bool switched = do_switchover(&found_curr_master, &found_new_master, error_out); const char AUTOSELECT[] = ""; const char* curr_master_name = found_curr_master ? found_curr_master->name() : AUTOSELECT; const char* new_master_name = found_new_master ? found_new_master->name() : AUTOSELECT; if (switched) { MXS_NOTICE("Switchover %s -> %s performed.", curr_master_name, new_master_name); rval = true; } else { string format = "Switchover %s -> %s failed"; bool failover_setting = config_get_bool(m_monitor->parameters, CN_AUTO_FAILOVER); if (failover_setting) { disable_setting(CN_AUTO_FAILOVER); format += ", automatic failover has been disabled."; } format += "."; PRINT_MXS_JSON_ERROR(error_out, format.c_str(), curr_master_name, new_master_name); } } return rval; } bool MariaDBMonitor::manual_failover(json_t** output) { bool rv = true; string failover_error; rv = failover_check(&failover_error); if (rv) { rv = do_failover(output); if (rv) { MXS_NOTICE("Failover performed."); } else { PRINT_MXS_JSON_ERROR(output, "Failover failed."); } } else { PRINT_MXS_JSON_ERROR(output, "Failover not performed due to the following errors: \n%s", failover_error.c_str()); } return rv; } bool MariaDBMonitor::manual_rejoin(SERVER* rejoin_server, json_t** output) { bool rval = false; if (cluster_can_be_joined()) { const char* rejoin_serv_name = rejoin_server->name; MXS_MONITORED_SERVER* mon_slave_cand = mon_get_monitored_server(m_monitor, rejoin_server); if (mon_slave_cand) { MariaDBServer* slave_cand = get_server_info(mon_slave_cand); if (server_is_rejoin_suspect(slave_cand, output)) { if (m_master->update_gtids()) { string no_rejoin_reason; if (slave_cand->can_replicate_from(m_master, &no_rejoin_reason)) { ServerArray joinable_server; joinable_server.push_back(slave_cand); if (do_rejoin(joinable_server, output) == 1) { rval = true; MXS_NOTICE("Rejoin performed."); } else { PRINT_MXS_JSON_ERROR(output, "Rejoin attempted but failed."); } } else { PRINT_MXS_JSON_ERROR(output, "Server '%s' cannot replicate from cluster master '%s': " "%s.", rejoin_serv_name, m_master->name(), no_rejoin_reason.c_str()); } } else { PRINT_MXS_JSON_ERROR(output, "Cluster master '%s' gtid info could not be updated.", m_master->name()); } } // server_is_rejoin_suspect has added any error messages to the output, no need to print here } else { PRINT_MXS_JSON_ERROR(output, "The given server '%s' is not monitored by this monitor.", rejoin_serv_name); } } else { const char BAD_CLUSTER[] = "The server cluster of monitor '%s' is not in a state valid for joining. " "Either it has no master or its gtid domain is unknown."; PRINT_MXS_JSON_ERROR(output, BAD_CLUSTER, m_monitor->name); } return rval; } /** * Generate a CHANGE MASTER TO-query. * * @param master_host Master hostname/address * @param master_port Master port * @return Generated query */ string MariaDBMonitor::generate_change_master_cmd(const string& master_host, int master_port) { std::stringstream change_cmd; change_cmd << "CHANGE MASTER TO MASTER_HOST = '" << master_host << "', "; change_cmd << "MASTER_PORT = " << master_port << ", "; change_cmd << "MASTER_USE_GTID = current_pos, "; change_cmd << "MASTER_USER = '" << m_replication_user << "', "; const char MASTER_PW[] = "MASTER_PASSWORD = '"; const char END[] = "';"; #if defined(SS_DEBUG) std::stringstream change_cmd_nopw; change_cmd_nopw << change_cmd.str(); change_cmd_nopw << MASTER_PW << "******" << END;; MXS_DEBUG("Change master command is '%s'.", change_cmd_nopw.str().c_str()); #endif change_cmd << MASTER_PW << m_replication_password << END; return change_cmd.str(); } /** * Redirects slaves to replicate from another master server. * * @param new_master The replication master * @param slaves An array of slaves * @param redirected_slaves A vector where to insert successfully redirected slaves. * @return The number of slaves successfully redirected. */ int MariaDBMonitor::redirect_slaves(MariaDBServer* new_master, const ServerArray& slaves, ServerArray* redirected_slaves) { ss_dassert(redirected_slaves != NULL); MXS_NOTICE("Redirecting slaves to new master."); string change_cmd = generate_change_master_cmd(new_master->m_server_base->server->address, new_master->m_server_base->server->port); int successes = 0; for (auto iter = slaves.begin(); iter != slaves.end(); iter++) { if ((*iter)->redirect_one_slave(change_cmd)) { successes++; redirected_slaves->push_back(*iter); } } return successes; } /** * Set the new master to replicate from the cluster external master. * * @param new_master The server being promoted * @param err_out Error output * @return True if new master accepted commands */ bool MariaDBMonitor::start_external_replication(MariaDBServer* new_master, json_t** err_out) { bool rval = false; MYSQL* new_master_conn = new_master->m_server_base->con; string change_cmd = generate_change_master_cmd(m_external_master_host, m_external_master_port); if (mxs_mysql_query(new_master_conn, change_cmd.c_str()) == 0 && mxs_mysql_query(new_master_conn, "START SLAVE;") == 0) { MXS_NOTICE("New master starting replication from external master %s:%d.", m_external_master_host.c_str(), m_external_master_port); rval = true; } else { PRINT_MXS_JSON_ERROR(err_out, "Could not start replication from external master: '%s'.", mysql_error(new_master_conn)); } return rval; } /** * Starts a new slave connection on a server. Should be used on a demoted master server. * * @param old_master The server which will start replication * @param new_master Replication target * @return True if commands were accepted. This does not guarantee that replication proceeds * successfully. */ bool MariaDBMonitor::switchover_start_slave(MariaDBServer* old_master, MariaDBServer* new_master) { bool rval = false; 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 (auto iter = joinable_servers.begin(); iter != joinable_servers.end(); iter++) { MariaDBServer* joinable = *iter; 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); } } 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) { ss_dassert(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 (auto iter = m_servers.begin(); iter != m_servers.end(); iter++) { if (server_is_rejoin_suspect(*iter, NULL)) { suspects.push_back(*iter); } } // 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_running() && !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. * * @param current_master Handle to current master server. If null, the autoselected server is written here. * @param new_master Handle to slave which should be promoted. If null, the autoselected server is written * here. * @param err_out json object for error printing. Can be NULL. * @return True if successful. If false, the cluster can be in various situations depending on which step * failed. In practice, manual intervention is usually required on failure. */ bool MariaDBMonitor::do_switchover(MariaDBServer** current_master, MariaDBServer** new_master, json_t** err_out) { ss_dassert(current_master && new_master); MariaDBServer* demotion_target = NULL; if (*current_master == NULL) { // Autoselect current master. if (m_master && m_master->is_master()) { demotion_target = m_master; *current_master = demotion_target; } else { PRINT_MXS_JSON_ERROR(err_out, "Could not autoselect current master for switchover. Cluster does " "not have a master or master is in maintenance."); return false; } } else { // No need to check a given current master, it has already been checked. demotion_target = *current_master; } if (m_master_gtid_domain == GTID_DOMAIN_UNKNOWN) { PRINT_MXS_JSON_ERROR(err_out, "Cluster gtid domain is unknown. Cannot switchover."); return false; } // 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. If we have a // user-defined master candidate, check it. Otherwise, autoselect. MariaDBServer* promotion_target = NULL; ServerArray redirectable_slaves; if (*new_master == NULL) { // Autoselect new master. promotion_target = select_new_master(&redirectable_slaves, err_out); if (promotion_target) { *new_master = promotion_target; } else { PRINT_MXS_JSON_ERROR(err_out, "Could not autoselect new master for switchover."); return false; } } else { // Check user-given new master. Some checks have already been performed but more is needed. if (switchover_check_preferred_master(*new_master, err_out)) { promotion_target = *new_master; /* User-given candidate is good. Update info on all slave servers. * The update_slave_info()-call is not strictly necessary here, but it should be ran to keep this * path analogous with failover_select_new_master(). The later functions can then assume that * slave server info is up to date. If the master is replicating from external master, it is * updated by update_slave_info() but not added to array. */ for (auto iter = m_servers.begin(); iter != m_servers.end(); iter++) { MariaDBServer* server = *iter; if (server != promotion_target && server->update_slave_info() && server != demotion_target) { redirectable_slaves.push_back(server); } } } else { return false; } } ss_dassert(demotion_target && promotion_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 err_out Json output * @return True if successful */ bool MariaDBMonitor::do_failover(json_t** err_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: Select new master. Also populate a vector with all slaves not the selected master. ServerArray redirectable_slaves; MariaDBServer* new_master = select_new_master(&redirectable_slaves, err_out); if (new_master == NULL) { return false; } time_t step1_time = time(NULL); seconds_remaining -= difftime(step1_time, start_time); bool rval = false; // Step 2: Wait until relay log consumed. if (new_master->failover_wait_relay_log(seconds_remaining, err_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(new_master, err_out)) { m_next_master = new_master; m_cluster_modified = true; // Step 4: Redirect slaves. ServerArray redirected_slaves; int redirects = redirect_slaves(new_master, 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(new_master, 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, err_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) { thread_millisleep(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; } /** * Select a new master. Also add slaves which should be redirected to an array. * * @param out_slaves Vector for storing slave servers. * @param err_out json object for error printing. Can be NULL. * @return The found master, or NULL if not found */ MariaDBServer* MariaDBMonitor::select_new_master(ServerArray* slaves_out, json_t** err_out) { ss_dassert(slaves_out && slaves_out->size() == 0); /* 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. */ MariaDBServer* current_best = NULL; string current_best_reason; // Servers that cannot be selected because of exclusion, but seem otherwise ok. ServerArray valid_but_excluded; // Index of the current best candidate in slaves_out int master_vector_index = -1; for (auto iter = m_servers.begin(); iter != m_servers.end(); iter++) { /* If a server cannot be connected to, it won't be considered for promotion or redirected. * Do not worry about the exclusion list yet, querying the excluded servers is ok. * If master is replicating from external master, it is updated by update_slave_info() * but not added to array. */ MariaDBServer* cand = *iter; if (cand->update_slave_info() && cand != m_master) { slaves_out->push_back(cand); // Check that server is not in the exclusion list while still being a valid choice. if (server_is_excluded(cand) && cand->check_replication_settings(WARNINGS_OFF)) { valid_but_excluded.push_back(cand); const char CANNOT_SELECT[] = "Promotion candidate '%s' is excluded from new " "master selection."; MXS_INFO(CANNOT_SELECT, cand->name()); } else if (cand->check_replication_settings()) { // If no new master yet, accept any valid candidate. Otherwise check. if (current_best == NULL || is_candidate_better(current_best, cand, m_master_gtid_domain, ¤t_best_reason)) { // The server has been selected for promotion, for now. current_best = cand; master_vector_index = slaves_out->size() - 1; } } } } if (current_best) { // Remove the selected master from the vector. auto it_remove = slaves_out->begin(); it_remove += master_vector_index; slaves_out->erase(it_remove); } // Check if any of the excluded servers would be better than the best candidate. for (auto iter = valid_but_excluded.begin(); iter != valid_but_excluded.end(); iter++) { MariaDBServer* excluded_info = *iter; const char* excluded_name = (*iter)->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(current_best, excluded_info, 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 == NULL) { PRINT_MXS_JSON_ERROR(err_out, "No suitable promotion candidate found."); } else if (!current_best_reason.empty()) { // If there was a specific reason this server was selected, print it now. It's possible that all // were equally good, in that case no need to print. MXS_NOTICE("%s", current_best_reason.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 current_best_info Server info of current best choice * @param candidate_info Server info of new candidate * @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* current_best, const MariaDBServer* candidate, uint32_t gtid_domain, std::string* reason_out) { string reason = string("'") + candidate->name() + "' is the best candidate because it "; 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 += "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 += "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 += "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 += "is not low on disk space."; } } } } if (reason_out && is_better) { *reason_out = reason; } return is_better; } /** * Check that the given server is a master and it's the only master. * * @param suggested_curr_master The server to check, given by user. * @param error_out On output, error object if function failed. * @return True if current master seems ok. False, if there is some error with the * specified current master. */ bool MariaDBMonitor::switchover_check_current(const MariaDBServer* suggested_curr_master, json_t** error_out) const { ss_dassert(suggested_curr_master); bool server_is_master = false; MariaDBServer* extra_master = NULL; // A master server which is not the suggested one for (auto iter = m_servers.begin(); iter != m_servers.end() && extra_master == NULL; iter++) { MariaDBServer* server = *iter; if (server->is_master()) { if (server == suggested_curr_master) { server_is_master = true; } else { extra_master = server; } } } if (!server_is_master) { PRINT_MXS_JSON_ERROR(error_out, "Server '%s' is not the current master or it's in maintenance.", suggested_curr_master->name()); } else if (extra_master) { PRINT_MXS_JSON_ERROR(error_out, "Cluster has an additional master server '%s'.", extra_master->name()); } return server_is_master && !extra_master; } /** * Check whether specified new master is acceptable. * * @param monitored_server The server to check against. * @param error On output, error object if function failed. * * @return True, if suggested new master is a viable promotion candidate. */ bool MariaDBMonitor::switchover_check_new(const MariaDBServer* new_master_cand, json_t** error) { bool is_master = new_master_cand->is_master(); bool is_slave = new_master_cand->is_slave(); if (is_master) { const char IS_MASTER[] = "Specified new master '%s' is already the current master."; PRINT_MXS_JSON_ERROR(error, IS_MASTER, new_master_cand->name()); } else if (!is_slave) { const char NOT_SLAVE[] = "Specified new master '%s' is not a slave."; PRINT_MXS_JSON_ERROR(error, NOT_SLAVE, new_master_cand->name()); } return !is_master && is_slave; } /** * Check that preconditions for a failover are met. * * @param error_out Error output * @return True if failover may proceed */ bool MariaDBMonitor::failover_check(string* error_out) { // Check that there is no running master and that there is at least one promotable slave in the cluster. // Also, all slaves must be using gtid-replication and the gtid-domain of the cluster must be known. bool error = false; string separator; // Topology has already been tested to be simple. if (m_master_gtid_domain < 0) { *error_out += "Cluster gtid domain is unknown. This is usually caused by the cluster never having " "a master server while MaxScale was running."; separator = "\n"; error = true; } int valid_slaves = 0; for (auto iter = m_servers.begin(); iter != m_servers.end(); iter++) { MariaDBServer* server = *iter; uint64_t status_bits = server->m_server_base->pending_status; uint64_t master_up = (SERVER_MASTER | SERVER_RUNNING); if ((status_bits & master_up) == master_up) { string master_up_msg = string("Master server '") + server->name() + "' is running"; if (status_bits & SERVER_MAINT) { master_up_msg += ", although in maintenance mode"; } master_up_msg += "."; *error_out += separator + master_up_msg; separator = "\n"; error = true; } else if (server->is_slave()) { // Gtid-replication is checked for all slaves, but only slaves not excluded are accepted. string gtid_error; if (server->uses_gtid(>id_error)) { if (!server_is_excluded(server)) { valid_slaves++; } } else { *error_out += separator + gtid_error; separator = "\n"; error = true; } } } if (valid_slaves == 0) { *error_out += separator + "No valid slaves to promote."; error = true; } return !error; } /** * @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() { const char RE_ENABLE_FMT[] = "To re-enable automatic failover, manually set '%s' to 'true' for monitor " "'%s' via MaxAdmin or the REST API, or restart MaxScale."; 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 problems = string_printf(PROBLEMS, cluster_issues.c_str()); string total_msg = problems + " " + string_printf(RE_ENABLE_FMT, CN_AUTO_FAILOVER, m_monitor->name); 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. string error_msg; if (failover_check(&error_msg)) { 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(NULL)) { const string FAILED = "Automatic failover failed, disabling automatic failover."; string error_msg = FAILED + " " + string_printf(RE_ENABLE_FMT, CN_AUTO_FAILOVER, m_monitor->name); MXS_ERROR("%s", error_msg.c_str()); m_auto_failover = false; disable_setting(CN_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. Errors: \n%s", error_msg.c_str()); 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) { if (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()) { 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. * If a server parameter is NULL, the corresponding output parameter is not written to. * * @param new_master New master requested by the user. Can be null for autoselect. * @param current_master Current master given by the user. Can be null for autoselect. * @param new_master_out Where to write found new master. * @param current_master_out Where to write found current master. * @param error_out Error output, can be null. * @return True if cluster is suitable and server parameters were valid and found. */ bool MariaDBMonitor::switchover_check(SERVER* new_master, SERVER* current_master, MariaDBServer** new_master_out, MariaDBServer** current_master_out, json_t** error_out) { bool new_master_ok = true, current_master_ok = true; const char NO_SERVER[] = "Server '%s' is not a member of monitor '%s'."; // Check that both servers are ok if specified. Null is a valid value. if (new_master) { auto mon_new_master = mon_get_monitored_server(m_monitor, new_master); if (mon_new_master == NULL) { new_master_ok = false; PRINT_MXS_JSON_ERROR(error_out, NO_SERVER, new_master->name, m_monitor->name); } else { MariaDBServer* found_new_master = get_server_info(mon_new_master); if (switchover_check_new(found_new_master, error_out)) { *new_master_out = found_new_master; } else { new_master_ok = false; } } } if (current_master) { auto mon_curr_master = mon_get_monitored_server(m_monitor, current_master); if (mon_curr_master == NULL) { current_master_ok = false; PRINT_MXS_JSON_ERROR(error_out, NO_SERVER, current_master->name, m_monitor->name); } else { MariaDBServer* found_curr_master = get_server_info(mon_curr_master); if (switchover_check_current(found_curr_master, error_out)) { *current_master_out = get_server_info(mon_curr_master); } else { current_master_ok = false; } } } // Check that all slaves are using gtid-replication. bool gtid_ok = true; for (auto iter = m_servers.begin(); iter != m_servers.end(); iter++) { MariaDBServer* server = *iter; string gtid_error; if (server->is_slave() && !server->uses_gtid(>id_error)) { gtid_ok = false; PRINT_MXS_JSON_ERROR(error_out, "%s", gtid_error.c_str()); } } return new_master_ok && current_master_ok && gtid_ok; } 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_running() && !server->is_master() && !server->is_relay_master()) { server->set_status(SERVER_MAINT); } } }