MaxScale/server/modules/monitor/mariadbmon/cluster_manipulation.cc

#include "mariadbmon.hh"

#include <sstream>
#include <maxscale/mysql_utils.h>

/*
 * 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: 2020-01-01
 *
 * 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.
 */

/**
 * 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 slaves An array of slaves
 * @param new_master The replication master
 * @param redirected_slaves A vector where to insert successfully redirected slaves.
 * @return The number of slaves successfully redirected.
 */
int MariaDBMonitor::redirect_slaves(MXS_MONITORED_SERVER* new_master, const ServerVector& slaves,
                                    ServerVector* redirected_slaves)
{
    ss_dassert(redirected_slaves != NULL);
    MXS_NOTICE("Redirecting slaves to new master.");
    string change_cmd = generate_change_master_cmd(new_master->server->name, new_master->server->port);
    int successes = 0;
    for (ServerVector::const_iterator iter = slaves.begin(); iter != slaves.end(); iter++)
    {
        if (redirect_one_slave(*iter, change_cmd.c_str()))
        {
            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(MXS_MONITORED_SERVER* new_master, json_t** err_out)
{
    bool rval = false;
    string change_cmd = generate_change_master_cmd(external_master_host, external_master_port);
    if (mxs_mysql_query(new_master->con, change_cmd.c_str()) == 0 &&
        mxs_mysql_query(new_master->con, "START SLAVE;") == 0)
    {
        MXS_NOTICE("New master starting replication from external master %s:%d.",
                   external_master_host.c_str(), external_master_port);
        rval = true;
    }
    else
    {
        PRINT_MXS_JSON_ERROR(err_out, "Could not start replication from external master: '%s'.",
                             mysql_error(new_master->con));
    }
    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(MXS_MONITORED_SERVER* old_master, SERVER* new_master)
{
    bool rval = false;
    string change_cmd = generate_change_master_cmd(new_master->name, new_master->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->server->unique_name, new_master->unique_name);
        rval = true;
    }
    else
    {
        MXS_ERROR("Old master '%s' could not start replication: '%s'.",
                  old_master->server->unique_name, mysql_error(old_master->con));
    }
    return rval;
}

/**
 * Redirect one slave server to another master
 *
 * @param slave Server to redirect
 * @param change_cmd Change master command, usually generated by generate_change_master_cmd()
 * @return True if slave accepted all commands
 */
bool MariaDBMonitor::redirect_one_slave(MXS_MONITORED_SERVER* slave, const char* change_cmd)
{
    bool rval = false;
    if (mxs_mysql_query(slave->con, "STOP SLAVE;") == 0 &&
        mxs_mysql_query(slave->con, "RESET SLAVE;") == 0 && // To erase any old I/O or SQL errors
        mxs_mysql_query(slave->con, change_cmd) == 0 &&
        mxs_mysql_query(slave->con, "START SLAVE;") == 0)
    {
        rval = true;
        MXS_NOTICE("Slave '%s' redirected to new master.", slave->server->unique_name);
    }
    else
    {
        MXS_WARNING("Slave '%s' redirection failed: '%s'.", slave->server->unique_name,
                    mysql_error(slave->con));
    }
    return rval;
}

uint32_t MariaDBMonitor::do_rejoin(const ServerVector& joinable_servers)
{
    SERVER* master = this->master->server;
    uint32_t servers_joined = 0;
    if (!joinable_servers.empty())
    {
        string change_cmd = generate_change_master_cmd(master->name, master->port);
        for (ServerVector::const_iterator iter = joinable_servers.begin();
             iter != joinable_servers.end();
             iter++)
        {
            MXS_MONITORED_SERVER* joinable = *iter;
            const char* name = joinable->server->unique_name;
            const char* master_name = master->unique_name;
            MySqlServerInfo* redir_info = get_server_info(this, joinable);

            bool op_success;
            if (redir_info->n_slaves_configured == 0)
            {
                MXS_NOTICE("Directing standalone server '%s' to replicate from '%s'.", name, master_name);
                op_success = join_cluster(joinable, change_cmd.c_str());
            }
            else
            {
                MXS_NOTICE("Server '%s' is replicating from a server other than '%s', "
                           "redirecting it to '%s'.", name, master_name, master_name);
                op_success = redirect_one_slave(joinable, change_cmd.c_str());
            }

            if (op_success)
            {
                servers_joined++;
            }
        }
    }
    return servers_joined;
}

bool MariaDBMonitor::cluster_can_be_joined()
{
    return (master != NULL && SERVER_IS_MASTER(master->server) && master_gtid_domain >= 0);
}