content: /*
   * Copyright (c) 2007, 2020, Oracle and/or its affiliates.
   *
   * This program is free software; you can redistribute it and/or modify it under
   * the terms of the GNU General Public License, version 2.0, as published by the
   * Free Software Foundation.
   *
   * This program is also distributed with certain software (including but not
   * limited to OpenSSL) that is licensed under separate terms, as designated in a
   * particular file or component or in included license documentation. The
   * authors of MySQL hereby grant you an additional permission to link the
   * program and your derivative works with the separately licensed software that
   * they have included with MySQL.
   *
   * Without limiting anything contained in the foregoing, this file, which is
   * part of MySQL Connector/J, is also subject to the Universal FOSS Exception,
   * version 1.0, a copy of which can be found at
   * http://oss.oracle.com/licenses/universal-foss-exception.
   *
   * This program is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
   * FOR A PARTICULAR PURPOSE. See the GNU General Public License, version 2.0,
   * for more details.
   *
   * You should have received a copy of the GNU General Public License along with
   * this program; if not, write to the Free Software Foundation, Inc.,
   * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA
   */
  
  package com.mysql.cj.jdbc.ha;
  
  import java.lang.reflect.InvocationHandler;
  import java.sql.SQLException;
  import java.util.List;
  import java.util.Map;
  
  import com.mysql.cj.jdbc.JdbcConnection;
  
  /**
   * Implement this interface to provide a new load balancing strategy for URLs of the form "jdbc:mysql:loadbalance://..", and provide the implementation class
   * name as the configuration parameter "loadBalanceStrategy".
   * 
   * The driver will not pass in a Connection instance when calling init(), but it will pass in the Properties, otherwise it acts like a normal Extension.
   * 
   * One instance of a strategy *per* JDBC connection instance will be created. If you need singleton-like behavior, you're on your own to provide it.
   */
  public interface BalanceStrategy {
      /**
       * Called by the driver to pick a new connection to route requests over.
       * See LoadBalancedConnectionProxy.createConnectionForHost(String)
       * 
       * @param proxy
       *            the InvocationHandler that deals with actual method calls to
       *            the JDBC connection, and serves as a factory for new
       *            connections for this strategy via the
       *            createConnectionForHost() method.
       * 
       *            This proxy takes care of maintaining the response time list, map of
       *            host/ports to live connections, and taking connections out of the live
       *            connections map if they receive a network-related error while they are in
       *            use by the application.
       * @param configuredHosts
       *            the list of hosts/ports (in "host:port" form) as passed in by
       *            the user.
       * @param liveConnections
       *            a map of host/ports to "live" connections to them.
       * @param responseTimes
       *            the list of response times for a <strong>transaction</strong>
       *            for each host in the configured hosts list.
       * @param numRetries
       *            the number of times the driver expects this strategy to re-try
       *            connection attempts if creating a new connection fails.
       * @return the physical JDBC connection for the application to use, based
       *         upon the strategy employed.
       * @throws SQLException
       *             if a new connection can not be found or created by this
       *             strategy.
       */
      abstract JdbcConnection pickConnection(InvocationHandler proxy, List<String> configuredHosts, Map<String, JdbcConnection> liveConnections,
              long[] responseTimes, int numRetries) throws SQLException;
  }
  