content: /*
   * Copyright (c) 2002, 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.ConnectionImpl;
  import com.mysql.cj.jdbc.JdbcConnection;
  
  public class BestResponseTimeBalanceStrategy implements BalanceStrategy {
  
      public BestResponseTimeBalanceStrategy() {
      }
  
      @Override
      public ConnectionImpl pickConnection(InvocationHandler proxy, List<String> configuredHosts, Map<String, JdbcConnection> liveConnections,
              long[] responseTimes, int numRetries) throws SQLException {
  
          Map<String, Long> blockList = ((LoadBalancedConnectionProxy) proxy).getGlobalBlocklist();
  
          SQLException ex = null;
  
          for (int attempts = 0; attempts < numRetries;) {
              long minResponseTime = Long.MAX_VALUE;
  
              int bestHostIndex = 0;
  
              // safety
              if (blockList.size() == configuredHosts.size()) {
                  blockList = ((LoadBalancedConnectionProxy) proxy).getGlobalBlocklist();
              }
  
              for (int i = 0; i < responseTimes.length; i++) {
                  long candidateResponseTime = responseTimes[i];
  
                  if (candidateResponseTime < minResponseTime && !blockList.containsKey(configuredHosts.get(i))) {
                      if (candidateResponseTime == 0) {
                          bestHostIndex = i;
  
                          break;
                      }
  
                      bestHostIndex = i;
                      minResponseTime = candidateResponseTime;
                  }
              }
  
              String bestHost = configuredHosts.get(bestHostIndex);
  
              ConnectionImpl conn = (ConnectionImpl) liveConnections.get(bestHost);
  
              if (conn == null) {
                  try {
                      conn = ((LoadBalancedConnectionProxy) proxy).createConnectionForHost(bestHost);
                  } catch (SQLException sqlEx) {
                      ex = sqlEx;
  
                      if (((LoadBalancedConnectionProxy) proxy).shouldExceptionTriggerConnectionSwitch(sqlEx)) {
                          ((LoadBalancedConnectionProxy) proxy).addToGlobalBlocklist(bestHost);
                          blockList.put(bestHost, null);
  
                          if (blockList.size() == configuredHosts.size()) {
                              attempts++;
                              try {
                                  Thread.sleep(250);
                              } catch (InterruptedException e) {
                              }
                              blockList = ((LoadBalancedConnectionProxy) proxy).getGlobalBlocklist(); // try again after a little bit
                          }
  
                          continue;
                      }
  
                      throw sqlEx;
                  }
              }
  
              return conn;
          }
  
          if (ex != null) {
              throw ex;
          }
  
          return null; // we won't get here, compiler can't tell
      }
  }
  