Logo Search packages:      
Sourcecode: mysql-connector-java version File versions  Download package

BestResponseTimeBalanceStrategy.java

/*
  Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved.

  The MySQL Connector/J is licensed under the terms of the GPLv2
  <http://www.gnu.org/licenses/old-licenses/gpl-2.0.html>, like most MySQL Connectors.
  There are special exceptions to the terms and conditions of the GPLv2 as it is applied to
  this software, see the FLOSS License Exception
  <http://www.mysql.com/about/legal/licensing/foss-exception.html>.

  This program is free software; you can redistribute it and/or modify it under the terms
  of the GNU General Public License as published by the Free Software Foundation; version 2
  of the License.

  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 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.jdbc;

import java.sql.SQLException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

00033 public class BestResponseTimeBalanceStrategy implements BalanceStrategy {

      /**
       * @param loadBalancingConnectionProxy
       */
00038       public BestResponseTimeBalanceStrategy() {
      }

00041       public void destroy() {
            // we don't have anything to clean up
      }

00045       public void init(Connection conn, Properties props) throws SQLException {
            // we don't have anything to initialize
      }

00049       public ConnectionImpl pickConnection(LoadBalancingConnectionProxy proxy,
                  List<String> configuredHosts, Map<String, ConnectionImpl> liveConnections, long[] responseTimes,
                  int numRetries) throws SQLException {
                        
            Map<String, Long> blackList = proxy.getGlobalBlacklist();
                        
            SQLException ex = null;

            for (int attempts = 0; attempts < numRetries; ) {
                  long minResponseTime = Long.MAX_VALUE;

                  int bestHostIndex = 0;

                  // safety
                  if (blackList.size() == configuredHosts.size()) {
                        blackList = proxy.getGlobalBlacklist();
                  }

                  for (int i = 0; i < responseTimes.length; i++) {
                        long candidateResponseTime = responseTimes[i];

                        if (candidateResponseTime < minResponseTime
                                    && !blackList.containsKey(configuredHosts.get(i))) {
                              if (candidateResponseTime == 0) {
                                    bestHostIndex = i;

                                    break;
                              }

                              bestHostIndex = i;
                              minResponseTime = candidateResponseTime;
                        }
                  }

                  String bestHost = configuredHosts.get(bestHostIndex);

                  ConnectionImpl conn = liveConnections.get(bestHost);

                  if (conn == null) {
                        try {
                              conn = proxy.createConnectionForHost(bestHost);
                        } catch (SQLException sqlEx) {
                              ex = sqlEx;

                              if (proxy.shouldExceptionTriggerFailover(sqlEx)) {
                                    proxy.addToGlobalBlacklist(bestHost);
                                    blackList.put(bestHost, null);


                                    if (blackList.size() == configuredHosts.size()) {
                                          attempts++;
                                          try {
                                                Thread.sleep(250);
                                          } catch (InterruptedException e) {
                                          }
                                          blackList = proxy.getGlobalBlacklist(); // try again after a little bit
                                    }

                                    continue;
                              } else {
                                    throw sqlEx;
                              }
                        }
                  }

                  return conn;
            }

            if (ex != null) {
                  throw ex;
            }

            return null; // we won't get here, compiler can't tell
      }
}

Generated by  Doxygen 1.6.0   Back to index