source: Ballon/out/artifacts/geisa_artifact/WEB-INF/lib/mysql-connector-java-5.1.21/src/com/mysql/jdbc/BestResponseTimeBalanceStrategy.java @ 848

/*
  Copyright (c) 2007, 2011, 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.List;
import java.util.Map;
import java.util.Properties;

public class BestResponseTimeBalanceStrategy implements BalanceStrategy {

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

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

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

        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;
                                        }
                                                
                                        throw sqlEx;
                                }
                        }

                        return conn;
                }

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

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