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 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

  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.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;

00033 public class RandomBalanceStrategy implements BalanceStrategy {

      public RandomBalanceStrategy() {

00038       public void destroy() {
            // we don't have anything to clean up

00042       public void init(Connection conn, Properties props) throws SQLException {
            // we don't have anything to initialize

00046       public ConnectionImpl pickConnection(LoadBalancingConnectionProxy proxy,
                  List<String> configuredHosts, Map<String, ConnectionImpl> liveConnections, long[] responseTimes,
                  int numRetries) throws SQLException {
            int numHosts = configuredHosts.size();

            SQLException ex = null;

            List<String> whiteList = new ArrayList<String>(numHosts);
            Map<String, Long> blackList = proxy.getGlobalBlacklist();

            Map<String, Integer> whiteListMap = this.getArrayIndexMap(whiteList);

            for (int attempts = 0; attempts < numRetries;) {
                  int random = (int) Math.floor((Math.random() * whiteList.size()));
                  if(whiteList.size() == 0){
                        throw SQLError.createSQLException("No hosts configured", null);

                  String hostPortSpec = whiteList.get(random);

                  ConnectionImpl conn = liveConnections.get(hostPortSpec);

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

                              if (proxy.shouldExceptionTriggerFailover(sqlEx)) {

                                    Integer whiteListIndex = whiteListMap.get(hostPortSpec);

                                    // exclude this host from being picked again
                                    if (whiteListIndex != null) {
                                          whiteListMap = this.getArrayIndexMap(whiteList);
                                    proxy.addToGlobalBlacklist( hostPortSpec );

                                    if (whiteList.size() == 0) {
                                          try {
                                          } catch (InterruptedException e) {

                                          // start fresh
                                          whiteListMap = new HashMap<String, Integer>(numHosts);
                                          blackList = proxy.getGlobalBlacklist();

                                          whiteListMap = this.getArrayIndexMap(whiteList);

                              } else {
                                    throw sqlEx;
                  return conn;

            if (ex != null) {
                  throw ex;

            return null; // we won't get here, compiler can't tell
      private Map<String, Integer> getArrayIndexMap(List<String> l) {
            Map<String, Integer> m = new HashMap<String, Integer>(l.size());
            for (int i = 0; i < l.size(); i++) {
                  m.put(l.get(i), Integer.valueOf(i));
            return m;


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