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

/*
 Copyright (c) 2007, 2012, 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.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;

public class RandomBalanceStrategy implements BalanceStrategy {

        public RandomBalanceStrategy() {
        }

        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 {
                int numHosts = configuredHosts.size();

                SQLException ex = null;

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

                whiteList.removeAll(blackList.keySet());
                
                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) {
                                                        whiteList.remove(whiteListIndex.intValue());
                                                        whiteListMap = this.getArrayIndexMap(whiteList);
                                                }
                                                proxy.addToGlobalBlacklist( hostPortSpec );

                                                if (whiteList.size() == 0) {
                                                        attempts++;
                                                        try {
                                                                Thread.sleep(250);
                                                        } catch (InterruptedException e) {
                                                        }

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

                                                        whiteList.removeAll(blackList.keySet());
                                                        whiteListMap = this.getArrayIndexMap(whiteList);
                                                }

                                                continue;
                                        }

                                        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;
                
        }

}