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/*
Copyright (c) 2007, 2015, 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 FOSS 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(LoadBalancedConnectionProxy 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.shouldExceptionTriggerConnectionSwitch(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;
}
}