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MySQL JDBC Type 4 driver
/*
Copyright (c) 2002, 2020, Oracle and/or its affiliates. All rights reserved.
The MySQL Connector/J is licensed under the terms of the GPLv2
, 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
.
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.List;
import java.util.Map;
import java.util.Properties;
public class BestResponseTimeBalanceStrategy implements BalanceStrategy {
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(LoadBalancedConnectionProxy proxy, List configuredHosts, Map liveConnections,
long[] responseTimes, int numRetries) throws SQLException {
List whiteList = new ArrayList(configuredHosts.size());
whiteList.addAll(configuredHosts);
Map blackList = proxy.getGlobalBlacklist();
whiteList.removeAll(blackList.keySet());
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(whiteList.get(i))) {
if (candidateResponseTime == 0) {
bestHostIndex = i;
break;
}
bestHostIndex = i;
minResponseTime = candidateResponseTime;
}
}
String bestHost = whiteList.get(bestHostIndex);
ConnectionImpl conn = liveConnections.get(bestHost);
if (conn == null) {
try {
conn = proxy.createConnectionForHost(bestHost);
} catch (SQLException sqlEx) {
ex = sqlEx;
if (proxy.shouldExceptionTriggerConnectionSwitch(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
}
}