/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.activemq.store.jdbc.adapter;
import java.io.IOException;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import org.apache.activemq.store.jdbc.DefaultDatabaseLocker;
import org.apache.activemq.store.jdbc.JDBCPersistenceAdapter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Represents an exclusive lock on a database to avoid multiple brokers running
* against the same logical database.
*
* @org.apache.xbean.XBean element="transact-database-locker"
*
*/
public class TransactDatabaseLocker extends DefaultDatabaseLocker {
private static final Logger LOG = LoggerFactory.getLogger(TransactDatabaseLocker.class);
@Override
public void doStart() throws Exception {
LOG.info("Attempting to acquire the exclusive lock to become the Master broker");
PreparedStatement statement = null;
while (true) {
try {
connection = dataSource.getConnection();
connection.setAutoCommit(false);
String sql = getStatements().getLockCreateStatement();
statement = connection.prepareStatement(sql);
if (statement.getMetaData() != null) {
ResultSet rs = statement.executeQuery();
// if not already locked the statement below blocks until lock acquired
rs.next();
} else {
statement.execute();
}
break;
} catch (Exception e) {
if (isStopping()) {
throw new Exception("Cannot start broker as being asked to shut down. Interrupted attempt to acquire lock: " + e, e);
}
if (exceptionHandler != null) {
try {
exceptionHandler.handle(e);
} catch (Throwable handlerException) {
LOG.error("The exception handler " + exceptionHandler.getClass().getCanonicalName() + " threw this exception: " + handlerException
+ " while trying to handle this excpetion: " + e, handlerException);
}
} else {
LOG.error("Failed to acquire lock: " + e, e);
}
} finally {
if (null != statement) {
try {
statement.close();
} catch (SQLException e1) {
LOG.warn("Caught while closing statement: " + e1, e1);
}
statement = null;
}
}
LOG.debug("Sleeping for " + lockAcquireSleepInterval + " milli(s) before trying again to get the lock...");
try {
Thread.sleep(lockAcquireSleepInterval);
} catch (InterruptedException ie) {
LOG.warn("Master lock retry sleep interrupted", ie);
}
}
LOG.info("Becoming the master on dataSource: " + dataSource);
}
}