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/**
* 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;
import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import org.apache.activemq.util.Handler;
import org.apache.activemq.util.ServiceStopper;
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="database-locker"
*
*/
public class DefaultDatabaseLocker extends AbstractJDBCLocker {
private static final Logger LOG = LoggerFactory.getLogger(DefaultDatabaseLocker.class);
protected volatile PreparedStatement lockCreateStatement;
protected volatile PreparedStatement lockUpdateStatement;
protected volatile Connection connection;
protected Handler exceptionHandler;
public void doStart() throws Exception {
LOG.info("Attempting to acquire the exclusive lock to become the Master broker");
String sql = getStatements().getLockCreateStatement();
LOG.debug("Locking Query is "+sql);
while (true) {
try {
connection = dataSource.getConnection();
connection.setAutoCommit(false);
lockCreateStatement = connection.prepareStatement(sql);
lockCreateStatement.execute();
break;
} catch (Exception e) {
try {
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 exception: "
+ e, handlerException);
}
} else {
LOG.debug("Lock failure: "+ e, e);
}
} finally {
// Let's make sure the database connection is properly
// closed when an error occurs so that we're not leaking
// connections
if (null != connection) {
try {
connection.rollback();
} catch (SQLException e1) {
LOG.debug("Caught exception during rollback on connection: " + e1, e1);
}
try {
connection.close();
} catch (SQLException e1) {
LOG.debug("Caught exception while closing connection: " + e1, e1);
}
connection = null;
}
}
} finally {
if (null != lockCreateStatement) {
try {
lockCreateStatement.close();
} catch (SQLException e1) {
LOG.debug("Caught while closing statement: " + e1, e1);
}
lockCreateStatement = null;
}
}
LOG.info("Failed to acquire lock. Sleeping for " + lockAcquireSleepInterval + " milli(s) before trying again...");
try {
Thread.sleep(lockAcquireSleepInterval);
} catch (InterruptedException ie) {
LOG.warn("Master lock retry sleep interrupted", ie);
}
}
LOG.info("Becoming the master on dataSource: " + dataSource);
}
public void doStop(ServiceStopper stopper) throws Exception {
try {
if (lockCreateStatement != null) {
lockCreateStatement.cancel();
}
} catch (SQLFeatureNotSupportedException e) {
LOG.warn("Failed to cancel locking query on dataSource" + dataSource, e);
}
try {
if (lockUpdateStatement != null) {
lockUpdateStatement.cancel();
}
} catch (SQLFeatureNotSupportedException e) {
LOG.warn("Failed to cancel locking query on dataSource" + dataSource, e);
}
// when the connection is closed from an outside source (lost TCP
// connection, db server, etc) and this connection is managed by a pool
// it is important to close the connection so that we don't leak
// connections
if (connection != null) {
try {
connection.rollback();
} catch (SQLException sqle) {
LOG.warn("Exception while rollbacking the connection on shutdown. This exception is ignored.", sqle);
} finally {
try {
connection.close();
} catch (SQLException ignored) {
LOG.debug("Exception while closing connection on shutdown. This exception is ignored.", ignored);
}
lockCreateStatement = null;
}
}
}
public boolean keepAlive() throws IOException {
boolean result = false;
try {
lockUpdateStatement = connection.prepareStatement(getStatements().getLockUpdateStatement());
lockUpdateStatement.setLong(1, System.currentTimeMillis());
setQueryTimeout(lockUpdateStatement);
int rows = lockUpdateStatement.executeUpdate();
if (rows == 1) {
result=true;
}
} catch (Exception e) {
LOG.error("Failed to update database lock: " + e, e);
} finally {
if (lockUpdateStatement != null) {
try {
lockUpdateStatement.close();
} catch (SQLException e) {
LOG.error("Failed to close statement",e);
}
lockUpdateStatement = null;
}
}
return result;
}
public long getLockAcquireSleepInterval() {
return lockAcquireSleepInterval;
}
public void setLockAcquireSleepInterval(long lockAcquireSleepInterval) {
this.lockAcquireSleepInterval = lockAcquireSleepInterval;
}
public Handler getExceptionHandler() {
return exceptionHandler;
}
public void setExceptionHandler(Handler exceptionHandler) {
this.exceptionHandler = exceptionHandler;
}
}