/*
* Copyright 2009 Red Hat, Inc.
* Red Hat 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.hornetq.core.server.impl;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileLock;
import org.hornetq.api.core.HornetQIllegalStateException;
import org.hornetq.api.core.SimpleString;
import org.hornetq.core.server.HornetQServerLogger;
import org.hornetq.core.server.NodeManager;
import org.hornetq.utils.UUID;
/**
* @author <a href="mailto:andy.taylor@jboss.com">Andy Taylor</a>
* Date: Oct 13, 2010
* Time: 2:44:02 PM
*/
public class FileLockNodeManager extends NodeManager
{
private static final int LIVE_LOCK_POS = 1;
private static final int BACKUP_LOCK_POS = 2;
private static final int LOCK_LENGTH = 1;
private static final byte LIVE = 'L';
private static final byte FAILINGBACK = 'F';
private static final byte PAUSED = 'P';
private static final byte NOT_STARTED = 'N';
private FileLock liveLock;
private FileLock backupLock;
protected boolean interrupted = false;
public FileLockNodeManager(final String directory, boolean replicatedBackup)
{
super(replicatedBackup, directory);
}
@Override
public synchronized void start() throws Exception
{
if (isStarted())
{
return;
}
if (!replicatedBackup)
{
setUpServerLockFile();
}
super.start();
}
@Override
public boolean isAwaitingFailback() throws Exception
{
return getState() == FileLockNodeManager.FAILINGBACK;
}
@Override
public boolean isBackupLive() throws Exception
{
FileLock liveAttemptLock;
liveAttemptLock = tryLock(FileLockNodeManager.LIVE_LOCK_POS);
if (liveAttemptLock == null)
{
return true;
}
else
{
liveAttemptLock.release();
return false;
}
}
public boolean isLiveLocked()
{
return liveLock != null;
}
@Override
public void interrupt()
{
interrupted = true;
}
@Override
public final void releaseBackup() throws Exception
{
if (backupLock != null)
{
backupLock.release();
backupLock = null;
}
}
@Override
public void awaitLiveNode() throws Exception
{
do
{
byte state = getState();
while (state == FileLockNodeManager.NOT_STARTED || state == FIRST_TIME_START)
{
HornetQServerLogger.LOGGER.debug("awaiting live node startup state='" + state + "'");
Thread.sleep(2000);
state = getState();
}
liveLock = lock(FileLockNodeManager.LIVE_LOCK_POS);
state = getState();
if (state == FileLockNodeManager.PAUSED)
{
liveLock.release();
HornetQServerLogger.LOGGER.debug("awaiting live node restarting");
Thread.sleep(2000);
}
else if (state == FileLockNodeManager.FAILINGBACK)
{
liveLock.release();
HornetQServerLogger.LOGGER.debug("awaiting live node failing back");
Thread.sleep(2000);
}
else if (state == FileLockNodeManager.LIVE)
{
HornetQServerLogger.LOGGER.debug("acquired live node lock state = " + (char)state);
break;
}
}
while (true);
}
@Override
public void startBackup() throws Exception
{
assert !replicatedBackup; // should not be called if this is a replicating backup
HornetQServerLogger.LOGGER.waitingToBecomeBackup();
backupLock = lock(FileLockNodeManager.BACKUP_LOCK_POS);
HornetQServerLogger.LOGGER.gotBackupLock();
if (getUUID() == null)
readNodeId();
}
@Override
public void startLiveNode() throws Exception
{
setFailingBack();
HornetQServerLogger.LOGGER.waitingToObtainLiveLock();
liveLock = lock(FileLockNodeManager.LIVE_LOCK_POS);
HornetQServerLogger.LOGGER.obtainedLiveLock();
setLive();
}
@Override
public void pauseLiveServer() throws Exception
{
setPaused();
if (liveLock != null)
{
liveLock.release();
}
}
@Override
public void crashLiveServer() throws Exception
{
if (liveLock != null)
{
liveLock.release();
liveLock = null;
}
}
private void setLive() throws Exception
{
writeFileLockStatus(FileLockNodeManager.LIVE);
}
private void setFailingBack() throws Exception
{
writeFileLockStatus(FAILINGBACK);
}
private void setPaused() throws Exception
{
writeFileLockStatus(PAUSED);
}
/**
* @param status
* @throws IOException
*/
private void writeFileLockStatus(byte status) throws IOException
{
if (replicatedBackup && channel == null)
return;
ByteBuffer bb = ByteBuffer.allocateDirect(1);
bb.put(status);
bb.position(0);
channel.write(bb, 0);
channel.force(true);
}
private byte getState() throws Exception
{
ByteBuffer bb = ByteBuffer.allocateDirect(1);
int read;
read = channel.read(bb, 0);
if (read <= 0)
{
return FileLockNodeManager.NOT_STARTED;
}
else
{
return bb.get(0);
}
}
@Override
public final SimpleString readNodeId() throws HornetQIllegalStateException, IOException
{
ByteBuffer id = ByteBuffer.allocateDirect(16);
int read = channel.read(id, 3);
if (read != 16)
{
throw new HornetQIllegalStateException("live server did not write id to file");
}
byte[] bytes = new byte[16];
id.position(0);
id.get(bytes);
setUUID(new UUID(UUID.TYPE_TIME_BASED, bytes));
return getNodeId();
}
protected FileLock tryLock(final int lockPos) throws Exception
{
return channel.tryLock(lockPos, LOCK_LENGTH, false);
}
protected FileLock lock(final int liveLockPos) throws IOException
{
while (!interrupted)
{
FileLock lock = null;
try
{
lock = channel.tryLock(liveLockPos, 1, false);
}
catch (java.nio.channels.OverlappingFileLockException ex)
{
// This just means that another object on the same JVM is holding the lock
}
if (lock == null)
{
try
{
Thread.sleep(500);
}
catch (InterruptedException e)
{
return null;
}
}
else
{
return lock;
}
}
// todo this is here because sometimes channel.lock throws a resource deadlock exception but trylock works,
// need to investigate further and review
FileLock lock;
do
{
lock = channel.tryLock(liveLockPos, 1, false);
if (lock == null)
{
try
{
Thread.sleep(500);
}
catch (InterruptedException e1)
{
//
}
}
if (interrupted)
{
interrupted = false;
throw new IOException("Lock was interrupted");
}
}
while (lock == null);
return lock;
}
}