package org.apache.helix.manager.zk;
/*
* 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.
*/
import java.util.LinkedList;
import java.util.List;
import org.I0Itec.zkclient.IZkStateListener;
import org.I0Itec.zkclient.ZkConnection;
import org.apache.log4j.Logger;
import org.apache.zookeeper.Watcher.Event.KeeperState;
public class ZkStateChangeListener implements IZkStateListener
{
private volatile boolean _isConnected;
private volatile boolean _hasSessionExpired;
private final ZKHelixManager _zkHelixManager;
// Keep track of timestamps that zk State has become Disconnected
// If in a _timeWindowLengthMs window zk State has become Disconnected
// for more than_maxDisconnectThreshold times disconnect the zkHelixManager
List<Long> _disconnectTimeHistory = new LinkedList<Long>();
int _timeWindowLengthMs;
int _maxDisconnectThreshold;
private static Logger logger = Logger.getLogger(ZkStateChangeListener.class);
public ZkStateChangeListener(ZKHelixManager zkHelixManager, int timeWindowLengthMs, int maxDisconnectThreshold)
{
this._zkHelixManager = zkHelixManager;
_timeWindowLengthMs = timeWindowLengthMs;
// _maxDisconnectThreshold min value is 1.
// We don't want to disconnect from zk for the first time zkState become Disconnected
_maxDisconnectThreshold = maxDisconnectThreshold > 0 ? maxDisconnectThreshold : 1;
}
@Override
public void handleNewSession()
{
// TODO:bug in zkclient .
// zkclient does not invoke handleStateChanged when a session expires but
// directly invokes handleNewSession
_isConnected = true;
_hasSessionExpired = false;
_zkHelixManager.handleNewSession();
}
@Override
public void handleStateChanged(KeeperState keeperState) throws Exception
{
switch (keeperState)
{
case SyncConnected:
ZkConnection zkConnection =
((ZkConnection) _zkHelixManager._zkClient.getConnection());
logger.info("KeeperState: " + keeperState + ", zookeeper:" + zkConnection.getZookeeper());
_isConnected = true;
break;
case Disconnected:
logger.info("KeeperState:" + keeperState + ", disconnectedSessionId: "
+ _zkHelixManager._sessionId + ", instance: "
+ _zkHelixManager.getInstanceName() + ", type: "
+ _zkHelixManager.getInstanceType());
_isConnected = false;
// Track the time stamp that the disconnected happens, then check history and see if
// we should disconnect the _zkHelixManager
_disconnectTimeHistory.add(System.currentTimeMillis());
if(isFlapping())
{
logger.error("isFlapping() returns true, so disconnect the helix manager. " + _zkHelixManager.getInstanceName() + " "
+ _maxDisconnectThreshold + " disconnects in " + _timeWindowLengthMs + " Ms.");
_zkHelixManager.disconnectInternal();
}
break;
case Expired:
logger.info("KeeperState:" + keeperState + ", expiredSessionId: "
+ _zkHelixManager._sessionId + ", instance: "
+ _zkHelixManager.getInstanceName() + ", type: "
+ _zkHelixManager.getInstanceType());
_isConnected = false;
_hasSessionExpired = true;
break;
}
}
boolean isConnected()
{
return _isConnected;
}
void disconnect()
{
_isConnected = false;
}
boolean hasSessionExpired()
{
return _hasSessionExpired;
}
/**
* If zk state has changed into Disconnected for _maxDisconnectThreshold times during previous _timeWindowLengthMs Ms
* time window, we think that there are something wrong going on and disconnect the zkHelixManager from zk.
* */
boolean isFlapping()
{
if(_disconnectTimeHistory.size() == 0)
{
return false;
}
long mostRecentTimestamp = _disconnectTimeHistory.get(_disconnectTimeHistory.size() - 1);
// Remove disconnect history timestamp that are older than _timeWindowLengthMs ago
while((_disconnectTimeHistory.get(0) + _timeWindowLengthMs) < mostRecentTimestamp)
{
_disconnectTimeHistory.remove(0);
}
return _disconnectTimeHistory.size() > _maxDisconnectThreshold;
}
}