package org.apache.helix.participant;
/*
* 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.List;
import org.apache.helix.ConfigChangeListener;
import org.apache.helix.ExternalViewChangeListener;
import org.apache.helix.HelixDataAccessor;
import org.apache.helix.HelixManager;
import org.apache.helix.LiveInstanceChangeListener;
import org.apache.helix.NotificationContext;
import org.apache.helix.NotificationContext.Type;
import org.apache.helix.PropertyKey.Builder;
import org.apache.helix.model.CurrentState;
import org.apache.helix.model.ExternalView;
import org.apache.helix.model.InstanceConfig;
import org.apache.helix.model.LiveInstance;
import org.apache.log4j.Logger;
public class CustomCodeInvoker implements
LiveInstanceChangeListener,
ConfigChangeListener,
ExternalViewChangeListener
{
private static Logger LOG = Logger.getLogger(CustomCodeInvoker.class);
private final CustomCodeCallbackHandler _callback;
private final String _partitionKey;
public CustomCodeInvoker(CustomCodeCallbackHandler callback, String partitionKey)
{
_callback = callback;
_partitionKey = partitionKey;
}
private void callParticipantCode(NotificationContext context)
{
// System.out.println("callback invoked. type:" + context.getType().toString());
if (context.getType() == Type.INIT || context.getType() == Type.CALLBACK)
{
// since ZkClient.unsubscribe() does not immediately remove listeners
// from zk, it is possible that two listeners exist when leadership transfers
// therefore, double check to make sure only one participant invokes the code
if (context.getType() == Type.CALLBACK)
{
HelixManager manager = context.getManager();
// DataAccessor accessor = manager.getDataAccessor();
HelixDataAccessor accessor = manager.getHelixDataAccessor();
Builder keyBuilder = accessor.keyBuilder();
String instance = manager.getInstanceName();
String sessionId = manager.getSessionId();
// get resource name from partition key: "PARTICIPANT_LEADER_XXX_0"
String resourceName = _partitionKey.substring(0, _partitionKey.lastIndexOf('_'));
CurrentState curState =
accessor.getProperty(keyBuilder.currentState(instance,
sessionId,
resourceName));
if (curState == null)
{
return;
}
String state = curState.getState(_partitionKey);
if (state == null || !state.equalsIgnoreCase("LEADER"))
{
return;
}
}
try
{
_callback.onCallback(context);
}
catch (Exception e)
{
LOG.error("Error invoking callback:" + _callback, e);
}
}
}
@Override
public void onLiveInstanceChange(List<LiveInstance> liveInstances,
NotificationContext changeContext)
{
LOG.info("onLiveInstanceChange() invoked");
callParticipantCode(changeContext);
}
@Override
public void onConfigChange(List<InstanceConfig> configs,
NotificationContext changeContext)
{
LOG.info("onConfigChange() invoked");
callParticipantCode(changeContext);
}
@Override
public void onExternalViewChange(List<ExternalView> externalViewList,
NotificationContext changeContext)
{
LOG.info("onExternalViewChange() invoked");
callParticipantCode(changeContext);
}
}