subprojects/s4-comm/src/main/java/org/apache/s4/comm/topology/ClusterFromHelix.java

/**
 * 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.s4.comm.topology;

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.inject.Inject;
import com.google.inject.name.Named;

import org.apache.helix.ConfigAccessor;
import org.apache.helix.ConfigScopeBuilder;
import org.apache.helix.HelixDataAccessor;
import org.apache.helix.HelixManager;
import org.apache.helix.HelixProperty;
import org.apache.helix.NotificationContext;
import org.apache.helix.PropertyKey.Builder;
import org.apache.helix.model.ExternalView;
import org.apache.helix.model.IdealState;
import org.apache.helix.model.InstanceConfig;
import org.apache.helix.spectator.RoutingTableProvider;

/**
 * Represents a logical cluster definition fetched from Zookeeper. Notifies
 * listeners of runtime changes in the configuration.
 * 
 */
public class ClusterFromHelix extends RoutingTableProvider implements Cluster
{

  private static Logger logger = LoggerFactory
      .getLogger(ClusterFromHelix.class);

  private final String clusterName;
  private final AtomicReference<PhysicalCluster> clusterRef;
  private final List<ClusterChangeListener> listeners;
  private final Lock lock;
  private final AtomicReference<Map<String, Integer>> partitionCountMapRef;

  /**
   * only the local topology
   */
  @Inject
  public ClusterFromHelix(@Named("s4.cluster.name") String clusterName,
      @Named("s4.cluster.zk_address") String zookeeperAddress,
      @Named("s4.cluster.zk_session_timeout") int sessionTimeout,
      @Named("s4.cluster.zk_connection_timeout") int connectionTimeout)
      throws Exception
  {
    this.clusterName = clusterName;
    Map<String, Integer> map = Collections.emptyMap();
    partitionCountMapRef = new AtomicReference<Map<String, Integer>>(map);
    this.clusterRef = new AtomicReference<PhysicalCluster>();
    this.listeners = new ArrayList<ClusterChangeListener>();
    lock = new ReentrantLock();

  }

  /**
   * any topology
   */
  public ClusterFromHelix(String clusterName, ZkClient zkClient,
      String machineId)
  {
    this.clusterName = clusterName;
    Map<String, Integer> map = Collections.emptyMap();
    partitionCountMapRef = new AtomicReference<Map<String, Integer>>(map);
    this.clusterRef = new AtomicReference<PhysicalCluster>();
    this.listeners = new ArrayList<ClusterChangeListener>();
    lock = new ReentrantLock();

  }

  @Override
  public void onExternalViewChange(List<ExternalView> externalViewList,
      NotificationContext changeContext)
  {
    lock.lock();
    try
    {
      logger.info("Start:Processing change in cluster topology");
      super.onExternalViewChange(externalViewList, changeContext);
      HelixManager manager = changeContext.getManager();
      HelixDataAccessor helixDataAccessor = manager.getHelixDataAccessor();
      ConfigAccessor configAccessor = manager.getConfigAccessor();
      ConfigScopeBuilder builder = new ConfigScopeBuilder();
      Builder keyBuilder = helixDataAccessor.keyBuilder();
      List<String> resources = helixDataAccessor.getChildNames(keyBuilder
          .idealStates());
      Map<String,Integer> map = new HashMap<String, Integer>();
      for (String resource : resources)
      {
        String resourceType = configAccessor.get(
            builder.forCluster(clusterName).forResource(resource)
                .build(), "type");
        if("Task".equalsIgnoreCase(resourceType)){
          String streamName = configAccessor.get(
              builder.forCluster(clusterName).forResource(resource)
                  .build(), "streamName");
          IdealState idealstate = helixDataAccessor.getProperty(keyBuilder.idealStates(resource));
          map.put(streamName, idealstate.getNumPartitions());
        }
      }
      partitionCountMapRef.set(map);
      for (ClusterChangeListener listener : listeners)
      {
        listener.onChange();
      }
      logger.info("End:Processing change in cluster topology");

    } catch (Exception e)
    {
      logger.error("", e);
    } finally
    {
      lock.unlock();
    }
  }

  @Override
  public PhysicalCluster getPhysicalCluster()
  {
    return clusterRef.get();
  }

  @Override
  public void addListener(ClusterChangeListener listener)
  {
    logger.info("Adding topology change listener:" + listener);
    listeners.add(listener);
  }

  @Override
  public void removeListener(ClusterChangeListener listener)
  {
    logger.info("Removing topology change listener:" + listener);
    listeners.remove(listener);
  }

  @Override
  public int hashCode()
  {
    final int prime = 31;
    int result = 1;
    result = prime * result
        + ((clusterName == null) ? 0 : clusterName.hashCode());
    return result;
  }

  @Override
  public boolean equals(Object obj)
  {
    if (this == obj)
      return true;
    if (obj == null)
      return false;
    if (getClass() != obj.getClass())
      return false;
    ClusterFromHelix other = (ClusterFromHelix) obj;
    if (clusterName == null)
    {
      if (other.clusterName != null)
        return false;
    } else if (!clusterName.equals(other.clusterName))
      return false;
    return true;
  }

  @Override
  public InstanceConfig getDestination(String streamName, int partitionId)
  {
    List<InstanceConfig> instances = getInstances(streamName, streamName + "_"
        + partitionId, "LEADER");
    if (instances.size() == 1)
    {
      return instances.get(0);
    } else
    {
      return null;
    }
  }
  
  @Override
  public Integer getPartitionCount(String streamName){
    Integer numPartitions = partitionCountMapRef.get().get(streamName);
    if(numPartitions==null){
      return -1;
    }
    return numPartitions;
  }

}