samoa-threads/src/main/java/org/apache/samoa/topology/impl/ThreadsProcessingItem.java

package org.apache.samoa.topology.impl;

/*
 * #%L
 * SAMOA
 * %%
 * Copyright (C) 2013 Yahoo! Inc.
 * %%
 * Licensed 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.
 * #L%
 */

import java.util.ArrayList;
import java.util.List;

import org.apache.samoa.core.ContentEvent;
import org.apache.samoa.core.Processor;
import org.apache.samoa.topology.AbstractProcessingItem;
import org.apache.samoa.topology.ProcessingItem;
import org.apache.samoa.topology.Stream;
import org.apache.samoa.utils.PartitioningScheme;
import org.apache.samoa.utils.StreamDestination;

/**
 * ProcessingItem for multithreaded engine.
 * 
 * @author Anh Thu Vu
 * 
 */
public class ThreadsProcessingItem extends AbstractProcessingItem {
  // Replicas of the ProcessingItem.
  // When ProcessingItem receives an event, it assigns one
  // of these replicas to process the event.
  private List<ThreadsProcessingItemInstance> piInstances;

  // Each replica of ProcessingItem is assigned to one of the
  // available threads in a round-robin fashion, i.e.: each
  // replica is associated with the index of a thread.
  // Each ProcessingItem has a random offset variable so that
  // the allocation of PI replicas to threads are spread evenly
  // among all threads.
  private int offset;

  /*
   * Constructor
   */
  public ThreadsProcessingItem(Processor processor, int parallelismHint) {
    super(processor, parallelismHint);
    this.offset = (int) (Math.random() * ThreadsEngine.getNumberOfThreads());
  }

  public List<ThreadsProcessingItemInstance> getProcessingItemInstances() {
    return this.piInstances;
  }

  /*
   * Connects to streams
   */
  @Override
  protected ProcessingItem addInputStream(Stream inputStream, PartitioningScheme scheme) {
    StreamDestination destination = new StreamDestination(this, this.getParallelism(), scheme);
    ((ThreadsStream) inputStream).addDestination(destination);
    return this;
  }

  /*
   * Process the received event.
   */
  public void processEvent(ContentEvent event, int counter) {
    if (this.piInstances == null || this.piInstances.size() < this.getParallelism())
      throw new IllegalStateException(
          "ThreadsWorkerProcessingItem(s) need to be setup before process any event (i.e. in ThreadsTopology.start()).");

    ThreadsProcessingItemInstance piInstance = this.piInstances.get(counter);
    ThreadsEventRunnable runnable = new ThreadsEventRunnable(piInstance, event);
    ThreadsEngine.getThreadWithIndex(piInstance.getThreadIndex()).submit(runnable);
  }

  /*
   * Setup the replicas of this PI. This should be called after the topology is
   * set up (all Processors and PIs are setup and connected to the respective
   * streams) and before events are sent.
   */
  public void setupInstances() {
    this.piInstances = new ArrayList<ThreadsProcessingItemInstance>(this.getParallelism());
    for (int i = 0; i < this.getParallelism(); i++) {
      Processor newProcessor = this.getProcessor().newProcessor(this.getProcessor());
      newProcessor.onCreate(i + 1);
      this.piInstances.add(new ThreadsProcessingItemInstance(newProcessor, this.offset + i));
    }
  }

}