contrib/src/main/java/org/apache/apex/malhar/contrib/zmq/SimpleSinglePortZeroMQPullInputOperator.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.apex.malhar.contrib.zmq;

import org.zeromq.ZMQ;

import org.apache.apex.malhar.lib.io.SimpleSinglePortInputOperator;

import com.datatorrent.api.Context;

/**
 * This is the base implementation of a simple single port ZeroMQ input operator. 
 * This simple operator will automatically receive data from a pusher, convert the byte message into a tuple,
 * the emit the tuple. 
 * Subclasses should implement the method which converts ZeroMQ byte messages into tuples.
 * <p></p>
 * @displayName Simple Single Port ZeroMQ Pull Input
 * @category Messaging
 * @tags input operator
 * @since 0.3.2
 */
public abstract class SimpleSinglePortZeroMQPullInputOperator<T> extends SimpleSinglePortInputOperator<T> implements Runnable
{
  private transient ZMQ.Context context;
  private transient ZMQ.Socket sock;
  private String zmqAddress = "tcp://127.0.0.1:5555";

  @SuppressWarnings("unused")
  private SimpleSinglePortZeroMQPullInputOperator()
  {
    super();
  }

  public SimpleSinglePortZeroMQPullInputOperator(String addr)
  {
    super();
    zmqAddress = addr;
  }

  @Override
  public void run()
  {
    while (true) {
      byte[] buf = sock.recv(0);
      if (buf == null) {
        continue;
      }
      outputPort.emit(convertFromBytesToTuple(buf));
    }
  }

  protected abstract T convertFromBytesToTuple(byte[] bytes);

  @Override
  public void setup(Context.OperatorContext ctx)
  {
    context = ZMQ.context(1);
    sock = context.socket(ZMQ.PULL);
    sock.connect(zmqAddress);
  }

  @Override
  public void teardown()
  {
    sock.close();
    context.term();
  }

}