contrib/src/main/java/com/datatorrent/contrib/rabbitmq/AbstractSinglePortRabbitMQInputOperator.java

/*
 * Copyright (c) 2013 DataTorrent, Inc. ALL Rights Reserved.
 *
 * 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.
 */
package com.datatorrent.contrib.rabbitmq;

import com.datatorrent.api.DefaultOutputPort;

/**
 * This is the base implementation of a single port RabbitMQ input operator. 
 * Subclasses should implement the methods which convert RabbitMQ messages to tuples.
 * <p>
 * <br>
 * Ports:<br>
 * <b>Input</b>: No input port<br>
 * <b>Output</b>: Can have one output port<br>
 * <br>
 * Properties:<br>
 * None<br>
 * <br>
 * Compile time checks:<br>
 * Class derived from this has to implement the abstract method getTuple() <br>
 * <br>
 * Run time checks:<br>
 * None<br>
 * <br>
 * <b>Benchmarks</b>: Blast as many tuples as possible in inline mode<br>
 * <table border="1" cellspacing=1 cellpadding=1 summary="Benchmark table for AbstractSinglePortRabbitMQInputOperator&lt;K,V extends Number&gt; operator template">
 * <tr><th>In-Bound</th><th>Out-bound</th><th>Comments</th></tr>
 * <tr><td><b>10 thousand K,V pairs/s</td><td>One tuple per key per window per port</td><td>In-bound rate is the main determinant of performance. Operator can emit about 10 thousand unique (k,v immutable pairs) tuples/sec as RabbitMQ DAG. Tuples are assumed to be
 * immutable. If you use mutable tuples and have lots of keys, the benchmarks may differ</td></tr>
 * </table><br>
 * <br>
 * </p>
 * @displayName Abstract Single Port RabbitMQ Input
 * @category Messaging
 * @tags input operator
 *
 * @since 0.3.2
 */
public abstract class AbstractSinglePortRabbitMQInputOperator<T> extends AbstractRabbitMQInputOperator
{
  /**
   * This is the output port on which tuples extracted from RabbitMQ messages are emitted.
   */
  final public transient DefaultOutputPort<T> outputPort = new DefaultOutputPort<T>();

  /**
   * Any concrete class derived from AbstractSinglePortRabbitMQInputOperator has to implement this method
   * so that it knows what type of message it is going to send to Malhar.
   * It converts a byte message into a Tuple. A Tuple can be of any type (derived from Java Object) that
   * operator user intends to.
   *
   * @param message
   */
    public abstract T getTuple(byte[] message);

    @Override
    public void emitTuple(byte[] message) {
      outputPort.emit(getTuple(message));
    }
}