ABSpout.java

// Copyright 2016 Twitter. 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.twitter.heron.integration_test.common.spout;

import java.util.Map;

import com.twitter.heron.api.spout.BaseRichSpout;
import com.twitter.heron.api.spout.SpoutOutputCollector;
import com.twitter.heron.api.topology.OutputFieldsDeclarer;
import com.twitter.heron.api.topology.TopologyContext;
import com.twitter.heron.api.tuple.Fields;
import com.twitter.heron.api.tuple.Values;


/**
 * A spout that emit "A" and "B" continuously in order, one word every "nextTuple()" called. If
 * {@code appendSequenceId} is true, appends and underscore followed by the sequence id.
 */
public class ABSpout extends BaseRichSpout {
  private static final long serialVersionUID = 3233011943332591934L;
  private static final String[] TO_SEND = new String[]{"A", "B"};

  private SpoutOutputCollector collector;
  private int emitted = 0;
  private boolean appendSequenceId;

  public ABSpout() {
    this(false);
  }

  public ABSpout(boolean appendSequenceId) {
    this.appendSequenceId = appendSequenceId;
  }

  @Override
  public void declareOutputFields(OutputFieldsDeclarer declarer) {
    declarer.declare(new Fields("word"));
  }

  @Override
  public void open(Map<String, Object> conf,
                   TopologyContext context,
                   SpoutOutputCollector newCollector) {
    this.collector = newCollector;
  }

  @Override
  public void nextTuple() {
    String word = TO_SEND[emitted % TO_SEND.length];
    if (appendSequenceId) {
      word = word + "_" + emitted;
    }
    collector.emit(new Values(word));
    emitted++;
  }
}