Checkins.java

package stormapplied.heatmap.topology;

import backtype.storm.spout.SpoutOutputCollector;
import backtype.storm.task.TopologyContext;
import backtype.storm.topology.OutputFieldsDeclarer;
import backtype.storm.topology.base.BaseRichSpout;
import backtype.storm.tuple.Fields;
import backtype.storm.tuple.Values;
import org.apache.commons.io.IOUtils;

import java.io.IOException;
import java.nio.charset.Charset;
import java.util.List;
import java.util.Map;

public class Checkins extends BaseRichSpout {
  private List<String> checkins;
  private int nextEmitIndex;
  private SpoutOutputCollector outputCollector;

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

  @Override
  public void open(Map map,
                   TopologyContext topologyContext,
                   SpoutOutputCollector spoutOutputCollector) {
    this.outputCollector = spoutOutputCollector;
    this.nextEmitIndex = 0;

    try {
      checkins = IOUtils.readLines(ClassLoader.getSystemResourceAsStream("checkins.txt"),
                                   Charset.defaultCharset().name());
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
  }

  @Override
  public void nextTuple() {
    String checkin = checkins.get(nextEmitIndex);
    String[] parts = checkin.split(",");
    Long time = Long.valueOf(parts[0]);
    String address = parts[1];
    outputCollector.emit(new Values(time, address));

    nextEmitIndex = (nextEmitIndex + 1) % checkins.size();
  }
}