AggregatorBolt.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.core;

import java.io.IOException;
import java.text.ParseException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.logging.Level;
import java.util.logging.Logger;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

import com.twitter.heron.api.bolt.OutputCollector;
import com.twitter.heron.api.topology.OutputFieldsDeclarer;
import com.twitter.heron.api.topology.TopologyContext;
import com.twitter.heron.api.tuple.Tuple;

/**
 * A Bolt which collects the tuples, converts them into json,
 * and posts the json into the given http server.
 */
public class AggregatorBolt extends BaseBatchBolt implements ITerminalBolt {
  private static final long serialVersionUID = -2994625720418843748L;
  private static final Logger LOG = Logger.getLogger(AggregatorBolt.class.getName());
  private static final ObjectMapper MAPPER = new ObjectMapper();

  private final String httpPostUrl;

  private final List<String> result;

  public AggregatorBolt(String httpPostUrl) {
    this.httpPostUrl = httpPostUrl;
    this.result = new ArrayList<String>();
  }

  @Override
  public void finishBatch() {
    // Convert to String and emit it
    writeFinishedData();
  }

  @Override
  public void prepare(Map<String, Object> map,
                      TopologyContext topologyContext,
                      OutputCollector outputCollector) {
  }

  @Override
  public void execute(Tuple tuple) {
    // Once we get something, convert to JSON String
    String tupleInJSON = "";
    try {
      tupleInJSON = MAPPER.writeValueAsString(tuple.getValue(0));
    } catch (JsonProcessingException e) {
      LOG.log(Level.SEVERE,
          "Could not convert map to JSONString: " + tuple.getValue(0).toString(), e);
    }
    result.add(tupleInJSON);
  }

  @Override
  public void declareOutputFields(OutputFieldsDeclarer outputFieldsDeclarer) {
    // The last bolt we append, nothing to emit.
  }

  public void writeFinishedData() {
    String resultJson = result.toString();
    LOG.info(String.format("Posting actual result to %s: %s",  httpPostUrl, resultJson));
    try {
      int responseCode = -1;
      for (int attempts = 0; attempts < 2; attempts++) {
        responseCode = HttpUtils.httpJsonPost(httpPostUrl, resultJson);
        if (responseCode == 200) {
          return;
        }
      }
      throw new RuntimeException(
          String.format("Failed to post actual result to %s: %s",  httpPostUrl, responseCode));
    } catch (IOException | ParseException e) {
      throw new RuntimeException(String.format("Posting result to %s failed",  httpPostUrl), e);
    }
  }
}