metron-streaming/Metron-Common/src/main/java/org/apache/metron/bolt/JoinBolt.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.metron.bolt;

import backtype.storm.task.OutputCollector;
import backtype.storm.task.TopologyContext;
import backtype.storm.topology.OutputFieldsDeclarer;
import backtype.storm.topology.base.BaseRichBolt;
import backtype.storm.tuple.Fields;
import backtype.storm.tuple.Tuple;
import backtype.storm.tuple.Values;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Sets;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;

public abstract class JoinBolt<V> extends BaseRichBolt {

  private static final Logger LOG = LoggerFactory
          .getLogger(JoinBolt.class);
  protected OutputCollector collector;
  protected ImmutableSet<String> streamIds;

  protected transient CacheLoader<String, Map<String, V>> loader;
  protected transient LoadingCache<String, Map<String, V>> cache;
  protected Long maxCacheSize;
  protected Long maxTimeRetain;

  public JoinBolt withMaxCacheSize(long maxCacheSize) {
    this.maxCacheSize = maxCacheSize;
    return this;
  }

  public JoinBolt withMaxTimeRetain(long maxTimeRetain) {
    this.maxTimeRetain = maxTimeRetain;
    return this;
  }

  @Override
  public void prepare(Map map, TopologyContext topologyContext, OutputCollector outputCollector) {
    this.collector = outputCollector;
    if (this.maxCacheSize == null)
      throw new IllegalStateException("maxCacheSize must be specified");
    if (this.maxTimeRetain == null)
      throw new IllegalStateException("maxTimeRetain must be specified");
    loader = new CacheLoader<String, Map<String, V>>() {
      public Map<String, V> load(String key) throws Exception {
        return new HashMap<>();
      }
    };
    cache = CacheBuilder.newBuilder().maximumSize(maxCacheSize)
            .expireAfterWrite(maxTimeRetain, TimeUnit.MINUTES)
            .build(loader);
    Set<String> temp = getStreamIds();
    temp.add("message");
    streamIds = ImmutableSet.copyOf(temp);
    prepare(map, topologyContext);
  }

  @SuppressWarnings("unchecked")
  @Override
  public void execute(Tuple tuple) {
    String streamId = tuple.getSourceStreamId();
    String key = (String) tuple.getValueByField("key");
    V value = (V) tuple.getValueByField("message");
    try {
      Map<String, V> streamValueMap = cache.get(key);
      if (streamValueMap.containsKey(streamId)) {
        LOG.warn(String.format("Received key %s twice for " +
                "stream %s", key, streamId));
      }
      streamValueMap.put(streamId, value);
      Set<String> streamValueKeys = streamValueMap.keySet();
      if (streamValueKeys.size() == streamIds.size() && Sets.symmetricDifference
              (streamValueKeys, streamIds)
              .isEmpty()) {
        collector.emit("message", tuple, new Values(key, joinValues
                (streamValueMap)));
        collector.ack(tuple);
        cache.invalidate(key);
      } else {
        cache.put(key, streamValueMap);
      }
    } catch (ExecutionException e) {
      LOG.error(e.getMessage(), e);
    }
  }

  @Override
  public void declareOutputFields(OutputFieldsDeclarer declarer) {
    declarer.declareStream("message", new Fields("key", "message"));
  }

  public abstract void prepare(Map map, TopologyContext topologyContext);

  public abstract Set<String> getStreamIds();

  public abstract V joinValues(Map<String, V> streamValueMap);
}