examples/storm-starter/src/jvm/org/apache/storm/starter/bolt/SingleJoinBolt.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.storm.starter.bolt;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.apache.storm.Config;
import org.apache.storm.generated.GlobalStreamId;
import org.apache.storm.task.OutputCollector;
import org.apache.storm.task.TopologyContext;
import org.apache.storm.topology.OutputFieldsDeclarer;
import org.apache.storm.topology.base.BaseRichBolt;
import org.apache.storm.tuple.Fields;
import org.apache.storm.tuple.Tuple;
import org.apache.storm.utils.TimeCacheMap;

/**
 * Example of a simple custom bolt for joining two streams.
 * NOTE: Prefer to use the built-in JoinBolt wherever applicable
 */
public class SingleJoinBolt extends BaseRichBolt {
    OutputCollector collector;
    Fields idFields;
    Fields outFields;
    int numSources;
    TimeCacheMap<List<Object>, Map<GlobalStreamId, Tuple>> pending;
    Map<String, GlobalStreamId> fieldLocations;

    public SingleJoinBolt(Fields outFields) {
        this.outFields = outFields;
    }

    @Override
    public void prepare(Map<String, Object> conf, TopologyContext context, OutputCollector collector) {
        fieldLocations = new HashMap<String, GlobalStreamId>();
        this.collector = collector;
        int timeout = ((Number) conf.get(Config.TOPOLOGY_MESSAGE_TIMEOUT_SECS)).intValue();
        pending = new TimeCacheMap<List<Object>, Map<GlobalStreamId, Tuple>>(timeout, new ExpireCallback());
        numSources = context.getThisSources().size();
        Set<String> idFields = null;
        for (GlobalStreamId source : context.getThisSources().keySet()) {
            Fields fields = context.getComponentOutputFields(source.get_componentId(), source.get_streamId());
            Set<String> setFields = new HashSet<String>(fields.toList());
            if (idFields == null) {
                idFields = setFields;
            } else {
                idFields.retainAll(setFields);
            }

            for (String outfield : outFields) {
                for (String sourcefield : fields) {
                    if (outfield.equals(sourcefield)) {
                        fieldLocations.put(outfield, source);
                    }
                }
            }
        }
        this.idFields = new Fields(new ArrayList<String>(idFields));

        if (fieldLocations.size() != outFields.size()) {
            throw new RuntimeException("Cannot find all outfields among sources");
        }
    }

    @Override
    public void execute(Tuple tuple) {
        List<Object> id = tuple.select(idFields);
        GlobalStreamId streamId = new GlobalStreamId(tuple.getSourceComponent(), tuple.getSourceStreamId());
        if (!pending.containsKey(id)) {
            pending.put(id, new HashMap<GlobalStreamId, Tuple>());
        }
        Map<GlobalStreamId, Tuple> parts = pending.get(id);
        if (parts.containsKey(streamId)) {
            throw new RuntimeException("Received same side of single join twice");
        }
        parts.put(streamId, tuple);
        if (parts.size() == numSources) {
            pending.remove(id);
            List<Object> joinResult = new ArrayList<Object>();
            for (String outField : outFields) {
                GlobalStreamId loc = fieldLocations.get(outField);
                joinResult.add(parts.get(loc).getValueByField(outField));
            }
            collector.emit(new ArrayList<Tuple>(parts.values()), joinResult);

            for (Tuple part : parts.values()) {
                collector.ack(part);
            }
        }
    }

    @Override
    public void declareOutputFields(OutputFieldsDeclarer declarer) {
        declarer.declare(outFields);
    }

    private class ExpireCallback implements TimeCacheMap.ExpiredCallback<List<Object>, Map<GlobalStreamId, Tuple>> {
        @Override
        public void expire(List<Object> id, Map<GlobalStreamId, Tuple> tuples) {
            for (Tuple tuple : tuples.values()) {
                collector.fail(tuple);
            }
        }
    }
}