/**
* 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 storm.starter.bolt;
import backtype.storm.Config;
import backtype.storm.topology.BasicOutputCollector;
import backtype.storm.topology.OutputFieldsDeclarer;
import backtype.storm.topology.base.BaseBasicBolt;
import backtype.storm.tuple.Fields;
import backtype.storm.tuple.Tuple;
import backtype.storm.tuple.Values;
import org.apache.log4j.Logger;
import storm.starter.tools.Rankings;
import storm.starter.util.TupleHelpers;
import java.util.HashMap;
import java.util.Map;
/**
* This abstract bolt provides the basic behavior of bolts that rank objects according to their count.
* <p/>
* It uses a template method design pattern for {@link AbstractRankerBolt#execute(Tuple, BasicOutputCollector)} to allow
* actual bolt implementations to specify how incoming tuples are processed, i.e. how the objects embedded within those
* tuples are retrieved and counted.
*/
public abstract class AbstractRankerBolt extends BaseBasicBolt {
private static final long serialVersionUID = 4931640198501530202L;
private static final int DEFAULT_EMIT_FREQUENCY_IN_SECONDS = 2;
private static final int DEFAULT_COUNT = 10;
private final int emitFrequencyInSeconds;
private final int count;
private final Rankings rankings;
public AbstractRankerBolt() {
this(DEFAULT_COUNT, DEFAULT_EMIT_FREQUENCY_IN_SECONDS);
}
public AbstractRankerBolt(int topN) {
this(topN, DEFAULT_EMIT_FREQUENCY_IN_SECONDS);
}
public AbstractRankerBolt(int topN, int emitFrequencyInSeconds) {
if (topN < 1) {
throw new IllegalArgumentException("topN must be >= 1 (you requested " + topN + ")");
}
if (emitFrequencyInSeconds < 1) {
throw new IllegalArgumentException(
"The emit frequency must be >= 1 seconds (you requested " + emitFrequencyInSeconds + " seconds)");
}
count = topN;
this.emitFrequencyInSeconds = emitFrequencyInSeconds;
rankings = new Rankings(count);
}
protected Rankings getRankings() {
return rankings;
}
/**
* This method functions as a template method (design pattern).
*/
@Override
public final void execute(Tuple tuple, BasicOutputCollector collector) {
if (TupleHelpers.isTickTuple(tuple)) {
getLogger().debug("Received tick tuple, triggering emit of current rankings");
emitRankings(collector);
}
else {
updateRankingsWithTuple(tuple);
}
}
abstract void updateRankingsWithTuple(Tuple tuple);
private void emitRankings(BasicOutputCollector collector) {
collector.emit(new Values(rankings.copy()));
getLogger().debug("Rankings: " + rankings);
}
@Override
public void declareOutputFields(OutputFieldsDeclarer declarer) {
declarer.declare(new Fields("rankings"));
}
@Override
public Map<String, Object> getComponentConfiguration() {
Map<String, Object> conf = new HashMap<String, Object>();
conf.put(Config.TOPOLOGY_TICK_TUPLE_FREQ_SECS, emitFrequencyInSeconds);
return conf;
}
abstract Logger getLogger();
}