| /** |
| * 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.examples.bolt; |
| |
| import java.util.List; |
| import java.util.Map; |
| import java.util.logging.Logger; |
| |
| import org.apache.storm.task.OutputCollector; |
| import org.apache.storm.task.TopologyContext; |
| import org.apache.storm.topology.OutputFieldsDeclarer; |
| import org.apache.storm.topology.base.BaseWindowedBolt; |
| import org.apache.storm.tuple.Fields; |
| import org.apache.storm.tuple.Tuple; |
| import org.apache.storm.tuple.Values; |
| import org.apache.storm.windowing.TupleWindow; |
| |
| |
| /** |
| * Computes sliding window sum |
| */ |
| public class SlidingWindowSumBolt extends BaseWindowedBolt { |
| private static final Logger LOG = Logger.getLogger(SlidingWindowSumBolt.class.getName()); |
| private static final long serialVersionUID = 1490605223057444309L; |
| |
| private int sum = 0; |
| private OutputCollector collector; |
| |
| @Override |
| @SuppressWarnings("HiddenField") |
| public void prepare(Map topoConf, TopologyContext context, OutputCollector |
| collector) { |
| this.collector = collector; |
| } |
| |
| @Override |
| public void execute(TupleWindow inputWindow) { |
| /* |
| * The inputWindow gives a view of |
| * (a) all the events in the window |
| * (b) events that expired since last activation of the window |
| * (c) events that newly arrived since last activation of the window |
| */ |
| List<Tuple> tuplesInWindow = inputWindow.get(); |
| List<Tuple> newTuples = inputWindow.getNew(); |
| List<Tuple> expiredTuples = inputWindow.getExpired(); |
| |
| LOG.fine("Events in current window: " + tuplesInWindow.size()); |
| /* |
| * Instead of iterating over all the tuples in the window to compute |
| * the sum, the values for the new events are added and old events are |
| * subtracted. Similar optimizations might be possible in other |
| * windowing computations. |
| */ |
| for (Tuple tuple : newTuples) { |
| sum += (int) tuple.getValue(0); |
| } |
| for (Tuple tuple : expiredTuples) { |
| sum -= (int) tuple.getValue(0); |
| } |
| collector.emit(new Values(sum)); |
| } |
| |
| @Override |
| public void declareOutputFields(OutputFieldsDeclarer declarer) { |
| declarer.declare(new Fields("sum")); |
| } |
| } |