CountVehiclesBolt.java

/*
 * #!
 * %
 * Copyright (C) 2014 - 2016 Humboldt-Universität zu Berlin
 * %
 * 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 de.hub.cs.dbis.lrb.operators;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

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 de.hub.cs.dbis.aeolus.utils.TimestampMerger;
import de.hub.cs.dbis.lrb.queries.utils.TopologyControl;
import de.hub.cs.dbis.lrb.types.PositionReport;
import de.hub.cs.dbis.lrb.types.internal.CountTuple;
import de.hub.cs.dbis.lrb.types.util.SegmentIdentifier;





/**
 * {@link CountVehiclesBolt} counts the number of vehicles within an express way segment (single direction) every
 * minute. The input is expected to be of type {@link PositionReport}, to be ordered by timestamp, and must be grouped
 * by {@link SegmentIdentifier}. A new count value is emitted each 60 seconds (ie, changing 'minute number' [see
 * Time.getMinute(short)]).<br />
 * <br />
 * The car count is a "count distinct", ie, if a car issue multiple {@link PositionReport}s within a single segment, the
 * car is only counted once.<br />
 * <br />
 * <strong>Input schema:</strong> {@link PositionReport}<br />
 * <strong>Output schema:</strong> {@link CountTuple} (stream: {@link TopologyControl#CAR_COUNTS_STREAM_ID})
 * 
 * @author mjsax
 */
public class CountVehiclesBolt extends BaseRichBolt {
	private static final long serialVersionUID = 6158421247331445466L;
	private static final Logger LOGGER = LoggerFactory.getLogger(CountVehiclesBolt.class);
	
	/** The Storm provided output collector. */
	private OutputCollector collector;
	
	/** Internally (re)used object to access individual attributes. */
	private final PositionReport inputPositionReport = new PositionReport();
	/** Internally (re)used object. */
	private final SegmentIdentifier segment = new SegmentIdentifier();
	
	/** Maps each segment to its set of cars. */
	private final Map<SegmentIdentifier, Set<Integer>> countsMap = new HashMap<SegmentIdentifier, Set<Integer>>();
	
	/** The currently processed 'minute number'. */
	private short currentMinute = -1;
	
	
	
	@Override
	public void prepare(@SuppressWarnings("rawtypes") Map stormConf, TopologyContext context, OutputCollector collector) {
		this.collector = collector;
	}
	
	@Override
	public void execute(Tuple input) {
		if(input.getSourceStreamId().equals(TimestampMerger.FLUSH_STREAM_ID)) {
			if(input.getValue(0) == null) {
				this.flushBuffer();
				this.collector.emit(TimestampMerger.FLUSH_STREAM_ID, new Values((Object)null));
			}
			this.collector.ack(input);
			return;
		}
		
		this.inputPositionReport.clear();
		this.inputPositionReport.addAll(input.getValues());
		LOGGER.trace(this.inputPositionReport.toString());
		
		short minute = this.inputPositionReport.getMinuteNumber();
		this.segment.set(this.inputPositionReport);
		
		assert (minute >= this.currentMinute);
		
		if(minute > this.currentMinute) {
			// emit all values for last minute
			// (because input tuples are ordered by ts (ie, minute number), we can close the last minute safely)
			if(this.countsMap.size() > 0) {
				this.flushBuffer();
				this.countsMap.clear();
			}
			this.currentMinute = minute;
			this.collector.emit(TimestampMerger.FLUSH_STREAM_ID, new Values(new Short((short)((minute * 60) - 61))));
		}
		
		Set<Integer> segCnt = this.countsMap.get(this.segment);
		if(segCnt == null) {
			segCnt = new HashSet<Integer>();
			segCnt.add(this.inputPositionReport.getVid());
			this.countsMap.put(this.segment.copy(), segCnt);
		} else {
			segCnt.add(this.inputPositionReport.getVid());
		}
		
		this.collector.ack(input);
	}
	
	private void flushBuffer() {
		for(Entry<SegmentIdentifier, Set<Integer>> entry : this.countsMap.entrySet()) {
			SegmentIdentifier segId = entry.getKey();
			
			// Minute-Number, X-Way, Segment, Direction, Avg(speed)
			this.collector.emit(TopologyControl.CAR_COUNTS_STREAM_ID, new CountTuple(new Short(
				(short)((this.currentMinute * 60) - 1)), segId.getXWay(), segId.getSegment(), segId.getDirection(),
				new Integer(entry.getValue().size())));
		}
	}
	
	@Override
	public void declareOutputFields(OutputFieldsDeclarer declarer) {
		declarer.declareStream(TopologyControl.CAR_COUNTS_STREAM_ID, CountTuple.getSchema());
		declarer.declareStream(TimestampMerger.FLUSH_STREAM_ID, new Fields("ts"));
	}
	
}