net.sf.sessionAnalysis.SessionVisitorSessionLengthNanosStatistics.java Source code

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Here is the source code for net.sf.sessionAnalysis.SessionVisitorSessionLengthNanosStatistics.java

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/***************************************************************************
 * Copyright (c) 2016 the WESSBAS project
 *
 * 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 net.sf.sessionAnalysis;

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.util.LinkedList;
import java.util.List;
import java.util.TreeMap;
import java.util.Map.Entry;
import java.util.concurrent.atomic.AtomicInteger;

import org.apache.commons.lang3.ArrayUtils;
import org.apache.commons.math3.stat.descriptive.moment.Mean;
import org.apache.commons.math3.stat.descriptive.moment.StandardDeviation;

/**
 * Computes a histogram of the lengths of the sessions passed to {@link #handleSession(Session)}.
 * 
 * @author Andre van Hoorn
 * 
 */
// TODO: Compute measures once handleEOF called and return precomputed values
// TODO: Probably quite stupid to collect the nano values in a TreeMap ... 
public class SessionVisitorSessionLengthNanosStatistics implements ISessionDatVisitor {
    private final TreeMap<Long, AtomicInteger> sessionLengthHistogram = new TreeMap<Long, AtomicInteger>();

    public void handleSession(Session session) {
        final long curLength = session.getSessionLengthNanos();
        AtomicInteger curFrequency = sessionLengthHistogram.get(curLength);
        if (curFrequency == null) { // session length not observed before
            curFrequency = new AtomicInteger(0);
            sessionLengthHistogram.put(curLength, curFrequency);
        }
        curFrequency.incrementAndGet();
    }

    public void handleEOF() {
        // nothing to do on termination
    }

    /**
     * The returned TreeMap contains the observed session lengths as keys
     * and their absolute frequencies values.
     */
    public TreeMap<Long, AtomicInteger> getSessionLengthHistogram() {
        return sessionLengthHistogram;
    }

    public double computeSessionLengthMean() {
        double[] lengths = computeLengthVector();
        Mean meanObj = new Mean();
        return meanObj.evaluate(lengths);
    }

    public double computeSessionLengthStdDev() {
        double[] lengths = computeLengthVector();
        StandardDeviation stdDevObj = new StandardDeviation();
        return stdDevObj.evaluate(lengths);
    }

    /**
     *  Transforms the aggregated length information in {@link #sessionLengthHistogram} 
     *  into a vector.   
     */
    public double[] computeLengthVector() {
        List<Double> lengths = new LinkedList<Double>();
        for (Entry<Long, AtomicInteger> entry : this.sessionLengthHistogram.entrySet()) {
            for (int i = 0; i < entry.getValue().get(); i++) {
                lengths.add((double) entry.getKey());
            }
        }
        return ArrayUtils.toPrimitive(lengths.toArray(new Double[] {}));
    }

    public void writeSessionsOverTime(final String outputDir) throws IOException {
        FileWriter fw = new FileWriter(
                outputDir + "/" + this.getClass().getSimpleName() + "-sessionLengthsNanoSeconds.csv");
        BufferedWriter writer = new BufferedWriter(fw);

        writer.write("lengthNanos");
        writer.newLine();
        for (double l : this.computeLengthVector()) {
            writer.write(Double.toString(l));
            writer.newLine();
        }

        writer.close();
        fw.close();
    }
}