JMeter example source code file (ConstantThroughputTimer.java)

This example JMeter source code file (ConstantThroughputTimer.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - JMeter tags/keywords

all, constantthroughputtimer, constantthroughputtimer, map, millisec_per_min, mutex, object, object, string, string, test, threading, threads, throughputinfo, throughputinfo, total, util

The JMeter ConstantThroughputTimer.java source code

/*
 * 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.jmeter.timers;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import org.apache.jmeter.engine.event.LoopIterationEvent;
import org.apache.jmeter.testbeans.TestBean;
import org.apache.jmeter.testelement.AbstractTestElement;
import org.apache.jmeter.testelement.TestListener;
import org.apache.jmeter.threads.JMeterContextService;
import org.apache.jmeter.threads.AbstractThreadGroup;
import org.apache.jmeter.util.JMeterUtils;
import org.apache.jorphan.logging.LoggingManager;
import org.apache.log.Logger;

/**
 * This class implements a constant throughput timer. A Constant Throughtput
 * Timer paces the samplers under its influence so that the total number of
 * samples per unit of time approaches a given constant as much as possible.
 *
 * There are two different ways of pacing the requests:
 * - delay each thread according to when it last ran
 * - delay each thread according to when any thread last ran
 */
public class ConstantThroughputTimer extends AbstractTestElement implements Timer, TestListener, TestBean {
    private static final long serialVersionUID = 3;

    private static class ThroughputInfo{
        final Object MUTEX = new Object();
        long lastScheduledTime = 0;
    }
    private static final Logger log = LoggingManager.getLoggerForClass();

    private static final double MILLISEC_PER_MIN = 60000.0;

    /**
     * Target time for the start of the next request. The delay provided by the
     * timer will be calculated so that the next request happens at this time.
     */
    private long previousTime = 0;

    private String calcMode; // String representing the mode
                                // (Locale-specific)

    private int modeInt; // mode as an integer

    /**
     * Desired throughput, in samples per minute.
     */
    private double throughput;

    //For calculating throughput across all threads
    private final static ThroughputInfo allThreadsInfo = new ThroughputInfo();

    //For holding the ThrougputInfo objects for all ThreadGroups. Keyed by AbstractThreadGroup objects
    private final static Map<AbstractThreadGroup, ThroughputInfo> threadGroupsInfoMap =
        new ConcurrentHashMap<AbstractThreadGroup, ThroughputInfo>();


    /**
     * Constructor for a non-configured ConstantThroughputTimer.
     */
    public ConstantThroughputTimer() {
    }

    /**
     * Sets the desired throughput.
     *
     * @param throughput
     *            Desired sampling rate, in samples per minute.
     */
    public void setThroughput(double throughput) {
        this.throughput = throughput;
    }

    /**
     * Gets the configured desired throughput.
     *
     * @return the rate at which samples should occur, in samples per minute.
     */
    public double getThroughput() {
        return throughput;
    }

    public String getCalcMode() {
        return calcMode;
    }

    // Needed by test code
    int getCalcModeInt() {
        return modeInt;
    }

    public void setCalcMode(String mode) {
        this.calcMode = mode;
        // TODO find better way to get modeInt
        this.modeInt = ConstantThroughputTimerBeanInfo.getCalcModeAsInt(calcMode);
    }

    /**
     * Retrieve the delay to use during test execution.
     *
     * @see org.apache.jmeter.timers.Timer#delay()
     */
    public long delay() {
        long currentTime = System.currentTimeMillis();

        /*
         * If previous time is zero, then target will be in the past.
         * This is what we want, so first sample is run without a delay.
        */
        long currentTarget = previousTime  + calculateDelay();
        if (currentTime > currentTarget) {
            // We're behind schedule -- try to catch up:
            previousTime = currentTime;
            return 0;
        }
        previousTime = currentTarget;
        return currentTarget - currentTime;
    }

    /**
     * @param currentTime
     * @return new Target time
     */
    // TODO - is this used? (apart from test code)
    protected long calculateCurrentTarget(long currentTime) {
        return currentTime + calculateDelay();
    }

    // Calculate the delay based on the mode
    private long calculateDelay() {
        long delay = 0;
        // N.B. we fetch the throughput each time, as it may vary during a test
        double msPerRequest = (MILLISEC_PER_MIN / getThroughput());
        switch (modeInt) {
        case 1: // Total number of threads
            delay = (long) (JMeterContextService.getNumberOfThreads() * msPerRequest);
            break;

        case 2: // Active threads in this group
            delay = (long) (JMeterContextService.getContext().getThreadGroup().getNumberOfThreads() * msPerRequest);
            break;

        case 3: // All threads - alternate calculation
            delay = calculateSharedDelay(allThreadsInfo,(long) msPerRequest);
            break;

        case 4: //All threads in this group - alternate calculation
            final org.apache.jmeter.threads.AbstractThreadGroup group =
                JMeterContextService.getContext().getThreadGroup();
            ThroughputInfo groupInfo;
            synchronized (threadGroupsInfoMap) {
                groupInfo = threadGroupsInfoMap.get(group);
                if (groupInfo == null) {
                    groupInfo = new ThroughputInfo();
                    threadGroupsInfoMap.put(group, groupInfo);
                }
            }
            delay = calculateSharedDelay(groupInfo,(long) msPerRequest);
            break;

        default: // e.g. 0
            delay = (long) msPerRequest; // i.e. * 1
            break;
        }
        return delay;
    }

    private long calculateSharedDelay(ThroughputInfo info, long milliSecPerRequest) {
        final long now = System.currentTimeMillis();
        final long calculatedDelay;

        //Synchronize on the info object's MUTEX to ensure
        //Multiple threads don't update the scheduled time simultaneously
        synchronized (info.MUTEX) {
            final long nextRequstTime = info.lastScheduledTime + milliSecPerRequest;
            info.lastScheduledTime = Math.max(now, nextRequstTime);
            calculatedDelay = info.lastScheduledTime - now;
        }

        return Math.max(calculatedDelay, 0);
    }

    private synchronized void reset() {
        allThreadsInfo.lastScheduledTime = 0;
        threadGroupsInfoMap.clear();
        previousTime = 0;
    }

    /**
     * Provide a description of this timer class.
     *
     * TODO: Is this ever used? I can't remember where. Remove if it isn't --
     * TODO: or obtain text from bean's displayName or shortDescription.
     *
     * @return the description of this timer class.
     */
    @Override
    public String toString() {
        return JMeterUtils.getResString("constant_throughput_timer_memo"); //$NON-NLS-1$
    }

    /**
     * Get the timer ready to compute delays for a new test.
     * <p>
     * {@inheritDoc}
     */
    public void testStarted()
    {
        log.debug("Test started - reset throughput calculation.");
        reset();
    }

    /**
     * {@inheritDoc}
     */
    public void testEnded() {
    }

    /**
     * {@inheritDoc}
     */
    public void testStarted(String host) {
        testStarted();
    }

    /**
     * {@inheritDoc}
     */
    public void testEnded(String host) {
    }

    /**
     * {@inheritDoc}
     */
    public void testIterationStart(LoopIterationEvent event) {
    }
}