性能工具之 JMeter 5.0 核心源码浅析（上）

引言

周末无聊看了下 JMeter5.0 的源码，本文就当做个小结，水平有限，如有理解不到位或错误的的地方，望大家指出，谢谢。

源码下载地址：
https://github.com/apache/jmeter
废话不多说，下面进入正题~

源码结构

工程目录

源码目录

源码分析

运行机制

• HashTree 是 JMeter 执行测试依赖的数据结构，在执行测试之前进行配置测试数据，HashTree将数据组织到一个递归树结构中，并提供了操作该结构的方法

• StandardJMeterEngine 执行JMeter 测试 ,直接用于本地 GUI 和非 GUI 调用，或者在服务器模式下运行时由 RemoteJMeterEngineImpl 启动

• JMeterEngine 接口被运行 JMeter的测试类实现，此接口共8个方法，JMeterEngine本质就是一个线程。

代码分析

此处以非GUI模式运行JMeter为例，了解下JMeter的运行机制。首先我们找到入口类 NewDriver。

main 方法代码如下：

 /**
     * The main program which actually runs JMeter.
     * mian方法
     * @param args
     *            the command line arguments
     */
    public static void main(String[] args) {
        if(!EXCEPTIONS_IN_INIT.isEmpty()) {
            System.err.println("Configuration error during init, see exceptions:"+exceptionsToString(EXCEPTIONS_IN_INIT));
        } else {
            Thread.currentThread().setContextClassLoader(loader);

            setLoggingProperties(args);

            try {
            	// 加载JMeter类
                Class<?> initialClass = loader.loadClass("org.apache.jmeter.JMeter");// $NON-NLS-1$
                // 获取JMeter类实例
				Object instance = initialClass.getDeclaredConstructor().newInstance();
				// 获取start方法类型实例
                Method startup = initialClass.getMethod("start", new Class[] { new String[0].getClass() });// $NON-NLS-1$
				// 反射调用JMeter类的start方法
				startup.invoke(instance, new Object[] { args });
            } catch(Throwable e){ // NOSONAR We want to log home directory in case of exception
                e.printStackTrace(); // NOSONAR No logger at this step
                System.err.println("JMeter home directory was detected as: "+JMETER_INSTALLATION_DIRECTORY);
            }
        }
    }

很明显，这里是通过反射调用 JMeter 类的 start 方法。
接下来我们看下 start 方法。

 /**
     * Takes the command line arguments and uses them to determine how to
     * startup JMeter.
     * 根据命令行执行不同的操作
	 * 主要功能为：1）startgui 2)startnogui
	 *
     * Called reflectively by {@link NewDriver#main(String[])}
     * @param args The arguments for JMeter
     */
    public void start(String[] args) {
    	// 解析命令号参数的类
        CLArgsParser parser = new CLArgsParser(args, options);
        // 错误信息
        String error = parser.getErrorString();
        if (error == null){// Check option combinations 检查选项组合
            boolean gui = parser.getArgumentById(NONGUI_OPT)==null;
            boolean nonGuiOnly = parser.getArgumentById(REMOTE_OPT)!=null
                               || parser.getArgumentById(REMOTE_OPT_PARAM)!=null
                               || parser.getArgumentById(REMOTE_STOP)!=null;
            if (gui && nonGuiOnly) {
                error = "-r and -R and -X are only valid in non-GUI mode";
            }
        }
        // 输出错误信息
        if (null != error) {
            System.err.println("Error: " + error);//NOSONAR
            System.out.println("Usage");//NOSONAR
            System.out.println(CLUtil.describeOptions(options).toString());//NOSONAR
            // repeat the error so no need to scroll back past the usage to see it
            System.out.println("Error: " + error);//NOSONAR
            return;
        }
        try {
        	// 初始化配置，同时初始化JMeter日志
            initializeProperties(parser); // Also initialises JMeter logging

            Thread.setDefaultUncaughtExceptionHandler(
                    (Thread t, Throwable e) -> {
                    if (!(e instanceof ThreadDeath)) {
                        log.error("Uncaught exception: ", e);
                        System.err.println("Uncaught Exception " + e + ". See log file for details.");//NOSONAR
                    }
            });

            if (log.isInfoEnabled()) {
                log.info(JMeterUtils.getJMeterCopyright());
                log.info("Version {}", JMeterUtils.getJMeterVersion());
                log.info("java.version={}", System.getProperty("java.version"));//$NON-NLS-1$ //$NON-NLS-2$
                log.info("java.vm.name={}", System.getProperty("java.vm.name"));//$NON-NLS-1$ //$NON-NLS-2$
                log.info("os.name={}", System.getProperty("os.name"));//$NON-NLS-1$ //$NON-NLS-2$
                log.info("os.arch={}", System.getProperty("os.arch"));//$NON-NLS-1$ //$NON-NLS-2$
                log.info("os.version={}", System.getProperty("os.version"));//$NON-NLS-1$ //$NON-NLS-2$
                log.info("file.encoding={}", System.getProperty("file.encoding"));//$NON-NLS-1$ //$NON-NLS-2$
                log.info("Max memory     ={}", Runtime.getRuntime().maxMemory());
                log.info("Available Processors ={}", Runtime.getRuntime().availableProcessors());
                log.info("Default Locale={}", Locale.getDefault().getDisplayName());
                log.info("JMeter  Locale={}", JMeterUtils.getLocale().getDisplayName());
                log.info("JMeterHome={}", JMeterUtils.getJMeterHome());
                log.info("user.dir  ={}", System.getProperty("user.dir"));//$NON-NLS-1$ //$NON-NLS-2$
                log.info("PWD       ={}", new File(".").getCanonicalPath());//$NON-NLS-1$
                log.info("IP: {} Name: {} FullName: {}", JMeterUtils.getLocalHostIP(), JMeterUtils.getLocalHostName(),
                        JMeterUtils.getLocalHostFullName());
            }
            setProxy(parser);

            updateClassLoader();
            if (log.isDebugEnabled())
            {
                String jcp=System.getProperty("java.class.path");// $NON-NLS-1$
                String[] bits = jcp.split(File.pathSeparator);
                log.debug("ClassPath");
                for(String bit : bits){
                    log.debug(bit);
                }
            }

            // Set some (hopefully!) useful properties 设置属性
            long now=System.currentTimeMillis();
            JMeterUtils.setProperty("START.MS",Long.toString(now));// $NON-NLS-1$
            Date today=new Date(now); // so it agrees with above
            JMeterUtils.setProperty("START.YMD",new SimpleDateFormat("yyyyMMdd").format(today));// $NON-NLS-1$ $NON-NLS-2$
            JMeterUtils.setProperty("START.HMS",new SimpleDateFormat("HHmmss").format(today));// $NON-NLS-1$ $NON-NLS-2$

			// 判断
            if (parser.getArgumentById(VERSION_OPT) != null) {
                displayAsciiArt();
            } else if (parser.getArgumentById(HELP_OPT) != null) {
                displayAsciiArt();
                System.out.println(JMeterUtils.getResourceFileAsText("org/apache/jmeter/help.txt"));//NOSONAR $NON-NLS-1$
            } else if (parser.getArgumentById(OPTIONS_OPT) != null) {
                displayAsciiArt();
                System.out.println(CLUtil.describeOptions(options).toString());//NOSONAR
            } else if (parser.getArgumentById(SERVER_OPT) != null) {
                // Start the server 启动服务
                try {
                    RemoteJMeterEngineImpl.startServer(RmiUtils.getRmiRegistryPort()); // $NON-NLS-1$
                    startOptionalServers();
                } catch (Exception ex) {
                    System.err.println("Server failed to start: "+ex);//NOSONAR
                    log.error("Giving up, as server failed with:", ex);
                    throw ex;
                }
            } else {
                String testFile=null;
                CLOption testFileOpt = parser.getArgumentById(TESTFILE_OPT);
                if (testFileOpt != null){
                    testFile = testFileOpt.getArgument();
                    if (USE_LAST_JMX.equals(testFile)) {
                        testFile = LoadRecentProject.getRecentFile(0);// most recent
                    }
                }
                CLOption testReportOpt = parser.getArgumentById(REPORT_GENERATING_OPT);
                if (testReportOpt != null) { // generate report from existing file 从现有文件生成报告
                    String reportFile = testReportOpt.getArgument();
                    extractAndSetReportOutputFolder(parser, false);
                    ReportGenerator generator = new ReportGenerator(reportFile, null);
                    generator.generate();
                } else if (parser.getArgumentById(NONGUI_OPT) == null) { // not non-GUI => GUI
                	// 在GUI模式下执行
                    startGui(testFile);
                    startOptionalServers();
                } else { // NON-GUI must be true 必须为无GUI模式
                    extractAndSetReportOutputFolder(parser, deleteResultFile);
                    
                    CLOption rem = parser.getArgumentById(REMOTE_OPT_PARAM);
                    if (rem == null) {
                        rem = parser.getArgumentById(REMOTE_OPT);
                    }
                    CLOption jtl = parser.getArgumentById(LOGFILE_OPT);
                    String jtlFile = null;
                    if (jtl != null) {
                        jtlFile = processLAST(jtl.getArgument(), ".jtl"); // $NON-NLS-1$
                    }
                    CLOption reportAtEndOpt = parser.getArgumentById(REPORT_AT_END_OPT);
                    if(reportAtEndOpt != null && jtlFile == null) {
                        throw new IllegalUserActionException(
                                "Option -"+ ((char)REPORT_AT_END_OPT)+" requires -"+((char)LOGFILE_OPT )+ " option");
                    }
                    // 无GUI执行
                    startNonGui(testFile, jtlFile, rem, reportAtEndOpt != null);
                    startOptionalServers();
                }
            }
        } catch (IllegalUserActionException e) {// NOSONAR
            System.out.println("Incorrect Usage:"+e.getMessage());//NOSONAR
            System.out.println(CLUtil.describeOptions(options).toString());//NOSONAR
        } catch (Throwable e) { // NOSONAR
            log.error("An error occurred: ", e);
            System.out.println("An error occurred: " + e.getMessage());//NOSONAR
            // FIXME Should we exit here ? If we are called by Maven or Jenkins
            System.exit(1);
        }
    }

start 方法主要还是根据命令执行不同的启动方法。

无 GUI 方法启动。

   private void startNonGui(String testFile, String logFile, CLOption remoteStart, boolean generateReportDashboard)
            throws IllegalUserActionException, ConfigurationException {
        // add a system property so samplers can check to see if JMeter
        // is running in NonGui mode
        System.setProperty(JMETER_NON_GUI, "true");// $NON-NLS-1$
        JMeter driver = new JMeter();// TODO - why does it create a new instance?
        driver.remoteProps = this.remoteProps;
        driver.remoteStop = this.remoteStop;
        driver.deleteResultFile = this.deleteResultFile;
        
        PluginManager.install(this, false);

        String remoteHostsString = null;
        if (remoteStart != null) {
            remoteHostsString = remoteStart.getArgument();
            if (remoteHostsString == null) {
                remoteHostsString = JMeterUtils.getPropDefault(
                        "remote_hosts", //$NON-NLS-1$
                        "127.0.0.1");//NOSONAR $NON-NLS-1$ 
            }
        }
        if (testFile == null) {
            throw new IllegalUserActionException("Non-GUI runs require a test plan");
        }
        // 运行场景
        driver.runNonGui(testFile, logFile, remoteStart != null, remoteHostsString, generateReportDashboard);
    }

GUI方法启动

 /**
     * Starts up JMeter in GUI mode
	 * JMeter GUI启动
     */
    private void startGui(String testFile) {
        System.out.println("================================================================================");//NOSONAR
        System.out.println("Don't use GUI mode for load testing !, only for Test creation and Test debugging.");//NOSONAR
        System.out.println("For load testing, use NON GUI Mode:");//NOSONAR
        System.out.println("   jmeter -n -t [jmx file] -l [results file] -e -o [Path to web report folder]");//NOSONAR
        System.out.println("& increase Java Heap to meet your test requirements:");//NOSONAR
        System.out.println("   Modify current env variable HEAP=\"-Xms1g -Xmx1g -XX:MaxMetaspaceSize=256m\" in the jmeter batch file");//NOSONAR
        System.out.println("Check : https://jmeter.apache.org/usermanual/best-practices.html");//NOSONAR
        System.out.println("================================================================================");//NOSONAR

		// 设置加载进度条  splash.setProgress(10/30/60/90/100)
        SplashScreen splash = new SplashScreen();
        splash.showScreen();
        String jMeterLaf = LookAndFeelCommand.getJMeterLaf();
        try {
            log.info("Setting LAF to: {}", jMeterLaf);
            UIManager.setLookAndFeel(jMeterLaf);
        } catch (Exception ex) {
            log.warn("Could not set LAF to: {}", jMeterLaf, ex);
        }
        splash.setProgress(10);
        JMeterUtils.applyHiDPIOnFonts();
        PluginManager.install(this, true);

        JMeterTreeModel treeModel = new JMeterTreeModel();
        splash.setProgress(30);
        JMeterTreeListener treeLis = new JMeterTreeListener(treeModel);
        final ActionRouter instance = ActionRouter.getInstance();
        instance.populateCommandMap(); //这个方法会去寻找<project>/lib/ext 下所有的jar
        splash.setProgress(60);
        treeLis.setActionHandler(instance);
        GuiPackage.initInstance(treeLis, treeModel);
        splash.setProgress(80);
        MainFrame main = new MainFrame(treeModel, treeLis);
        splash.setProgress(100);
        ComponentUtil.centerComponentInWindow(main, 80);
        main.setLocationRelativeTo(splash);
        main.setVisible(true);
        main.toFront();
        instance.actionPerformed(new ActionEvent(main, 1, ActionNames.ADD_ALL));
        if (testFile != null) {
            try {
                File f = new File(testFile);
				log.info("Loading file: {}", f);
                FileServer.getFileServer().setBaseForScript(f);

                HashTree tree = SaveService.loadTree(f);

                GuiPackage.getInstance().setTestPlanFile(f.getAbsolutePath());

                Load.insertLoadedTree(1, tree);
            } catch (ConversionException e) {
                log.error("Failure loading test file", e);
                JMeterUtils.reportErrorToUser(SaveService.CEtoString(e));
            } catch (Exception e) {
                log.error("Failure loading test file", e);
                JMeterUtils.reportErrorToUser(e.toString());
            }
        } else {
            JTree jTree = GuiPackage.getInstance().getMainFrame().getTree();
            TreePath path = jTree.getPathForRow(0);
            jTree.setSelectionPath(path);
            FocusRequester.requestFocus(jTree);
        }
        splash.setProgress(100);
        splash.close();
    }

在来看下 runNonGui 方法，主要功能是执行脚本。

// run test in batch mode  批处理运行测试
    private void runNonGui(String testFile, String logFile, boolean remoteStart, String remoteHostsString, boolean generateReportDashboard) {
        try {
        	// 获取脚本文件
            File f = new File(testFile);
            if (!f.exists() || !f.isFile()) {
                println("Could not open " + testFile);
                return;
            }
            // 设置脚本文件
            FileServer.getFileServer().setBaseForScript(f);

            HashTree tree = SaveService.loadTree(f);

            @SuppressWarnings("deprecation") // Deliberate use of deprecated ctor
            JMeterTreeModel treeModel = new JMeterTreeModel(new Object());// NOSONAR Create non-GUI version to avoid headless problems
            JMeterTreeNode root = (JMeterTreeNode) treeModel.getRoot();
            treeModel.addSubTree(tree, root);

            // Hack to resolve ModuleControllers in non GUI mode
            SearchByClass<ReplaceableController> replaceableControllers =
                    new SearchByClass<>(ReplaceableController.class);
            tree.traverse(replaceableControllers);
            Collection<ReplaceableController> replaceableControllersRes = replaceableControllers.getSearchResults();
            for (ReplaceableController replaceableController : replaceableControllersRes) {
                replaceableController.resolveReplacementSubTree(root);
            }

            // Ensure tree is interpreted (ReplaceableControllers are replaced)
            // For GUI runs this is done in Start.java
			// 将测试文件(.jmx文件)解析成HashTree
            HashTree clonedTree = convertSubTree(tree, true);
            
            Summariser summariser = null;
            String summariserName = JMeterUtils.getPropDefault("summariser.name", "");//$NON-NLS-1$
            if (summariserName.length() > 0) {
                log.info("Creating summariser <{}>", summariserName);
                println("Creating summariser <" + summariserName + ">");
                summariser = new Summariser(summariserName);
            }
            ResultCollector resultCollector = null;
            if (logFile != null) {
                resultCollector = new ResultCollector(summariser);
                resultCollector.setFilename(logFile);
                clonedTree.add(clonedTree.getArray()[0], resultCollector);
            }
            else {
                // only add Summariser if it can not be shared with the ResultCollector
                if (summariser != null) {
                    clonedTree.add(clonedTree.getArray()[0], summariser);
                }
            }

            if (deleteResultFile) {
                SearchByClass<ResultCollector> resultListeners = new SearchByClass<>(ResultCollector.class);
                clonedTree.traverse(resultListeners);
                Iterator<ResultCollector> irc = resultListeners.getSearchResults().iterator();
                while (irc.hasNext()) {
                    ResultCollector rc = irc.next();
                    File resultFile = new File(rc.getFilename());
                    if (resultFile.exists() && !resultFile.delete()) {
                        throw new IllegalStateException("Could not delete results file " + resultFile.getAbsolutePath()
                            + "(canRead:"+resultFile.canRead()+", canWrite:"+resultFile.canWrite()+")");
                    }
                }
            }
            ReportGenerator reportGenerator = null;
            if (logFile != null && generateReportDashboard) {
                reportGenerator = new ReportGenerator(logFile, resultCollector);
            }

            // Used for remote notification of threads start/stop,see BUG 54152
            // Summariser uses this feature to compute correctly number of threads 
            // when NON GUI mode is used
            clonedTree.add(clonedTree.getArray()[0], new RemoteThreadsListenerTestElement());

            List<JMeterEngine> engines = new LinkedList<>();
            clonedTree.add(clonedTree.getArray()[0], new ListenToTest(remoteStart && remoteStop ? engines : null, reportGenerator));
            println("Created the tree successfully using "+testFile);
            if (!remoteStart) {
            	// 实例化一个JMeterEngine来对付脚本，JMeterEngine本质就是一个线程
                JMeterEngine engine = new StandardJMeterEngine();
                engine.configure(clonedTree);
                long now=System.currentTimeMillis();
                println("Starting the test @ "+new Date(now)+" ("+now+")");
                // 调用runTest方法
                engine.runTest();
                engines.add(engine);
            } else {
                java.util.StringTokenizer st = new java.util.StringTokenizer(remoteHostsString, ",");//$NON-NLS-1$
                List<String> hosts = new LinkedList<>();
                while (st.hasMoreElements()) {
                    hosts.add((String) st.nextElement());
                }
                
                DistributedRunner distributedRunner=new DistributedRunner(this.remoteProps);
                distributedRunner.setStdout(System.out); // NOSONAR
                distributedRunner.setStdErr(System.err); // NOSONAR
                distributedRunner.init(hosts, clonedTree);
                engines.addAll(distributedRunner.getEngines());
                distributedRunner.start();
            }
            startUdpDdaemon(engines);
        } catch (Exception e) {
            System.out.println("Error in NonGUIDriver " + e.toString());//NOSONAR
            log.error("Error in NonGUIDriver", e);
        }
    }
    

整体再来梳理下JMeter类逻辑，抛开 GUI 和 Remote test相关的代码，简单说，JMeter 做的事情主要有：

• 解析命令行参数，加载配置文件；
• 将 .Jmx 文件解析成 HashTree；
• 实例化一个StandardJMeterEngine,并把测试的工作交给JMeterEngine；

当然，JMeter类还有其他重要的职责，比如监听所有的 JMeterEngine ,当接收到 GUI 的 StopTestNow / Shutdown 等命令时候来调用JMeterEngine接口相应的方法。

接下来看下JMeterEngine，看下这个接口都提供哪些方法？

/**
 * This interface is implemented by classes that can run JMeter tests.
 */
public interface JMeterEngine {
    /**
     * Configure engine
	 * 配置引擎
     * @param testPlan the test plan
     */
    void configure(HashTree testPlan);

    /**
     * Runs the test
	 * 执行测试
     * @throws JMeterEngineException if an error occurs
     */
    void runTest() throws JMeterEngineException;

    /**
     * Stop test immediately interrupting current samplers
	 * 停止测试，立即打断当前samplers
     */
    default void stopTest() {
        stopTest(true);
    }
    /**
     * 停止测试，根据参数是否立即打断当前samplers
     * @param now boolean that tell wether stop is immediate (interrupt) or not (wait for current sample end)
     */
    void stopTest(boolean now);

    /**
     * Stop test if running
	 * 停止测试运行
     */
    void reset();

    /**
     * set Properties on engine
	 * 设置引擎属性
     * @param p the properties to set
     */
    void setProperties(Properties p);

    /**
     * Exit engine
	 * 退出引擎
     */
    void exit();
    
    /**
	 * 引擎是否活跃
     * @return boolean Flag to show whether engine is active (true when test is running). Set to false at end of test
     */
    boolean isActive();
}

JMeterEngine 依赖于 HashTree，而 HashTree 是由 jmx 文件解析而来,每一个 JMeter 测试计划都会对应一个 jmx 文件。所以我们只要生成合理的 jmx 文件，就可以通过 JMeterEngine 压测引擎去执行测试任务。

具体 jmx 文件的生成方式，我们可以借鉴JMeter GUI模式下 jmx 文件生成方式。在这里我们的演示的处理方式是，先定义每个组件的生成方式，然后再按一定结构组装各个组件，示意代码如下。