arthas源码刨析：arthas-core (2)

arthas-core的启动可以从上一篇做参考

参考 pom，即启动是调用的 Arthas 的 main 方法

attach JVM

JVM提供了 Java Attach 功能，能够让客户端与目标JVM进行通讯从而获取JVM运行时的数据，甚至可以通过Java Attach 加载自定义的代理工具，实现AOP、运行时class热更新等功能。

private void attachAgent(Configure configure) throws Exception {VirtualMachineDescriptor virtualMachineDescriptor = null;for (VirtualMachineDescriptor descriptor : VirtualMachine.list()) {String pid = descriptor.id();if (pid.equals(Long.toString(configure.getJavaPid()))) {virtualMachineDescriptor = descriptor;break;}}VirtualMachine virtualMachine = null;try {if (null == virtualMachineDescriptor) { // 使用 attach(String pid) 这种方式virtualMachine = VirtualMachine.attach("" + configure.getJavaPid());} else {virtualMachine = VirtualMachine.attach(virtualMachineDescriptor);}……try {virtualMachine.loadAgent(arthasAgentPath,configure.getArthasCore() + ";" + configure.toString());} catch (IOException e) {}

VirtualMachine.list() 相当于 jps 的功能：

attach是依靠这条代码：

virtualMachine = VirtualMachine.attach(virtualMachineDescriptor);

之后就是 loadAgent 并传入 core 和 configure 参数。

agent

agent 的代码很简单，只有2个类：

核心就是 AgentBootstrap ，对于 javaagent来说核心的启动入口：

    public static void premain(String args, Instrumentation inst) {main(args, inst);}public static void agentmain(String args, Instrumentation inst) {main(args, inst);} 

神奇不，在 arthas-core 里传入的 -core 参数实际上是透传给agent的。整的很绕。 通过 bind 方法进行线程绑定，这一步和 arthas-boot 很像。

private static synchronized void main(String args, final Instrumentation inst) {// 尝试判断arthas是否已在运行，如果是的话，直接就退出try {Class.forName("java.arthas.SpyAPI"); // 加载不到会抛异常if (SpyAPI.isInited()) {ps.println("Arthas server already stared, skip attach.");ps.flush();return;}} catch (Throwable e) {// ignore}try {ps.println("Arthas server agent start...");// 传递的args参数分两个部分:arthasCoreJar路径和agentArgs, 分别是Agent的JAR包路径和期望传递到服务端的参数if (args == null) {args = "";}args = decodeArg(args);String arthasCoreJar;final String agentArgs;int index = args.indexOf(';');if (index != -1) {arthasCoreJar = args.substring(0, index);agentArgs = args.substring(index);} else {arthasCoreJar = "";agentArgs = args;}File arthasCoreJarFile = new File(arthasCoreJar);if (!arthasCoreJarFile.exists()) {ps.println("Can not find arthas-core jar file from args: " + arthasCoreJarFile);// try to find from arthas-agent.jar directoryCodeSource codeSource = AgentBootstrap.class.getProtectionDomain().getCodeSource();if (codeSource != null) {try {File arthasAgentJarFile = new File(codeSource.getLocation().toURI().getSchemeSpecificPart());arthasCoreJarFile = new File(arthasAgentJarFile.getParentFile(), ARTHAS_CORE_JAR);if (!arthasCoreJarFile.exists()) {ps.println("Can not find arthas-core jar file from agent jar directory: " + arthasAgentJarFile);}} catch (Throwable e) {ps.println("Can not find arthas-core jar file from " + codeSource.getLocation());e.printStackTrace(ps);}}}if (!arthasCoreJarFile.exists()) {return;}/*** Use a dedicated thread to run the binding logic to prevent possible memory leak. #195*/final ClassLoader agentLoader = getClassLoader(inst, arthasCoreJarFile);Thread bindingThread = new Thread() {@Overridepublic void run() {try {bind(inst, agentLoader, agentArgs);} catch (Throwable throwable) {throwable.printStackTrace(ps);}}};bindingThread.setName("arthas-binding-thread");bindingThread.start();bindingThread.join();} catch (Throwable t) {t.printStackTrace(ps);try {if (ps != System.err) {ps.close();}} catch (Throwable tt) {// ignore}throw new RuntimeException(t);}}

ArthasBootstrap

bind 有调用了 core 里面 ArthasBootstrap.getInstance

private static void bind(Instrumentation inst, ClassLoader agentLoader, String args) throws Throwable {/*** <pre>* ArthasBootstrap bootstrap = ArthasBootstrap.getInstance(inst);* </pre>*/Class<?> bootstrapClass = agentLoader.loadClass(ARTHAS_BOOTSTRAP);Object bootstrap = bootstrapClass.getMethod(GET_INSTANCE, Instrumentation.class, String.class).invoke(null, inst, args);boolean isBind = (Boolean) bootstrapClass.getMethod(IS_BIND).invoke(bootstrap);if (!isBind) {String errorMsg = "Arthas server port binding failed! Please check $HOME/logs/arthas/arthas.log for more details.";ps.println(errorMsg);throw new RuntimeException(errorMsg);}ps.println("Arthas server already bind.");}

而在 ArthasBootstrap中 我们用的 terminal，也就是 ShellServer， 就在 6. start agent server

private ArthasBootstrap(Instrumentation instrumentation, Map<String, String> args) throws Throwable {this.instrumentation = instrumentation;initFastjson();// 1. initSpy()initSpy();// 2. ArthasEnvironmentinitArthasEnvironment(args);String outputPathStr = configure.getOutputPath();if (outputPathStr == null) {outputPathStr = ArthasConstants.ARTHAS_OUTPUT;}outputPath = new File(outputPathStr);outputPath.mkdirs();// 3. init loggerloggerContext = LogUtil.initLogger(arthasEnvironment);// 4. 增强ClassLoaderenhanceClassLoader();// 5. init beansinitBeans();// 6. start agent serverbind(configure);executorService = Executors.newScheduledThreadPool(1, new ThreadFactory() {@Overridepublic Thread newThread(Runnable r) {final Thread t = new Thread(r, "arthas-command-execute");t.setDaemon(true);return t;}});shutdown = new Thread("as-shutdown-hooker") {@Overridepublic void run() {ArthasBootstrap.this.destroy();}};transformerManager = new TransformerManager(instrumentation);Runtime.getRuntime().addShutdownHook(shutdown);}

ShellServerImpl 的 bind 这段实现中，BuiltinCommandPack 完成了命名的声明并与 cli 输入内容进行命名绑定。并用 Netty 开启server。

 /*** Bootstrap arthas server** @param configure 配置信息* @throws IOException 服务器启动失败*/private void bind(Configure configure) throws Throwable {long start = System.currentTimeMillis();if (!isBindRef.compareAndSet(false, true)) {throw new IllegalStateException("already bind");}// init random portif (configure.getTelnetPort() != null && configure.getTelnetPort() == 0) {int newTelnetPort = SocketUtils.findAvailableTcpPort();configure.setTelnetPort(newTelnetPort);logger().info("generate random telnet port: " + newTelnetPort);}if (configure.getHttpPort() != null && configure.getHttpPort() == 0) {int newHttpPort = SocketUtils.findAvailableTcpPort();configure.setHttpPort(newHttpPort);logger().info("generate random http port: " + newHttpPort);}// try to find appNameif (configure.getAppName() == null) {configure.setAppName(System.getProperty(ArthasConstants.PROJECT_NAME,System.getProperty(ArthasConstants.SPRING_APPLICATION_NAME, null)));}try {if (configure.getTunnelServer() != null) {tunnelClient = new TunnelClient();tunnelClient.setAppName(configure.getAppName());tunnelClient.setId(configure.getAgentId());tunnelClient.setTunnelServerUrl(configure.getTunnelServer());tunnelClient.setVersion(ArthasBanner.version());ChannelFuture channelFuture = tunnelClient.start();channelFuture.await(10, TimeUnit.SECONDS);}} catch (Throwable t) {logger().error("start tunnel client error", t);}try {ShellServerOptions options = new ShellServerOptions().setInstrumentation(instrumentation).setPid(PidUtils.currentLongPid()).setWelcomeMessage(ArthasBanner.welcome());if (configure.getSessionTimeout() != null) {options.setSessionTimeout(configure.getSessionTimeout() * 1000);}this.httpSessionManager = new HttpSessionManager();if (IPUtils.isAllZeroIP(configure.getIp()) && StringUtils.isBlank(configure.getPassword())) {// 当 listen 0.0.0.0 时，强制生成密码，防止被远程连接String errorMsg = "Listening on 0.0.0.0 is very dangerous! External users can connect to your machine! "+ "No password is currently configured. " + "Therefore, a default password is generated, "+ "and clients need to use the password to connect!";AnsiLog.error(errorMsg);configure.setPassword(StringUtils.randomString(64));AnsiLog.error("Generated arthas password: " + configure.getPassword());logger().error(errorMsg);logger().info("Generated arthas password: " + configure.getPassword());}this.securityAuthenticator = new SecurityAuthenticatorImpl(configure.getUsername(), configure.getPassword());shellServer = new ShellServerImpl(options);List<String> disabledCommands = new ArrayList<String>();if (configure.getDisabledCommands() != null) {String[] strings = StringUtils.tokenizeToStringArray(configure.getDisabledCommands(), ",");if (strings != null) {disabledCommands.addAll(Arrays.asList(strings));}}BuiltinCommandPack builtinCommands = new BuiltinCommandPack(disabledCommands);List<CommandResolver> resolvers = new ArrayList<CommandResolver>();resolvers.add(builtinCommands);//worker groupworkerGroup = new NioEventLoopGroup(new DefaultThreadFactory("arthas-TermServer", true));// TODO: discover user provided command resolverif (configure.getTelnetPort() != null && configure.getTelnetPort() > 0) {logger().info("try to bind telnet server, host: {}, port: {}.", configure.getIp(), configure.getTelnetPort());shellServer.registerTermServer(new HttpTelnetTermServer(configure.getIp(), configure.getTelnetPort(),options.getConnectionTimeout(), workerGroup, httpSessionManager));} else {logger().info("telnet port is {}, skip bind telnet server.", configure.getTelnetPort());}if (configure.getHttpPort() != null && configure.getHttpPort() > 0) {logger().info("try to bind http server, host: {}, port: {}.", configure.getIp(), configure.getHttpPort());shellServer.registerTermServer(new HttpTermServer(configure.getIp(), configure.getHttpPort(),options.getConnectionTimeout(), workerGroup, httpSessionManager));} else {// listen local address in VM communicationif (configure.getTunnelServer() != null) {shellServer.registerTermServer(new HttpTermServer(configure.getIp(), configure.getHttpPort(),options.getConnectionTimeout(), workerGroup, httpSessionManager));}logger().info("http port is {}, skip bind http server.", configure.getHttpPort());}for (CommandResolver resolver : resolvers) {shellServer.registerCommandResolver(resolver);}shellServer.listen(new BindHandler(isBindRef));if (!isBind()) {throw new IllegalStateException("Arthas failed to bind telnet or http port! Telnet port: "+ String.valueOf(configure.getTelnetPort()) + ", http port: "+ String.valueOf(configure.getHttpPort()));}//http api session managersessionManager = new SessionManagerImpl(options, shellServer.getCommandManager(), shellServer.getJobController());//http api handlerhttpApiHandler = new HttpApiHandler(historyManager, sessionManager);logger().info("as-server listening on network={};telnet={};http={};timeout={};", configure.getIp(),configure.getTelnetPort(), configure.getHttpPort(), options.getConnectionTimeout());// 异步回报启动次数if (configure.getStatUrl() != null) {logger().info("arthas stat url: {}", configure.getStatUrl());}UserStatUtil.setStatUrl(configure.getStatUrl());UserStatUtil.setAgentId(configure.getAgentId());UserStatUtil.arthasStart();try {SpyAPI.init();} catch (Throwable e) {// ignore}logger().info("as-server started in {} ms", System.currentTimeMillis() - start);} catch (Throwable e) {logger().error("Error during start as-server", e);destroy();throw e;}}

参考：

https://blog.csdn.net/tianjindong0804/article/details/128423819