jenkins源码分析 —— 发送远程请求（二）

谁借莪１个温暖的怀抱￠ 2022-05-24 00:49 220阅读 0赞

本文解析jenkins主节点向从节点发送远程请求过程的源码

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMzODczNDMx_size_16_color_FFFFFF_t_70][]

### job执行shell命令入口 ###

入口位于jenkins-core项目下的CommandInterpreter类

**public** boolean perform(AbstractBuild<?,?> build, Launcher launcher, TaskListener listener) **throws** InterruptedException \{   
...  
 r = join(launcher.launch().cmds(buildCommandLine(script)).envs(envVars).stdout(listener).pwd(ws).start());  
...  
\}

### 通过上面的start方法启动一个新的进程 ###

跳转到jenkins-core项目下的launcher类

**public** Proc start() **throws** IOException \{   
    **return** launch(**this**);  
\}

然后调用launcher类的内部类RemoteLauncher的launch方法

**public** Proc launch(ProcStarter ps) **throws** IOException \{   
   ...  
   **return** **new** ProcImpl(getChannel().call(**new** RemoteLaunchCallable(ps.commands, ps.masks, ps.envs, in, ps.reverseStdin, out, ps.reverseStdout, err, ps.reverseStderr, ps.quiet, workDir, listener)));  
   ...  
\}

### 通过Channel.call()发送远程请求 ###

通过getChannel().call()调用remoting项目(即从节点的slave.jar)的Channel类的call方法

**public** <V,T **extends** Throwable> V call(Callable<V,T> callable) **throws** IOException, T, InterruptedException \{   
           ...  
            request = **new** UserRequest<V, T>(**this**, callable);  
            UserResponse<V,T> r = request.call(**this**);  
           **return** r.retrieve(**this**, UserRequest.getClassLoader(callable));  
           ...  
\}

然后通过new UserRequest<V, T>(this, callable)方法来序列化callable(传入的是实现callable接口的RemoteLaunchCallable)并创建字节数组

### 通过new UserReques初始化UserRequest ###

位于remoting项目UserRequest类的构造方法

**public** UserRequest(Channel local, Callable<?,EXC> c) **throws** IOException \{   
        exports = local.startExportRecording();  
       **try** \{   
            request = serialize(c,local);  
       \} **finally** \{   
            exports.stopRecording();  
       \}  
  
       **this**.toString = c.toString();  
        ClassLoader cl = getClassLoader(c);  
        classLoaderProxy = RemoteClassLoader.export(cl,local);  
   \}

1.通过serialize方法序列化RemoteLaunchCallable并创建字节数组

**private** byte\[\] \_serialize(Object o, **final** Channel channel) **throws** IOException \{   
        Channel old = Channel.setCurrent(channel);  
       **try** \{   
            ByteArrayOutputStream baos = **new** ByteArrayOutputStream();  
            ObjectOutputStream oos;  
           **if** (channel.remoteCapability.supportsMultiClassLoaderRPC())  
                oos = **new** MultiClassLoaderSerializer.Output(channel,baos);  
           **else**  
                oos = **new** ObjectOutputStream(baos);  
  
            oos.writeObject(o);  
           **return** baos.toByteArray();  
       \} **finally** \{   
            Channel.setCurrent(old);  
       \}  
   \}

2. 创建一个ClassLoader代理

ClassLoader cl = getClassLoader(c);  
classLoaderProxy = RemoteClassLoader.export(cl,local);

3. 回到getChannel().call()方法，发送UserRequest到slave节点

UserResponse<V,T> r = request.call(**this**);  
**return** r.retrieve(**this**, UserRequest.getClassLoader(callable));

通过request.call(this)调用remoting项目的Request类的call方法来发送UserRequest

//Sends this request to a remote system, and blocks until we receives a response.  
    **public** **final** RSP call(Channel channel) **throws** EXC, InterruptedException, IOException \{   
       ...            
       // Channel.send() locks channel, and there are other call sequences  
       // (  like Channel.terminate()->Request.abort()->Request.onCompleted()  )  
       // that locks channel -> request, so lock objects in the same order  
       **synchronized**(channel) \{   
           **synchronized**(**this**) \{   
                response=**null**;  
  
                channel.pendingCalls.put(id,**this**);  
                channel.send(**this**);  
           \}  
       \}  
       ...  
   \}

通过channel.send(this)方法，channel把UserRequest对象写入输出流

然后等待response响应

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