Hadoop Map/Reduce执行全流程关键代码

 转: http://blog.csdn.net/flyingpig4/article/details/7987009

Hadoop Map/Reduce 执行流程关键代码

JobClient.runJob(conf) | 运行job
|-->JobClient jc = new JobClient(job);
|-->RunningJob rj = jc.submitJob(job);
	|-->submitJobInternal(job);
		|-->int reduces = job.getNumReduceTasks();
		|-->JobContext context = new JobContext(job, jobId);
		|-->maps = writeOldSplits(job, submitSplitFile);
		|-->job.setNumMapTasks(maps);
		|-->job.writeXml(out);
		|-->JobStatus status = jobSubmitClient.submitJob(jobId);

JobTracker.submitJob(JobId) |提交job
|-->JobInProgress job = new JobInProgress(jobId, this, this.conf);
|-->checkAccess(job, QueueManager.QueueOperation.SUBMIT_JOB);  |检查权限
|-->checkMemoryRequirements(job);  |检查内存需求
|-->addJob(jobId, job);  |添加至job队列
	|-->jobs.put(job.getProfile().getJobID(), job);
	|--> for (JobInProgressListener listener : jobInProgressListeners) ｜添加至监听器，供调度使用
		|-->listener.jobAdded(job);

JobTracker.heartbeat()  |JobTracker启动后供TaskTracker以RPC方式来调用，返回Response集合
|-->List<TaskTrackerAction> actions = new ArrayList<TaskTrackerAction>();
|-->tasks = taskScheduler.assignTasks(taskTrackerStatus);  |通过调度器选择合适的tasks
|-->for (Task task : tasks)
	|-->expireLaunchingTasks.addNewTask(task.getTaskID());
	|-->actions.add(new LaunchTaskAction(task));  |实际actions还会添加commmitTask等
|-->response.setHeartbeatInterval(nextInterval);
|-->response.setActions(actions.toArray(new TaskTrackerAction[actions.size()]));
|-->return response;


TaskTracker.offerService |TaskTracker启动后通过offerservice()不断发心跳至JobTracker中
|-->transmitHeartBeat()
	|-->HeartbeatResponse heartbeatResponse = jobClient.heartbeat(status, justStarted, justInited,askForNewTask, heartbeatResponseId);
|-->TaskTrackerAction[] actions = heartbeatResponse.getActions();
|-->for(TaskTrackerAction action: actions)
	|-->if (action instanceof LaunchTaskAction)
		|-->addToTaskQueue((LaunchTaskAction)action);  |添加至执行Queue，根据map/reduce task分别添加
			|-->if (action.getTask().isMapTask()) {
				|-->mapLauncher.addToTaskQueue(action);
					|-->TaskInProgress tip = registerTask(action, this);
					|-->tasksToLaunch.add(tip);
					|-->tasksToLaunch.notifyAll();  |唤醒阻塞进程
			|-->else 
				|-->reduceLauncher.addToTaskQueue(action);

TaskLauncher.run()
|--> while (tasksToLaunch.isEmpty()) 
             |-->tasksToLaunch.wait();
|-->tip = tasksToLaunch.remove(0);
|-->startNewTask(tip);
	|-->localizeJob(tip);
		|-->launchTaskForJob(tip, new JobConf(rjob.jobConf)); 
			|-->tip.setJobConf(jobConf);
			|-->tip.launchTask();  |TaskInProgress.launchTask()
				|-->this.runner = task.createRunner(TaskTracker.this, this); |区分map/reduce
				|-->this.runner.start();
MapTaskRunner.run()  |执行MapTask
|-->File workDir = new File(lDirAlloc.getLocalPathToRead()  |准备执行路径
|-->String jar = conf.getJar();  |准备jar包
|-->File jvm = new File(new File(System.getProperty("java.home"), "bin"), "java");  |获取jvm
|-->vargs.add(Child.class.getName());  ｜添加参数，Child类作为main主函数启动
|-->tracker.addToMemoryManager(t.getTaskID(), t.isMapTask(), conf, pidFile);  |添加至内存管理
|-->jvmManager.launchJvm(this, jvmManager.constructJvmEnv(setup,vargs,stdout,stderr,logSize,  |统一纳入jvm管理器当中并启动
				workDir, env, pidFile, conf));
		|-->mapJvmManager.reapJvm(t, env);  |区分map/reduce操作

JvmManager.reapJvm()  |
|--> while (jvmIter.hasNext())
	|-->JvmRunner jvmRunner = jvmIter.next().getValue();
	|-->JobID jId = jvmRunner.jvmId.getJobId();
	|-->setRunningTaskForJvm(jvmRunner.jvmId, t);
|-->spawnNewJvm(jobId, env, t);
	|-->JvmRunner jvmRunner = new JvmRunner(env,jobId);
        |-->jvmIdToRunner.put(jvmRunner.jvmId, jvmRunner);
	|-->jvmRunner.start();   |执行JvmRunner的run()方法
		|-->jvmRunner.run()
			|-->runChild(env);
				|-->List<String> wrappedCommand =  TaskLog.captureOutAndError(env.setup, env.vargs, env.stdout, env.stderr,
						 env.logSize, env.pidFile);  |选取main函数
				|-->shexec.execute();  |执行
				|-->int exitCode = shexec.getExitCode(); ｜获取执行状态值
				|--> updateOnJvmExit(jvmId, exitCode, killed); ｜更新Jvm状态

Child.main() 执行Task(map/reduce)
|-->JVMId jvmId = new JVMId(firstTaskid.getJobID(),firstTaskid.isMap(),jvmIdInt);
|-->TaskUmbilicalProtocol umbilical = (TaskUmbilicalProtocol)RPC.getProxy(TaskUmbilicalProtocol.class,
		TaskUmbilicalProtocol.versionID, address, defaultConf);
|--> while (true) 
	|-->JvmTask myTask = umbilical.getTask(jvmId);
	|-->task = myTask.getTask();
	|-->taskid = task.getTaskID();
	|-->TaskRunner.setupWorkDir(job);
	|-->task.run(job, umbilical);   |以maptask为例
		|-->TaskReporter reporter = new TaskReporter(getProgress(), umbilical);
		|-->if (useNewApi)
			|-->runNewMapper(job, split, umbilical, reporter);
		|-->else
			|-->runOldMapper(job, split, umbilical, reporter);
				|-->inputSplit = (InputSplit) ReflectionUtils.newInstance(job.getClassByName(splitClass), job);
				|-->MapRunnable<INKEY,INVALUE,OUTKEY,OUTVALUE> runner =  ReflectionUtils.newInstance(job.getMapRunnerClass(), job);
				|-->runner.run(in, new OldOutputCollector(collector, conf), reporter);

MapRunner.run()
|--> K1 key = input.createKey();
|-->V1 value = input.createValue();
|-->while (input.next(key, value)) 
	|-->mapper.map(key, value, output, reporter);
	|--> if(incrProcCount) 
		|-->reporter.incrCounter(SkipBadRecords.COUNTER_GROUP, 
                |-->SkipBadRecords.COUNTER_MAP_PROCESSED_RECORDS, 1);
|-->mapper.close();