作业启动注释添加

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/MRAppMaster.java

@@ -1676,6 +1676,7 @@ public static void main(String[] args) {
       ShutdownHookManager.get().addShutdownHook(
         new MRAppMasterShutdownHook(appMaster), SHUTDOWN_HOOK_PRIORITY);
       JobConf conf = new JobConf(new YarnConfiguration());
+      // 加载job.xml信息
       conf.addResource(new Path(MRJobConfig.JOB_CONF_FILE));
       
       MRWebAppUtil.initialize(conf);

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/commit/CommitterEventHandler.java

@@ -252,6 +252,7 @@ public void run() {
     @SuppressWarnings("unchecked")
     protected void handleJobSetup(CommitterJobSetupEvent event) {
       try {
+        // 主要是创建attempt路径
         committer.setupJob(event.getJobContext());
         context.getEventHandler().handle(
             new JobSetupCompletedEvent(event.getJobID()));

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/job/impl/JobImpl.java

@@ -1455,6 +1455,7 @@ public JobStateInternal transition(JobImpl job, JobEvent event) {
       }
       
       try {
+        // 初始化token等信息。
         setup(job);
         job.fs = job.getFileSystem(job.conf);