作业启动注释添加

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSOutputStream.java

@@ -277,6 +277,7 @@ static DFSOutputStream newStreamForCreate(DFSClient dfsClient, String src,
       while (shouldRetry) {
         shouldRetry = false;
         try {
+          // 通过rpc调用namenode(或者router，router最终还是会调用到namnode)创建文件。
           stat = dfsClient.namenode.create(src, masked, dfsClient.clientName,
               new EnumSetWritable<>(flag), createParent, replication,
               blockSize, SUPPORTED_CRYPTO_VERSIONS, ecPolicyName,

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/qjournal/protocol/QJournalProtocol.java

@@ -42,6 +42,9 @@
  * 
  * This is responsible for sending edits as well as coordinating
  * recovery of the nodes.
+ * 主要适用于Journal组件中处理edits log：
+ * 1、 接受edit log
+ * 2、 发送edit给namenode，方便恢复
  */
 @KerberosInfo(
     serverPrincipal = DFSConfigKeys.DFS_JOURNALNODE_KERBEROS_PRINCIPAL_KEY,

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNodeRpcServer.java

@@ -785,6 +785,7 @@ public HdfsFileStatus create(String src, FsPermission masked,
       String storagePolicy)
       throws IOException {
     checkNNStartup();
+    // 获取客户端的ip
     String clientMachine = getClientMachine();
     if (stateChangeLog.isDebugEnabled()) {
       stateChangeLog.debug("*DIR* NameNode.create: file "

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/Job.java

@@ -1669,12 +1669,14 @@ public void submit()
          throws IOException, InterruptedException, ClassNotFoundException {
     ensureState(JobState.DEFINE);
     setUseNewAPI();
+    // 连接RM
     connect();
     final JobSubmitter submitter = 
         getJobSubmitter(cluster.getFileSystem(), cluster.getClient());
     status = ugi.doAs(new PrivilegedExceptionAction<JobStatus>() {
       public JobStatus run() throws IOException, InterruptedException, 
       ClassNotFoundException {
+        // 提交作业
         return submitter.submitJobInternal(Job.this, cluster);
       }
     });