HADOOP-19283. Move all DistCp execution logic to execute() (#7060)

Co-authored-by: Felix Nguyen <kokonguyen191@gmail.com>

hadoop-tools/hadoop-distcp/src/main/java/org/apache/hadoop/tools/DistCp.java

@@ -140,9 +140,7 @@ public class DistCp extends Configured implements Tool {
     
     try {
       context = new DistCpContext(OptionsParser.parse(argv));
-      checkSplitLargeFile();
-      setTargetPathExists();
-      LOG.info("Input Options: " + context);
+      LOG.info("Input Options: {}", context);
     } catch (Throwable e) {
       LOG.error("Invalid arguments: ", e);
       System.err.println("Invalid arguments: " + e.getMessage());
@@ -152,7 +150,7 @@ public class DistCp extends Configured implements Tool {
 
     Job job = null;
     try {
-      job = execute();
+      job = execute(true);
     } catch (InvalidInputException e) {
       LOG.error("Invalid input: ", e);
       return DistCpConstants.INVALID_ARGUMENT;
@@ -169,7 +167,7 @@ public class DistCp extends Configured implements Tool {
       LOG.error("Exception encountered ", e);
       return DistCpConstants.UNKNOWN_ERROR;
     } finally {
-      //Blocking distcp so close the job after its done
+      // Blocking distcp so close the job after it's done
       if (job != null && context.shouldBlock()) {
         try {
           job.close();
@@ -181,15 +179,31 @@ public class DistCp extends Configured implements Tool {
     return DistCpConstants.SUCCESS;
   }
 
+  /**
+   * Original entrypoint of a distcp job. Calls {@link DistCp#execute(boolean)}
+   * without doing extra context checks and setting some configs.
+   * @return Job handle
+   * @throws Exception when fails to submit distcp job or distcp job fails
+   */
+  public Job execute() throws Exception {
+    return execute(false);
+  }
+
   /**
    * Implements the core-execution. Creates the file-list for copy,
    * and launches the Hadoop-job, to do the copy.
+   * @param extraContextChecks if true, does extra context checks and sets some configs.
    * @return Job handle
-   * @throws Exception
+   * @throws Exception when fails to submit distcp job or distcp job fails, or context checks fail
    */
-  public Job execute() throws Exception {
+  public Job execute(boolean extraContextChecks) throws Exception {
     Preconditions.checkState(context != null,
         "The DistCpContext should have been created before running DistCp!");
+    if (extraContextChecks) {
+      checkSplitLargeFile();
+      setTargetPathExists();
+    }
+
     Job job = createAndSubmitJob();
 
     if (context.shouldBlock()) {

hadoop-tools/hadoop-distcp/src/test/java/org/apache/hadoop/tools/TestExternalCall.java

@@ -156,7 +156,10 @@ public class TestExternalCall {
     DistCp distcp = mock(DistCp.class);
     Job job = spy(Job.class);
     Mockito.when(distcp.getConf()).thenReturn(conf);
-    Mockito.when(distcp.execute()).thenReturn(job);
+    Mockito.when(distcp.createAndSubmitJob()).thenReturn(job);
+    Mockito.when(distcp.execute()).thenCallRealMethod();
+    Mockito.when(distcp.execute(Mockito.anyBoolean())).thenCallRealMethod();
+    Mockito.doReturn(true).when(job).waitForCompletion(Mockito.anyBoolean());
     Mockito.when(distcp.run(Mockito.any())).thenCallRealMethod();
     String[] arg = { soure.toString(), target.toString() };