HDFS-17922 rename2 in the router asynchronous RPC is missing an async path

[dParikesit]

Description of PR

JIRA: HDFS-17922

In RouterAsyncClientProtocol:rename2, there is a path that returns synchronously if we have empty locations if (locs.isEmpty).

@Override
  public void rename2(
      final String src, final String dst,
      final Options.Rename... options) throws IOException {
    ...
    if (locs.isEmpty()) {
      rbfRename.routerFedRename(src, dst, srcLocations, dstLocations);
      // Missing async handling
      return;
    }
    ...
    asyncApply((AsyncApplyFunction<Boolean, Boolean>) isMultiDestDirectory -> {
      if (isMultiDestDirectory) {
        ...
        rpcClient.invokeConcurrent(locs, method);
      } else {
        rpcClient.invokeSequential(locs, method, null, null);
      }
    });
  }

There are other paths that behave similarly, such as msync()

@Override
  public void msync() throws IOException {
    rpcServer.checkOperation(NameNode.OperationCategory.READ, true);
    ...
    if (namespacesEligibleForObserverReads.isEmpty()) {
      asyncCompleteWith(CompletableFuture.completedFuture(null));
      return;
    }
    rpcClient.invokeConcurrent(namespacesEligibleForObserverReads, method);
  } 

We propose to add a patch to add asyncComplete(null); before the return.

How was this patch tested?

mvn -am -pl hadoop-hdfs-project/hadoop-hdfs-rbf -Dtest=TestRouterAsyncFederationRename test

[dParikesit]

Hello @KeeProMise , would you be able to help review this PR? This is similar to the router async rpc problem in #8297. Thank you very much!

[hadoop-yetus]

🎊 +1 overall

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+1 💚	@author	0m 0s		The patch does not contain any @author tags.
+1 💚	test4tests	0m 0s		The patch appears to include 2 new or modified test files.
			_ trunk Compile Tests _
+1 💚	mvninstall	26m 11s		trunk passed
+1 💚	compile	0m 43s		trunk passed with JDK Ubuntu-21.0.10+7-Ubuntu-124.04
+1 💚	compile	0m 51s		trunk passed with JDK Ubuntu-17.0.18+8-Ubuntu-124.04.1
+1 💚	checkstyle	0m 38s		trunk passed
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+1 💚	javadoc	0m 38s		trunk passed with JDK Ubuntu-21.0.10+7-Ubuntu-124.04
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+1 💚	spotbugs	1m 25s		trunk passed
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			_ Patch Compile Tests _
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+1 💚	javac	0m 29s		the patch passed
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			_ Other Tests _
+1 💚	unit	37m 28s		hadoop-hdfs-rbf in the patch passed.
+1 💚	asflicense	0m 26s		The patch does not generate ASF License warnings.
		108m 5s

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[KeeProMise]

LGTM. @hfutatzhanghb if you have time, please help to take a look at this PR, thanks!

[hfutatzhanghb]

@KeeProMise Thanks a lot for involving me. Thanks @dParikesit report this issue, make sense to me. But i suggest to update the unit test case to better clarify the bug. When i drop asyncComplete(null);, the unit test you submit can also pass.

[dParikesit]

Hello, @hfutatzhanghb Thanks for reviewing the pr.

When i drop asyncComplete(null);, the unit test you submit can also pass.

Interesting. Can you elaborate more about your setup and how you run the test? I'm testing it on an Intel Xeon Silver 4310 with Ubuntu 22.04. It passed with the asyncComplete, and gave this assertion error without the asyncComplete.

[hfutatzhanghb]

Hello, @hfutatzhanghb Thanks for reviewing the pr.

When i drop asyncComplete(null);, the unit test you submit can also pass.

Interesting. Can you elaborate more about your setup and how you run the test? I'm testing it on an Intel Xeon Silver 4310 with Ubuntu 22.04. It passed with the asyncComplete, and gave this assertion error without the asyncComplete.

LGTM. +1
I compile and run the unit test again, it behavied as expected.