HDFS-16496. Snapshot diff on snapshotable directory fails with not snapshottable error

[sodonnel]

Description of PR

Running a snapshot diff against some snapshotable folders gives an error:

org.apache.hadoop.hdfs.protocol.SnapshotException: Directory is neither snapshottable nor under a snap root!
	at org.apache.hadoop.hdfs.server.namenode.snapshot.SnapshotManager.checkAndGetSnapshottableAncestorDir(SnapshotManager.java:395)
	at org.apache.hadoop.hdfs.server.namenode.snapshot.SnapshotManager.diff(SnapshotManager.java:744)
	at org.apache.hadoop.hdfs.server.namenode.FSDirSnapshotOp.getSnapshotDiffReportListing(FSDirSnapshotOp.java:200)
	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getSnapshotDiffReportListing(FSNamesystem.java:6983)
	at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.getSnapshotDiffReportListing(NameNodeRpcServer.java:1977)
	at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.getSnapshotDiffReportListing(ClientNamenodeProtocolServerSideTranslatorPB.java:1387)
	at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
	at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:533)
	at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:1070)
	at org.apache.hadoop.ipc.Server$RpcCall.run(Server.java:989)
	at org.apache.hadoop.ipc.Server$RpcCall.run(Server.java:917)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAs(Subject.java:422)
	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1898)
	at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2894)

This is caused by HDFS-15483 (in order snapshot delete), and the issue is in the following method in SnapshotManager:

  public INodeDirectory getSnapshottableAncestorDir(final INodesInPath iip)
      throws IOException {
    final String path = iip.getPath();
    final INode inode = iip.getLastINode();
    final INodeDirectory dir;
    if (inode instanceof INodeDirectory) { // THIS SHOULD BE TRUE - change to inode.isDirectory()
      dir = INodeDirectory.valueOf(inode, path);
    } else {
      dir = INodeDirectory.valueOf(iip.getINode(-2), iip.getParentPath());
    }
    if (dir.isSnapshottable()) {
      return dir;
    }
    for (INodeDirectory snapRoot : this.snapshottables.values()) {
      if (dir.isAncestorDirectory(snapRoot)) {
        return snapRoot;
      }
    }
    return null;
  }

After adding some debug, I found the directory which is the snapshot root is not an instance of INodeDirectory, but instead is an "INodeReference$DstReference". I think the directory becomes an instance of this class, if the directory is renamed and one of its children has been moved out of another snapshot.

The fix is simple - just check inode.isDirectory() instead.

How was this patch tested?

Manually against an affected image with the problem.

For code changes:

[szetszwo]

+1 the change looks good. Thanks, @sodonnel !

[hadoop-yetus]

💔 -1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	0m 54s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 0s		No case conflicting files found.
+0 🆗	codespell	0m 0s		codespell was not available.
+1 💚	@author	0m 0s		The patch does not contain any @author tags.
-1 ❌	test4tests	0m 0s		The patch doesn't appear to include any new or modified tests. Please justify why no new tests are needed for this patch. Also please list what manual steps were performed to verify this patch.
			_ trunk Compile Tests _
+1 💚	mvninstall	35m 15s		trunk passed
+1 💚	compile	1m 30s		trunk passed with JDK Ubuntu-11.0.13+8-Ubuntu-0ubuntu1.20.04
+1 💚	compile	1m 23s		trunk passed with JDK Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
+1 💚	checkstyle	0m 59s		trunk passed
+1 💚	mvnsite	1m 28s		trunk passed
+1 💚	javadoc	1m 2s		trunk passed with JDK Ubuntu-11.0.13+8-Ubuntu-0ubuntu1.20.04
+1 💚	javadoc	1m 33s		trunk passed with JDK Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
+1 💚	spotbugs	3m 24s		trunk passed
+1 💚	shadedclient	25m 59s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	1m 19s		the patch passed
+1 💚	compile	1m 25s		the patch passed with JDK Ubuntu-11.0.13+8-Ubuntu-0ubuntu1.20.04
+1 💚	javac	1m 25s		the patch passed
+1 💚	compile	1m 15s		the patch passed with JDK Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
+1 💚	javac	1m 15s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	checkstyle	0m 50s		the patch passed
+1 💚	mvnsite	1m 22s		the patch passed
+1 💚	javadoc	0m 53s		the patch passed with JDK Ubuntu-11.0.13+8-Ubuntu-0ubuntu1.20.04
+1 💚	javadoc	1m 26s		the patch passed with JDK Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
+1 💚	spotbugs	3m 32s		the patch passed
+1 💚	shadedclient	25m 51s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
-1 ❌	unit	376m 56s	/patch-unit-hadoop-hdfs-project_hadoop-hdfs.txt	hadoop-hdfs in the patch passed.
+1 💚	asflicense	0m 41s		The patch does not generate ASF License warnings.
		485m 50s

Reason	Tests
Failed junit tests	hadoop.hdfs.server.namenode.snapshot.TestSnapshotDiffReport
	hadoop.hdfs.server.namenode.snapshot.TestRenameWithOrderedSnapshotDeletion

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-4051/1/artifact/out/Dockerfile
GITHUB PR	#4051
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell
uname	Linux 516427fdccea 4.15.0-166-generic #174-Ubuntu SMP Wed Dec 8 19:07:44 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / d1c9a05
Default Java	Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
Multi-JDK versions	/usr/lib/jvm/java-11-openjdk-amd64:Ubuntu-11.0.13+8-Ubuntu-0ubuntu1.20.04 /usr/lib/jvm/java-8-openjdk-amd64:Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-4051/1/testReport/
Max. process+thread count	1987 (vs. ulimit of 5500)
modules	C: hadoop-hdfs-project/hadoop-hdfs U: hadoop-hdfs-project/hadoop-hdfs
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-4051/1/console
versions	git=2.25.1 maven=3.6.3 spotbugs=4.2.2
Powered by	Apache Yetus 0.14.0-SNAPSHOT https://yetus.apache.org

This message was automatically generated.

[sodonnel]

The failing tests were related. One due to changing the error message and the other was because the inode in getSnapshottableAncestorDir can be null sometimes, so I added a null check there too. Tests now passing locally. @szetszwo could you give another check and re-confirm your +1 if you are happy with these additional minor changes? Thanks.

[hadoop-yetus]

🎊 +1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	0m 38s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 0s		No case conflicting files found.
+0 🆗	codespell	0m 0s		codespell was not available.
+1 💚	@author	0m 0s		The patch does not contain any @author tags.
+1 💚	test4tests	0m 0s		The patch appears to include 1 new or modified test files.
			_ trunk Compile Tests _
+1 💚	mvninstall	32m 4s		trunk passed
+1 💚	compile	1m 26s		trunk passed with JDK Ubuntu-11.0.13+8-Ubuntu-0ubuntu1.20.04
+1 💚	compile	1m 19s		trunk passed with JDK Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
+1 💚	checkstyle	1m 0s		trunk passed
+1 💚	mvnsite	1m 25s		trunk passed
+1 💚	javadoc	1m 3s		trunk passed with JDK Ubuntu-11.0.13+8-Ubuntu-0ubuntu1.20.04
+1 💚	javadoc	1m 32s		trunk passed with JDK Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
+1 💚	spotbugs	3m 11s		trunk passed
+1 💚	shadedclient	22m 19s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	1m 16s		the patch passed
+1 💚	compile	1m 19s		the patch passed with JDK Ubuntu-11.0.13+8-Ubuntu-0ubuntu1.20.04
+1 💚	javac	1m 19s		the patch passed
+1 💚	compile	1m 13s		the patch passed with JDK Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
+1 💚	javac	1m 13s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	checkstyle	0m 50s		the patch passed
+1 💚	mvnsite	1m 16s		the patch passed
+1 💚	javadoc	0m 49s		the patch passed with JDK Ubuntu-11.0.13+8-Ubuntu-0ubuntu1.20.04
+1 💚	javadoc	1m 27s		the patch passed with JDK Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
+1 💚	spotbugs	3m 14s		the patch passed
+1 💚	shadedclient	22m 13s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
+1 💚	unit	228m 30s		hadoop-hdfs in the patch passed.
+1 💚	asflicense	0m 45s		The patch does not generate ASF License warnings.
		326m 42s

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-4051/2/artifact/out/Dockerfile
GITHUB PR	#4051
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell
uname	Linux 8bcabe86db18 4.15.0-156-generic #163-Ubuntu SMP Thu Aug 19 23:31:58 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / d0375ca
Default Java	Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
Multi-JDK versions	/usr/lib/jvm/java-11-openjdk-amd64:Ubuntu-11.0.13+8-Ubuntu-0ubuntu1.20.04 /usr/lib/jvm/java-8-openjdk-amd64:Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-4051/2/testReport/
Max. process+thread count	3175 (vs. ulimit of 5500)
modules	C: hadoop-hdfs-project/hadoop-hdfs U: hadoop-hdfs-project/hadoop-hdfs
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-4051/2/console
versions	git=2.25.1 maven=3.6.3 spotbugs=4.2.2
Powered by	Apache Yetus 0.14.0-SNAPSHOT https://yetus.apache.org

This message was automatically generated.