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From "Ben Podgursky (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-10323) transient deleteOnExit failure in ViewFileSystem due to close() ordering
Date Thu, 21 Apr 2016 21:59:13 GMT
Ben Podgursky created HDFS-10323:
------------------------------------

             Summary: transient deleteOnExit failure in ViewFileSystem due to close() ordering
                 Key: HDFS-10323
                 URL: https://issues.apache.org/jira/browse/HDFS-10323
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: federation
            Reporter: Ben Podgursky


After switching to using a ViewFileSystem, fs.deleteOnExit calls began failing frequently,
displaying this error on failure:

16/04/21 13:56:24 INFO fs.FileSystem: Ignoring failure to deleteOnExit for path /tmp/delete_on_exit_test_123/a438afc0-a3ca-44f1-9eb5-010ca4a62d84

Since FileSystem eats the error involved, it is difficult to be sure what the error is, but
I believe what is happening is that the ViewFileSystem’s child FileSystems are being close()’d
before the ViewFileSystem, due to the random order ClientFinalizer closes FileSystems; so
then when the ViewFileSystem tries to close(), it tries to forward the delete() calls to the
appropriate child, and fails because the child is already closed.

I’m unsure how to write an actual Hadoop test to reproduce this, since it involves testing
behavior on actual JVM shutdown.  However, I can verify that while

{code:java}
fs.deleteOnExit(randomTemporaryDir);

{code}

regularly (~50% of the time) fails to delete the temporary directory, this code:

{code:java}
ViewFileSystem viewfs = (ViewFileSystem)fs1;
for (FileSystem fileSystem : viewfs.getChildFileSystems())
{
  if (fileSystem.exists(randomTemporaryDir)) {
    fileSystem.deleteOnExit(randomTemporaryDir);

 }
}

{code}

always successfully deletes the temporary directory on JVM shutdown.

I am not very familiar with FileSystem inheritance hierarchies, but at first glance I see
two ways to fix this behavior:

1)  ViewFileSystem could forward deleteOnExit calls to the appropriate child FileSystem, and
not hold onto that path itself.

2) FileSystem.Cache.closeAll could first close all ViewFileSystems, then all other FileSystems.
 

Would appreciate any thoughts of whether this seems accurate, and thoughts (or help) on the
fix.



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