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From "Aaron T. Myers (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-3835) Long-lived 2NN cannot perform a checkpoint if security is enabled and the NN restarts without outstanding delegation tokens
Date Wed, 22 Aug 2012 01:18:38 GMT
Aaron T. Myers created HDFS-3835:
------------------------------------

             Summary: Long-lived 2NN cannot perform a checkpoint if security is enabled and
the NN restarts without outstanding delegation tokens
                 Key: HDFS-3835
                 URL: https://issues.apache.org/jira/browse/HDFS-3835
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: name-node, security
    Affects Versions: 2.0.0-alpha
            Reporter: Aaron T. Myers
            Assignee: Aaron T. Myers


When the 2NN wants to perform a checkpoint, it figures out the highest transaction ID of the
fsimage files on the NN, and if the 2NN has a copy of that fsimage file (because it created
that merged fsimage file the last time it did a checkpoint) then the 2NN won't download the
fsimage file from the NN, and instead only gets the new edits files from the NN. In this case,
the 2NN also doesn't even bother reloading the fsimage file it has from disk, since it has
all of the namespace state in-memory. This all works just fine.

When the 2NN _doesn't_ have a copy of the relevant fsimage file (for example, if the NN had
restarted since the last checkpoint) then the 2NN blows away its in-memory namespace state,
downloads the fsimage file from the NN, and loads the newly-downloaded fsimage file from disk.
The bug is that when the 2NN clears its in-memory state, it only resets the namespace, but
not the delegation token map.

The fix is pretty simple - just make the delegation token map get cleared as well as the namespace
state when a running 2NN needs to load a new fsimage from disk.

Credit to Stephen Chu for identifying this issue.

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