Erik Krogen created HDFS-11352:
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             Summary: Potential deadlock in NN when failing over
                 Key: HDFS-11352
                 URL: https://issues.apache.org/jira/browse/HDFS-11352
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: namenode
    Affects Versions: 2.7.4, 2.6.6
            Reporter: Erik Krogen
            Assignee: Erik Krogen


HDFS-11180 fixed a general class of deadlock that can occur when failing over  
between the MetricsSystemImpl and FSEditLog (see comments on that JIRA for more 
details). In trunk and branch-2/branch-2.8 this fix was successful by making 
the metrics calls not synchronize on FSEditLog.

In branch-2.6 and branch-2.7 there is one more method, 
{{FSNamesystem#getTransactionsSinceLastCheckpoint}}, which still requires the 
lock on FSEditLog and thus can result in the same deadlock scenario. This can 
be seen by running {{TestFSNamesystemMBean#testWithFSEditLogLock}} _with the 
patch in HDFS-11290_ on either of these branches (it fails currently).



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