Uma Maheswara Rao G created HDFS-5474:
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             Summary: Deletesnapshot can make Namenode in safemode on NN 
restarts.
                 Key: HDFS-5474
                 URL: https://issues.apache.org/jira/browse/HDFS-5474
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: snapshots
            Reporter: Uma Maheswara Rao G
            Assignee: sathish


When we deletesnapshot, we are deleting the blocks associated to that snapshot 
and after that we do logsync to editlog about deleteSnapshot.
There can be a chance that blocks removed from blocks map but before log sync 
if there is BR ,  NN may finds that block does not exist in blocks map and may 
invalidate that block. As part HB, invalidation info also can go. After this 
steps if Namenode shutdown before actually do logsync,  On restart it will 
still consider that snapshot Inodes and expect blocks to report from DN.

Simple solution is, we should simply move down that blocks removal after 
logsync only. Similar to delete op.



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