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From "Uma Maheswara Rao G (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-11334) Handle the case when NN switch and rescheduling movements can lead to have more than one coordinator for same file block
Date Wed, 11 Jan 2017 22:11:16 GMT
Uma Maheswara Rao G created HDFS-11334:
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             Summary: Handle the case when NN switch and rescheduling movements can lead to
have more than one coordinator for same file block 
                 Key: HDFS-11334
                 URL: https://issues.apache.org/jira/browse/HDFS-11334
             Project: Hadoop HDFS
          Issue Type: Sub-task
          Components: datanode, namenode
    Affects Versions: HDFS-10285
            Reporter: Uma Maheswara Rao G
            Assignee: Rakesh R


I am summarizing the scenarios here what Rakesh and me discussed offline:
Here we need to handle couple of cases:
# NN switch - it will freshly start scheduling for all files.
       At this time, old co-ordinators may continue movement work and send results back. This
could confuse NN SPS that which result is right one.
  *NEED TO HANDLE*
# DN disconnected for heartbeat expiry - If DN disconnected for long time(more than heartbeat
expiry), NN will remove this nodes. After SPS Monitor time out, it may retry for files which
were scheduled to that DN. But if it reconnects back after NN reschedules, it may lead to
get different results from deferent co-ordinators.
*NEED TO HANDLE*
# NN Restart- Should be same as point 1
# DN disconnect - here When DN disconnected simply and reconnected immediately (before heartbeat
expiry), there should not any issues
*NEED NOT HANDLE*, but can think of more scenarios if any thing missing
# DN Restart- If DN restarted, DN can not send any results as it will loose everything. After
NN SPS Monitor timeout, it will retry.
*NEED NOT HANDLE*, but can think of more scenarios if any thing missing



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