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  1. Hadoop Common
  2. HADOOP-8217

Edge case split-brain race in ZK-based auto-failover

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Details

    • Bug
    • Status: Open
    • Major
    • Resolution: Unresolved
    • 0.24.0
    • None
    • auto-failover, ha
    • None

    Description

      As discussed in HADOOP-8206, the current design for automatic failover has the following race:

      • ZKFC1 gets active lock
      • ZKFC1 is about to send transitionToActive() and machine freezes (eg GC pause + swapping)
      • ZKFC1 loses its ZK lock, ZKFC2 gets ZK lock
      • ZKFC2 calls transitionToStandby on NN1, and transitions NN2 to active
      • ZKFC1 wakes up from pause, calls transitionToActive(), now we have a bad situation

      This is rare, since it requires ZKFC1 to freeze longer than its ZK session timeout, but worth fixing, since the results can be disastrous.

      Attachments

        1. hadoop-8217-testcase.txt
          10 kB
          Todd Lipcon

        Issue Links

        is related to

        Bug - A problem which impairs or prevents the functions of the product. HADOOP-13515 Redundant transitionToActive call can cause a NameNode to crash

        • Minor - Minor loss of function, or other problem where easy workaround is present.
        • Open
        relates to

        New Feature - A new feature of the product, which has yet to be developed. HADOOP-8206 Common portion of ZK-based failover controller

        • Major - Major loss of function.
        • Closed

        New Feature - A new feature of the product, which has yet to be developed. HDFS-3042 Automatic failover support for NN HA

        • Major - Major loss of function.
        • Closed

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            tlipcon Todd Lipcon
            tlipcon Todd Lipcon
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            Dates

              Created:
              Updated:

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