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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

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              tlipcon Todd Lipcon
              tlipcon Todd Lipcon
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              Dates

                Created:
                Updated: