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  1. Core Server
  2. SERVER-12264

replicaset nodes appear to be down during compact

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: Major - P3
    • Resolution: Fixed
    • Affects Version/s: 2.4.8, 2.5.4
    • Fix Version/s: 2.4.10, 2.5.5
    • Component/s: Replication, Storage
    • Labels:
      None
    • Operating System:
      ALL

      Description

      Issue Status as of March 31, 2014

      ISSUE SUMMARY

      During a compact operation, heartbeats to and from the node fail and the node can appear to be offline to the rest of the replica set ("... thinks that we are down..." log messages). This is because a global write lock is taken before checking if the node is running a compact.

      USER IMPACT

      Running compact makes the node appear to be down to other members, which can affect majority concerns in a replica set (write concern, voting, etc). Running compact on several secondaries in one replica set can cause loss of majority and a step-down of the primary node, rendering the replica set read-only.

      SOLUTION

      To fix the issue, the global write lock is not acquired if the node is running compact or other maintenance tasks.

      WORKAROUNDS

      Run compact only on one secondary at a time for each replica set, making sure that the quorum is not affected. The secondary can temporarily be replaced with an arbiter node to ensure high availability.

      AFFECTED VERSIONS

      All recent production release versions up to 2.4.9 are affected.

      PATCHES

      The fix is included in the 2.4.10 production release and the 2.5.5 development version, which will evolve into the 2.6.0 production release.

      Original Description

      Heartbeats fail in both directions on the node running compact().

      On the send side of a heartbeat, the sender need to up() the receiver node, which calls addToElectable() set which needs the rsbase mutex. The rsbase mutex is held by the syncthread as it tryToGoLiveAsSecondary()s, but the syncthread has to wait on a global write lock which it can't get because compact is holding a write lock.

      On the receiving side, the issue is the exact same only the receiver is looking for the rsbase mutex in iAmElectable().

      It might be possible to make tryToGoLiveAsSecondary() return prior to the global writeLock request if we are running compact.

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                • Created:
                  Updated:
                  Resolved: