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  1. Core Server
  2. SERVER-9730

Asymmetrical network partition can cause the election of two PRIMARY nodes

    Details

    • Type: Bug
    • Status: Closed
    • Priority: Critical - P2
    • Resolution: Fixed
    • Affects Version/s: 2.2.4, 2.4.3, 2.5.0
    • Fix Version/s: 2.2.5, 2.4.4, 2.5.1
    • Component/s: Replication
    • Labels:
      None
    • Operating System:
      ALL

      Description

      Consider a replica set with three nodes: A, B, C. 'A' is PRIMARY, 'B' and 'C' are SECONDARY.

      If there is a network partition between 'A' and 'C', then:

      • A is still PRIMARY because it can see a majority of the set
      • C will start an election trying to become PRIMARY
        • It can see a majority of the set
        • It cannot see a primary

      If, for whatever reason, 'B' allows 'C' to become PRIMARY, then the set will have two PRIMARY nodes until one of them is stepped down.

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                • Created:
                  Updated:
                  Resolved: