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  1. Core Server
  2. SERVER-57262

Allow nodes to vote for candidates with higher config

    • Type: Icon: Bug Bug
    • Resolution: Fixed
    • Priority: Icon: Major - P3 Major - P3
    • 5.0.3, 4.4.9, 5.1.0-rc0
    • Affects Version/s: None
    • Component/s: None
    • Labels:
    • Fully Compatible
    • ALL
    • v5.0, v4.4
    • Repl 2021-06-28, Repl 2021-07-26, Repl 2021-08-09

      Currently we only allow voting for candidates with same config as ours, due to the issue stated in SERVER-46387.  However this causes a liveness issue where if a primary is stuck in catchup/drain mode with a lower config, catchup takeover cannot bail it out because catchup takeover requires vote from primary and primary cannot install a new config during catchup/drain mode. If that happens, the whole replica set will hang because there will be no writable primary. It should be safe to allow voting for candidates with higher config as we used to do, which was also verified by TLA+, but we need to take care of the issue stated in SERVER-46387.

            wenbin.zhu@mongodb.com Wenbin Zhu
            ali.mir@mongodb.com Ali Mir
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