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  1. Core Server
  2. SERVER-22572

readConcern majority doesn't consider replica-set changes

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: Major - P3
    • Resolution: Duplicate
    • Affects Version/s: 3.2.1
    • Fix Version/s: None
    • Component/s: Replication
    • Labels:
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      Description

      It would appear the only reason to throw away the set of snapshots used for readConcern is if the local node enters ROLLBACK:
      https://github.com/mongodb/mongo/blob/f8dadcefeef7e738d7063ae2df57b9c856b402da/src/mongo/db/repl/replication_coordinator_impl.cpp#L2518

      Replica-set reconfigs would seem to be another way to change the conditions needed to fulfill readConcern majority. For example, in a 5-member replica-set where 2 members are non-voting requires only 2 of the voting members to fulfill a majority readConcern. Reconfig to allow the other 2 members to vote means the set should now demand 3 members to achieve readConcern majority. However, the existing 'verified' snapshot on all members would continue to be used for this purpose despite it (not necessarily) fulfilling the current requirements.

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              Assignee:
              scotthernandez Scott Hernandez
              Reporter:
              andrew.ryder Andrew Ryder
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