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  1. Core Server
  2. SERVER-53953

Fix invariant failure when downgrading FCV with an index build in progress

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: Major - P3
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 4.9.0
    • Component/s: None
    • Labels:
      None
    • Backwards Compatibility:
      Fully Compatible
    • Operating System:
      ALL
    • Sprint:
      Repl 2021-02-08, Repl 2021-02-22, Repl 2021-03-08

      Description

      In the ticket SERVER-50423, we've added reconfigs to the upgrade/downgrade path that will change the name of the delay field name on replica set member configs. This behavior is hidden behind a feature flag. When the feature flag is enabled and we perform a reconfig on downgrade to change the field name from secondaryDelaySecs to slaveDelay, the test index_downgrade_fcv.js fails due to an invariant failure here. The error code is ReadConcernMajorityNotAvailableYet, which makes me suspect the index build component failed while attempting to establish a read concern majority cursor for the collection scan, as the system was in the middle of a reconfig. One potential solution is to busy-wait until read concern majority is available, which we seem to do here

      As a note, we have disabled the index_downgrade_fcv.js test for feature flag enabled variants in SERVER-50423. We should make sure to enable this test again once this ticket is closed.

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              Assignee:
              samy.lanka Samyukta Lanka
              Reporter:
              ali.mir Ali Mir
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