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  1. Documentation
  2. DOCS-13482

Investigate changes in SERVER-46288: Reconfig in 4.2 style with the current config on FCV downgrade

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    Details

    • Type: Task
    • Status: Closed
    • Priority: Major - P3
    • Resolution: Works as Designed
    • Affects Version/s: None
    • Fix Version/s: 4.3.4
    • Component/s: manual

      Description

      Description

      Downstream Change Summary

      FCV downgrade from 4.4 to 4.2 does a reconfig automatically and waits for the new config to replicate on all nodes in the replica set, including non-voting nodes and arbiters.

      Description of Linked Ticket

      Safe reconfig introduces a new field on the config which will make 4.2 binary to fail to start up. Now that we allow 4.4 binary to use and store a config with the new field. We cannot just remove the extra field on downgrade on each node as in SERVER-45092, since in mixed version replset, a reconfig can propagate the config with the extra field to 4.4 binary with FCV 4.2. That will fail 4.2 binary after downgrade.

      Instead, we'll do a reconfig with a higher config version but no term if the last config has a term field with the same configuration and wait for it to replicate to all nodes before downgrading FCV.

      Also remove the FCV check in ReplSetHeartbeatArgsV1::addToBSON, we don't need to check FCV to decide whether to include "configTerm" in heartbeats.

      Scope of changes

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              Assignee:
              kay.kim Kay Kim (Inactive)
              Reporter:
              backlog-server-pm Backlog - Core Eng Program Management Team
              Participants:
              Last commenter:
              Siyuan Zhou Siyuan Zhou
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                1 year, 31 weeks, 2 days ago
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