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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



    • Task
    • Status: Closed
    • Major - P3
    • Resolution: Works as Designed
    • None
    • 4.3.4
    • manual



      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

      Impact to Other Docs

      MVP (Work and Date)

      Resources (Scope or Design Docs, Invision, etc.)


        Issue Links



              kay.kim@mongodb.com Kay Kim (Inactive)
              backlog-server-pm Backlog - Core Eng Program Management Team
              Jess Mokrzecki Jess Mokrzecki
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                2 years, 46 weeks, 4 days ago