Introduce getFeatureCompatibilityVersion command

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    • Type: Improvement
    • Resolution: Unresolved
    • Priority: Major - P3
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    • Affects Version/s: None
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      Problem

      Changing the FCV can be done through the  setFeatureCompatibiltyVersion  , on the other hand the symmetric getFeatureCompatibiltyVersion command does not exist.

      The way to inspect current FCV state is to run:

      db.adminCommand(
   {
      getParameter: 1,
      featureCompatibilityVersion: 1
   }
 )

      This has several limitations/downsides:

      • The command does not report if there is an ongoing FCV transition operation. The user needs to call $currentOp aggregation stage (SERVER-111153)
      • On sharded cluster the command will not work on mongos and the user need to run it against the config server primary node. (SERVER-39052)

      Proposal

      Expose a new command getFeatureCompatibilityVersion that return:

      • The current state of the FCV (downgraded, downgrading, upgrading, upgraded)
      • If there is an ongoing setFCV operation and relative information about its progresses (e.g. expected amount of work/time left to complete)

      The command will be available both on replicaset primary and mongos'es in sharded clusters.

            Assignee:
            Unassigned
            Reporter:
            Tommaso Tocci
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              Created:
              Updated: