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  1. Node.js Driver
  2. NODE-6223

Document the lack of CSOT support MongoClient.connect and auto-connect

    • Type: Icon: Task Task
    • Resolution: Fixed
    • Priority: Icon: Major - P3 Major - P3
    • 6.11.0
    • Affects Version/s: None
    • Component/s: CSOT
    • 1
    • Not Needed
    • Not Needed

      Use Case

      Currently, `topology.selectServer` instantiates its own timeout context using `timeoutMS` from the client options when running `ping`. In the case of auto connect, this can result in an operation taking up to operation timeoutMS + client timeoutMS.

      User Impact

      • Without this CSOT can be inconsistently observed if the operation with a timeoutMS is the connecting operation.

      Dependencies

      • None

      Unknowns

      • Our intent is to race connect with a timeout and reject if connect doesn't finish in time.
        • Is this a good user experience? timeoutMS for a connected operation vs timeoutMS for an operation that is connecting could be surprisingly different
        • timeoutMS is for bounding the operation, auto-connect is a shortcut but not part of the operation
        • It is unpleasant when timeoutMS is "unusable" in the sense that it doesn't actually bound the operation
        • Should we force users into using MongoClient.connect()
        • NB: selectServer should do all the things relating to connect
        • What is the risk of allowing connect to continue without awaiting the result?
      • Should connect take a new options.timeoutMS API?
        • No, because if connect were to support timeoutMS directly then it would need to be better than a race with a timeout to account for squashing errors like FS access.

      Acceptance Criteria

      Implementation Requirements

      • timeoutMS will not control auto-connect, users should connect explicitly.
      • document the behavior on connect

      Testing Requirements

      • Unskip tests skipped in NODE-6092
      • Write tests checking duration and rejection scenarios

      Documentation Requirements

      • Yes, update the API docs on client.connect()

      Follow Up Requirements

      • None

      Notable Not Doing

      • Potential implementation - race operation timeout with autoconnect so that if the autoconnect doesn't finish before the timeout, then the operation that triggered the autoconnect will throw a timeout error, but the autoconnect will proceed.
        • Determine if this is the desired behavior for CSOT with auto connect.
        • Should operation timeoutMS govern auto connect, or should the ping be governed by client timeoutMS?
        • If necessary, align the implementation to match the outcome of 1.

            Assignee:
            neal.beeken@mongodb.com Neal Beeken
            Reporter:
            bailey.pearson@mongodb.com Bailey Pearson
            Aditi Khare
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              Created:
              Updated:
              Resolved: