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.