RUST-935 direct retries to different mongos

[abr-egn]

RUST-935

I opted to introduce the SelectionRetry wrapper so that the actual details of what it is and how it's used only need to be known within attempt_to_select_server - callers just need to preserve it and pass it back in. I did consider making this part of SelectionCriteria, but that would have been a pretty major refactoring since that would have to move from the current enum to a struct with a "kind" enum.

[isabelatkinson]

I opted to introduce the SelectionRetry wrapper so that the actual details of what it is and how it's used only need to be known within attempt_to_select_server

just personal preference, but I think the indirection here makes it a little less clear what's going on in the executor; I would probably prefer including the field directly or naming the wrapper something a bit more specific, but up to you 🙂

looks like there are also some prose tests that need to be implemented as part of this ticket: mongodb/specifications@86d961f

[abr-egn]

just personal preference, but I think the indirection here makes it a little less clear what's going on in the executor; I would probably prefer including the field directly or naming the wrapper something a bit more specific, but up to you 🙂

Yeah, good call. I've got a bee in my bonnet about trying to keep reasoning as local as possible, but that didn't work out here. Updating this also brought it more in line with the way the spec describes the logic, which should help future maintainability.

looks like there are also some prose tests that need to be implemented as part of this ticket: mongodb/specifications@86d961f

Derp. Added.