fix prometheus interceptors not converting context errors to gRPC codes

[vtermanis]

First of all - thank you for a great library!

---

• I added CHANGELOG entry for this change. (I don't see a changelog file - what am I missing?)
• Change is not relevant to the end user.

Changes

fix prometheus interceptors not converting context errors to gRPC codes

• Previously context.(Canceled|DeadlineExceeded) would result in an "Unknown" grpc_code.

We use the interceptors to not only track failures but also identify when we've accidentally passed back non-grpc errors. With this fix the context errors are correctly mapped to their gRPS status counterparts. This behaves the same as what happens in the golang server code. Something similar but old existed in your deprecated repo (grpc-ecosystem/go-grpc-prometheus#84) but it was never released nor did it make it across, it would appear.

Verification

Added unit test which triggers context.Canceled to verify it's no longer recorded as grpc_code="Unknown"

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[johanbrandhorst]

Hi, could you make this change against v2? v1 is kinda maintenance mode.

[vtermanis]

@johanbrandhorst - is this what you meant? (I didn't realise v2 branch was current given main also had activity on it)

Edit: But how does that work with the releases for the prometheus interceptor - e.g. here it's against the main branch not v2 - from what I can tell. How will that work with the v2 branch? (Or maybe I'm missing something obvious.)

[vtermanis]

The unit & lint test checks don't run for some reason. Any chance one of the maintainers could take a look why that is? (I don't believe I have access to see.)

[vtermanis]

@johanbrandhorst - apologies for the ping but it would be great to for this to be considered.

The unit & lint test checks don't run for some reason (they do pass). Any chance you or one of the maintainers could take a look why that is? (I don't believe I have access to see/re-run the tests)

[johanbrandhorst]

@johanbrandhorst - apologies for the ping but it would be great to for this to be considered.

The unit & lint test checks don't run for some reason (they do pass). Any chance you or one of the maintainers could take a look why that is? (I don't believe I have access to see/re-run the tests)

Sorry to have missed this - we merged v2 into main so this should be targeted at main now. Please update again 😅.

[vtermanis]

note: Do not merge - the added failing test still shows the suite as passing (which obv. is wrong). I'll try to figure out what is wrong.

[vtermanis]

Ok, now it passes:

• Corrected labels to use bidi_stream (instead of server_stream)
• Fixed typo of Canceled (was Cancelled)

Ready for review

[johanbrandhorst]

Thanks for your contribution!