Outlier detection needs to log and handle grpc-status sent as trailers

[wenbozhu]

Title: Outlier detection needs to log and handle grpc-status sent as trailers

Description:

Outlier detection currently doesn't check response trailers, which may contain an error grpc-status when a gRPC stream is closed.

Relevant Links:

See the discussion on the original issue for adding grpc-status support in Outlier Detection.

[wenbozhu]

@cpakulski could you comment on how we may want to fix this? We think this issue is important to fix for gRPC users, i.e. for gRPC-based streaming services.

@louiscryan

[cpakulski]

Sorry, I was away - will comment within a day or two. Thanks!

[rcash]

Hi @wenbozhu and @cpakulski I'm a student in UT Austin's Virtualization & Containers class. Are you still looking for help in adding support for gRPC response trailers? Thanks!

[wenbozhu]

We probably need some design inputs from @cpakulski first ...

@htuch

[htuch]

Yeah, I think if you want to help drive the design here and propose a strawman @rcash that might be a reasonable start.

[cpakulski]

@rcash, @wenbozhu Please look at #7942 as that solved similar case of passing gRPC codes to outlier detector. Let me know if you get stuck in design or understanding the code flow.