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Support WithOutgoingTrailerMatcher #1697

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maja42 opened this issue Sep 25, 2020 · 3 comments · May be fixed by #1721
Open

Support WithOutgoingTrailerMatcher #1697

maja42 opened this issue Sep 25, 2020 · 3 comments · May be fixed by #1721
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@maja42
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@maja42 maja42 commented Sep 25, 2020

🚀 Feature

grpc-gateway offers the possibility do define custom outgoingHeaderMatcher to decide which grpc-headers should be forwarded as http-headers via a ServeMuxOption. However, grpc trailer-headers are always forwarded in the http-trailers.

In my case, I don't want to forward any grpc metadata to the http API. So I defined a headerMatcher that always returns false. But I can't do the same for trailers. It would be nice to have that possibility.

(As a side note: sending http trailers also removes the Content-Length Header from the response)
@johanbrandhorst
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@johanbrandhorst johanbrandhorst commented Sep 25, 2020

This sounds reasonable! A side note; we disabled headers altogether for clients that don't include the "TE" header, see https://github.com/grpc-ecosystem/grpc-gateway/blob/v2/runtime/errors.go#L113, but it seems we only disabled it in our error handler, not in our general purpose message handler, see https://github.com/grpc-ecosystem/grpc-gateway/blob/v2/runtime/handler.go#L140. I'd love to have the previous logic added to this section of the code as well, to be compliant with RFC 7230. Would this be enough of a fix for your use case? Would you be willing to add this functionality?
@johanbrandhorst johanbrandhorst changed the title Support outgoingTrailerMatcher Allow client to disable sending of trailers by omitting "TE" header. Sep 25, 2020
@maja42
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@maja42 maja42 commented Oct 1, 2020

This sounds good, but it doesn't solve my use-case completely. I'd still like to have a outgoingTrailerMatcher.

Reason: We are using the grpc-gateway to provide an external API for our grpc-based microservice architecture. So it acts as a single-point-of-entry and we must be careful about which internal information we want to expose.

We use grpc-headers and trailers to transmit internal information between services, and their content should generally not be exposed via the http API. So even if the browser/user would send a "TE" header (request trailer data), I don't want to return any internal trailer information.
@johanbrandhorst
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@johanbrandhorst johanbrandhorst commented Oct 1, 2020

Fair enough, sorry for hijacking this issue, I'll change the title and open a separate one for the bug I mentioned.
@johanbrandhorst johanbrandhorst mentioned this issue Oct 1, 2020
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@johanbrandhorst johanbrandhorst changed the title Allow client to disable sending of trailers by omitting "TE" header. Support WithOutgoingTrailerMatcher Oct 1, 2020
@ghost ghost linked a pull request that will close this issue Oct 5, 2020
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added trailer match capability #1709
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