bug: grpc-web plugin causing missing trailers issue

[Affanmir]

Current Behavior

When i use the grpc-web plugin and cors plugin to communicate from my fronted to my backend, the response I receive an error missing trailers. I've tried the same thing using envoy and it works. There seems to be some misconfiguration is the response body which does not allow the response to

Expected Behavior

Envoy Response: (CORRECT AND DOES NOT CAUSE ISSUE)

Hello! Mohsin Javed� grpc-status:0
grpc-message:OK

Headers:

HTTP/1.1 200 OK
content-type: application/grpc-web+proto
grpc-accept-encoding: identity,deflate,gzip
grpc-encoding: identity
date: Fri, 24 Nov 2023 06:04:45 GMT
x-envoy-upstream-service-time: 12
access-control-allow-origin: http://localhost:58653/
access-control-expose-headers: custom-header-1,grpc-status,grpc-message
server: envoy
transfer-encoding: chunked

API SIX Response:: (INCORRECT

AND CAUSES ISSUE MISSING TRAILERS)

Hello! World

Headers:
HTTP/1.1 200 OK
Date: Fri, 24 Nov 2023 06:13:48 GMT
Content-Type: application/grpc-web+proto
Transfer-Encoding: chunked
Connection: keep-alive
grpc-accept-encoding: identity,deflate,gzip
grpc-encoding: identity
Server: APISIX/3.6.0
Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: *
Access-Control-Max-Age: 5
Access-Control-Expose-Headers: *
Access-Control-Allow-Headers: *

Error Logs

Steps to Reproduce

enable grpc-web and cors plugin on a route that communicates from any frontend / backend service that implemented a grpc service using a proto definition.

Environment

Please take a clone of this mmj-dev-git/grpc_with_envoy_and_apisix#1 All steps to reproduce are mentioned in the README.md

This is a small local setup with node as the back end and flutter as the frontend

[shreemaan-abhishek]

could you please provide me with reproduction steps and reproduction environment identical to yours? This will save us a lot of back and forth.

[Affanmir]

@shreemaan-abhishek Please take a clone of this PR All steps to reproduce are mentioned in the README.md

This is a small local setup with node as the back end and flutter as the frontend

[kayx23]

same issue: #10254

[kayx23]

See projectcontour/contour#3233

[shreemaan-abhishek]

@Affanmir I'm taking a look at this, mean while could you please share your route and upstream configuration? I want to confirm if you have used the grpc scheme correctly:

[Affanmir]

@shreemaan-abhishek You can find the schema in the PR I've linked, rest of the configuration I've mentioned below

[alifahadk]

@shreemaan-abhishek We are trying to use this plugin for proxying between a gRPC-web client (more specifically, the gRPC-dart web client) and a gRPC-java server.

Our gRPC-java server does not return a gRPC-web-compliant HTTP/1.1 response on its own (with the trailers present in the response body). Is this plugin meant to cater to such a scenario (similar to the support provided by the gRPC-web filter by Envoy)? Our initial assumption was that it does that, but latest explorations suggest otherwise.

tldr; we are looking for a way to transform the HTTP/2 based gRPC response from upstream into a HTTP/1.1 response for downstream with in-body gRPC trailers as required by the gRPC-web specification

[shreemaan-abhishek]

I am no expert in this field but

with in-body gRPC trailers as required by the gRPC-web specification

I remember reading this somewhere. Does it mean that grpc-web plugin not supporting trailers (as part of headers) is by design?

EDIT:

looks like trailers as part of response body is also not being supported.

[Affanmir]

@shreemaan-abhishek
looks like trailers as part of response body is also not being supported.
Yes exactly on point. Is this by design or a bug?

[shreemaan-abhishek]

Not a bug, it's just not supported. You may take this up if you want to fix this.