GRPCIO on appengine standard?

[i...@lumapps.com]

I am following the grpcio tutorial https://grpc.io/docs/quickstart/go.html. 

I would like to expose the grpc service as an http handler of an appengine standard application.

Is there any example available? Someone is aware of some limitation that won't allow me to complete this task?

[Ivo Bellin Salarin]

Reference:

https://cloud.google.com/endpoints/docs/grpc/about-grpc

This document speaks about the fact that the cloud endpoints management over gRPC is not available out of GCE (but this is not gRPC)

https://groups.google.com/forum/#!topic/google-appengine-go/IlnY1YDoNFE

This conversation is about a gRPC client addressing a gRPC server hostend on GKE

https://github.com/philips/grpc-gateway-example

This example shows how to expose an http/swagger api for a gRPC server, and would be my favourite way to implement this.

The question is: will it work on GAE standard or flexible?

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[Sylvain Le Gall]

Hi,

GAE uses HTTP 1.1 and gRPC uses HTTP 2.0. So it is not possible to directly expose gRPC service on GAE.

You use grpc-getaway to expose it:

https://github.com/grpc-ecosystem/grpc-gateway

I did that ~3 times for different servers:

1. You build your entire service using gRPC

2. You create a fake "Listener", using io.Pipe

https://golang.org/pkg/net/#Listener

3. You generate the grpc-getaway definition

4. You set up GAE application to do:

grpc-getaway -> fake Listener -> your internal service

It is a hack and it is not great. I would recomment to just get a nano-VM to do the same thing with a standard gRPC server, it will be much simpler.

[Ivo Bellin Salarin]

great. Thanks a lot Sylvain!

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[Ben Guild]

Hey Sylvain,

Are you saying that this emulates the endpoints so that any gRPC client can connect to the server without modification? If so, do you have a tutorial on how to implement this by any chance?

[Sylvain Le Gall]

No it doesn't expose gRPC directly. It exposes an REST API service, because this is what grpc- gateway will produce.

You will have to use REST clients.

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[Ben Guild]

Got it. I thought you were saying it was possible to emulate non-streaming endpoints that were compatible with gRPC clients over HTTP 1.1, but yeah, that's a hard pass then.

Thanks for your message back!

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[Ben Guild]

I may actually use this for one small thing, but I'm worried about memory/implementation. As a test I pulled in this library and it works fine on GAE Standard with some light testing: https://github.com/k2wanko/grpc-pipe/gateway

Is this what you're also using? Would you be willing to share or compare your implementation, by any chance?

I was debating a different approach, but I'm not sure if it's going to be necessary in this case.

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[Sylvain Le Gall]

Unfortunately, I cannot share my code.

The idea is to

- create a datastructure PipeListener that implements a Listener https://godoc.org/net#Listener

- implement a Dial function with the PipeListener

- use a Pipe in https://godoc.org/net#Pipe

- use the listener with grpc.Server https://godoc.org/google.golang.org/grpc#Server.Serve

- use the dial function in grpc.WithDialer

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