grpc: use ServiceServer generated stubs out of cashapp/misk

[mgenov]

Is it possible ServiceServer generated stubs to be used out of cashapp/misk?

As I looked into examples, they are using cashapp/misk which is using internally WebActionsServlet to dispatch gRPC calls to the proper method of the service stub.

[oldergod]

We added a few helper methods to help building fakes in 3.4.

See https://github.com/square/wire/blob/master/wire-library/wire-grpc-client/src/jvmMain/kotlin/com/squareup/wire/GrpcCalls.kt

[swankjesse]

Yep. Here's help:

https://github.com/square/wire/blob/master/wire-library/docs/wire_grpc.md#implementing-client-interfaces

[swankjesse]

Or is this request about using Wire on a different server framework?

[mgenov]

Yes, using wire with different server framework.

My current issue is that I have a kotlin backend that is using sparkjava for REST and I'm trying to expose some of it's existing REST services as gRPC ones.

Other ideas for similar transition are also welcome.

[swankjesse]

@mgenov can you fork the gRPC servlet code from Misk in your application? It's almost a standard servlet with one exception; we need to configure this in Jetty:

https://github.com/cashapp/misk/blob/c7e51cbb1ff6947f17839b6cb21c797c8d397593/misk/src/main/kotlin/misk/web/jetty/JettyService.kt#L335

Unfortunately it's likely necessary to configure this into each Java web framework independently, or to build a single servlet that doesn't hook into those frameworks’ authentication, management, and observability systems.

[mgenov]

Thanks @swankjesse . I'll look into it.

In grpc-java the API is really simple and the gRPC services could be served directly using usePlainText without any complexity. I know that it's a security issue, but envoy could do the SSL offloading which could simplify the application code. What I saw in misk is that WebConfig.ssl is used when starting jetty and I suppose jetty is doing the SSL stuff on it's own but I'll take a deeper look into it.

Here is an example API with grpc-java

  val gRpcServer = ServerBuilder.forPort(50051)
            .addService(MyService())
            .intercept(InternalServerSecurityInterceptor())
            .build()
  gRpcServer.start()

with grpc-java client code is able to pass service implementations and interceptors (security checks and etc).

[iTanChi]

is it possible to have an adapter to map wire Service to io.grpc BindableService?

[swava29]

So did it go thru

On Mon, Nov 30, 2020, 9:54 PM iTanChi notifications@github.com wrote:

is it possible to have an adapter to map wire Service to io.grpc BindableService?

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[swankjesse]

@iTanChi nothing built in but you could create one.

[iTanChi]

@mgenov @swankjesse with the latest version, can it resolve this issue:

Code generation for plain gRPC server. The Kotlin target now has a new grpcServerCompatible option which if set to true will generate gRPC server-compatible classes.

[RdeWilde]

@iTanChi Thank you for referencing this, I was looking for exactly that.

Only thing is that the output has an error for me:

  public abstract class GreeterImplBase : BindableService {
    public open fun sayHello(request: HelloRequest, response: StreamObserver<HelloReply>) = throw
        UnsupportedOperationException()

Producing this error:

'Nothing' return type needs to be specified explicitly

Any clue how to solve this?

Also seems to lack a class like GreetersayHelloBlockingServer

Edit; I decided to open another issue for this #1903 I'll leave this for reference.