Grpc-web: Question: Custom interceptor

[nucle]

Hi,

is it possible to write a custom interceptor?
Can i access the custom metadata?

In kotlin i do something like this:

CustomInterceptor :  ServerInterceptor{
private var codeKey: Metadata.Key<Int> = Metadata.Key.of("meta1", IntMarshaller())
    private var messageKey: Metadata.Key<String> =  Metadata.Key.of("meta2", UTF8Marshaller())
    override fun <ReqT : Any?, RespT : Any?> interceptCall(call: ServerCall<ReqT, RespT>?, headers: Metadata?, next: ServerCallHandler<ReqT, RespT>?): ServerCall.Listener<ReqT> {
        val delegate = next!!.startCall(call, headers)
        return object : SimpleForwardingServerCallListener<ReqT>(delegate) {

            override fun onHalfClose() {
                    call?.close(Status.UNKNOWN, customMetadata)
                }
            }
        }
    }}

[stanley-cheung]

We have plans to add Interceptor support in the future. We will start with an API proposal first.

[nucle]

Good news! Thx for your feedback!

[stanley-cheung]

Prior art: gRPC Node interceptors: https://github.com/grpc/grpc-node/pull/59

[rogchap]

Do we have any movement on client interceptors?
Can we take the proposal for Node and port it for grpc-web? https://github.com/grpc/proposal/blob/master/L5-node-client-interceptors.md

[mmohaveri]

As far as I understand client interceptor is necessary for creating a centralized authentication mechanism (one that you don't have to add the auth token to request metadata on each request manually) and also for creating PWA's. Am I right? or is there another way to do these things?

[rogchap]

I've submitted a new issue that defines an API Proposal for client interceptors for gRPC-Web #555
Heavily "copy+pasted" from the NodeJS proposal, but have tailored for gRPC-Web and how the current API is structured (ie. the rpcCall and serverStreaming)

Feedback welcome/required.

The way NodeJS native library uses call stacks is very different to the web implementation, so still fleshing out how the InterceptingCall stack will function for this implementation.

[stanley-cheung]

This has been implemented yay

[mfickett]

Blog post for posterity: https://grpc.io/blog/grpc-web-interceptor/