How send request header as response header using go-kit

Question

I'm developing a service rest in Go using go-kit. I need send a header response. This header response should have the same value of request header.

This is a part of my transport.go:

func MakeHandler(m **http.ServeMux) http.Handler {
    const URL = "..."

    var serverOptions []kithttp.ServerOption

    logger := log.NewLogfmtLogger(os.Stderr)

    var svc repositories.SignDocumentRepository

    impl := persistence.NewSignerDocumentRepository()

    svc = middleware.LoggingMiddlewareSignDocument{Logger: logger, Next: impl}

    registerHandler := kithttp.NewServer(
        makeSignDocumentEndpoint(svc),
        decodeRequest,
        encodeResponse,
        serverOptions...,
    )

    r := mux.NewRouter()
    r.Handle(URL, handlers.LoggingHandler(os.Stdout, registerHandler))
    (*m).Handle(URL, r)

    return nil
}


func decodeRequest(_ context.Context, r *http.Request) (interface{}, error) {
    return r, nil
}

func encodeResponse(_ context.Context, w http.ResponseWriter, response interface{}) error {
    w.Header().Set("headerA", "val1")
    w.Header().Set("headerB", "") // This header should be equal that a header request
    switch response.(type) {
    case model.MsgRsHdr:
        w.WriteHeader(http.StatusPartialContent)
    default:
        w.WriteHeader(http.StatusAccepted)
    }
    if response != nil {
        return json.NewEncoder(w).Encode(response)
    }
    return nil
}

How do I get a request header in encodeResponse method?

Mukesh Sharma · Accepted Answer · 2020-11-20 01:23:05Z

3

You can use ServerBefore to put *http.Request in the context, and can get it in encodeResponse to read request headers.

type ctxRequestKey struct{}

func putRequestInCtx(ctx context.Context, r *http.Request, _ Request) context.Context {
    return context.WithValue(ctx, ctxRequestKey{}, r)
}

func encodeResponse(ctx context.Context, w http.ResponseWriter, response interface{}) error {
    r := ctx.Value(ctxRequestKey{}).(*http.Request)
    // can use r.Header.Get here to read request here.
}

serverOptions := []kithttp.ServerOptions{
    kithttp.ServerBefore(putRequestInCtx),
}

registerHandler := kithttp.NewServer(
        makeSignDocumentEndpoint(svc),
        decodeRequest,
        encodeResponse,
        serverOptions...,
)

answered Nov 20, 2020 at 1:23

Mukesh Sharma

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1 Comment

Rajat Doshi Over a year ago

Is there any other clean way of achieving the same ? encodeResponse() ideally should just write in the ResponseWriter stream. Would it be right to use ServerAfter in such situations (here once again requestObj is not available).

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