Dear Eric,
Thank you so much for your reply, and apologies for not replying in turn.
It was one of those situations in which I posted a question and then in the
process of actually formulating the question, I solved the question. I
thought I'd deleted my post before anyone saw it!
For posterity's sake, I did what you suggested. For the gateway, we have to
ensure the header is passed through, so add an incoming header matcher to
the mux:
addr := fmt.Sprintf(":%d", opts.RESTPort)
dialOpts := []grpc.DialOption{grpc.WithInsecure()} // TODO:use better
options
mux := runtime.NewServeMux(runtime.WithIncomingHeaderMatcher
(headerMatcher))
where headerMatcher func is defined as:
// ensures GRPC gateway passes through the standard HTTP header
Accept-Language as "accept-language"
// rather than munging the name prefixed with grpcgateway.
// delegates to default implementation for other headers.
func headerMatcher(headerName string) (mdName string, ok bool) {
if headerName == "Accept-Language" {
return "accept-language", true
}
return runtime.DefaultHeaderMatcher(headerName)
}
And then in my grpc-server implementation, I have this helper func:
// determine preferred language tags from the context, or fallback to a
reasonable default
func (ss *coreServer) languageTags(ctx context.Context) ([]language.Tag,
error) {
if md, ok := metadata.FromIncomingContext(ctx); ok {
preferred := md.Get("accept-language")
if len(preferred) > 0 {
pref := strings.Join(preferred, ";")
tags, _, err := language.ParseAcceptLanguage(pref)
if err != nil {
return nil, status.Errorf(codes.InvalidArgument, "invalid
accept-language header: %s", err)
}
return tags, nil
}
}
return ss.lang, nil
}
which I use like this in any endpoint it is needed:
func (ss *coreServer) GetExtendedConcept(ctx context.Context, conceptID
*snomed.SctID) (*snomed.ExtendedConcept, error) {
tags, err := ss.languageTags(ctx)
if err != nil {
return nil, err
}
return ss.svc.ExtendedConcept(conceptID.Identifier, tags)
}
Best wishes,
Mark
On Friday, 16 November 2018 18:24:06 UTC, Eric Anderson wrote:
>
> It's not outrageous to read HTTP standard headers from gRPC. I'm not
> super-well versed with grpc-gateway, but I'm not seeing any configuration
> for this supported by grpc-gateway. (SystemParameters
> <https://cloud.google.com/service-infrastructure/docs/service-management/reference/rpc/google.api#google.api.SystemParameters>
> *may* be a solution, but it doesn't seem supported by grpc-gateway and
> is unclear if it is the "right" solution.)
>
> So I guess either just read from Accept-Language directly or add
> the "string language_preferences=2" and read from Accept-Language if
> language_preferences is empty.
>
> On Mon, Nov 12, 2018 at 5:28 AM Mark Wardle <[email protected]
> <javascript:>> wrote:
>
>>
>> Dear all,
>>
>> I have a gRPC service that provides results that can be localized. I am
>> using gRPC as well as the grpc-gateway to automatically generate a REST
>> service running in parallel.
>>
>> The usual way of specifying locale preferences in REST services is via
>> Accept-Language tags. As this is, strictly speaking, part of the API
>> contract, does it make sense to write a gRPC service description that
>> explicitly documents this parameter. I could therefore easily add a "string
>> language_preferences=2" to the request message definition? If so, is there
>> a clever way to populate this in the grpc-gateway much like URL parameters?
>>
>> Or is there a better way of handling language preferences in grpc and
>> grpc-gateway?
>>
>> Many thanks,
>>
>> Mark
>>
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