How to define a client interceptor ?

I have a spring-boot app and I’m trying to define a client interceptor for my grpc service, so that I can set some custom headers in the response (which will be transcoded to html)

My interceptor definition looks like this:

import io.grpc.CallOptions;
import io.grpc.Channel;
import io.grpc.ClientCall;
import io.grpc.ClientInterceptor;
import io.grpc.ForwardingClientCall.SimpleForwardingClientCall;
import io.grpc.ForwardingClientCallListener.SimpleForwardingClientCallListener;
import io.grpc.Metadata;
import io.grpc.MethodDescriptor;
import net.devh.boot.grpc.client.interceptor.GrpcGlobalClientInterceptor;

@GrpcGlobalClientInterceptor
public class HeaderClientInterceptor implements ClientInterceptor {

  static final Metadata.Key<String> CUSTOM_HEADER_KEY =
      Metadata.Key.of("custom_client_header_key", Metadata.ASCII_STRING_MARSHALLER);

  @Override
  public <ReqT, RespT> ClientCall<ReqT, RespT> interceptCall(MethodDescriptor<ReqT, RespT> method,
      CallOptions callOptions, Channel next) {
    System.out.println("====log====================");
    return new SimpleForwardingClientCall<ReqT, RespT>(next.newCall(method, callOptions)) {
        @Override
        public void sendMessage(ReqT message) {
            System.out.println("====log send====================");
            super.sendMessage(message);
        }
        @Override
        public void start(Listener<RespT> responseListener, Metadata headers) {
            headers.put(CUSTOM_HEADER_KEY, "customRequestValue");
            super.start(new SimpleForwardingClientCallListener<RespT>(responseListener) {
                @Override
                public void onHeaders(Metadata headers) {
                    System.out.println("====head===================="+headers);
                    super.onHeaders(headers);
                }
            }, headers);
        }
    };
  }
}

No matter what I’ve tried, the response doesn’t want o go through that code. Just note that I also have a ServerInterceptor define in my code, and that logic works fine.

My .proto api definition looks like:

rpc DownloadBuild(DownloadBuildRequest) returns (stream google.api.HttpBody) {
    option (google.api.http) = {
      get : "/v4/projects/{projectId}/types/{buildType}/builds/{buildVersion}/.download"
    };
    option (grpc.gateway.protoc_gen_swagger.options.openapiv2_operation) = {
      description: "Download build.";
      summary: "Download build.";
      tags: "Builds";
      responses: {
        key: "200"
        value: {
          description: "Download build";
        }
      }
      responses: {
        key: "401"
        value: {
          description: "Request could not be authorized";
        }
      }
      responses: {
        key: "404"
        value: {
          description: "Build not found";
        }
      }
      responses: {
        key: "500"
        value: {
          description: "Internal server error";
        }
      }
    };
  }

while my grpc implementation looks like this:

...
@GrpcService
public class GrpcAPIService extends MixAPIGrpc.MixAPIImplBase {
...
 @Override
    public void downloadBuild(DownloadBuildRequest request, StreamObserver<com.google.api.HttpBody> responseObserver) {
        handleDownloadGrpcCall("downloadBuild", mwProxy::downloadBuild, request, responseObserver);
    }
...
 private <T, R> void handleDownloadGrpcCall(String grpcMethodName, Function<T, byte[]> serviceMethod, T request,
            StreamObserver<com.google.api.HttpBody> streamObserver) {
        log.debug("{}: >>>, request:[{}]", grpcMethodName, request);
        try {
            Instant start = Instant.now();
            byte[] bytes = serviceMethod.apply(request);
            BufferedInputStream stream = new BufferedInputStream(new ByteArrayInputStream(bytes));

            int bufferSize = 1 * 1024;// 1KB
            byte[] buffer = new byte[bufferSize];
            int length;
            boolean addExtension = true;
            while ((length = stream.read(buffer, 0, bufferSize)) != -1) {
                streamObserver.onNext(com.google.api.HttpBody.newBuilder()
                        .setData(ByteString.copyFrom(buffer, 0, length))
                        .setContentType("application/octet-stream")
                        .build());
            }
            stream.close();
            streamObserver.onCompleted();
            Instant end = Instant.now();
            timingService.logMethodExecution(grpcMethodName, start, end, request);
        } catch (Exception e) {
            handleException(e, streamObserver, request, grpcMethodName);
        }
        log.debug("{}: <<<<", grpcMethodName);
    }
...

Any idea what could be wrong ?

[ghevge]

@ST-DDT Thanks! I’ve managed to set it.

[ghevge]

No I’m good!