gogrpcmiddlewaregrpc-go

Chain custom GRPC client interceptors/DialOptions


I want to chain some DialOptions/client-side interceptors. But for some reason only the latest of my custom interceptors will be invoked:

myOpt1 := grpc.WithUnaryInterceptor(func(ctx context.Context, method string, req, reply any, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
    print("testInterceptor invoked")
    return invoker(ctx, method, req, reply, cc, opts...)
})
myOpt2 := grpc.WithUnaryInterceptor(func(ctx context.Context, method string, req, reply any, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
    print("testInterceptor2 invoked")
    return invoker(ctx, method, req, reply, cc, opts...)
})
opts := []grpc.DialOption{
        grpc.WithTransportCredentials(insecure.NewCredentials()),
        myOpt1, // will be skipped
        myOpt2, // will get invoked
}

conn, err := grpc.DialContext(context.Background(), "my-adress:443", opts...) // err is nil
myService := pbAugment.NewMyServiceClient(conn)
myService.MyFunction(context.Background()) // prints: testInterceptor2 invoked

I've added TransportCredentials so I don't get an error on startup (about missing transport security).

What am I missing here?


Solution

  • You must chain (Client|Server) interceptors:

    See grpc.WithChainUnaryInterceptor

    E.g.:

    func main() {
        myInt1 := func(ctx context.Context, method string, req, reply any, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
            print("testInterceptor invoked")
            return invoker(ctx, method, req, reply, cc, opts...)
        }
        myInt2 := func(ctx context.Context, method string, req, reply any, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
            print("testInterceptor2 invoked")
            return invoker(ctx, method, req, reply, cc, opts...)
        }
        opts := []grpc.DialOption{
            grpc.WithTransportCredentials(insecure.NewCredentials()),
            grpc.WithChainUnaryInterceptor(
                myInt1,
                myInt2,
            ),
        }
    
        _, err := grpc.DialContext(context.Background(), "my-adress:443", opts...)
        if err != nil {
            log.Fatal(err)
        }
    }