Is it possible to write a gRPC gateway in .Netcore for existing rest endpoints?

Question

I have two microservices namely ProductService and BillingService. Both are written in .Net core web API project.

1. Product service has an endpoint like : httpget- v1/product/bed/b1

2. BillingService has an endpoint like: httpget - v1/billing/b1

Product service will in return call billing service via the httpget - v1/billing/b1 to get the price details. Now they both talk over http1 / rest representation.

My requirement is to make them communicate (product talk to billing) via gRPC, in .Net core.

After some analysis found grpc http api plugin for .Net core which will be able to expose the grpc service as a rest endpoint, but its still in experimental state

So now my other option is gRPC gateway

My question is can I write a grpc gateway in .Net core ? Most of the examples of grpc gateway is written in GO language.

How can I write a gRPC gateway in .Net core, for existing http rest APIs ? How to convert the existing rest APIs to gRPC services ?

Any comment is super helpful !

Answer 1

As you pointed out, the feature for converting gRPC endpoint to HTTP/REST is currently experimental (see https://github.com/grpc/grpc-dotnet/issues/167), but work it being done to provide stable support (might be coming in .NET 7). But (as you also said), it only exposes the gRPC service as HTTP/REST API, not the other way round.

For converting an existing HTTP/REST API to gRPC service would basically require implementing it from scratch (come up with gRPC/Protobuf contract for the service and the implement a gRPC service that implements that contract and forwards all the calls to an HTTP/REST API). Doing so is likely non-trivial if the service is non-trivial (it's easy to do this conversion with handwritten code for one or two simple methods, but to do this in generality and robustness is a big project).

Your options:

• if gRPC gateway support the conversion from HTTP/JSON REST to gRPC (it's the first time I'm hearing about it supporting that direction of the conversion), use can use the gRPC gateway written in golang as a proxy.
• otherwise it would probably be less work for you to convert your existing service to use gRPC and then use the HTTP/REST transcoding to expose your gRPC service as HTTP/JSON (or again use a gRPC gateway proxy to do this conversion for you).

Implementing the HTTP/JSON -> gRPC conversion is a big undertaking and I'd advise against trying that (unless of course you want to spend your summer working on this fun project).