This document outlines how to get started with a hybrid REST and gRPC service using ASP.NET Core 5.0.

While looking at migrating existing APIs from REST to gRPC, I struggled to find a working C# example, where I could run a hybrid between the two. I did not want to convert an existing service strictly to gRPC and throw away the REST implementation since many legacy services may still depend on it. Instead, I wondered if it could be possible to add the gRPC component on top of an existing REST service and expose separate ports to run HTTP/1.x and HTTP/2 connections. For a relatively simple idea, I had hoped their would-be various documentation for how this could be achieved, but after a bit of researching, I decided to create my own example.

You can import the code straight into your preferred IDE (i.e. Visual Studio) or run the sample using the dotnet CLI commands (in the root project folder).

>  dotnet build
>  dotnet .\aspnetapp\bin\Debug\net5.0\aspnetapp.dll

After the application runs, navigate to http://localhost:4999/swagger in your web browser to access the Swagger UI. Enter a value in the name field and it should return something similar like this below:

{
  "message": "Hello Ben"
}

For the gRPC piece, you can install a gRPC client (i.e. BloomRPC). Import the greet.proto file to the client and enter the server address as localhost:5000.

You can build and run the sample in Docker using the following commands. Navigate to the folder where the Dockerfile lies.

>  docker build -t aspnetapp-k8s .
>  docker run -it --rm -p 9500:4999 -p 9001:5000 --name aspnetcore-sample aspnetapp-k8s

After the application starts, navigate to http://localhost:9500/swagger in your web browser.

Note: The run command -p argument maps ports 9500 and 9001 on the local machine to ports 4999 and 5000 in the container (the form of the port mapping is host:container).

If you want to run Kubernetes locally, you can spin up a whole cluster manually. Another solution is to use minikube.

You can build and run the sample locally with minikube. This document won't show you how to install minikube or the command line tool kubectl.

If this is your first time setting up minikube, the Docker daemon in minikube may not initally know about the Docker daemon in your host. You can share the context by running the following commmands:

>  minikube docker-env
>  SET DOCKER_TLS_VERIFY=1
>  SET DOCKER_HOST=tcp://172.17.13.216:2376
>  SET DOCKER_CERT_PATH=C:\Users\[USERNAME]\.minikube\certs
>  REM Run this command to configure your shell:
>  REM @FOR /f "tokens=*" %i IN ('minikube docker-env') DO @%i

minikube also provides a port range between 30000–32767 for services, so when a new service gets created a random port gets choosen. You can specify the nodePort range by running a similar command like this one below:

>  minikube start --extra-config=apiserver.service-node-port-range=80-30000

Note: To stop the local minikube cluster, run the command: minikube stop

Next, build the docker image:

>  docker build -t aspnetapp-k8s .

Create a service and a deployment:

>  cd aspnetapp
>  kubectl create -f service.yaml
>  kubectl create -f deployment.yaml

Note: To delete a service and deployment, you can run the following commands: kubectl delete service aspnetapp-k8s and kubectl delete deployment aspnetapp-k8s.

Now check if the deployment succeeded:

>  kubectl get deployments

You can also check the statuses of your pods:

>  kubectl get pods

To find out which IP and ports have been exposed, use this command (this is different when using managed k8s):

>  minikube service aspnetapp-k8s --url

You'll get an output similar to this:

http://192.168.99.100:4999
http://192.168.99.100:5000

Navigate to http://192.168.99.100:4999/swagger in your web browser to test the REST component.

And again for the gRPC piece, you can use a gRPC client (i.e. BloomRPC) to connect to 192.168.99.100:5000.