gRPC echo service

Heavily inspired by the official grpc helloworld example but with a fully working Kubernetes deployment example.

Will only work on your machine.

The echo-service works as follows: The server will answer pong on any ping request sent using the gRPC client. The pong response and ping message are hardcoded in the server and client.

Prerequisites

• Docker
• kind
• protoc and Go plugins for the protocol compiler
• Go

How to

1. See the prerequisites here to install protoc and the Go plugins needed.
2. In the root of this repository run:

make gen-proto

3. Start the kind cluster:

kind create cluster --name k8s-1.19.7 --config kind/k8s-1.19.7.yaml

4. Install metallb to be able to create a Service of type LoadBalancer in Kubernetes:

kubectl apply -f https://raw.githubusercontent.com/metallb/metallb/master/manifests/namespace.yaml
kubectl create secret generic -n metallb-system memberlist --from-literal=secretkey="$(openssl rand -base64 128)" 
kubectl apply -f https://raw.githubusercontent.com/metallb/metallb/master/manifests/metallb.yaml

5. Identify the CIDR network used by Docker:

docker network inspect -f '{{.IPAM.Config}}' kind

6. Create and apply a ConfigMap using a subset of the addresses in the CIDR from the output above, you should replace the IP addresses addresses field below:

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: ConfigMap
metadata:
  namespace: metallb-system
  name: config
data:
  config: |
    address-pools:
    - name: default
      protocol: layer2
      addresses:
      - 172.18.255.200-172.18.255.250
EOF

7. Build the grpc-echo-service Docker image:

docker build . -t grpc-echo-service:v0.1.0

8. Push the built grpc-echo-service Docker image to a registry.
9. Change the image in manifests/deployment.yaml pointing to the one you've just pushed.
10. Apply the deployment.yaml and service.yaml files.

kubectl apply -f manifests/deployment.yaml
kubectl apply -f manifests/service.yaml

11. Take a note of the Load Balancer IP the Service have received from MetalLB:

kubectl get svc grpc-echo-service -o=jsonpath='{.status.loadBalancer.ingress[0].ip}'

12. Add the Load Balancer IP to the cert/echo_client-ext.cnf and cert/echo_server-ext.cnf files.
13. Re-generate the certificates:

make gen-cert

14. Re-build and re-push the Docker image.
15. Restart the Deployment of grpc-echo-service server component:

kubectl deployment rollout restart grpc-echo-service

16. Run the gRPC client:

go run echo_client/*.go -addr "172.18.255.200:8443" -cert cert/client-cert.pem -key cert/client-key.pem

you should see an output similar to this one:

2021/05/02 22:40:35 Starting gRPC echo service client..
2021/05/02 22:40:35 Echoes service replied: pong