Apache Pekko gRPC on Kubernetes

Apache Pekko gRPC Kubernetes

This is an example of an Apache Pekko HTTP service communicating with a gRPC service. Both services are deployed to Kubernetes. The HTTP service uses Kubernetes API discovery mechanism to find the gRPC service and send messages to the gRPC service.

The Apache Pekko HTTP application discovers the gRPC application using Pekko Discovery. It uses the pekko-dns mechanism which relies on the SRV records created by Kubernetes. All the technologies used in this example are open source.

Usage

Prerequisites

Install the following:

• Docker
• Kubectl
• Minikube
• Sbt

Publish images

You can publish the Docker images of the grpcservice and httptogrpc applications. You can use the sbt docker:publishLocal command to publish the images to your local Docker registry.

Running

Once minikube is running and ingress enabled with minikube addons enable ingress, the two applications can be deployed using:

kubectl apply -f kubernetes/grpcservice.yml

and

kubectl apply -f kubernetes/httptogrpc.yml

Verify the deployments:

$ kubectl get deployments
NAME                          DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
grpcservice-v0-1-0-snapshot   1         1         1            1           40s
httptogrpc-v0-1-0-snapshot    1         1         1            1           40s

There are services for both:

$ kubectl get services
NAME          TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)    AGE
grpcservice   ClusterIP   10.106.188.203   <none>        8080/TCP   1m
httptogrpc    ClusterIP   10.103.134.197   <none>        8080/TCP   1m

Ingress just for the HTTP app:

$ kubectl get ingress
NAME         HOSTS              ADDRESS   PORTS     AGE
httptogrpc   superservice.com             80        2m

The HTTP application periodically hits the gRPC application. You can view the logs of the HTTP application by running

$ kubectl logs service/httptogrpc
10/01 18:18:10 INFO [HttpToGrpc-pekko.actor.default-dispatcher-34] o.a.p.a.ActorSystemImpl - Scheduled say hello to chris
10/01 18:18:10 INFO [HttpToGrpc-pekko.actor.default-dispatcher-28] o.a.p.a.ActorSystemImpl - Scheduled say hello response Success(HelloReply(Hello, Christopher,UnknownFieldSet(Map())))

And you can send a HTTP request via Ingress to the httptogrpc application:

$ curl -v --header 'Host: superservice.com' $(minikube ip)/hello/donkey
> GET /hello/donkey HTTP/1.1
> Host: superservice.com
> User-Agent: curl/7.59.0
> Accept: */*
> 
< HTTP/1.1 200 OK
< Server: nginx/1.13.12
< Date: Wed, 15 Aug 2018 07:03:56 GMT
< Content-Type: text/plain; charset=UTF-8
< Content-Length: 13
< Connection: keep-alive
< 
* Connection #0 to host 192.168.99.100 left intact
Hello, donkey%

The Host header needs to be set as that is how minikube Ingress routes requests to services.