kubernetes-service-discovery example

This example shows how to run a simple backend with groupcache with multiple instances on k8s.

• simple endpoint is implemented /key/:key_id that loads a value for :key_id from groupcache, which mimics a fetch from database lasting 100ms.
• kubernetes API server is used for service discovery.
• backend is written using axum framework, exposing both application HTTP/JSON endpoints and groupcache gRPC endpoint on the same port.

Running example on minikube

Make sure all dependencies are installed and running see Dependencies.

Deploy groupcache-powered-backend with a couple of instances:

kubectl apply -f k8s/groupcache-powered-backend/role.yaml
kubectl apply -f k8s/groupcache-powered-backend/role-binding.yaml
kubectl apply -f k8s/groupcache-powered-backend/deployment.yaml
kubectl apply -f k8s/groupcache-powered-backend/service.yaml

To view logs from the backends we just deployed run:

kubectl logs -l app=groupcache-powered-backend -f

So far they're not doing anything interesting, but we can run a small load test:

kubectl apply -f k8s/k6/load-test-job.yaml

Now logs should show that backends are serving requests, grafana should also show some activity. To stop the load test run:

kubectl delete job.batch/load-test-job

Dependencies

Minikube

Download minikube using your preferred method https://minikube.sigs.k8s.io/docs/start/.

Start kubernetes locally:

minikube start

Backend docker image

To build example as a docker, uncomment groupcache dependency in Cargo.toml and run:

docker build . -t groupcache-powered-backend:latest

Load image in minikube:

minikube image load groupcache-powered-backend:latest

Observability

Optional, but allows you to see what is going on in the cluster and see metrics exported by groupcache:

• groupcache_*

And metrics exported from axum via prometheus_exporter crate:

• axum_*

There is a prepared dashboard for HTTP requests in grafana called groupcache-powered-backend.

Installing prometheus:

helm install -f k8s/prometheus-community/values.yaml prometheus prometheus-community/prometheus --version 25.3.1

Installing grafana:

helm install -f k8s/grafana/values.yaml grafana grafana/grafana --version 6.61.1

To access grafana run: minikube service grafana