controller-rs

A rust kubernetes reference controller for a Foo resource using kube-rs, with observability instrumentation.

The Controller object reconciles Foo instances when changes to it are detected, and writes to its .status object.

Requirements

• A kube cluster / minikube / k3d.
• The CRD
• Opentelemetry collector (optional when building locally)

CRD

Generate the CRD from the rust types and apply it to your cluster:

cargo run --bin crdgen > yaml/foo-crd.yaml
kubectl apply -f yaml/foo-crd.yaml

Opentelemetry

When using the telemetry feature, you need an opentelemetry collector configured. Anything should work, but you might need to change the exporter in main.rs if it's not grpc otel.

If you have a running Tempo agent, you can simply:

make forward-tempo &
make run

Otherwise, run without the telemetry feature via: cargo run.

Local Config

You need a valid local kube config with rbac privilages described in the deployment.yaml. A default k3d setup will work.

In-cluster Config

Deploy as a deployment with scoped access via a service account. See yaml/deployment.yaml as an example. Note that the image on dockerhub is built with the telemetry feature.

kubectl apply -f yaml/deployment.yaml
sleep 10 # wait for docker pull and start on kube side
export FOO_POD="$(kubectl get pods -n default -lapp=foo-controller --no-headers | awk '{print $1}')"
kubectl port-forward ${FOO_POD} -n default 8080:8080 &

Usage

Once the app is running, you can see that it observes foo events.

Try some of:

kubectl apply -f yaml/instance-good.yaml -n default
kubectl delete foo good -n default
kubectl edit foo good # change info to contain bad

The reconciler will run and write the status object on every change. You should see results in the logs of the pod, or on the .status object outputs of kubectl get foos -oyaml.

Webapp output

The sample web server exposes some example metrics and debug information you can inspect with curl.

$ kubectl apply -f yaml/instance-good.yaml -n default
$ curl 0.0.0.0:8080/metrics
# HELP handled_events handled events
# TYPE handled_events counter
handled_events 1
$ curl 0.0.0.0:8080/
{"last_event":"2019-07-17T22:31:37.591320068Z"}

Events

The example reconciler only checks the .spec.info to see if it contains the word bad. If it does, it updates the .status object to reflect whether or not the instance is_bad.

While this controller has no child objects configured, there is a configmapgen_controller example in kube-rs.