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controller-rs

A rust kubernetes reference controller for a Document resource using kube, with observability instrumentation.

The Controller object reconciles Document instances when changes to it are detected, writes to its .status object, creates associated events, and uses finalizers for guaranteed delete handling.

Installation

CRD

Apply the CRD from cached file, or pipe it from crdgen to pickup schema changes:

cargo run --bin crdgen | kubectl apply -f -

Controller

Install the controller via helm by setting your preferred settings. For defaults:

helm template charts/doc-controller | kubectl apply -f -
kubectl wait --for=condition=available deploy/doc-controller --timeout=30s
kubectl port-forward service/doc-controller 8080:80

Opentelemetry

Build and run with telemetry feature, or configure it via helm:

helm template charts/doc-controller --set tracing.enabled=true | kubectl apply -f -

This requires an opentelemetry collector in your cluster. Tempo / opentelemetry-operator / grafana agent should all work out of the box. If your collector does not support grpc otlp you need to change the exporter in telemetry.rs.

Note that the images are pushed either with or without the telemetry feature depending on whether the tag includes otel.

Metrics

Metrics is available on /metrics and a ServiceMonitor is configurable from the chart:

helm template charts/doc-controller --set serviceMonitor.enabled=true | kubectl apply -f -

Running

Locally

cargo run

or, with optional telemetry:

OPENTELEMETRY_ENDPOINT_URL=https://0.0.0.0:55680 RUST_LOG=info,kube=trace,controller=debug cargo run --features=telemetry

In-cluster

For prebuilt, edit the chart values or snapshotted yaml and apply as you see fit (like above).

To develop by building and deploying the image quickly, we recommend using tilt, via tilt up instead.

Usage

In either of the run scenarios, your app is listening on port 8080, and it will observe Document events.

Try some of:

kubectl apply -f yaml/instance-lorem.yaml
kubectl delete doc lorem
kubectl edit doc lorem # change hidden

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 doc -oyaml.

Webapp output

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

$ kubectl apply -f yaml/instance-lorem.yaml
$ curl 0.0.0.0:8080/metrics
# HELP doc_controller_reconcile_duration_seconds The duration of reconcile to complete in seconds
# TYPE doc_controller_reconcile_duration_seconds histogram
doc_controller_reconcile_duration_seconds_bucket{le="0.01"} 1
doc_controller_reconcile_duration_seconds_bucket{le="0.1"} 1
doc_controller_reconcile_duration_seconds_bucket{le="0.25"} 1
doc_controller_reconcile_duration_seconds_bucket{le="0.5"} 1
doc_controller_reconcile_duration_seconds_bucket{le="1"} 1
doc_controller_reconcile_duration_seconds_bucket{le="5"} 1
doc_controller_reconcile_duration_seconds_bucket{le="15"} 1
doc_controller_reconcile_duration_seconds_bucket{le="60"} 1
doc_controller_reconcile_duration_seconds_bucket{le="+Inf"} 1
doc_controller_reconcile_duration_seconds_sum 0.013
doc_controller_reconcile_duration_seconds_count 1
# HELP doc_controller_reconciliation_errors_total reconciliation errors
# TYPE doc_controller_reconciliation_errors_total counter
doc_controller_reconciliation_errors_total 0
# HELP doc_controller_reconciliations_total reconciliations
# TYPE doc_controller_reconciliations_total counter
doc_controller_reconciliations_total 1
$ curl 0.0.0.0:8080/
{"last_event":"2019-07-17T22:31:37.591320068Z"}

The metrics will be scraped by prometheus if you setup aServiceMonitor for it.

Events

The example reconciler only checks the .spec.hidden bool. If it does, it updates the .status object to reflect whether or not the instance is_hidden. It also sends a Kubernetes event associated with the controller. It is visible at the bottom of kubectl describe doc samuel.

To extend this controller for a real-world setting. Consider looking at the kube.rs controller guide.