CoreDB Operator

A Rust-based Kubernetes Controller for a CoreDB Resource using kube-rs.

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

Requirements

• A Kubernetes cluster
• The CRD
• Opentelemetry collector (optional)

Linting

Run linting with cargo fmt and clippy

Clippy:

bash rustup component add clippy cargo clippy

cargo fmt:

bash rustup component add rustfmt --toolchain nightly cargo +nightly fmt

Testing

Unit testing

bash cargo test

Integration testing

To automatically set up a local cluster for functional testing, use this script

bash ./scripts/reset-local-test-cluster.sh

Or, you can follow the below steps.

• Connect to a cluster that is safe to run the tests against
• Set your kubecontext to any namespace, and label it to indicate it is safe to run tests against this cluster (do not do against non-test clusters)

bash kubectl label namespace default safe-to-run-coredb-tests=true

• Start or install the controller you want to test (see the following sections)
• Run the integration tests

bash cargo test -- --ignored

• The integration tests assume you already have installed or are running the operator connected to the cluster.

Other testing notes

• Include the --nocapture flag to show print statements during test runs

Cluster

As an example; install kind. Once installed, follow these instructions to create a kind cluster connected to a local image registry.

CRD

Apply the CRD from cached file, or pipe it from crdgen (best if changing it):

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

OpenTelemetry (optional)

Setup 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 main.rs.

Running

Locally

sh cargo run

• Or, you can run with auto-reloading your local changes.
• First, install cargo-watch

bash cargo install cargo-watch

• Then, run with auto-reload

bash cargo watch -x 'run'

• Or, with optional telemetry (change as per requirements):

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

In-cluster

Compile the controller with:

sh just compile

Build an image with:

sh just build

Push the image to your local registry with:

sh docker push localhost:5001/controller:<tag>

Edit the deployment's image tag appropriately, then run:

sh kubectl apply -f yaml/deployment.yaml kubectl port-forward service/coredb-controller 8080:80

NB: namespace is assumed to be default. If you need a different namespace, you can replace default with whatever you want in the yaml and set the namespace in your current-context to get all the commands here to work.

Usage

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

Try some of:

sh kubectl apply -f yaml/sample-coredb.yaml kubectl delete coredb sample-coredb kubectl edit coredb sample-coredb # change replicas

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 coredb -o yaml.

Webapp output

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

```sh $ kubectl apply -f yaml/sample-coredb.yaml $ curl 0.0.0.0:8080/metrics

HELP cdbcontrollerreconciledurationseconds The duration of reconcile to complete in seconds

TYPE cdbcontrollerreconciledurationseconds histogram

cdbcontrollerreconciledurationsecondsbucket{le="0.01"} 1 cdbcontrollerreconciledurationsecondsbucket{le="0.1"} 1 cdbcontrollerreconciledurationsecondsbucket{le="0.25"} 1 cdbcontrollerreconciledurationsecondsbucket{le="0.5"} 1 cdbcontrollerreconciledurationsecondsbucket{le="1"} 1 cdbcontrollerreconciledurationsecondsbucket{le="5"} 1 cdbcontrollerreconciledurationsecondsbucket{le="15"} 1 cdbcontrollerreconciledurationsecondsbucket{le="60"} 1 cdbcontrollerreconciledurationsecondsbucket{le="+Inf"} 1 cdbcontrollerreconciledurationsecondssum 0.013 cdbcontrollerreconciledurationseconds_count 1

HELP cdbcontrollerreconciliationerrorstotal reconciliation errors

TYPE cdbcontrollerreconciliationerrorstotal counter

cdbcontrollerreconciliationerrorstotal 0

HELP cdbcontrollerreconciliations_total reconciliations

TYPE cdbcontrollerreconciliations_total counter

cdbcontrollerreconciliationstotal 1 $ curl 0.0.0.0:8080/ {"lastevent":"2019-07-17T22:31:37.591320068Z"} ```

The metrics will be auto-scraped if you have a standard PodMonitor for prometheus.io/scrape.

Development

Updating the CRD:

• Edit the CoreDBSpec struct as needed.

• > cargo run --bin crdgen > yaml/crd.yaml