Watchtower is an excellent tool for keeping your containers up to date. It’s a process that runs on a schedule and checks for new versions of your containers, and if it finds one, it pulls the new image and recreates the container with the latest image. It’s built for Docker, and it works great for Docker. But what about Kubernetes?

Keel, a Kubernetes operator, also achieves what Watchtower can do but can automate Helm, DaemonSet, StatefulSet & Deployment updates. It also has a friendly UI to see the status of the updates it is managing.

Installing Keel

The first step to utilizing Keel is installing it in your Kubernetes cluster. You can use Helm, the Kubernetes package manager, for this purpose:

export KEEL_NAMESPACE=keel
export KEEL_ADMIN_USER=keel
export KEEL_ADMIN_PASS=keel
kubectl apply -f https://sunstone.dev/keel?namespace=$KEEL_NAMESPACE\&username=$KEEL_ADMIN_USER\&password=$KEEL_ADMIN_PASS\&tag=latest

Configuring your Deployments for Keel

Once you have installed Keel, you’ll need to configure your deployments to use it. This is as simple as adding a few annotations to your Kubernetes deployment specifications. Keel uses SemVer (Semantic Versioning), and its policies can be all, major, minor, or patch. For example:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
  labels:
    keel.sh/policy: major
...

The above configuration means Keel will update the deployment whenever there’s a new major version of the container image.

Handling private images and rate limits

If you’re using private images or Docker Hub with its strict rate limit, you’ll need to configure Keel to authenticate with your registry. Keel also supports secrets for pulling images. Keel will use existing secrets that Kubernetes uses to pull the image so no additional configuration required.

Keel UI

One of the unique features of Keel is its UI which allows you to see at a glance the status of your deployments and any updates it’s managing. You can access it via a Kubernetes ingress or use kubectl port-forward:

kubectl -n keel port-forward service/keel 9300 

Wrapping Up

Keel is a powerful tool that brings the simplicity and automation of Watchtower to the Kubernetes ecosystem. Whether you have simple Deployments, use Helm, or have more complex DaemonSets or StatefulSets, Keel has you covered.

Remember, automating your image updates saves you time and ensures that you’re running the latest and potentially more secure version of your containers. As always, it’s essential to have robust rollback strategies and test pipelines in place, especially when using automatic updates.