dockerhub - Kubernetes: --image-pull-policy always does not work

Question

I have a Kubernetes deployment which uses image: test:latest (not real image name but it's the latest tag). This image is on docker hub. I have just pushed a new version of test:latest to dockerhub. I was expecting a new deployment of my pod in Kubernetes but nothing happends.

I've created my deployment like this:

kubectl run sample-app --image=`test:latest` --namespace=sample-app --image-pull-policy Always

Why isn't there a new deployment triggered after the push of a new image?

Answer 1

Kubernetes is not watching for a new version of the image. The image pull policy specifies how to acquire the image to run the container. Always means it will try to pull a new version each time it's starting a container. To see the update you'd need to delete the Pod (not the Deployment) - the newly created Pod will run the new image.

There is no direct way to have Kubernetes automatically update running containers with new images. This would be part of a continuous delivery system (perhaps using kubectl set image with the new sha256sum or an image tag - but not latest).