Update a Deployment image in Kubernetes

docker kubernetes minikube
yuval simhon picture yuval simhon · Jan 19, 2017 · Viewed 17.5k times · Source

I'm very new to Kubernetes and using k8s v1.4, Minikube v0.15.0 and Spotify maven Docker plugin.
The build process of my project creates a Docker image and push it directly into the Docker engine of Minikube.

The pods are created by the Deployment I've created (using replica set), and the strategy was set to type: RollingUpdate.

I saw this in the documentation:

Note: a Deployment’s rollout is triggered if and only if the Deployment’s pod template (i.e. .spec.template) is changed.


I'm searching for an easy way/workaround to automate the flow: Build triggered > a new Docker image is pushed (withoud version changing) > Deployment will update the pod > service will expose the new pod.

Answer

pagid picture pagid · Jan 19, 2017

when not changing the container image name or tag you would just scale your application to 0 and back to the original size with sth like:

kubectl scale --replicas=0 deployment application
kubectl scale --replicas=1 deployment application

As mentioned in the comments already ImagePullPolicy: Always is then required in your configuration.

When changing the image I found this to be the most straight forward way to update the 

kubectl set image deployment/application app-container=$IMAGE

Not changing the image has the downsite that you'll have nothing to fall back to in case of problems. Therefore I'd not suggest to use this outside of a development environment.

Edit: small bonus - keeping the scale in sync before and after could look sth. like:

replica_spec=$(kubectl get deployment/applicatiom -o jsonpath='{.spec.replicas}')
kubectl scale --replicas=0 deployment application
kubectl scale --replicas=$replica_spec deployment application

Cheers

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