Rolling Back

Mistakes will happen during deployment, and when they do, Helm makes it easy to undo, or “roll back” to the previously deployed version.

Update the demo application chart with a breaking change

Open values.yaml and modify the image name under nodejs.image to brentley/ecsdemo-nodejs-non-existing. This image does not exist, so this will break our deployment.

Deploy the updated demo application chart:

helm upgrade workshop ~/environment/eksdemo

The rolling upgrade will begin by creating a new nodejs pod with the new image. The new ecsdemo-nodejs Pod should fail to pull non-existing image. Run kubectl get pods to see the ImagePullBackOff error.

kubectl get pods

NAME                               READY   STATUS             RESTARTS   AGE
ecsdemo-crystal-844d84cb86-56gpz   1/1     Running            0          23m
ecsdemo-crystal-844d84cb86-5vvcg   1/1     Running            0          23m
ecsdemo-crystal-844d84cb86-d2plf   1/1     Running            0          23m
ecsdemo-frontend-6df6d9bb9-dpcsl   1/1     Running            0          23m
ecsdemo-frontend-6df6d9bb9-lzlwh   1/1     Running            0          23m
ecsdemo-frontend-6df6d9bb9-psg69   1/1     Running            0          23m
ecsdemo-nodejs-6fdf964f5f-6cnzl    1/1     Running            0          23m
ecsdemo-nodejs-6fdf964f5f-fbcjv    1/1     Running            0          23m
ecsdemo-nodejs-6fdf964f5f-v88jn    1/1     Running            0          23m
ecsdemo-nodejs-7c6575b56c-hrrsp    0/1     ImagePullBackOff   0          15m

Run helm status workshop to verify the LAST DEPLOYED timestamp.

helm status workshop

LAST DEPLOYED: Thu Nov  7 11:11:38 2019
NAMESPACE: default
This should correspond to the last entry on helm history workshop

helm history workshop

Rollback the failed upgrade

Now we are going to rollback the application to the previous working release revision.

First, list Helm release revisions:

helm history workshop

Then, rollback to the previous application revision (can rollback to any revision too):

# rollback to the 1st revision
helm rollback workshop 1

Validate workshop release status with:

helm status workshop