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Manually Updating Application Images

Overview

GitHub Action workflows create and push docker images to Docker Hub when PRs merges to their main branch. The images have tags with the git commit sha for the merge.

You can view all available docker images on docker hub: https://hub.docker.com/r/metacpan/metacpan-web/tags

What is running?

The kubernetes manifests maintain what image is running as part of the deployment. We use an application called kustomize that patches the base manifests, to make changes. In the manifest repo (this one), you can view the contents of the kustomization.yaml for the application in each environment.

Using the web application as an example:

$ cat apps/web/environments/prod/kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
- ../../base/
images:
- name: metacpan/metacpan-web
  newTag: dfae65b61899cfe8e9e6a8d7d39eb437849e6629

Shows that the web application in the production environment (we only have one but can support more!), we're using the metacpan/metacpan-web image with the tag (at the time of this writing) dfae65b61899cfe8e9e6a8d7d39eb437849e6629.

Updating to a newer image

Kustomize can automatically update the image in the appropriate kustomization.yaml. This update must occur in the directory for the environment. Using the web application production environment again as the example:

Visit https://hub.docker.com/r/metacpan/metacpan-web/tags and find the latest sha tagged image. The images are listed in order they were pushed, usually the first image is the latest tag, and the second image is the sha tag for the same image.

Within an up to date metacpan-k8s repository, on a new branch:

cd apps/web/environments/prod
kustomize edit set image "metacpan/metacpan-web:latest" "metacpan/metacpan-web:dfae65b61899cfe8e9e6a8d7d39eb437849e6629"
git add -u
git commit -m "Update to latest metacpan-web"
gh pr create --fill

Where dfae65b61899cfe8e9e6a8d7d39eb437849e6629 represents the latest sha image.

Push the branch to GitHub and open a PR. When approved and merged, the application will automatically deploy. Monitor the deployment status in Argo CD by visiting https://argocd.hz.metacpan.org