Deploying with helm from CI using --reuse-values and adding new values to your values.yaml file
2019-03-05

I use helm and circleci to update the production and staging deployments of this blog (yes I actually have a staging deployment for a blog) in my kubernetes cluster running on google cloud. The helm chart for this project has two deployments, two services, and one ingress resource that routes requests to either production or staging service based on the http host header of the request.

Two deployments, two services, one ingress

$ tree ./helm
./helm
├── Chart.yaml
├── templates
│   ├── NOTES.txt
│   ├── _helpers.tpl
│   ├── deployment-develop.yaml
│   ├── deployment-master.yaml
│   ├── ingress.yaml
│   ├── service-develop.yaml
│   └── service-master.yaml
└── values.yaml

CI script that conditionally updates helm deployment

// .circleci/config.yml
- run:
  name: Deploy to Kubernetes
  command: |
    if [[ "$CIRCLE_BRANCH" == "develop" ]]; then
      helm upgrade --install blog --reuse-values --debug \
      --set develop_image=cflynnus/blog:${CIRCLE_BRANCH}-${CIRCLE_SHA1} \
      ./helm
    elif [[ "$CIRCLE_BRANCH" == "master" ]]; then
      helm upgrade --install blog --reuse-values --debug \
      --set master_image=cflynnus/blog:${CIRCLE_BRANCH}-${CIRCLE_SHA1} \
      ./helm
    fi
    kubectl rollout status deployment/${PROJECT_NAME}-${CIRCLE_BRANCH}-app

I ran into a problem when I added a new variable to my helm chart values.yaml file.

// values.yaml
develop_image: “cflynnus/blog:latest”
master_image: “cflynnus/blog:latest”
google_analytics: “UA-000000000-1” # New variable

My CI uses helm upgrade with the --reuse-values flag to update either my production or my staging environment depending on whether I’ve just pushed to my master or develop branches. This flag instructs tiller to generate the yaml kubernetes resources using the computed values from my last deployment and accepting values passed to helm upgrade via the --set flag. This works most of the time but becomes an issue when you want to add a value to your values.yaml file in your helm chart. When running helm upgrade --reuse-values --set ... tiller will not use new values in values.yaml. This leads to template errors, where the template expects certain values to be present but are not.

The way I get around this, is to do idempotent deploy from my local machine with the new variable, then push code to my remote git/github repo and have my CI run the deployment job. Since the value is already present in tiller, using --reuse-values will lead to the correct yaml being generated.

// This won't cause any changes to kubernetes resources since no resources use 'google_analytics' yet
$ helm upgrade --install YOUR_DEPLOYMENT --set google_analytics="xxxxxxxxxxxxxxx" .

After doing this, code can be pushed to the remote git repository and trigger the CI deployment job shown above.

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