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Simple deploy of helm chart to a kubernetes by docker

From drone.io, I am used to deploy helm charts through the helm-plugin. I wanted something similar in Gitlab CI, ideally based on a simple docker image.

Since helm needs to know where to connect, some cluster specification must be supplied. I didn't find a better way than creating a kube config in a home directory which get's populated on fly. I also wanted to have it generic in a way to use the same deployment step parametrized by the env variables. And here is the result. First of all, you need to create the minimal config template:

# deploy/kube-config-for-helm
apiVersion: v1  
clusters:  
- cluster:
    insecure-skip-tls-verify: true
    server: https://{{ KUBE_API_ADDRESS }}
  name: helm
contexts:  
- context:
    cluster: helm
    namespace: default
    user: helm
  name: helm
current-context: "helm"  
kind: Config  
preferences: {}  
users:  
- name: helm
  user:
    token: {{ TILLER_USER_TOKEN }}

The deployment step in gitlab CI looks like this:

deploy:  
  stage: deploy
  image:
    name: alpine/helm:2.9.0
    entrypoint: ["/bin/sh", "-c"]
  variables:
    # helm's user token from the cluster, it's stored in secrets
    HELM_TOKEN: ${TILLER_USER_TOKEN_STAGING}
    # IP of the cluster without `https://` prefix
    K8S_API_SERVER: ${KUBE_API_ADDRESS_STAGING}
  before_script:
  # creates a kube config used by helm to connect to the server
  - mkdir -p /root/.kube
  - cp deploy/kube-config-for-helm /root/.kube/config
  - sed -i "s/{{ TILLER_USER_TOKEN }}/${HELM_TOKEN}/g" /root/.kube/config
  - sed -i "s/{{ KUBE_API_ADDRESS }}/${K8S_API_SERVER}/g" /root/.kube/config
  script:
  - helm upgrade --install yourReleaseName --namespace gitlab-ci --debug deploy/chart

From the above, you can also figure out how to deploy just by using this docker container. Basically replaying the before_script with script.