Update and Apply Kubernetes Configurations

Composite Github action to update k8 configurations with environment variables and then apply them with kubectl.

This requires that kubectl be installed and configured. Github's hosted runners already have kubectl installed. If you're using StrongDM to manage access to your k8 cluster, then checkout configure-kubectl-with-strongdm.

Usage

See action.yaml

Example usage

Given kubernetes configurations that are committed to the codebase.

k8/deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app-deployment
  labels:
    app: my-app
  annotations:
    kubernetes.io/change-cause: ${CHANGE_CAUSE}
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: api
        image: xxxxxxxxxxxx.dkr.ecr.us-west-2.amazonaws.com/unicorn/my-app:${IMAGE_TAG}
        ports:
        - containerPort: 80

k8/config-staging.yaml

kind: ConfigMap
apiVersion: v1
metadata:
  name: my-app
  namespace: default
data:
  APP_ENV: 'staging'
  SOME_CONFIG: 'hello'

This action uses envsubst to replace values in form $VARIABLE or ${VARIABLE} that are found in the list of configuration files. See below for the different replacement options. The k8 templates do not need to define any replacements, like the k8/config-staging.yaml above. It's still useful to apply these during the deployment so that configurations can be managed through git.

The order that you list the files for k8-config-file-paths is the order that they will be applied to your cluster. So, you probably want to apply any configMap updates before applying the deployment.

The files will be applied to kubectl's current-context, so make sure to set it to the correct one before this action runs.

- name: Switch to staging cluster
  run: kubectl config use-context staging
- uses: swdotcom/update-and-apply-kubernetes-configs@v1
  with:
    k8-config-file-paths: |
      k8/config-staging.yaml
      k8/deployment.yaml
    replacement-method: defined
  env:
    IMAGE_TAG: ${{ github.sha }}
    CHANGE_CAUSE: ${{ github.event.release.tag_name }}

Config files can also be defined on one line with a space delimiter.

- name: Switch to staging cluster
  run: kubectl config use-context staging
- uses: swdotcom/update-and-apply-kubernetes-configs@v1
  with:
    k8-config-file-paths: k8/config-staging.yaml k8/deployment.yaml
    replacement-method: defined
  env:
    IMAGE_TAG: ${{ github.sha }}
    CHANGE_CAUSE: ${{ github.event.release.tag_name }}

Replacement Method - defined (Default)

Any value matching the format $VARIABLE or ${VARIABLE} will be replaced by a matching ENV variable. If no ENV variable is defined with that name, it will be unmodified.

Replacement Method - list

Any value matching the format $VARIABLE or ${VARIABLE} will be replaced by a matching ENV variable. If the ENV variable is not in the predefined list of replacement, it will be unmodified. This is useful for situations where you have a legitimate value that matches $VAR or ${VAR} and you want it to be applied exactly as is to kubernetes.

- uses: swdotcom/update-and-apply-kubernetes-configs@v1
  with:
    k8-config-file-paths: k8/config-staging.yaml k8/deployment.yaml
    replacement-method: list
    env-replacement-list: |
      ONLY_ME
  env:
    ONLY_ME: hi

Replacement Method - all

Any value matching the format $VARIABLE or ${VARIABLE} will be replaced by a matching ENV variable. If no ENV variable is defined with that name, it will be replaced with nothing. So, it would be best practice to wrap ENV vars in quotes to avoid errors when applying an invalid configuration to kubernetes.

Applying Resources to a Namespace

The namespace option allows you to apply the list of files to a specific namespace. This is useful when you need to apply a shared configMap to multiple namespaces. Your k8 resource definition must not have a namespace specified for this to work. If a namespace is specified in your file, then it will take precedence. Once this action completes, the namespace will be returned to the original namespace if it was set, otherwise will be returned to default.

- uses: swdotcom/update-and-apply-kubernetes-configs@v1
  with:
    namespace: custom-namespace
    k8-config-file-paths: k8/config-staging.yaml

k8/config-staging.yaml

kind: ConfigMap
apiVersion: v1
metadata:
  name: my-app
data:
  APP_ENV: 'staging'
  SOME_CONFIG: 'hello'