MyApp deployment operater

readme.md

• Use bonny to define a MyApp CRD and Controller
  • CRD has a few fields:
    • image
    • deployment_template
• Define a DBMigration CRD and Controller
  • CRD has a few fields:
    • image
    • migration_template
• The templates are ConfigMap’s
  • deployment_template is a k8s Deployment YAML manifest w/ no image set (runs ~mix run —no-halt)
  • migration_template is a k8s Job YAML manifest w/ no images set (runs ~mix ecto.migrate)
• On add/modify of MyApp
  • Creates a DBMigration Job, waits for success
    • On success deploys Deployment
      • CRD controller fetches the template name in the incoming event
      • Injects the image name into the template
    • On failure pagerduty

Instead of deploying a Deployment we deploy a MyApp

apiVersion: "builds.example.com/v1"
kind: MyApp
metadata:
  labels:
    env: staging
spec:
  deployment_template: "name-of-current-configmap-with-deployment-template"
  image: myapp:v1.10.1

We lean on Github Actions to automatically deploy pr-based versions of the app:

apiVersion: "builds.example.com/v1"
kind: MyApp
metadata:
  labels:
    env: pr-78
spec:
  deployment_template: "name-of-current-configmap-with-deployment-template"
  image: myapp:pr-78

Using two CRDs allows us to migrate out-of-band with a deployment, for instance on staging to see if it breaks the current deployed version, since it should be backwards compat.

apiVersion: "builds.example.com/v1"
kind: DBMigration
metadata:
  labels:
    env: staging
spec:
  deployment_template: "name-of-current-configmap-with-migration-template"
  image: myapp:v1.10.1

Orignally we had it as a single CRD, but found value in breaking into two pieces to let us easily play out the scenario of the latest migration being applied while a previous container version was running.

• Bonny: https://github.com/coryodaniel/bonny
• Example Controller: https://github.com/coryodaniel/hello_operator/blob/master/lib/hello_operator/controllers/v1/greeting.ex#L60
• Waiting on Status: https://hexdocs.pm/k8s/usage.html#wait-on-a-resource
• Creating an Operation from a YAML file: https://hexdocs.pm/k8s/usage.html#creating-a-deployment-from-a-yaml-file