Components

  • This is a feature of kustomize.

    • Provides the ability to define reusable pieces of configuration logic (resources + patches) that can be included in multiple overlays.

    • Useful in situations where applications support multiple optional features that need to be enabled only in a subset of overlays.

    • Components are essentially reusable blocks of Kubernetes configurations.

      • All of the config-maps etc go into a Component.

  • For example, we have an application that is deployed on different configurations:

    • base

    • dev

    • Premium - Premium Customers

    • Self-hosted

  • Our application has an optional feature called Caching, this is available for Premium and Self-hosted customers only.

    • Need to enable a Redis database and all of the configs with Redis to enable caching.

  • An external Postgres database is also needed in the dev / Premium spaces.

  • Where do we put the caching config in the directory structure?

    • Only self-hosted and Premium should have this.

    • Can copy the config into Premium and Self-hosted, however that causes double-work.

      * Components are reusable blocks of code that we can use in all of the overlays.

  • At the root directory, we add another directory called Components and this includes caching and db.

    • Contains all of the configs that we need for a specific feature.

  • For all of the overlays that import the database, they can import the database component.

  • Under components/db you would have the following:

    • kustomization.yaml

    • deployment-patch.yaml

    • postgres-depl.yaml

  • The postgres-depl.yaml file is a deployment for a postgres database.

  • The postgres-depl.yaml looks like this:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: postgres-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      component: postgres
  template:
     metadata:
       labels:
         component: postgres
     spec:
       containers:
         - name: postgres
           image: postgres
  • The kustomization.yaml file looks like this:
apiVersion:
kustomize.config.k8s.io/v1alpha1
kind: Component

resources:
  - postgres-depl.yaml
  
secretGenerator:
  - name: postgres-cred
    literals:
      - password=postgres123

patches:
  - deployment-patch.yaml

  • resources is where we input the yaml file we need.

  • secretGenerator is where we need to add a password.

  • patches is an environment variable, so it provides the password to the database.

  • deployment-patch looks like this:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: api-deployment
spec:
  template:
    spec:
      containers:
        - name: api
          env:
            - name: DB_PASSWORD
              valueFrom:
                secretKeyRef:
                  name: postgres-cred
                  key: password

  • There is also the kustomization.yaml file in the Overlays, we need to import the Components from above.

  • Example of Overlay/premium/kustomization:

bases:
  - ../../base
  
components:
  - ../../components/db

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