Configuring managed application instances

KuberLogic runs application in Kubernetes pods. It expects that an application container image will be self-contained and will have everything that the application requires.

Still, applications need to be configured and there are a number of ways to do so. All examples show how to configure an application via docker-compose.yml.

Environment variables

Standard de-facto in a Kubernetes world. Application container will have the environment variable TOKEN set to test.

version: "3"
services:
  - name: my-service
    image: my-image
    environment:
      - TOKEN=test

You can also use templating functions that are provided by Kuberlogic:

version: "3"
services:
  - name: my-service
    image: my-image
    environment:
      - BASE_URL={{ Endpoint "localhost" }}

To learn more about templating, see this page.

Providing secret configuration parameters

An example above shows how to configure a static environment variable. This method has one downside: all your application instances will have environment variable TOKEN set to the same value.

This can be changed, when using combining templating with x-kuberlogic-secrets extension.

version: "3"
x-kuberlogic-secrets: # this extension can only be set at the root of docker-compose
  token: "{{ GenerateKey 16 }}"

services:
  - name: my-service
    image: my-image
    environment:
      - TOKEN={{ Secrets "token" }} # we reference a secret `token` defined in `x-kuberlogic-secrets` extension.

In this example all application instances will have a TOKEN variable set to the random 16 characters string.

note

Secrets defined in x-kuberlogic-secrets are static during the application instance lifetime. They will not be updated if already set.

Providing configuration files

Some applications also require config files to be available locally. Configuration files content can be set with x-kuberlogic-file-configs extension on the service level.

Example:

version: "3"
x-kuberlogic-secrets:
  key: {{ GenerateKey 16 }}

services:
  - name: web
    image: my-image
    x-kuberlogic-file-confis:
      /etc/app.cfg: |
        app=web
        api-key={{ Secret "key" }}
  - name: api
    image: my-api
    x-kuberlogic-file-configs:
      /etc/app.cfg: |
        app=api
        api-key={{ Secret "key" }}

In the example above, both container will have the file /etc/web.cfg available locally, but the content will be specific for each service.

tip

You can also you docker-compose.yml templating when providing configuration files content.