Application Variables

Application variables are very powerful, they can be used both in configuration files and as environment variables.

note

This describes how to declare your own variables, for built-in variables see the reference docs

The example application below illustrates the usage of variables. You declare variables within the context of a service and use them as input to your containers in different ways. A variable has a name and a value, where the value can be explicitely set (SECRET_NUMBER) or picked up from a vault secret (DB_USERNAME, DB_PASSWORD).

The example below shows two ways of passing the variable values to the container:

• Expanded into a config file via a volume mount.
• Passed as environment variables.

The environment variable list in the example below also illustrates the usage of Avassa built-in variables. SITE_NAME will be assigned the name of the site in the Avassa system.

name: my-app
version: "1.0"
services:
  - name: my-svc
    variables:
      - name: DB_USERNAME
        value-from-vault-secret:
          vault: my-db
          secret: credentials
          key: username
      - name: DB_PASSWORD
        value-from-vault-secret:
          vault: my-db
          secret: credentials
          key: password
      - name: SECRET_NUMBER
        value: "42"
    volumes:
      - name: config
        config-map:
         - name: my-config
           data: |
             This is my config file
             ${DB_USERNAME} will be replaced at instantiation, ${DB_PASSWORD} as well.
             The secret number is ${SECRET_NUMBER} at site ${SYS_SITE}.
    containers:
      - name: my-db
        env:
          USERNAME: ${DB_USERNAME}
          PASSWORD: ${DB_PASSWORD}
          SECRET_NUMBER: ${SECRET_NUMBER}
          SITE_NAME: ${SYS_SITE}
        mounts:
          - name: config
            files:
                - name: my-config
                  mount-path: /etc/my-cfg

if the my-db vault secret (credentials) contains username=fredrik and password=foobar, the container will be started with environment variables:

USERNAME=fredrik
PASSWORD=foobar
SECRET_NUMBER=42
SITE_NAME=my-site-name

The config file (mounted at /etc/my-cfg) will look like this:

 This is my config file
 fredrik will be replaced at instantiation, foobar as well.
 The secret number is 42 at site my-site-name.