ruamel.dcw 0.1.1

docker-compose wrapper allowing for user data and env. var defaults

docker-compose wrapper allowing for user data and env. var defaults

dcw can be invoked with exactly the same commands as docker-compose. If -f/--file is specified as the first option the filename to be read will be taken from there. Otherwise docker-compose.yml is assumed (currently the alternative default files are not tested/read) the YAML file.

The YAML file has to be in the version: “2” format.

dcw then processes the YAML file and invokes docker-compose --file=- and the original commandline arguments, then pipes in the processed data (as YAML).

processing

The following subsections describe the processing that dcw does and the reasons for doing so.

reading defaults

The key value pairs under user-data -> env-defaults are taken to populate os.environ, unless the key already exists. This means you can set defaults for the environment variables used in the docker-compose YAML file.

stripping user-data

Any existing top-level key “user-data” or starting with “user-data-” is removed. This allows for storing additional data in the file (which would require yet another configuration file or extraction from YAML comments).

Example

This is the first part of one of my docker-compose.yml files:

version: '2'
user-data:
  author: Anthon van der Neut <[e-mail]>
  description: mongo container
  env-defaults:
    PORT: 587    # override during development
services:
  submission:
    container_name: submission
    build: .
    ports:
    - ${PORT}:587

The “author” and “description” information can easily be extracted and used by other processes.

While developing I cannot use the submission port (587) as that is already taken, and there I do export PORT=10587. On my deployment machine I don’t want to have to set PORT to the default value. With dcw the PORT env. var is set to 587 because there is no environment var “PORT” defined on that machine.