Allow environment variables in crontab file

[topiaruss]

I want to set environment variables, specifically DB paths, in my docker-compose.yml file.

Why?

This is the path of least resistance when you quickly want to override a setting that is closely linked to the location of the deployment, to support commands exposed by Kronos. Bear in mind that the Docker environment exists during the deployment, but not while your tasks run. So what is not captured into a settings file during deployment is relatively hard to influence later.

Here's a piece of YML, demonstrating how to set KRONOS_ENV

web:
  restart: always
  environment:
    DB_USER: postgres
    KRONOS_ENV: DB_SERVICE=myappdb1.cyweh001arg.eu-west-1.rds.amazonaws.com\nFOO=bar
  build: ./web
  expose:
    - "8000"
  links:
    - redis:redis
  volumes:
    - /var/run/docker.sock:/tmp/docker.sock:ro
    - /usr/src/app/static
  command: /usr/src/app/do_run_server

The KRONOS_ENV values appear at the top of the crontab file, tagged with new breadcrumbs :

# KRONOS_ENV_BREAD_CRUMB for next
DB_SERVICE=myappdb1.cyweh001arg.eu-west-1.rds.amazonaws.com
# KRONOS_ENV_BREAD_CRUMB for next
FOO=bar
5 * * * * python manage.py my_little_command
5 * * * * python manage.py my_other_command

The entries will be removed when uninstall is invoked, and updated as the setting changes.

The settings apply to all tasks in the file.

If you accept the PR, I'll extend the doc.

[jgorset]

This directory is specific to your development environment, so you should probably add it to your global ignore file and remove it from this one.

[topiaruss]

Fair comment.

Russ Ferriday
M: +44 7429 518822
Skype: ferriday

On 7 Jan 2016, at 17:39, Johannes Gorset notifications@github.com wrote:

In .gitignore:

@@ -2,3 +2,4 @@ build
*.pyc
dist
django_kronos.egg-info
+.idea/
This directory is specific to your environment, so you should probably add it to your global ignore file and remove it from this one.

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[jgorset]

Hey thanks, @topiaruss, and sorry for taking so long to get around to this! I think this makes sense, so I'd be happy to accept the pull request if you can find the time to document it. ✨ 🍰 ✨

[topiaruss]

Thanks.
Let me conjure a little time to do that.

Russ Ferriday
M: +44 7429 518822
Skype: ferriday

On 7 Jan 2016, at 17:43, Johannes Gorset notifications@github.com wrote:

Hey thanks, @topiaruss, and sorry for taking so long to get around to this! I think this makes sense, so I'd be happy to accept the pull request if you can find the time to document it.

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[jgorset]

Cool! I'll make a new release when you do. Maybe even v1.0!