Extend your dockerfiles with Jinja2 syntax and logic.

Create new filter and functions for Jinja with simple datasource files.

Build status:

Clone this repo. Navigate to root of repo. Run pip install . to install.

Install package into your system python or into a virtualenv (This is recommended way)

Create a Dockerfile.jinja that contains all regular Dockerfile build steps and the jinja syntax

Run dj command. For example

dj --dockerfile Dockerfile.jinja --outfile Dockerfile --env OS=ubuntu:12.04 --datasource test-datasource.py --config test-config.json

Run regular Docker build/run command as usual

• 2.7
• 3.3
• 3.4

Python 3.2 will not be supported because Jinja2 is only supported on python >= 3.3 (Reference: http://jinja.pocoo.org/docs/intro/). If other rendering engines would be supported then python 3.2 can be supported for those engines.

Python 2.6 will not be supported.

If you want to extend the Jinja syntax with additional filters and global functions you have the datasource pattern to help you.

A datasource file is a python script that can contain any code you want so you can extend dj to be capable to perform any task you want.

You can tell dj to load a datasource file in multiple ways.

• In any config file create a key datasources with a list of strings paths pointing to all files that dj should import. (Must be absolute path)
• Point to a file with cli key -s/--datasource and dj will load that file. (Relative paths is supported)
• Add a python file to contrib folder and it will auto load during execution.

Global functions ################

A global function is a regular python function that you can call from jinja. These functions can be used to perform any usefull task you require.

To create a global function you define a method within a datasource and its name should starts with _global_ and then follow by the name you want to use in your Dockerfile.

For example if you have the following code:

def _global_foo():
    return "bar" 

You can call it from jinja with:

RUN echo '{{ foo() }}'

and it will render into

RUN echo 'bar'

Filter functions ################

To create a new filter function you define a method within a datasource and its name should starts with _filter_ and then follow by the name you want to use in your Dockerfile.

For example if you have the following code

def _filter_bar(arg):
    return arg.upper()

You can call it from jinja with:

RUN echo '{{ "opa"|bar }}'

and it will render into

RUN echo 'OPA'

It is possible to create predefined configuration files with settings, enviroment variables and datasources.

dj tries to load the following configuration files in the following order:

• /etc/dj.yaml
• /etc/dj.json
• ~/.dj.yaml
• ~/.dj.json
• $CWD + '.dj.yaml'
• $CWD + '.dj.json'

YAML is the file format to prefer but json is also supported.

Currently it is not possible to automatically load a config file next to the source Dockerfile.

Currently only Jinja2 is supported as rendering engine.

In the future the possibility to add new engines will be added.

Open an Issue on github describing the problem you have.

If you have a fix for the problem or want to add something to contrib library, open a PR with your fix. The PR must contain some test to verify that it work if it is a bugfix or new feature. All tests in all supported python environments must pass on TravisCI before a PR will be accepted.

All PR:s should have their commits squashed to a single commit.

See LICENSE file. (MIT)