A Python port of daemontools' envdir.
envdir runs another program with a modified environment according to files in a specified directory.
So for example, imagine a software you want to run on a server but don’t want to leave certain configuration variables embedded in the program’s source code. A common pattern to solve this problem is to use environment variables to separate configuration from code.
envdir allows you to set a series of environment variables at once to simplify maintaining complicated environments, for example in which you have multiple sets of those configuration variables depending on the infrastructure you run your program on (e.g. Windows vs. Linux, Staging vs. Production, Old system vs. New system etc).
Let’s have a look at a typical envdir:
$ tree envs/prod/ envs/prod/ ├── DJANGO_SETTINGS_MODULE ├── MYSITE_DEBUG ├── MYSITE_DEPLOY_DIR ├── MYSITE_SECRET_KEY └── PYTHONSTARTUP 0 directories, 3 files $ cat envs/prod/DJANGO_SETTINGS_MODULE mysite.settings $
As you can see each file has a capitalized name and contains the value of the environment variable to set when running your program. To use it, simply prefix the call to your program with envdir:
$ envdir envs/prod/ python manage.py runserver
That’s it, nothing more and nothing less. The way you structure your envdir is left to you but can easily match your configuration requirements and integrate with other configuration systems. envdirs contain just files after all.
An interesting summary about why it’s good to store configuration values in environment variables can be found on the 12factor site.
This Python port behaves different for multi line environment variables. It will not only read the first line of the file but the whole file. Take care with big files!
- Use exec (os.execvpe) to replace the envdir process with the child process (fixes #20).
- Change isenvvar() to only check for = in var names.
- Fixed handling SIGTERM signals to make sure all children of the forked process are killed, too. Thanks to Horst Gutmann for the report and help fixing it.
- Rewrote tests with pytest.
- Vastly extended Python API.
- Added Sphinx based docs: http://envdir.readthedocs.org/
- Fixed killing child process when capturing keyboard interrupt.
- Added standalone script based on PEPs 441 and 397, compatible with Python Launcher for Windows. See the installation instructions for more info.
- Added check if the the provided path is a directory and throw an error if not. This adds compatibility to the daemontools’ envdir.
- Make sure to convert Nulls (\0) to newlines as done so in daemontools’ envdir.
- Fixed envdir.read() to actually work with already existing environment variables. Extended docs to test Python use.
Added envshell command which launches a subshell using the environment as defined in the given envdir. Example:
$ envshell ~/mysite/envs/prod/ Launching envshell for /home/jezdez/mysite/envs/prod. Type 'exit' or 'Ctrl+D' to return. $ python manage.py runserver ..
- Catch KeyboardInterrupt exceptions to not show a traceback from envdir but the repsonse from the called command.
- Allow multiline environment variables. Thanks to Horst Gutmann for the suggestion. This is a departure from daemontools’ standard which only allows the first line of the environment variable file.
- Fixed python -m envdir
- Extended README to better describe the purpose
- Added ability to use envdir from Python.
- Initial release.
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