[Web-SIG] A Python Web Application Package and Format

[Daniel Holth]

I am fine with the idea of passing a standard [YAML] container-resources 
configuration file to applications, but I mostly care about the orthogonal 
underlying 'copy a virtualenv to another server' use case. My proposal:

site.py should honor a new environment variable PYTHONAPPBASE, similar to 
PYTHONUSERBASE or PYTHONHOME.

PYTHONAPPBASE causes site.py to add an additional site-packages directory in 
PYTHONAPPBASE/lib/python2.7/site-packages or Lib/site-packages etc. in the 
same way the current site-packages paths are chosen.

(Optional) If that's not good enough, PYTHONAPPSITE specifies a directory 
that is given to site.addsitepackages(). A maximum of 1 directory within 
PYTHONAPPBASE can be added.

site.py gains APP_BASE and APP_SITE in the same way it currently contains 
USER_BASE and USER_SITE.

All other paths such as PYTHONAPPBASE/src/mypackage-0.1/src/__init__.py are 
resolved with .pth files that must contain relative paths only.

Definitions:

runtime: Python libraries available to but outside the webapp. Chosen by 
setting PYTHONHOME. The application metadata might choose a runtime by name, 
and the application server might display the results of 'pip freeze' for the 
runtime to help you build a matching development environment.

app.wsgi is the initial entry point /for the WSGI application/ but scripts 
can be run by setting up the environment in the same way.

To configure such an application with uWSGI then, if the Python runtime is 
in /runtimeA and the web application package is in /application, you would 
provide the following uWSGI configuration:

[uwsgi]
pyhome=/runtimeA
chdir=/application
file=/application/app.wsgi
env=PYTHONAPPBASE=/application
# to be specified later:
env=STANDARD_CONFIGURATION_FILE=/some-container-services.yaml

When app.wsgi starts it can access any libraries from 
/runtimeA/lib/python2.7/site-packages and any libraries from 
/application/lib/python2.7/site-packages

Since PYTHONPATH comes from site.py, not app.wsgi, it's very easy to perform 
the same setup for any other scripts within /application/


Is this anything?

Daniel Holth
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