van.static 0.9

Tools for managing Pyramid static files on a CDN
================================================

Serving static files from a CDN
-------------------------------

A Content Delivery Network (CDN) allows you to serve static files to
users faster. For a web application the primary benefit is that your
pages render faster, giving a better user experience.

Additionally, content such as JavaScript or CSS files should be
"slimmed" before being placed on a CDN. By decreasing the file size you
further improve the user experience with even faster loading.

van.static gives you a tool to optionally deploy files to a CDN without
making the development process more onerous.

Workflow
++++++++

This tool aids in implementing a very specific workflow using static files and
pyramid:

* During development static files are stored in subversion and are configured
as normal in Pyramid applications.
* Before deployment, the static files are extracted from the eggs by the
system administrator and uploaded to a CDN. The URL on the CDN varies
depending on the egg version the files where extracted from.
* During extraction, CSS and JS files can be optionally minified.
* In production, the system administrator configures the application to use
static files from the CDN.

This workflow has these advantages:

* Minimal impact on development. Changes to files are immediately visible,
also developers work with un-compressed files.
* CDN served files can have very long cache-control times while still allowing
them to be updated almost immediately on application upgrade.

Testing an extraction
+++++++++++++++++++++

You can try out the extract tool by running the ``cdn.py`` file directly. The
following commands will extract the ``static`` resource from the ``deform``
package to the ``test_extract`` directory:

$ mkdir test_extract
$ python van/static/cdn.py --target "file://$(pwd)/test_extract" --resource deform:static

NOTE: the deform package must be on the python path.

If you use a url like this ``s3://mybucket/path/to/files/`` the extracted
resources will be placed directly in Amazon S3. You need to manually install
``boto`` to be able to use this functionality.

Implementing in your application
++++++++++++++++++++++++++++++++

One way would be to have code like this in your package:

>>> def my_extract_filesystem_command():
... """Customized extract command for my application"""
... cdn.extract_cmd(['myapp:static', 'deform:static'], yui_compressor=True)

>>> from pyramid.config import Configurator
>>> def make_pyramid_app(cdn_url=None):
... config = Configurator()
... config.include('van.static.cdn')
... config.add_cdn_view(cdn_url or 'myapp_static', 'myapp:static')
... config.add_cdn_view(cdn_url or 'deform_static', 'deform:static')
... return config.make_wsgi_app()

You would make ``my_extract_filesystem_command`` a command line script
for the system administrator to run on deployment. Likewise the
``cdn_url`` configuration option is set by the system administrator to
the url where the files were exported to.

APT integration
+++++++++++++++

For system administrators who use APT to install packages, a useful trick is
put a snippet into ``/etc/apt/apt.conf.d/``::

DPkg::Post-Invoke:: "/path/to/extraction/script";

So that the extraction script runs whenever packages are installed on the
application servers. Note that if you have ``etckeeper`` installed, this should
be placed afterwards.

JSLint testing support
----------------------

NOTE: To use this functionality you must have a ``jslint`` command on your PATH.

This allows you to run ``jslint`` on all the files in a directory from a
unittest. For example:

>>> import unittest

>>> class TestJSLint(unittest.TestCase):
...
... def test_static(self):
... from van.static.testing import assert_jslint_dir
... from pkg_resources import resource_filename, cleanup_resources
... assert_jslint_dir(resource_filename('vanguardistas.publicview', 'static/js'))
... cleanup_resources()

YUI3 loader configuration helper
--------------------------------

``van.static.yui`` holds utilities to simplify setting up a YUI3 loader
configuration from a directory of JS modules.

Contributing
------------

If you're interested, the primary development repository over at github
https://github.com/jinty/van.static


.. comment::
Test... Make sure we can actually create the app:

>>> app = make_pyramid_app()