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WSGI middleware for statistical HTML browser resource squeezing.

Project description

This package provides a WSGI middleware component which “squeezes” HTML documents by merging browser resources (javascript and stylesheets).

It uses statistical analysis to determine the optimal bundles based on the HTML documents that pass through it. Vary-headers are observed, as are resource expiration dates.

Documents that are not squeezed are given the ‘no-cache’ pragma in an expectation that we will be able to squeeze it after sufficient burn-in. Squeezed documents are served with expiration dates no later than the expiration dates of the squeezed resources which it references.


Configure the middleware with the following two options (required):

@cache_dir: Relative path to a directory where we store squeezed resources

@url_prefix: Path segment or full base URL that will be used to serve the cache directory as static files.

The following option is optional:

@threshold: Floating-point parameter that controls the merge to apperances threshold. This parameter can normally be left at the default (0.5).

In addition, you must configure the WSGI application to serve the file cache directory from the url_prefix (e.g. “cache”).


To invalidate the file cache, upstream applications can set the “X-Squeeze-Invalidate” header to a true value; note that before the application is called, the middleware adds this key to the environment such that applications which can’t modify the environment can still flag for invalidation:

>>> invalidate = environ["X-Squeeze-Invalidate"]
>>> invalidate()

This will reset the file cache registry; note that no cache files are ever deleted (to preserve web server integrity). You can manually purge the file cache at any time be deleting the files (this is allowed at run-time).


0.4.4 (released 2009-06-22)

  • Fixed edge-case where a response would not have a character set defined and hence couldn’t be expressed as unicode. [malthe]

  • Fixed edge-case with self-closing style elements. [malthe]

  • Fixed edge-case issue with missing ttl-value. [malthe]

0.4.3 (released 2009-05-11)

  • Added environment variable control of file cache invalidation. [malthe]

0.4.2 (released 2009-05-11)

  • Add semicolon after javascripts to make sure any function-block is properly terminated (necessary due to concatenation). [malthe]

0.4.1 (released 2009-04-20)

  • Parse unicode body to ensure correct character decoding. [malthe]

0.4 (released 2009-04-15)

  • If a response has status ‘304 Not Modified’, update the ttl but not the content. [malthe]

  • If a script- or style-tag does not have a source or link, ignore it. [malthe]

  • Unquote request URL when querying cache. [malthe]

  • Added support for repoze.xmliter which allows reusing an lxml document tree between middlewares. [malthe]

  • Media types for stylesheets are now taken into account when merging the resources. Squeze uses CSS2 @media <type> syntax. [jvloothuis]

0.3 (released 2008-10-08)

  • Relative URLs appearing in stylesheets are now made absolute before merging. [malthe]

0.2 (released 2008-10-03)

  • Add setuptools as a dependency. [malthe]

0.1 (released 2008-10-02)

  • Initial release.

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