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wesgi implements an ESI Processor as a WSGI middeware. It is primarily aimed at development environments to simulate the production ESI Processor. Under certain conditions it may be used in production as well.

This implementation currently only implements <esi:include> and <!--esi --> comments. The relevant specifications and documents are:

• http://www.w3.org/TR/esi-lang
• http://www.akamai.com/dl/technical_publications/esi_faq.pdf

An ESI processor generally makes a lot of network calls to other services in the process of putting together a page. So, in general, to reach very high levels of performance it should be asynchronous. Standard Python and WSGI is synchronous, placing an upper limit on performance which depends on the following:

• How many threads are used
• How many ESI includes used per page
• The speed of the servers serving the ESI Includes
• Whether wesgi uses a cache and if the ESI includes come with Cache-Control headers

Depending on the situation, wesgi may be performant enough for you.

There are also a number of ways to run WSGI applications asynchronously, with varying definitions of "asynchronous".

>>> from wesgi import MiddleWare
>>> from wsgiref.simple_server import demo_app

To use it in it's default configuration for a development server:

>>> app = MiddleWare(demo_app)

To simulate an Akamai Production environment:

>>> app = MiddleWare(demo_app, policy='akamai')

To simulate an Akamai Production environment with "chase redirect" turned on:

>>> from wesgi import AkamaiPolicy
>>> policy = AkamaiPolicy()
>>> policy.chase_redirect = True
>>> app = MiddleWare(demo_app, policy=policy)

If you wish to use it for a production server, it's advisable to turn debug mode off and enable some kind of cache:

>>> from wesgi import LRUCache
>>> from wesgi import Policy
>>> policy.cache = LRUCache()
>>> app = MiddleWare(demo_app, debug=False, policy=policy)

The LRUCache is a memory based cache using an approximation of the LRU algorithm. The good parts of it were inspired by Raymond Hettinger's lru_cache recipe.

Other available caches that can be easily integrated are httplib2's FileCache or memcache. See the httplib2 documentation for details.

Development on wesgi is centered around this github branch:

https://github.com/jinty/wesgi