WSGI, Repoze, Deliverence

WSGI, Repoze, Deliverence Mykola Kharechko © Quintagroup, 2008

Overview

Connection between WSGI, Repoze, Deliverance

WSGI

Repoze

Deliverance

Connection between WSGI, Repoze, Deliverance WSGI WSGI Zope Repoze Deliverance

WSGI – The Problem ● Lots of web frameworks: Zope, Quixote, Webware, SkunkWeb and Twisted Web etc. ● Applications written for one framework often weren't compatible with the server components of the others ● Made the choosing a Python web framework hard as there were so many different and incompatible options ● The PEP compares the situation to Java which had its Servelet API

WSGI `Hello World`

from wsgiref import simple_server

def app(env, start_response):

start_response('200 OK', [('Content-type', 'text/html')])

return ['<h1>Hello, World!</h1>']

server=simple_server.make_server('', 8000, app)

server.serve_forever()

What makes this a WSGI application

● It is a callable (in this case a simple function)

taking environ and start_response as

positional parameters.

● It calls start_response() with a status code

and a list of tuple pairs of headers before it

returns a value. It should only be called

once.

● The response it returns is an iterable (in this

case a list with just one string).

WSGI - Middleware 1. Acts like a WSGI application 2. Follows the WSGI Spec 3. Looks like a server to another piece of middleware or an application 4. Could decide to give its own response, or call your app

WSGI Middleware Example try: my_app_resp = my_app(env, my_start_response) start_response(status, header) except: start_response('500 Internal error', some_headers) my_app_resp = ['Sorry'] return my_app_resp

WSGI Summary ● WSGI isn't too complicated ● If your app is WSGI compliant you can instantly deploy it on a number of servers ● There are lots of powerful tools and middleware already in existence and you can easily re-use them -> see wsgi.org ● I'll be talking about Pylons later today which is one of the first projects to use WSGI throughout its stack.

Repoze – The Problem

Zope isn't compatible with WSGI

Top-Level Packages

repoze.zope2

repoze.plone

repoze.grok

repoze.zope2

Re-implementation of Zope 2's ZPublisher to fit into a WSGI stack "natively".

As a result, run Zope2 within Apache using mod_wsgi.

Goal: 100% backwards compatibility with all Zope 2 products.

Goal: 100% egg-based package installation.

Goal: move many Zope 2 features out into middleware.

Repoze - Installing and Starting

easy_install and virtualenv based via http://repoze.org/quickstart.html.

Buildout-based via http://svn.repoze.org/buildouts.

bin/paster serve etc/zope2.ini

Motivation to Deliverance

Zope and Content Management System forces web designers to learn a complex page templating language. It makes designing web pages slow to develop and hard to debug. There should be an easier way to take the content from a CMS and style it in various ways without understanding the architecture of the CMS and without even knowing the origin of the content. This would create a formal distinction between content production and content delivery.

Deliverance Components

The content is the information you want to style with the theme. It can be a live website or a static file, specified with a URI.

The theme contains the style and layout information you want to apply to the content. It can be a live website or a static file, specified with a URI.

The rules tell Deliverance how to apply the theme to the content.

Introduction example

Content: <html><body><div id="bar">Real Content</div></body></html>

Theme:<html><head><title>Blah</title></head><body><div id="foo">Dummy Content</div></body></html>

Rule: <replace theme="//div[@id='foo']" content="//div[@id='bar']" />

Result:<html><head><title>Blah</title></head><body><div id="bar">Real Content</div></body></html>

Deliverance. Simple Example. Page with content <html> <head> <title>my boring todo page</title> <head> <body> <div id="todo"> <h1>Things To Do</h1> <ul> <li>Feed the cat</li> <li>Wash the dishes</li> </ul> </div> </body> </html>

Deliverance. Simple Example. Page with theme <html> <head> <style type="text/css"> div {background: #00ffdd;} li {list-style-type: disc;} </style> <title>my exciting home page</title> </head> <body> <h1>Deliverance User's Exciting Page</h1> <div id="wishes"> I wish my todo list looked this cool </div> </body> </html>

Deliverance. Simple Example. Rule File <?xml version="1.0" encoding="UTF-8"?> <rules xmlns="http://www.plone.org/deliverance" > <replace theme="//div[@id='wishes']" content="//div[@id='todo']" /> </rules>

Deliverance. Simple Example. Output div {background: #00ffdd;} li {list-style-type: disc;} </style> <title>my exciting home page</title> </head> <body> <h1>Deliverance User's Exciting Page</h1> <div id="todo"> <h1>Things To Do</h1> <ul> <li>Feed the cat</li> <li>Wash the dishes</li> <ul>

Deliverance directives