Bfg Ploneconf Oct2008

the repoze.bfg web framework Presented By Chris McDonough Agendaless Consulting Plone Conference 2008

• About a year old. • Allow Zope developers to use WSGI technologies more easily. • Allow non-Zope developers to use Zope technologies without using all of Zope.

• repoze.bfg: July 2008 • Chris McDonough, Tres Seaver, Paul Everitt, Carlos de la Guardia, Malthe Borch, Stefan Eletzhofer, Fernando Neto-Correa. • Big f'ing gun -OR- big friendly giant: you choose.

WHY? • Zope2: still kicking, but only due to Plone • Zope3: big, many dependencies. App developers encouraged to use CA. • Grok: quot;making Z3 easier to usequot; (see Zope 3). • Django: nice, but Z2-like. • Pylons/TG2: nice, but geared towards RDB / URL dispatch apps. • Others: not Zope-like / no traction.

Goals • Familiarity: like Zope, but less • Simplicity: pay only for what you eat • Speed: go as fast as possible while still actually doing something • Documentation: the lack of formal documentation of a feature or API is a bug • Collaboration: culture of using and promoting non-Zope stuff

What BFG Does • Maps URLs to code • Provides mechanisms that allow developers to make declarative security assertions • Provides text and HTML templating facilities • Allows for use of existing Zope libs (via ZCML).

What BFG Doesn't Do • Database / persistence • Sessions • Indexing / searching • ZMI / TTW code • View code sharing with Z3 / Five • etc...

The Application is the Application • You don't write quot;Productsquot; to plug into BFG. Extensibility is via normal Python packages and ZCML as necessary. • An application is generated for you; you develop the application and run the application; you don't run the framework.

Graph Traversal and URL Dispatch • BFG supports both graph traversal (ala Zope) and quot;URL dispatchquot; (ala everything else) to map URLs to code. • URL dispatch is backed by Routes.

Zope CA • The Zope Component Architecture was used to construct BFG. • BFG application developers don't need to use the CA. It's a framework implementation detail.

Components • WSGI pipeline. • Router (aka Publisher). • quot;Application registryquot; (ZCML / decorators). • Views (aka quot;controllersquot; in Pylons/Rails). • Templates (chameleon/XSL/other).

Dependencies Paste-1.7.1-py2.4.egg zope.deferredimport-3.4.0-py2.4.egg PasteDeploy-1.3.2-py2.4.egg zope.deprecation-3.4.0-py2.4.egg PasteScript-1.6.3-py2.4.egg zope.event-3.4.0-py2.4.egg Routes-1.9.2-py2.4.egg zope.exceptions-3.5.2-py2.4.egg WebOb-0.9.2-py2.4.egg zope.hookable-3.4.0-py2.4-macosx-10.5-i386.egg zope.i18n-3.5.0-py2.4.egg zope.proxy-3.4.1-py2.4-macosx-10.5-i386.egg elementtree-1.2.6_20050316-py2.4.egg zope.i18nmessageid-3.4.3-py2.4-macosx-10.5-i386.egg lxml-2.1.1-py2.4-macosx-10.5-i386.egg zope.interface-3.4.1-py2.4-macosx-10.5-i386.egg pytz-2008c-py2.4.egg zope.location-3.4.0-py2.4.egg setuptools-0.6c8-py2.4.egg zope.publisher-3.5.3-py2.4.egg zope.schema-3.4.0-py2.4.egg zope.traversing-3.5.0a3-py2.4.egg z3c.pt-1.0a1-py2.4.egg zope.security-3.5.1-py2.4-macosx-10.5-i386.egg zope.component-3.4.0-py2.4.egg zope.testing-3.5.1-py2.4.egg zope.conﬁguration-3.4.0-py2.4.egg Many are due to inappropriate dependencies in Zope eggs.

How it Works

Models • quot;contentquot; objects • typically arranged in a graph (although not required) • For Zope people: think ZODB • ZODB not required for repoze.bfg applications: ﬁlesystem directories, XML documents, RDF graphs, SQL databases, etc. can be the source of model data

A Model from zope.interface import implements from zope.interface import Interface class IMyModel(Interface): pass class MyModel(object): implements(IMyModel) def __init__(self, name): self.name = name

Views • Views are functions which accept a quot;contextquot; (a model object) and a quot;requestquot;. • Views must return a response. Unlike Zope. • The view may use a template to generate the response body, or not.

A View from webob import Response def hello_world(context, request): return Response('Hello world!')

A View That Renders a chameleon.zpt Template from repoze.bfg.chameleon_zpt import render_template_to_response def hello_world(context, request): render_template_to_response( 'templates/hello.pt', context=context, myname='chris')

Using Model Data from a View from webob import Response def hello_world(context, request): name = context.name return Response('Hello %s!' % name)

Templates • Default templating engine: chalmeleon by Malthe Borch. ZPT or Genshi syntax. ~ 10X - 15X faster than zope.pagetemplate. • Included: XSLT. • Add-on: jinja2 (Django-style, via repoze.bfg.jinja2) • Any other you'd like to use; bindings are simple to create (see the jinja2 bindings).

Traversal • The BFG router traverses the model graph based on the path segments in the URL (like Zope does). • If traversal quot;falls offquot; the end of the model graph, and there are path segments remaining, it looks for a view registered against the interface of the last model traversed using the next path segment as the view name. • If there are no segments remaining, the default view is used. • If no view is found, a 404 not found error is returned.

View Registrations <conﬁgure xmlns=quot;http://namespaces.zope.org/zopequot; xmlns:bfg=quot;http://namespaces.repoze.org/bfgquot; i18n_domain=quot;repoze.bfgquot;> <include package=quot;repoze.bfgquot; /> <— default view for .interfaces.IMyModel —> <bfg:view for=quot;.interfaces.IMyModelquot; view=quot;.views.my_viewquot; /> <— named view for .interfaces.IMyModel —> <bfg:view for=quot;.interfaces.IMyModelquot; view=quot;.views.other_viewquot; name=quot;otherquot; /> </conﬁgure>

View Registrations via Decorators from webob import Response from repoze.bfg.convention import bfg_view @bfg_view(name='hello.html') def hello_world(context, request): name = context.name return Response('Hello %s!' % name)

Speed <html xmlns=quot;http://www.w3.org/1999/xhtmlquot; xmlns:tal=quot;http://xml.zope.org/namespaces/talquot;> <head> <title tal:content=quot;context.titlequot;>The title</title> <meta http-equiv=quot;content-typequot; content=quot;text/html;charset=utf-8quot;/> </head> <body> <h2><span tal:replace=quot;context.title_or_id()quot;>content title or id</span> <span tal:condition=quot;context.titlequot; tal:replace=quot;context.titlequot;>optional template title</span></h2> This is Page Template <em tal:content=quot;request.view_namequot;>template id</em>. </body> </html> Zope 2.10 view page template: 309 req/sec vs. BFG view + chameleon.zpt template: 869 req/sec

Memory Usage and Process Sharing • Existing Zope 2 and Zope 3 apps cannot run side-by-side in the same process due to globals sharing (ZCML global registry, database references); BFG has been written to make such a conﬁguration work by default. • Lower memory requirements per application instance (BFG minimum ~15 MB vs. Zope 3 minimum ~50MB).

Startup Speed • repoze.bfg caches the ZCML registry as a pickle for faster startup. • Startup time with a single view deﬁned: 900ms.

Paste-Derived Reload Feature [chrism@vitaminf myproj]$ ../bin/paster serve myproj.ini —reload Starting subprocess with ﬁle monitor Starting server in PID 61405. serving on 0.0.0.0:6543 view at http://127.0.0.1:6543 /Users/chrism/projects/repoze/bfgenv/myproj/myproj/run.py changed; reloading... —————————— Restarting —————————— Starting server in PID 61409. serving on 0.0.0.0:6543 view at http://127.0.0.1:6543

Template Auto-Reload Feature • Templates auto-reload by default. • This can be turned off for speed.

WSGI-Middleware- Derived Features • Proﬁler (repoze.proﬁle) • Alternate exception handlers (paste.evalexception). • Caching (repoze.accelerator) • Theming (Deliverance). • Transaction management (repoze.tm2) • etc...

Project Setup Demo

Futures • Vudo CMS (http://docs.vudo.me) to be implemented using repoze.bfg, hopefully. Work towards this: repoze.bfg.skins, repoze.bfg.layout, repoze.bitblt, repoze.squeeze. • BFG will stay minimal. Add-ons and superframeworks like vudo and repoze.lemonade will provide functionality.

The End • For a more in-depth exploration of how a bfg app is written, see the screencast at http://static.repoze.org/presentations/repozebfg-wiki.mov

Bfg Ploneconf Oct2008

by Alex Clark on Oct 20, 2008

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