Fetchez le Python

Technical blog on the Python programming language, in a pure Frenglish style. Main topics are Python and Mozilla – This blog does not engage my employer

Tag: zope

Plone Conference 2008 in Washington D.C. – summary

I am back from the Plone Conference in D.C., and the jetlag is gone. The jetlag is gone for weeks now but it’s hard to find the time to blog these days :/

On the talks I have seen and topics I have chatted about

There were a lot of great talks in D.C., and it was hard to decide which one to look at. In any case it was easy to meet the speaker if I had missed the talk, because the Plone Conference, unlike big conferences like OSCON, is a place where everyone hangs around the same spot after a talk is over.

Here’s a list of some topics I have seen or I have talked about with some people.

Deliverance – Ian Bicking

If you look at what Ian has produced in the past 5 years, he is one of the most prolific contributor of tools that become standards in the Python web development web community. Think about Python Paste or virtualenv, and many others. Deliverance might be the next big one.

Take a bunch of micro web applications you want to join to build a full web system, for historical reasons or just because you believe a particular feature just won’t fit in Plone but will do great in Pylons.

Now ask a designer to glue everything together under the same look. He (or the guy that integrates his design) will probably hates you: he will have to learn how to integrate in heterogeneous environments. This is easy under some systems that let you stick a layout and a css in a simple way. This is not easy under Plone, unless you learn how to do it (but this will be improved in the future).

Deliverance is a proxy that let you skin any application that spits html content, by running some XPATH rules on the content and applying some changes to produce a new output. Basically, you have a simple html page that just provides the layout you want to have, without any content, and a xml file that explains how to extract some content from the page produced by the third-party application and where to inject it in your empty html page. The great thing is that you can call different third-party servers given the path you are in, and even call several servers to build one single page. This opens a lot of perspectives.

The first caveat of this approach is that you have to provide a Single-Sign On feature to avoid people having to connect several times. This can be a problem sometimes with some applications if they are not open enough to let you do it. But most of the time, it is not a problem : if the users are all located in a LDAP it is easiy.

Furthermore, if you use only Python-based applications, you can use a WSGI envrionment and a middleware like repoze.who to glue together let’s say, a Plone app and a Pylons app. Products.oopas is the PAS plugin that can be used for that on Plone side to grab the authentication context and use it.

The second problem I can see is about response headers. One example: if a page is composed of elements that comes from several pages, and if the page has a Last-Modifier header, I don’t think Deliverance handles this correctly yet, to make sure to present the newest Last-Modified header from all third-party servers that where called to build that page. But this more likely to be a detail compared to the single authentication problem.

In any case this is a very promising tool !

Content Mirror – Kapil Thangavelu

I didn’t see that talk, but I have talked about this tool with a few people. The idea is to serialize the content of a Plone instance into a relational database (eg Postgresql), as it happens, using events.

I need to give a try and check it deeper, to see how the overhead is dealt, and how the aggregator I have read about is doing (it collects mirorring operations to perform in a transaction, and optimize the calls at the end of the transaction to avoid redudant calls if I understood correctly). I don’t know yet for example if there’s a pool of jobs for the mirroring tasks to avoid a point of failure. But I am pretty sure this is taking care of. The other point I need to see if there’s a round trip. e.g. if there’s a way to apply a relational database change back into Plone.

But in any case I can already see various use cases for my customers. For instance, having a plone instance as a back office, with complex workflows for editors and contributors, and a lightweight Pylons application as the front application, that concentrates into displaying the relational database as fast as possible, makes a lot of sense in big environments. It just scales better.

So this is a interesting tool as well.

repoze.bfg – Chris McDonough

Chris gave a talk about repoze.bfg, which is a new web framework that takes back the good bits from Zope and push them into a WSGI world, using the Pylons approach I would say. That is : “here’s the template engine you can use in repoze, but really, use the one you like”.

Frankly, I am really seeing this new effort as one of the most promising one in the Zope community. Already, repoze.auth is a major middleware in WSGI : Zope’s Pluggable Authentication Service outside Zope, usable with any WSGI application. This is a blast !

And people are starting to contribute a lot of interesting middlewares under the repoze namespace.

Now I didn’t really try repoze.bfg itself yet, but given the people that are behind it, I am pretty sure this framework will meet success in the future. Having a MVC framework ala Pylons that let you use Zope packages with a “this zope package is repoze/wsgi compliant” label on each one of them is very cool.

collective.indexing – Andreas Zeidler and al

At the snow sprint, we worked with the Enfold crew that did a great work in integrating the Solr/Lucene system so it can be used from Plone. We replaced a few fields like the searchable text and indexed it on Solr side, just to give it a try. The snow work was really focusing on providing a buildout, a few recipes and a bench to say : “Hey, Plone community, this is a blast ! let’s do more of it”

Later Andreas Zeidler and a few other guys continued the work on indexing matter and they delivered collective.indexing, which provides two things:

  • a queue that collects all indexing to be done, and optimize the call to the catalog
  • a bridge to use collective.solr

I didn’t follow the latest development and I didn’t know how far the guys went, but I had the chance to hang around with Andreas and Tom Lazar in D.C., so now I know that this package is production ready 😀

So in other words : I’ll probably use it as a mandatory package for all the big plones out there.

The queuing part imho, should go into the catalog itself because there’s no other way to make sure a third-party product is not calling the catalog during the transaction wile another product does the same.

Server-Side Include (SSI)

Tom Lazar worked during the Snow Sprint on lovely.remoteinclude to make Plone portlets accessible via unique URLs. From there, it is possible to push a page that contains a list of urls rather than the calculated page, to a front server that knows how to read SSI directive, and builds the page.

This is great for performances, and is a lot like ESI (Edge Side Include) we use to have in CPSSkins.

I am wondering if both could be implemented in the same tool in fact.

Tom told me that he will try to continue this work at the performance sprint in Bristol in december, so let’s keep an eye on this !

I have seen many other talks and topics, but these few ones where the ones I really needed to talk about.

On the conference organization

I am helping in the organization of Pycon FR in Paris since 2 years now. I know what is means to organize such events : it is a LOT OF WORK.

You know when an event is well organized when you don’t feel it is organized.

That was the case in D.C. Bravo Alex, Amy and all the others !

The only problem (wifi) was not the organizers fault, and I have never been to any event where it is not cahotic at some point (besides OSCON) so… 🙂

On the community

I love you all guys. It is an amazing community.

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My OSCON slides online (zc.buildout)

After a few attempts to make my screencast look nice under Google Video, I decided I would just upload the original ones (.mov and .m4v files) and a PDF export of my presentation.

So everything is available here: http://ziade.org/oscon

Slides: http://ziade.org/oscon/oscon.pdf

The .mov files are streamed automatically in your browser I believe, not the m4v ones.

Thanks to Jim Fulton for the quick feedback.

Pycon FR is coming up – may 17/18 – ask the program

Pycon FR will take place in Paris, may 17/18, at the Cité des sciences et de la Villette.

A very rich program will be presented:

  • Learn Python first ! (Eric LEBIGOT)
  • Graphviz made easier with GvGen (Sebastien Tricaud)
  • Genes research with Python (Andre Espaze)
  • CouchDB (Benoit Chesneau)
  • PyPy explained (Victor Stinner)
  • Quality Assurance (Julien Jehannet)
  • Zope 3 overview (Christophe Combelles)
  • Scapy in action (Renaud Lifchitz)
  • E-sonoclaste, multimedia annotations (Vincent Rioux)
  • Why Django ? (David Larlet)
  • PLUIE project (Michel Claveau)
  • WSGI in practice using Paste (Gael Pasgrimaud)
  • Distributed Version Control with Mercurial (Michael SCHERER)
  • Create and deploy Python apps with zc.buildout (Tarek Ziadé)
  • Django everyday: quality and performance (David Larlet)
  • Python 3000 (Victor Stinner)

There will be lightning talks as well, and the French speaking user group (Afpy) will have its annual meeting on sunday morning. A second room will be available for sprints and BoF sessions as well. All the talks will be in French this year

If you are around Paris, please join use ! It free !

Otherwise, watch the talks in the live stream: http://fr.pycon.org/stream-live

Thanks to our partners, for making this happen:

  • The Python Software Foundation
  • Logilab
  • Nerim
  • Ingeniweb
  • Resolver Systems
  • Pilot Systems
  • WingWare
  • Makina Corpus
  • Toonux
  • ActiveState
  • Gymglish
  • Eyrolles
  • Cité des Sciences et de la Vilette