PyCon 2010: I Want to Present Something

I’ve been racking my brains to find something to present at PyCon 2010. I have been trying to find something good to present since PyCon 2003, when I last presented at PyCon.  (I talked about Ape, the Adaptable Persistence Engine for Zope.)  I really liked the experience of presenting and it led to a lot of interesting conversations. Since then, however, nothing has really struck me as a good idea for a presentation. The right idea has to fit at least these criteria:

  • It’s something I’m good at.
  • At least a handful of PyCon attendees would like to learn more about it in a presentation.
  • I can’t spend weeks to prepare for the presentation.

This year, I was planning to do a really fun presentation by writing some Python scripts for controlling a RepRap, then I was going to present the hardware and software.  That didn’t work out, however, because the warping issues with ABS (a type of plastic) are just too severe to print useful parts, so my RepRap has sat idle.  (I’m now considering PLA, but it’s a newish and expensive material.)

Here are a few other ideas for a presentation topic.  What do you think?  Any other ideas?

  • RelStorage.  I could talk about future plans, why I think it is an improvement over ZEO, and why you should use it.  There seem to be a lot of people with questions about RelStorage, so it would be nice to have some time to answer the questions in a big room so others can hear the answers.
  • KARL and BFG.  This would probably be a team presentation.  KARL is some fairly interesting software that I got to help develop this year.  I could talk about the software, along with the development experience and style.  In KARL we made a conscious choice to ignore certain apparent DRY violations, leading to significant productivity gains.
  • A friendly introduction to Buildout.  Buildout is a tool that a lot of developers need, but don’t know it yet.  The function that Buildout performs is as important as version control and automated testing.  Come find out why Buildout is far better than a pile of Makefiles.
  • An introduction to Buildout (zc.buildout) for people familiar with Apache Maven.  Buildout and Maven fill approximately the same niche, but for different audiences.  (Buildout for Python, Maven for Java.)  Maybe there are Mavenites at the conference who would like to switch to a more Python centric system.
  • A discussion of text indexing in Plone and BFG.  This might be a narrow topic, but I find it interesting and important.  I have found ways to reduce complex 90 second text searches to 1 second.  The solution is not pure Python, unfortunately. 😉  I have also thought about how to expand into areas like faceted search/browse functionality.

Feedback encouraged!

RelStorage 1.3.0b1, Now With Blob Support

I have just released two versions of RelStorage. Version 1.3.0b1 adds full support for ZODB blobs stored on the filesystem. Version 1.2.0 is currently the better choice if you’re upgrading a production system and don’t need blob support.

People have been asking for blob support for months. I am glad to finally get it done, with a little help from a customer. With blob support, now we can easily store large artifacts on the filesystem, while keeping all metadata in the database.

To celebrate the new release, I have created a sample buildout.cfg that builds Plone with RelStorage, PostgreSQL, and blob support. (Thanks goes to Hanno Schlichting, who released a compatible version of plone.recipe.zope2instance only moments after I requested it.) Here it is:

[buildout]
parts = plone zope2 instance zopepy
find-links =
    http://dist.plone.org
    http://download.zope.org/ppix/
    http://download.zope.org/distribution/
    http://effbot.org/downloads
    http://packages.willowrise.org
eggs =
    elementtree
    PILwoTk
    RelStorage
    psycopg2
versions = versions

[versions]
ZODB3 = 3.8.3-polling
RelStorage = 1.3.0b1

[plone]
recipe = plone.recipe.plone

[zope2]
recipe = plone.recipe.zope2install
url = ${plone:zope2-url}

[instance]
recipe = plone.recipe.zope2instance
zope2-location = ${zope2:location}
user = admin:admin
products = ${plone:products}
eggs =
    ${buildout:eggs}
    ${plone:eggs}
    plone.app.blob
zcml = plone.app.blob
rel-storage =
    type postgresql
    dsn dbname='plone' user='plone' host='localhost' password='plone'
    blob-dir var/blobs

[zopepy]
recipe = zc.recipe.egg
eggs = ${instance:eggs}
interpreter = zopepy
extra-paths = ${instance:zope2-location}/lib/python
scripts = zopepy zodbconvert

P.S. I have been told that a very prominent Plone developer recently configured RelStorage with master/slave replication on MySQL, and that it works smoothly. I expect him to announce his success soon!

Book Review: Practical Plone 3

Packt Publishing asked me to review their new book, Practical Plone 3: A Beginner’s Guide to Building Powerful Websites. The book impressed me, but not in the way I expected at first.

As I read the instructions in chapter two about how to install Plone, I considered the experience my Dad would have gone through if he had this book when we were setting up Plone to run his company’s web site. My Dad is a power user, but not a programmer or systems administrator, so with this book, he probably would have installed Plone himself on a spare Windows computer. This book would have provided him enough direction to set up a lot of the functionality he needed, without my help. He would have immediately started publishing pages with Plone’s many features.

However, I imagine that a short time later, something would go seriously wrong. The computer’s IP address would change because the DHCP lease expired, the database would lose some transactions due to some misbehaving application, or a mischevious virus would rename files with a “py” extension to “rb”. All of those problems are outside Plone’s control, so this book does not try to address them.

Plone beginners like my Dad are not prepared to handle the problems that occur when a computer is used as a web server. In that light, I wondered if it really is possible to run Plone (or any content management system) without deep technical experience. I thought for a moment that this book is not for beginners after all.

Even after that logic, I decided I still want very much to give my Dad a copy of this book next time we set up a Plone web site. He will read it to find out what the latest version of Plone can do. He will install it on his own computer for his own education, but I will set up the production web site on a server.

The first twelve chapters (250 pages) are intended for Plone users. Beginners will enjoy all of those chapters, I think. As I read them, I even picked up a few things I haven’t learned, like how to use content rules.

I think beginners might struggle the most with chapter nine, which explains how to control workflow. Controlling workflow in Plone is not as easy as other Plone functions, because Plone falls back to the less polished Zope Management Interface for workflow design. Matt Bowen handled the difficult topic gracefully.

The rest of the book (almost 300 pages) is for developers, not power users. The contrast is sharp. While the first half of the book tells the reader what buttons to push, the second half tells the reader how to modify their Buildout configuration and what to type in a terminal session.

Each chapter is written by a different author. I noticed two interesting effects of multiple authorship. First, each author is enthusiastic about the particular topic, so even LDAP (which I generally find quite boring) gets a chapter of quality treatment. Second, there is more redundancy than you would find in most technical books, but redundancy is probably good in this case.

I do have one quibble with the book’s organization. When the technology behind Plone was invented, CSS was still a baby and browsers did not support it well. Back then, changing a site’s appearance meant changing nested tables in HTML, so the developers of Zope (including myself) invented ways to manage that task. That is how the portal_skins tool came about. The theming chapters explain how to use the latest version of that technology.

Today, we can expect all of our customers to use browsers that support CSS, so the chapters on theming should start by explaining how to customize the web site’s CSS. Developers will make much faster progress that way than if they have to learn the many theming-related abstractions Plone has today.

In conclusion, Practical Plone 3 is more than just a beginner’s book. I plan to use this book as a communication tool with my Plone customers. The book is a menu telling my customers who are beginners to Plone what we can set up together without a lot of work. I will also use it to help developers come up to speed on Plone.

How to Install Plone with RelStorage and MySQL

These step by step instructions describe how to install Plone on Ubuntu with RelStorage connected to MySQL as the main database. Familiarity with Linux systems administration is expected. Update: These instructions were revised in August 2009 for Plone 3.2.3 and RelStorage 1.2.0.

Continue reading How to Install Plone with RelStorage and MySQL

RelStorage: New MySQL Adapter

I was interested in adding MySQL 5.0+ support to RelStorage, so I went ahead and did it. The code is in Subversion now.

The tests I’ve run suggest the MySQL adapter is already a lot faster than ZEO and both of the other adapters. The MySQL adapter has consistently finished the tests 40% faster than the PostgreSQL adapter. I haven’t tested PostgreSQL 8.3 yet; perhaps that will make a difference. I don’t know yet how the reliability of each adapter compares.

The port took all day. (My wife and I both have a cold, making it unwise to go to work today.) I didn’t think it would take that long, but I had to slow down to figure out the strange relationship between locks and transactions in MySQL. The LOCK TABLE statement is full of surprises! I ended up using GET_LOCK and RELEASE_LOCK and row-level locks instead.

So after editing queries to fit MySQL’s rules and fixing miscellaneous details, RelStorage now has a third database adapter. I’m excited to see what happens next. For one thing, MySQL support could have a major positive effect on Plone.

By the way, MySQLdb version 1.2.2 is required. Version 1.2.1 has a bug involving BLOBs; RelStorage depends heavily on BLOBs.

RelStorage: A New ZODB Storage

I’m writing RelStorage, a new storage implementation for ZODB / Zope / Plone. RelStorage replaces PGStorage. I’ve put up a RelStorage Wiki page and the zodb-dev mailing list has been discussing it. There is no stable release yet, but a stable release is planned for this month.

While performance is not the main goal (reliability and scalability are more important), I was pleasantly surprised to discover last week that creating a Plone 3 site in RelStorage on PostgreSQL 8.1 is a bit faster than doing the same thing in FileStorage, the default ZODB storage. Clearly, the PostgreSQL team is doing a great job!

Several years ago I put together an early prototype of PGStorage. I recall discovering that PostgreSQL was terribly slow at storing a lot of BLOBs. I read about the soon-to-come TOAST feature, but I wasn’t sure it would solve the problem, so I discarded the whole idea for years. Today, PostgreSQL seems to have no problem at all with this kind of work. It sure has come a long way.

RelStorage also connects to Oracle 10g. According to benchmarks, Oracle has a slight performance advantage, perhaps due to the “read only” isolation mode that Oracle provides. It might be useful for PostgreSQL to get that feature too.

I’m considering setting up a MySQL adapter for RelStorage as well. When the database is in MySQL and Zope is running in mod_wsgi, we could say that the “P” in LAMP stands for Plone!