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Google Summer of Code Mentors Summit

By Selena Deckelmann
October 28, 2009

I was able to attend the Google Summer of Code (GSoC) Mentors Summit last weekend in sunny Mountain View, CA. I’d spent the previous few days working with a team to write a mentor’s manual, so was full of ideas when it came time to create the actual sessions during the unconference.

The Mentors Summit is a great opportunity to mingle with the leaders in our many diverse communities. This year, the student participants were capped at 1000, and there were 150 participating open source projects mentoring them. Most of the projects were represented at the Summit.

I attended or presented at three sessions that I’ll quickly summarize:

• Casablanca: This wasn’t a presentation so much as a discussion. There’s one room designed to be a salon—​with lots of interesting gadgets, toys and clay. A group of about 20 of us talked about what they’d learned about mentoring that year, and strategies for getting the most out of students, and recovering from student and mentor failures. Some of the smaller project representatives were in awe of the level of discipline and organization of the larger projects. Several useful wiki templates were shared, as were best practices—​like having scheduled, …

Pentaho Reporting 3.5 for Java Developers

By Josh Tolley
October 28, 2009

I was recently asked to review a copy of Will Gorman’s Pentaho Reporting 3.5 for Java Developers, and came to a few important realizations. Principal among these is that my idea of what “reporting” means includes far too little. Reporting includes much more than just creating a document with some graphs on it—​any document or presentation including information from a “data source” comprises a “report”. This includes the typical sheaf of boardroom presentation slides, but also includes dashboards within an application, newsletters, or even form letters. I recently discovered that a local church group uses a simple reporting application to print its membership directory. In short, it’s not just the analysts and managers that can use reporting.

The book gives the reader a tour of Pentaho’s newest Pentaho Reporting system, which consists of a desktop application where users define reports, and a library by which developers can integrate those reports into their own applications. So as an example, not only can Pentaho Reporting publish weekly sales printouts, but it can also produce real-time inventory information in a J2EE-based web application or even a Swing application running on a …

Performance optimization of icdevgroup.org

By Jon Jensen
October 23, 2009

Some years ago Davor Ocelić redesigned icdevgroup.org, Interchange’s home on the web. Since then, most of the attention paid to it has been on content such as news, documentation, release information, and so on. We haven’t looked much at implementation or optimization details. Recently I decided to do just that.

Interchange optimizations

There is currently no separate logged-in user area of icdevgroup.org, so Interchange is primarily used here as a templating system and database interface. The automatic read/write of a server-side user session is thus unneeded overhead, as is periodic culling of the old sessions. So I turned off permanent sessions by making all visitors appear to be search bots. Adding to interchange.cfg:

RobotUA *

That would not work for most Interchange sites, which need a server-side session for storing mv_click action code, scratch variables, logged-in state, shopping cart, etc. But for a read-only content site, it works well.

By default, Interchange writes user page requests to a special tracking log as part of its UserTrack facility. It also outputs an X-Track HTTP response header with some information about the visit which can be used by a (to my …

Upgrading from RHEL 5.2 to CentOS 5.4

By Jon Jensen
October 22, 2009

I have a testing server that was running RHEL 5.2 (x86_64) but its RHN entitlement ran out and I wanted to upgrade it to CentOS 5.4. I found a few tips online about how to do that, but they were a little dated so here are updated instructions showing the steps I took:

yum clean all
mkdir ~/centos
cd ~/centos
wget http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
wget http://mirror.centos.org/centos/5/os/x86_64/CentOS/centos-release-5-4.el5.centos.1.x86_64.rpm
wget http://mirror.centos.org/centos/5/os/x86_64/CentOS/centos-release-notes-5.4-4.x86_64.rpm
wget http://mirror.centos.org/centos/5/os/x86_64/CentOS/yum-3.2.22-20.el5.centos.noarch.rpm
wget http://mirror.centos.org/centos/5/os/x86_64/CentOS/yum-updatesd-0.9-2.el5.noarch.rpm
wget http://mirror.centos.org/centos/5/os/x86_64/CentOS/yum-fastestmirror-1.1.16-13.el5.centos.noarch.rpm
rpm --import RPM-GPG-KEY-CentOS-5 
rpm -e --nodeps redhat-release
rpm -e yum-rhn-plugin yum-updatesd
rpm -Uvh *.rpm
yum -y upgrade
# edit /etc/grub.conf to point to correct new kernel (with Xen, in my case)
shutdown -r now

It has worked well so far.

Talk slides are available! Bucardo: Replication for PostgreSQL

By Selena Deckelmann
October 17, 2009

I’m in Seattle for the PostgreSQL Conference West today! I just finished giving a talk on Bucardo, a master-slave and multi-master replication system for Postgres.

The talk was full, and had lots of people who’ve used Slony in the past, so I got lots of great questions. I realized we should publish some “recommended architectures” for setting up the Bucardo control database, and provide more detailed diagrams for how replication events actually occur. I also talked to someone interested in using Bucardo to show DDL differences between development databases and suggested he post to the mailing list. Greg has created scripts to do similar things in the past, and it would be really cool to have Bucardo output runnable SQL for applying changes.

I also made a hard pitch for people to start a SEAPUG, and it sounds like some folks from the Fred Hutchinson Cancer Research Center are interested. (I’m naming names, hoping that we can actually do it this time. :D) If you are from the Seattle area, go ahead and subscribe to the seapug@postgresql.org mailing list (pick ‘seapug’ from the list dropdown menu)!

Thanks …

Rails Approach for Spree Shopping Cart Customization

By Steph Skardal
October 12, 2009

Recently, I was assigned a project to develop Survival International’s ecommerce component using Spree. Survival International is a non-profit organization that supports tribal groups worldwide in education, advocacy and campaigns. Spree is an open source Ruby on Rails ecommerce platform that was sponsored by End Point from its creation in early 2008 until May 2009, and that we continue to support. End Point also offers a hosting solution for Spree (SpreeCamps), that was used for this project.

Spree contains ecommerce essentials and is intended to be extended by developers. The project required customization including significant cart customization such as adding a buy 4 get 1 free promo discount, adding free giftwrap to the order if the order total exceeded a specific preset amount, adding a 10% discount, and adding a donation to the order. Some code snippets and examples of the cart customization in rails are shown below.

An important design decision that came up was how to store the four potential cart customizations (buy 4 get 1 free promo, free giftwrap, 10% discount, and donation). The first two items (4 get 1 free and free gift wrap) are dependent on the cart contents, …

Fun with SQL

By Josh Tolley
October 10, 2009

Many programmers, I expect, have a favorite obscure language or two they’d like to see in wider use. Haskell has quite a following, though it sees relatively little use; the same can be said for most pure functional languages. Prolog seemed like a neat idea when I first read about it, but I’ve never heard of anyone using it for something serious (caveat: there are lots of things I’ve never heard of).

My own favorite underused language is SQL. Although most programmers have at least a passing familiarity with SQL, and many use it daily, few seem to achieve real SQL fluency. This is unfortunate; SQL databases are powerful and ubiquitous tools, and even the least among them can generally manage a great deal more than the fairly simple uses to which they are commonly put.

I recently had the opportunity to trot out this curmudgeonly opinion of mine at the Utah Open Source Conference. Now in its third year, this annual conference continues to surprise me. Utah is home to an extraordinarily vibrant open source community, and it shows, in the attendance (over 400 expected), the number of presentations (92 by my count of the schedule, perhaps minus a few that aren’t …

New End Point site launched: Rails, jQuery, Flot, blog feed

By Steph Skardal
October 7, 2009

This week we launched a new website for End Point. Not only did the site get a facelift, but the backend content management system was entirely redesigned.

Goodbye Old Site:

Hello New Site:

Our old site was a Rails app with a Postgres database running on Apache and Passenger. It used a custom CMS to manage dynamic content for the bio, articles, and service pages. The old site was essentially JavaScript-less, with the exception of Google Analytics.

Although the new site is still a Rails application, it no longer uses the Postgres database. As developers, we found that it is more efficient to use Git as our “CMS” rather than developing and maintaining a custom CMS to meet our ever-changing needs. We also trimmed down the content significantly, which further justified the design; the entire site and content is now comprised of Rails views and partial views. Also included in the new site is cross browser functioning jQuery and flot. Some of the interesting implementation challenges are discussed below.

jQuery Flot Integration

The first interesting JavaScript component I worked on was using flot to improve interactivity to the site and to decrease the excessive text that …