Mission Data Blog
Louisville-based Web Development & Software Engineering

Treetop was one of the more exciting projects I saw at last year’s RubyConf. Nathan Sobo’s Treetop talk is available online and I urge you to watch it. Nathan did a great job of explaining the basics of syntactic analysis, and then got into the specifics of using Treetop’s implementation of parsing expression grammars to put the concepts to work.

Treetop appeared to gather all the concepts together into an understandable domain specific language. All of the tokenization and node structure can go into a single file, and the interactive nature of Ruby makes for the perfect sand box. I felt like I could get somewhere if I invested just an hour into this. I was happy to find that my impressions were correct.

After a short time I had caught on enough to start writing my own code. Once over the hump the rest was easy. I was able to write and test a Treetop grammar for parsing CSV files within a few hours. I chose CSV parsing because I was already familiar with the format, and I could compare my implementation to not just one but two existing Ruby libraries.
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Capistrano is a tool for automating tasks via SSH on remote servers. It has many uses, I (and many others) use it to deploy their (rails) applications. The best I can tell there is no built in way to deploy a branch from your source code control system. There are a couple ways of accomplishing this. I chose passing in the branch as a parameter to the Capistrano command:

cap --set-before branch=testbranch  deploy

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If you have a model that uses set_table_name you may hit a snag when trying to use fixtures and unit tests. The solution is twofold: name the fixture file using the legacy table name, and use the set_fixture_class method in your unit test. I coudn’t find this method mentioned in Agile Web Development with Rails, and there’s only a brief mention on the rubyonrails.com site. Still, some web searches turned up the answers.

Here is a simple example:

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We had the need to hook up a simple ruby web process (non-rails) to our production apache server. As Leslie Hensley pointed out, fcgi and scgi are on the way out, and mongrel + mod_proxy_balancer is the new way to go. We use mongrel extensively in our rails deploys, but always just used WEBrick to do simple serving. To make a long story short, we had to ask ourselves….is mongrel that much better (and in this case better == faster) than WEBrick?

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Updated Rails 1.2 performance numbers have been released. While these number look pretty good it is hard to get a good idea of exactly what the performance of Rails is. A couple of other benchmarks that include Rails such as performance tests for 6 frameworks and Grails vs Rails benchmarks show a different picture. Both of these come up with much worse performance than the first. Maybe the issue is that the second two benchmarks are using Apache ab but the first uses a new version of rails bench. Of course most people probably aren’t that worried about the benchmarks that much because you can find ways to make anything fast as shown with Rails doing 4000 requests a second.

I was tickled when I ran across the GoogleLookup and GoogleFinance functions in Google Spreadsheets. I was very tickled when I found there was a REST API for interacting with the spreadsheets.

So not only can you lookup the current volume of Google stock in a spreadsheet (=GoogleFinance(”GOOG”, “volume”)) or find out Roger Clemens’s ERA (=GoogleLookup(”Roger Clemens”,”earned run average”)) you can access those values real time using an open API. I cobbled together a quick ruby program that can retrieve values from a private or public (published) Google spreadsheet.

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In an earlier post, we detailed a method for removing stale Rails session files. In more recent version of Rails, there is a Rake task built in for this administration task.

rake tmp:sessions:clear # Clears all files in tmp/sessions

I’m not sure if something isn’t set up correctly of if this is just a fact of life with rails but the sessions it creates never seem to go away. I think before rails 1.1 the sessions where stored in /tmp and now they are stored in the apps directory along with everything else so they is probably no internal mechanism to delete them. I only noticed because after about a month of an certain app running the disk on the machine started to fill up. After digging a little I found 50K ruby_sess.* files hanging out in the rails session directory.

Anyway it was easy enough to clean up the stale ruby_sess files by going into the rails webapp/session directory and then running the following command:

find -type f -name "ruby_sess*" -exec rm -f {} \\;

I’m not sure why the app is creating sessions but it isn’t something that stores state so I didn’t have to worry about killing active sessions here. If you do need to worry about that you will probably want to toss a time on the find command.

After looking a little more I found a post about this that has a ruby way of cleaning up the sessions.

The slides for the presentation are finally available, along with a zipfile, on the Presentation: You’ll Be Seeing Ruby page.

It’s been a month now since our last performance, but it all comes back every time I look at the slides.

iSeries systems and Ruby are separate universes right now; I know of no native Ruby way to connect to an AS400 system. However, with the help of Java we can bridge the gap.

Probably the simplest example is connecting to an iSeries system using JDBC to select from some tables, and with the right libraries it is straightforward. It’s also fun to be doing some nifty quick Ruby but with some preexisting and proven Java libraries.

Also, if you use Java and Ruby, definitely put arton’s RubyJavaBridge in your pocket; you’ll end up using it more than once.

What you’ll need:

• Ruby (well yea)
• Java (ok)
• access to an AS400 system (that’s the whole point here…)
  For testing, I’ve been using a free account available from Holger Scherer Software und Beratung.
• jt400.jar jdbc drivers from JTOpen, a great open-source Java library for AS400 access.
• RubyJavaBridge is the keystone for this.

Installing the software is the hardest part of this exercise, but it’s more tedium than anything. Once you’ve got it all downloaded and running the fun can begin.

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