OSCON 2008: Mastering Perl

It’s early on Monday morning and I’m in my first tutorial session of the day, following the continental breakfast provided in Convention Hall E. I wasn’t overly impressed with the tutorial options this year. So, being who I am, I mostly opted for the Perl track. That brings me to where I sit now: D136, listening to brian d foy teach us about Mastering Perl. I almost didn’t attend this tutorial, since I’ve read the book and, while I found it excellent, I learned very little from it. I took this to mean that I’ve already mastered Perl. But, like I said, my options are limited—I’m not very interested in the introductory Python tutorial.

The idea behind Mastering Perl is not to talk about Perl to a group of Perl masters. Instead, it’s about mastering Perl in the guild sense (and not of the SCA variety). Back in the day, and still existing in some professions today, there was an apprentice system. A neophyte—in today’s nomenclature, a noob—would begin acquiring skills under a master of the art. As he progressed, he would be entrusted with more and more responsibility, until finally he became a master himself and took people under his own wings.

This apprenticeship system, somewhat unfortunately, does not exist in the computing world. That’s where brian d foy feels that Mastering Perl fits. Lacking true masters, the book acts as a substitute. Someday, we may even create a guild system. But then we’d probably have to pay dues and follow rules, and that’s not very attractive. That said, it’s the model I’m hoping to use at my own place of work. I’d like to hire one or two developers who I can take under my own wing and mentor them in the ways of Perl and the grid.

The first two topics covered are tools for optimization, profiling and benchmarking. Often mis-attributed to Donald Knuth, Tony Hoare once said, “Premature optimization is the root of all evil.” What this means is that one should never assume what requires optimization. Let the testing be the guide.

While profiling is objective, benchmarks, like statistics, are not always objective. Everyone has an agenda and benchmarks are subjective. Often, benchmarks are short-sighted. For example, benchmarking code run time and attempting to optimize for it may not be worth the expense of the developer time required to make the requisite changes. It’s worth analysing what is important before blindly following benchmarks.

I’ve been on the receiving end of misplaced premature optimization. I worked with a development group that put far too much emphasis on achieving perfect results on their Devel::Cover reports. This led to strange bugs in their code, and a strong belief that “new() doesn’t work that way.” As it turns out, their test suite was calling new() in two ways. I forget what the second method was, but it was not used anywhere else in their code. However, in order to get this test code to run, and get 100% coverage, they added code to the constructor for every class. Code that prevented inheritance of the method. The team then convinced themselves that constructors could not be inherited in Perl, rather than realizing that their own habits were the problem.

After the mid-morning break, we wrapped up the discussion on profiling and benchmarking, and moved into configuration. This is a vital topic for anyone who desires the ability to pass a program off to users without being bothered to modify it later in response to users’ desire to customize the program for a slightly different use.

External configuration, particularly via the command line, is something I depend on heavily, even in very simple Perl or Bourne shell scripts. I almost always create command line options for performing a dry run or output debugging information. Not only are these useful for development, they can live on in the final program, providing help to the final user, who more often than not is me. Sometimes I will even add configuration to values that never change, just for when they eventually do.

Jumping past configuration, we move on to logging. It’s really easy to add to a program, and it’s really useful to leave in a program when it’s released. The ability to enable logging on the fly sure beats adding a bunch of print() calls in the code when it inevitably breaks at three in the morning. The Log::Log4perl module is a particularly powerful method of adding logging to programs. It’s well worth investigating for anyone who wants to easily add logging functionality to their code.

The final topic of the day is lightweight persistence. It’s always nice to have data stick around between program invocations. The easy way (and everything in the second half of the tutorial is easy) to add persistence to code is to not use DBI. While DBI is powerful, it also tends to require a database server (ignoring SQLite for the moment). Modules such as Data::Dumper, YAML or Storable are ideal for easily storing and retrieving data in code.

After the tutorial, brian will be available at the Powell’s Books mini store, located near the registration desk, to sign copies of Mastering Perl. I already have a copy, thanks to my local Perl Mongers group, but it’s all marked up with the group name, and I wouldn’t mind having a signed copy.

Now it’s time for lunch, which is good, because I’m quite hungry. I hope the conference-provided lunch is decent during the tutorials, as it was last year.

[tags]oscon, oscon08, perl[/tags]