mod_perl2 User's Guide (modperl2book.org) by Stas Bekman and Jim Brandt has just been published by Onyx Neon, and Amazon says it's shipping. I can't think of the last time I've been as excited to see a Perl book get published. Besides brian d foy's Mastering Perl, there hasn't been a significant Perl book in quite a while. Perlbuzz is going to work with Onyx Neon to have a book giveaway, so watch this space in the next few days.
Jim Brandt took some time to talk with me about the book, why you need to switch to mod_perl 2, and why it took so long to get the book to market.
Andy: Your new book mod_perl 2 User's Guide is now shipping. It's an update to Practical mod_perl, probably the thickest Perl book ever. (So thick that Liz Cortell once made a lunchbox out of one!) How does this one compare?
Jim: In many ways it's not an update to the first book in the 1st edition, 2nd edition sense. Like Apache 1 and 2 and mod_perl 1 and 2, the new book is coverage of the new stuff in mod_perl 2. Much of the content of Practical mod_perl is still relevant. But Apache 2 brought many changes, so mod_perl 2 had to change too. That's what the book's about. And it's not as thick.
Andy: Did you pull stuff out?
Jim: We started fresh, so we weren't working with Practical mod_perl as a starting point.
Andy: And so you didn't have to go Creative Commons licensing.
Jim: Right. It's a completely new book, so were could do what we wanted. This version is "owned" by the Apache Software Foundation. The full content will also be released on-line, as with Practical mod_perl. Also, it's an edited and updated version of the content from the mod_perl site, so in a sense it's out there now.
Andy: So how did you get involved? How much is you, how much is Stas?
Jim: Stas created all of the original content as documentation in the mod_perl 2 section of perl.apache.org. Allison (Randal, publisher) began working on pulling it together into book form and was looking for an editor. brian d foy mentioned it to me, I got involved, then became more of an author as I got to work on editing and re-writing sections. Stas was available throughout to answer questions. So I guess if you run a big diff between the book and the mod_perl 2 docs on perl.apache.org, you'll see how much was me. :-)
Andy: How long did it take?
Jim: Well, a bit too long, and that was my fault. I had a few life events that got in the way a bit. I got started nearly 2 years ago. We wanted it done by YAPC this year, but that slipped to OSCON and we missed it. But Allison and Tom McTighe (the real editor) really stepped up at the end and we finally pulled it together in August.
Andy: What surprised you most about the project?
Jim: I suppose learning how much is behind mod_perl and how much work a core group of people do to make it happen. In that way, it's similar to Perl itself in that the more you know the more you appreciate the efforts of a small group of very dedicated and very smart people.
Andy: Please tell me there's good stuff in the book about migrating mod_perl 1 to mod_perl 2. It's something I've muddled through before, and I need to do it again, and I'm not looking forward to the trip.
Jim: There are several chapters dedicated to just that. And good information on the tools available, including a walkthrough of migrating an actual module from 1 to 2. There are several utilities available to help you look up methods that have moved, which will be the first thing people hit. And the Apache2::Compat module gets you running quickly while you make the changes you need to make.
Andy: What in your Day Job brought you to the mod_perl 2 book project?
Jim: We use mod_perl, but we've been stuck at 1 because we were using an auth module that only worked with Apache 1. So I guess you could say nothing directly from my job was related to mod_perl 2. It just seemed like the book needed to be out there.
Andy: I figured there was some tale of mod_perl 2 hell that led you down this path.
Jim: No, I did what no one does. I read the instructions (and wrote them) first.
Andy: What should people know about mod_perl 2?
Jim: I think the main message I'd like to get out there is that Apache 2 and mod_perl 2 have been out for a while, they are stable, and they are the future. That's where much of the new development effort is going. It's time to upgrade. With no vendor out there to "desupport" you, people tend to hold off, but I think it's really time. I know I'll be getting our Apache 2 / mod_perl 2 migration plan going at work and we'll be looking to move over the next year or so.
Andy: You say that mod_perl 2 is the future, but what if I've got a perfectly good, working stable app running under Apache 1 and mod_perl 1. Staying on mod_perl 1 is certainly building up technical debt, but what does mod_perl 2 give me for my troubles?
Jim: It depends on how you're using it. If you're just using it for CGI acceleration, you could stay where you are. The risk you run is that some Apache 1 module you rely on might not get that next security update. I don't know that anyone is saying they are going to stop support in their Apache 1 tree just yet, but it will happen.
If you use mod_perl for true module development, there are some new features that you'll want. The biggest is probably the access to Apache configuration info and new ways to pass in configuration info from Apache to your handlers. You can add custom Apache configuration directives in pure Perl, where with mod_perl 1 you needed XS. So if you want the module user to pass some info, you can have them load the module and it can create an Apache directive like "PerlGods" that takes "Andy" and "Jim" as two parameters. There's a full Perl interface for defining how these directives should be parsed and evaluated by Apache.
Other new features: It is now usable on Win32 because you can run it threaded. You have more access to input and output filters than before. And, with Apache 2 and mod_perl 2 you're also not limited to just the HTTP protocol any more. They've both been redesigned to serve any protocol, so you could write an FTP or SMTP server in mod_perl 2.
Andy: Would you want to?
Jim: Ah, good question. I think this area hasn't really been tapped much yet, so those are the sorts of examples that we used to explain the idea. My guess is this flexibility will be used to serve things we haven't thought of yet.
Andy: You alluded to life changes earlier. Care to elaborate for the reading public?
Jim: Well, my wife and I had triplets, and adding that many babies to our already busy household put a major demand on my time. Triplets are an amazing amount of work anyway, and trying to squeeze in time for the book in addition to the day job was really tough, and that's why things stalled for a while.
Andy: Which is more likely: Working on another book, or having more triplets?
Jim: I can see working on another book if one comes along that I can contribute to. No more triplets, I can say that for sure.
Andy: Thanks for talking with Perl Buzz. Good luck with the book. I hope it takes off!
Jim: Thanks! Hope you enjoy it.