It’s been said that the two last hard problems in programming are naming things and expiring caches. The first is going to be hard to sidestep entirely, but what if we could the second? Tobi arrived at a eureka moment for just that using Memcached and various kinds of caching. Instead of manually expiring things, just ask for a specific version, and let the caching engine take care of dumping that which isn’t used any more.

Read more on The Secret to Memcached.

From the awesome gang of Gregg Pollack and Jason Seifer.

The upcoming Capistrano 2.0 release continues to evolve! Remote administration of single servers and server clusters has never been easier. With Capistrano, you can:

• Deploy web applications with a single command
• Keep software in sync across multiple machines
• Install entire servers with just a few keystrokes
• Impress the ladies with your leet sysadmin skills

Ok, well, maybe not that last, unless she’s a really special lady. But the rest certainly apply.

Capistrano 2.0 Preview Release 2 is now available (version 1.99.1). You can only grab it from the Rails beta gem server:

NOTE that Capistrano 2.0 is not 100% backwards-compatible with Capistrano 1.x recipes. For more information on upgrading, check out http://www.capify.org/upgrade.

To install the preview release, you’ll need to make sure you’ve already got the following gems installed, too, which Capistrano depends on (and which can be found in the main Rubygems repository):

• net-ssh
• net-sftp
• highline

Download it, install it, try it out. Kick the tires. Report what doesn’t work. We’re getting close to a general release!

SO. Now that all of that is out of the way, let’s talk about what’s new in PR2. First, the bug fixes:

• The “copy” deployment strategy now checks out the local copy to a temporary directory, rather than using the current working directory. This makes it possible to use with some picky SCM’s that don’t like checkouts being made into an existing checkout.
• The “deploy:check” task was broken for some deployment strategies. It should work now for all of the pre-packaged strategies.
• The “shell” task should actually work now.
• The “desc” keyword will apply to the next defined task, regardless of which namespace the task is defined in.
• Don’t retry failed connections when an explicit :auth_methods list is given via :ssh_options.
• Fixed a few minor documentation typos.

Next, the new features:

Feature: The “deploy:cold” task will run migrations before starting the app. If it is the first time you’ve deployed your app, chances are the database needs setting up, too!

Feature: The old method of extending tasks (e.g., tasks named “before_deploy” and “after_deploy” extending the “deploy” task) is now discouraged (though not formally deprecated, yet). The new approach uses some new keywords:

More generally, you can attach tasks of your own creation to arbitrary “events”, using the “on” keyword:

The :before event gets triggered before any event is invoked, and :after gets called immediately after the event finishes successfully. There are four other events currently supported by Capistrano:

• :start is triggered when a task is invoked via the command-line
• :finish is triggered when a task invoked via the command-line finishes successfully
• :load is triggered after all recipes have loaded, but before any tasks are executed
• :exit is triggered after all tasks have been executed

You can even define your own events, and then trigger them using the “trigger” method.

Feature: The “deploy:app” namespace has been axed. The tasks that it contained now live in the “deploy” namespace directly. Thus, “deploy:app:start” and “deploy:app:stop” are now “deploy:start” and “deploy:stop”, respectively.

Feature: If your “scm_command” is set to a custom value because your SCM lives in a non-standard location on the remote host, you previously ran into problems if your SCM command did not live at the same location on your local host. Now, if you need different settings for the scm_command depending on whether it is being invoked locally or remotely, you have the option of specifying either one separately:

Note that if “scm_command” is set, “local_scm_command” will default to that value, but if “local_scm_command” is set, “scm_command” is unaffected.

Feature: Servers are now uniquely identified by Capistrano based on their full connection information, including hostname, username, and port. (Before, servers were only unique based on the hostname.) This makes it possible to use Capistrano in a NAT’ed environment, where all of your servers are using the same hostname, with different port numbers.

Feature: The “capify” command now understands the “-h” switch, which should make it behave a little more like people expect.

O’Reilly has analyzed the book sales once again. Here are the juicy bits about Ruby and Rails books:

In the Web design and development area, it’s worth noting that Ruby on Rails has continued its blazing growth, but Ajax books have not. The decline of both PHP and ASP are striking…

…Rails in the bottom middle was a small speck in last year’s first quarter post. Now the size of the box fits the size of its name at least. And its market share is almost equal to SQL and has surpassed VBA, Perl and Python. Python is also experiencing good growth, just not at the blazing velocity of Ruby. I would expect by next year, we will see Ruby have an even larger share/square.

Joyent’s Slingshot technology for creating offline-capable Rails applications has gone public. They’re even doing a competition to celebrate: The best ports of various open source Rails applications can win a 1-year big Accelerator ($1250 value). Now there’s a project you can hack on the plane to Portland in a few weeks ;).

The first Czech Ruby on Rails conference is coming to Ostrava this summer: mark your calendar for June 22-23. Talks are in English and registration is open now!

Capistrano 2.0 Preview 1 is now available for installing and testing:

gem install -s http://gems.rubyonrails.com capistrano

(It’ll show up as version 1.99.0; the 1.99.x series will be used as the preview releases for 2.0)

For those of you late to the party, Capistrano is a utility for executing remote commands in parallel on multiple remote servers. It is ideal for system administration, and for deploying web applications.

Note, though, that this release is not entirely backwards compatible with Capistrano 1.x, so you may need to massage your recipes a little to make them work smoothly under the new version. In order to make the upgrade process as smooth as possible, I’ve begun compiling a few documents to point out new features, gotchas, and upgrade paths:

http://www.capify.org/upgrade

Like Capistrano 2.0, the new www.capify.org website is still a bit rough in spots, and will see more documentation appearing over the next few weeks. If you have any feedback for either Capistrano 2.0 or the website, please join us on the Capistrano mailing list and make your voice heard!

We’re putting the finishing touches on the RailsConf 2007 schedule this week. Given the huge number of high quality proposals (well over 3 times the number from last year), we’re working on putting together a fourth track.

We have also finalized an exciting lineup of keynote speakers for the conference. I was frankly a bit worried about the keynote lineup as we started initial planning of RailsConf 2007. Last year’s keynotes were going to be hard to live up to. My fears were ill-founded. We ended up with a program to be really excited about.

Tim Bray, Sun, Co-creator of XML and Atom

Avi Bryant, Creator of Seaside and DabbleDB

Ze Frank, Comedic Digital Savant

David Heinemeier Hansson, 37 Signals, Creator of Ruby on Rails

Dave Thomas, The Pragmatic Programmers

The RailsConf program promises to be thought-provoking, trend-starting, entertaining, tone-setting, and, most of all, fun.

See you in May!

Eric Mill went ahead and created Jester, a library that lets you manipulate your Rails-style resources with javascript models. I think it’s great that we’re seeing implementations in other languages. This python port of Routes implements map.resources, can a python port of ActiveResource be far behind?

Stephan Kaes, our resident performance expert, has released a new version of RailsBench. He then created new Rails 1.2 vs Rails 1.1 benchmarks, discovering that things aren’t as bad as they seem. Of course, those numbers won’t mean a whole lot until you read the full report