Capify my App

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After a complete Saturday of vegging out, I decided to accomplish something today. My initial target was to pull Craigslist rental listings for my housing app, but that led to me learning more about plugins, which somehow led me to reading about Capistrano. Yak shave, anyone?

I blazed through the book Deploying Rails Applications: A Step-by-Step Guide (Facets of Ruby). I skimmed through the first 4 chapters because they didn't present anything new to me. I spent much more time reading through chapter 5: the what, why, and how of Capistrano. After my first reading, I decided to test it out with my Dreamhost setup of housing app to try my luck.

One thing that threw me off initially was roles. Roles are simply different servers that are involed in the deployment. Each Capistrano recipe is run for all roles by default. For example, the deploy:setup recipe creates the initial directory structure on the server for checking out the Rails application. Capistrano tried to run this recipe on both my :db and :app roles. I couldn't find a way of adding an exception to what roles an existing recipe is run on, so I removed the :db role entirely. I didn't have a use for a :db role anyways, but I could see that as a problem in the future.

Next, I wrote a small task to keep database.yml the same between deployments:

task :fix\_config, :except => { :no\_release => true } do
  run "ln -s #{shared_path}/config/database.yml #{release\_path}/config/database.yml"

after 'deploy:symlink', 'fix_config'

I also overrode the deploy:restart task to fit with Phusion Passenger.

namespace(:deploy) do
  desc "Restart Passenger.  The file is deleted when it restarts"
  task :restart do
    run "touch #{current_path}/tmp/restart.txt"

After that, it was clear sailing. The deployments were unacceptably slow because a checkout of my project is 62MB (darn your edge rails!). I found the Rails site guide to Capistrano to be very good. The same can't be said for the main Capistrano site. The saving grace for that is all the methods are well commented and straightfoward if you read through the Capistrano source.

If I had to summarize Capistrano, I'd call it an interpreter for a Rake-like domain specific language to records and play back commands. Specifically, it's useful for Rails deployment because it automates tedious and error prone sequences of commands to deploy a bundle of code to a web directory, run any scripts or rake tasks, and kick any servers or services. As an added bonus, it sets a cute convention for directory structure and allows you rollback to different deployments. It's especially easy to pick up if you've written any Rake tasks in the past. I can see how Capistrano can be useful outside of Rails projects as well. It's simply a great little tool for automating commands.

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