10 Sep 2012

The One Where You Run Rake Commands With Capistrano

Simple Enough, right? Run some rake tasks on your servers. You think it’d be built in, but nope. Drink some sake and let capistrano do the work!

tl;dr Use my codes to only precompile assets on cap:deploy when there is a change to assets or gems.

First Off, Sake is not sake

Defunkt wrote sake in ought-eight (2008) for system wide rake tasks. This isn’t it; this is just a file, name it what you want.

Background

I’ll use rake tasks to do data-migrations that I don’t want to stick around in db/migrations. Or to do one-off things like re-process images.

But it’s not all that awesome to actually run those things in production when you need to. Here’s a way!

config/recipes/sake.rb 
namespace :sake do
  desc "Run a task on a remote server."
  # run like: cap staging rake:invoke task=a_certain_task  
  task :invoke do
    run("cd #{deploy_to}/current && bundle exec rake #{ENV['task']} RAILS_ENV=#{rails_env}")
  end
end

Then, make sure you require it

config/deploy.rb 
load "config/recipes/assets"

And that’s it! Now, when you want to run that code, say to migrate a database:

cap sake:invoke task="db:migrate"

This is not mind-blowing, but it’s not very obvious for new deployers, so I wanted to add it here for the googlers.

Naming Notes

Don’t name your task rake – newer versions of rake (0.9.2) are not pleased with that. That’s how I ended on sake. (rake => sake).

Credit

This answer on Stack Overflow had some good stuffs. I modified from there.