Migrake

A simple Rake extension that lets you define tasks that are divided into multiple smaller "versions". When you run the task in a given host, it will only run the "versions" that haven't yet been run in that host. Think something similar to ActiveRecord::Migration for Rake tasks.

This is specially useful to define tasks that should be run on deploy, in order to do some sort of house cleaning that should be run once. For example, some complex data migrations, or re-processing your user avatars because now the UI shows them in a different size.

The important thing is these tasks should only be run once when you deploy to a given environment, and they should be run immediately.

An example

In lib/tasks/migrake.rake:

require "migrake"

migrake Set.new([
  "data:set_default_user_state",
  "twitter:purge_cache",
  # etc, etc
])

This would define a task called :migrake that, when called, will invoke the tasks in that set unless they have been invoked before. This means that after each deploy you can run this task (with a capistrano hook, for example) and any tasks that need to be run in this environment will be run.

How it works

This will keep a file named MIGRAKE_STATUS, that will contain the name of the tasks that were ran in the past. Whenever you run rake migrake migrake will check that file, see which tasks in the set aren't in it, and will run those tasks (no order is guaranteed, if you need tasks to run in order, define the dependencies in the task themselves.)

Overriding where to keep the MIGRAKE_STATUS file

The file will be located, by default, at whichever directory rake is invoked from. In order to change that (for example, to put it in capistrano's shared directory), do either of the following:

Define Migrake.status_file_directory before running the tasks (so, for example, at the top of your migrake.rake):

Migrake.status_file_directory = File.expand_path("../tmp", __FILE__)

Or as an alternative, pass it as an environment variable to Rake:

MIGRAKE_STATUS_DIR=./some/path bundle exec rake migrake

The latter lets you define it within the capistrano definition file, like this:

namespace :deploy do
  task :migrake do
    run "MIGRAKE_STATUS_DIR=#{shared_path} bundle exec rake migrake"
  end
end

after "deploy:migrations", "deploy:migrake"

Bootstrapping a new environment

When you bootstrap a new environment you don't need to run migrake tasks that have been already run. For this, when the migrake method is invoked we also define a migrake:ready task, that forces all tasks defined in the migrake set into the MIGRAKE_STATUS file.

This way you can just run that when you bootstrap the environment and then keep running rake migrake when you deploy.

License

(The MIT License)

Copyright (c) 2012 Nicolas Sanguinetti, with the support of Cubox

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.