combostrikehq/rails_migrate_mutex

Runs rails migrations in a redis-backed mutex.

Rails db:migrate:mutex

Runs Rails migrations in a Redis-backed mutex.

If you deploy your application to multiple servers and do not use a deployment tool like Capistrano, this gems makes sure that only one of your servers run the database migrations.

Running Rails migrations on multiple instance at the same time should not cause any real trouble, because they are run inside transactions, but can cause excessive DB load and Ruby exceptions.

Usage

Run rake db:migrate:mutex instead of rake db:migrate to ensure that the migrations are only run on one server at the same time.

Installation

Add the gem to your Gemfile:

gem 'rails_migrate_mutex'

If Redis.current does not contain a valid Redis connection, you might need to set it manually:

# config/initializers/redis_classy.rb
RedisClassy.redis = Redis.new(...)

Contributing

Feel free to fork and submit pull requests!

License

MIT, see LICENSE.txt.

rails_migrate_mutex's Issues

environment/initializers not loaded

Not sure if this is something wrong in my setup, but this wasn't working for me since I need to set the RedisClassy/Redis instance based on an initializer (as mentioned in the readme).

Got it to work by overriding task with my own, where I depend on environment:

namespace :db do
  namespace :migrate do
    desc 'Runs db:migrate in a redis-backed mutex'
    # this change let me load initializers
    task :mutex => :environment do
      TIMEOUT = 5 * 60 * 60

      RedisClassy.redis ||= Redis.current

      RedisMutex.with_lock('db-migrate-mutex', block: TIMEOUT, expire: TIMEOUT) do
        Rake::Task['db:migrate'].invoke
      end
    end
  end
end

Am I missing something or should I open a PR with this change?