FAQ

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## How do you pronounce Resque?

/ˈreskyo͞o/

How to perform the same job on all the connected workers?

For example, Perform a disk space check on every machine in a cluster, every machine will runs a worker.

My workers are getting stuck in a weird state.

Are you using newrelic_rpm? This is a known bug: https://github.com/defunkt/resque/issues/180

What's the best way to restart workers using capistrano?

With Foreman and Upstart

This may not be the "best" way, but it's an option. You can manage resque and any of the other services your app runs with foreman (using upstart or init scripts on the remote server). See "Managing and monitoring your Ruby application with Foreman and Upstart" for a great guide on getting Foreman running. Once that's done, here's a sample cap task to manage your processes:

namespace :foreman do
  desc "Start the application services"
  task :start, :roles => :app do
    sudo "start #{application}"
  end

  desc "Stop the application services"
  task :stop, :roles => :app do
    sudo "stop #{application}"
  end

  desc "Restart the application services"
  task :restart, :roles => :app do
    run "sudo start #{application} || sudo restart #{application}"
  end

  desc "Display logs for a certain process - arg example: PROCESS=web-1"
  task :logs, :roles => :app do
    run "cd #{current_path}/log && cat #{ENV["PROCESS"]}.log"
  end

  desc "Export the Procfile to upstart scripts"
  task :export, :roles => :app do
    # 5 resque workers, 1 resque scheduler
    run "cd #{release_path} && rvmsudo bundle exec foreman export upstart /etc/init -a #{application} -u #{user} -l #{shared_path}/log  -f #{release_path}/Procfile.production -c worker=5 scheduler=1"
  end 
end

Graceful Shutdown

When you write a restart task for resque, you may want to think what happens to a job running at that time. If you want to make sure the job finishes properly, you better send QUIT signal to the existing resque worker process so that the worker process will stop gracefully.

Check out Readme to know more how Resque worker responds signals.

How do I ensure my Rails classes/environment is loaded?

Make sure you start your workers by specifying environment as part of your rake execution, e.g.

QUEUE=* rake environment resque:work

Some users also see issues where Rails models are lazy-loaded in the Job execution and due to some internal class loading wackiness this results in LoadErrors or Uninitialized Constant exceptions. This can be solved by forcing ActiveRecord models to load, by creating a lib/tasks/resque.rake

# load the Rails app all the time
namespace :resque do
  puts "Loading Rails environment for Resque"
  task :setup => :environment do
    ActiveRecord::Base.descendants.each { |klass|  klass.columns }
  end
end

How to make Resque job to wait for ActiveRecord transaction commit, so that it see all changes made by that transaction?

The first way is enqueue job only in after_commit hook in models. But after_commit solves the problem only in model create/update use case . In general task should be put to redis only after all transactions get closed. Otherwise serious problems may appear.

In order to do that use ar_after_transaction gem that provides after_transaction hook whenever you need it:

ActiveRecord::Base.after_transaction do
  Resque.enqueue(SyncronizationWithGithubWorker, asset.id)
end 

If you want to keep entire team free from knowledge about transaction isolation level and this problem, you should monkey patch Resque.enqueue to be performed always after transaction completes.

require 'ar_after_transaction'
require 'resque'
Resque.class_eval do
  class << self
    alias_method :enqueue_without_transaction, :enqueue
    def enqueue(*args)
      ActiveRecord::Base.after_transaction do
        enqueue_without_transaction(*args)
      end
    end
  end
end

How do I print SQL statements in resque?

Add ActiveRecord::Base.logger = Logger.new(STDOUT) to your ruby class.

How do I override the views when mounted in a rails app?

No answer.

Why might Resque be serving up completely blank asset files (CSS & JS) when used with Rails 3.1?

No answer.

How to work arount "MySQL server has gone away" error ?

In your perform method add the following line:

class MyTask
  def perform
    ActiveRecord::Base.verify_active_connections!

    # rest of your code
  end
end

The Rails doc says the following about verify_active_connections!:

Verify active connections and remove and disconnect connections associated with stale threads.