Introducing Resqued

Resqued (res-kyu-dee) is a prefork daemon that manages a pool of resque workers. It’s designed to support continuous deployment, long-running jobs, and high availability.

The resqued daemon can be restarted, paused, or stopped gracefully via signals. On restart, resqued reloads your configuration in a new process. When the new process is ready, the old workers are spun down and new workers are forked. If the configuration does not load, the old workers will continue running. Workers that exit unexpectedly are restarted.

Using resqued

Resqued is configured with a ruby-based configuration file. It includes a command-line program that starts the daemon either in the foreground or background.

$ resqued --help
Usage: resqued [options] resqued-config-files...
    -h, --help                       Show this message
    -v, --version                    Show the version
        --test                       Report which worker would start
    -p, --pidfile PIDFILE            Store the pid of the master process in PIDFILE
    -l, --logfile LOGFILE            Write output to LOGFILE instead of stdout
    -D, --daemonize                  Run daemonized in the background

For a typical rails application, create config/resqued.rb:

# Run 4 workers
worker_pool 4

before_fork do
# Load the app environment.
require File.expand_path('config/environment.rb')
# Free up a DB connection.
ActiveRecord::Base.connection.disconnect!
end

after_fork do |worker|
# Reconnect to the database.
ActiveRecord::Base.establish_connection
end

You can see which workers will be started:

$ resqued --test config/resqued.rb
Workers defined in config/resqued.rb
1: *
2: *
3: *
4: *

To start the daemon in the foreground:

$ resqued config/resqued

In production, you would start the daemon like this:

$ resqued -D -p tmp/pids/resqued.pid -l log/resqued.log config/resqued.rb

Migrating from rake resque:work

If you’ve got an existing pool of workers, you’re probably doing something like this:

$ rake resque:work QUEUE=high
$ rake resque:work QUEUE=high
$ rake resque:work QUEUE=high,normal
$ rake resque:work QUEUE=high,normal

To reproduce this in resqued, you would create a config file that looks like this:

# before_fork and after_fork as above

worker_pool 4
queue 'high'
queue 'normal', :count => 2

without a pool

The worker pool might not work for you if you’re doing something like this:

$ rake resque:work QUEUE=high
$ rake resque:work QUEUE=high
$ rake resque:work QUEUE=normal
$ rake resque:work QUEUE=*

To reproduce this in resqued, you would create a config file like this:

# before_fork and after_fork as above

2.times { worker 'high' }
worker 'normal'
worker '*'

Many variants of worker configuration are documented in the worker specs.