Rubygem-que

Job queue that uses PostgreSQL advisory locks for speed and reliability

Que is a high-performance job queue that improves the reliability of your application by protecting your jobs with the same ACID guarantees as the rest of your data.

Que is a queue for Ruby and PostgreSQL that manages jobs using advisory locks, which gives it several advantages over other RDBMS-backed queues

• Concurrency - Workers don’t block each other when trying to lock jobs, as often occurs with “SELECT FOR UPDATE”-style locking. This allows for very high throughput with a large number of workers.
• Efficiency - Locks are held in memory, so locking a job doesn’t incur a disk write. These first two points are what limit performance with other queues. Under heavy load, Que’s bottleneck is CPU, not I/O.
• Safety - If a Ruby process dies, the jobs it’s working won’t be lost, or left in a locked or ambiguous state - they immediately become available for any other worker to pick up.