View Source Defining Queues

Queues are defined as a keyword list where the key is the name of the queue and the value is the maximum number of concurrent jobs. The following configuration would start four queues with concurrency ranging from 5 to 50:

config :my_app, Oban,
  queues: [default: 10, mailers: 20, events: 50, media: 5],
  repo: MyApp.Repocopy

You may also use an expanded form to configure queues with individual overrides:

queues: [
  default: 10,
  events: [limit: 50, paused: true]
]copy

The events queue will now start in a paused state, which means it won't process anything until Oban.resume_queue/2 is called to start it.

There isn't a limit to the number of queues or how many jobs may execute concurrently in each queue. Some additional guidelines:

• Each queue will run as many jobs as possible concurrently, up to the configured limit. Make sure your system has enough resources (such as database connections) to handle the concurrent load.

• Queue limits are local (per-node), not global (per-cluster). For example, running a queue with a local limit of 2 on three separate nodes is effectively a global limit of six concurrent jobs. If you require a global limit, you must restrict the number of nodes running a particular queue or consider Oban Pro's Smart Engine, which can manage global concurrency automatically!

• Only jobs in the configured queues will execute. Jobs in any other queue will stay in the database untouched.

• Pay attention to the number of concurrent jobs making expensive system calls (such as calls to resource-intensive tools like FFMpeg or ImageMagick). The BEAM ensures that the system stays responsive under load, but those guarantees don't apply when using ports or shelling out commands.