v2.6.0

Pluggable Queue Engines

Queue producers now use an "engine" callback module to manage demand and work
with the database. The engine provides a clean way to expand and enhance the
functionality of queue producers without modifying the solid foundation of queue
supervision trees. Engines make enhanced functionality such as global
concurrency, local rate limiting and global rate limiting possible!

The BasicEngine is the default, and it retains the exact functionality of
previous Oban versions. To specify the engine explicitly, or swap in an
alternate engine, set it in your configuration:

config :my_app, Oban,
  engine: Oban.Queue.BasicEngine,
  ...

See the v2.6 upgrade guide for instructions on swapping in an alternate
engine.

Recursive Queue Draining

The ever-handy Oban.drain_queue/1,2 function gained a new with_recursion
option, which makes it possible to test jobs that insert more jobs when they
execute. When with_recursion is enabled the queue will keep executing until no
jobs are available. It even composes with with_scheduled!

In practice, this is especially useful for testing dependent workflows.

Gossip Plugin for Queue Monitoring

The new gossip plugin uses PubSub to efficiently exchange queue state
information between all interested nodes. This allows Oban instances to
broadcast state information regardless of which engine they are using, and
without storing anything in the database.

See the v2.6 upgrade guide for details on switching to the gossip
plugin.

Added

• [Oban.Job] Inject the current conf into the jobs struct as virtual field,
  making the complete conf available within perform/1.

• [Oban.Notifier] Add unlisten/2, used to stop a process from receiving
  notifications for one or more channels.

Changed

• [Oban.Telemetry] Stop emitting circuit events for queue producers. As
  producers no longer poll, the circuit breaker masked real errors more than it
  guarded against sporatic issues.

• [Oban.Telemetry] Delay [:oban, :supervisor, :init] event until the complete
  supervision tree finishes initialization.

• [Oban.Migration] Stop creating an oban_beats table entirely.

Fixed

• [Oban.Plugins.Cron] Prevent schedule overflow right before midnight