View Source Oban.Notifiers.Postgres (Oban v2.19.0)
A Postgres LISTEN/NOTIFY based Notifier.
Connection Pooling
Postgres PubSub is fine for most applications, but it doesn't work with connection poolers
like PgBouncer when configured in transaction or statement mode, which is
standard. Notifications are required for some core Oban functionality, and you should
consider using an alternative notifier such as Oban.Notifiers.PG
.
Usage
Specify the Postgres
notifier in your Oban configuration:
config :my_app, Oban,
notifier: Oban.Notifiers.Postgres,
...
Transactions and Testing
The notifications system is built on PostgreSQL's LISTEN/NOTIFY
functionality. Notifications
are only delivered after a transaction completes and are de-duplicated before publishing.
This means that notifications sent during a transaction will not be sent if the transaction is
rolled back, providing consistency; this is the only notifer which provides that guarantee.
However, it is not as scalable as other notifiers because because each notification requires a
separate query and notifications can't exceed 8kb.
Typically, applications run Ecto in sandbox mode while testing, but sandbox mode wraps each test in a separate transaction that's rolled back after the test completes. That means the transaction is never committed, which prevents delivering any notifications.
To test using notifications you must run Ecto without sandbox mode enabled, or use
Oban.Notifiers.PG
instead.