Troubleshooting

PG Bouncer

No Notifications with Transaction Pooling

Using PG Bouncer's "Transaction Pooling" setup disables all of PostgreSQL's LISTEN and NOTIFY activity. Some functionality, such as triggering job execution, scaling queues, canceling jobs, etc. rely on those notifications.

To ensure full functionality you must use a Repo that connects directly to the database, or use another mode like "Session Pooling" if possible.

If you must use "Transaction Pooling" you can use the Repeater plugin to ensure that queues keep processing jobs:

config :my_app, Oban,
  plugins: [Oban.Plugins.Pruner, Oban.Plugins.Stager, Oban.Plugins.Repeater],
  ...

Note: The Repeater plugin keeps jobs processing, it will not facilitate other notification based functionality, e.g. scaling queues.

Heroku

Elixir and Erlang Versions

If your app crashes on launch, be sure to confirm you are running the correct version of Elixir and Erlang (view requirements). If using the hashnuke/elixir buildpack, you can update the elixir_buildpack.config file in your application's root directory to something like:

# Elixir version
elixir_version=1.9.0

# Erlang version
erlang_version=22.0.3

Available Erlang versions are available here.

Database Connections

Make sure that you have enough available database connections when running on Heroku. Oban uses a database connection in order to listen for Pub/Sub notifications. This is in addition to your Ecto Repo pool_size setting.

Heroku's Hobby tier Postgres plans have a maximum of 20 connections, so if you're using one of those plan accordingly.