Notifications and emails

This is a quick summary of how the email notifications that we generate work. In-app notifications are processed independently - this is purely about emails.

We queue notifications and process them in the background. This means that the web front-end is not delayed while we send out email notifications to Mailgun, and so that they can be retried if there is an issue. The default queue is set to use the database so that they are not lost.

We run queue:work in the background. On dev this is kept alive via monit and on live via supervisor (this difference is not intentional, and it would be better if it was consistent).

Jobs are retried for max 4 days, at which point they are marked as failed, appear in failed_jobs, and we’re alerted in Sentry. We check Sentry regularly and should investigate and resolve any issues.