Cron worker that automatically retries failed delivery receipts.

Runs periodically via Oban.Plugins.Cron. Queries for delivery receipts that:

• Have status == :failed (temporary failure)
• Have retry_count < max_retries (default: 5)
• Either haven't been retried yet OR last retry was > retry_delay_minutes ago
• Are not permanently failed (:failed_permanent)

For each eligible receipt:

1. Re-enqueues appropriate Oban worker (SendEmail for now)
2. Updates receipt status to :scheduled
3. Increments retry_count
4. Sets last_retry_at timestamp

If a receipt has hit max_retries, it will be marked as :failed_permanent by the SendEmail worker on the final attempt.

Configuration

Configure retry behavior:

config :ash_dispatch,
  max_retries: 5,              # Max retry attempts before permanent failure
  retry_delay_minutes: 15      # Minutes to wait between retries

Scheduling

Add to Oban cron config:

config :my_app, Oban,
  plugins: [
    {Oban.Plugins.Cron,
     crontab: [
       # Retry failed deliveries every 15 minutes
       {"*/15 * * * *", AshDispatch.Workers.RetryFailedDeliveries}
     ]}
  ]

Exponential Backoff

The retry delay is constant (15 minutes by default), but you can implement exponential backoff by checking retry_count in the worker:

# Custom delay based on retry count
delay_minutes = retry_delay_minutes * (2 ** retry_count)

Example Output

[info] RetryFailedDeliveries: Found 3 failed deliveries to retry
[info] Retried delivery: receipt_id=abc123, event=order.created, transport=email, retry_count=2
[info] Retry results: 3 succeeded, 0 failed

Monitoring

Track retry metrics in your monitoring system:

• Number of failed receipts retried per run
• Success/failure rate of retries
• Receipts hitting max_retries (becoming :failed_permanent)