If a job fails halfway through, do you know where it stopped? If you retry it, will it send a second invoice to the customer?
What is Idempotency?
An operation is idempotent if it can be performed multiple times without changing the result beyond the initial application.
Strategies for Background Jobs
- Unique Keys: Use transaction IDs or UUIDs to ensure database inserts don't duplicate.
- State Checking: "If processed == true, return early."
- Atomic Operations: Wrap your work in database transactions.
Resilient workers assume they will fail and will be retried. Monitoring these with CronRabbit helps you identify jobs that are "Stuck" (Started but never Finished), indicating a logic error rather than a crash.