queue

The queue namespace pushes a message onto a named queue through the configured messaging provider. A queue is point-to-point: each message is handled by exactly one consumer, declared elsewhere with on queue.

When to use

Use a queue to hand work off so a route can return immediately, when each message should be processed once by a single consumer (sending an email, resizing an image). To broadcast an event to several independent subscribers instead, use topic.

See Process work asynchronously with a queue for the producer, the consumer, and ack/nack semantics.

Operations

queue.push enqueues a message. Add as <Schema> to validate and strip it to the declared fields before it goes out:

queue.push "welcome_emails" as Signup, payload

The consumer is a top-level handler, not a method on this namespace:

on queue "welcome_emails" take signup as Signup
    log.info("sending to #{signup.email}")

Notes

• The messaging provider must be configured and reachable before marreta serve. Run marreta doctor to check the connection.
• A consumer acknowledges on a clean run. A runtime error or a schema mismatch nacks without requeue, and only nack requeue retries. See ack and nack.