Dead Letter Queues

A Dead Letter Queue (DLQ) is a common concept in a messaging system, and represents where messages are sent when a delivery failure occurs with a consumer after max_retries is reached. A Dead Letter Queue is like any other queue, and can be produced to and consumed from independently.

With Cloudflare Queues, a Dead Letter Queue is defined within your consumer configuration. Messages are delivered to the DLQ when they reach the configured retry limit for the consumer. Without a DLQ configured, messages that reach the retry limit are deleted permanently.

For example, the following consumer configuration would send messages to our DLQ named "my-other-queue" after retrying delivery (by default, 3 times):

You can also configure a DLQ when creating a consumer from the command-line using wrangler:

To process messages placed on your DLQ, you need to configure a consumer for that queue as you would with any other queue.

Messages delivered to a DLQ without an active consumer will persist for four (4) days before being deleted from the queue.