Document updated on Jan 24, 2022

Gateway integration with RabbitMQ consumers

The AMQP component allows to send and receive messages to and from a queue through the API Gateway.

The configuration of the queue is a straightforward process. To connect the endpoints to the messaging system you only need to include the extra_config key with the namespaces backend/amqp/consumer or backend/amqp/producer.

To create Async agents that consume messages asynchronously and without requiring a user request, see Async Agents.

The parameters of this integration follow the AMQP specification. To understand what are the implications of a certain parameter, see the AMQP Complete Reference Guide.

KrakenD creates both the exchange and the queue for you.

Configuration

The consumer retrieves messages from the queue when a KrakenD endpoint plugs to its AMQP backend. The recommendation is to connect consumers to GET endpoints.

A single endpoint can consume messages from N queues, or can consume N messages from the same queue by adding N backends with the proper queue name.

See Async Agents to consume messages without an endpoint.

The needed configuration to run a consumer is:

{
    "backend": [{
        "host": ["amqp://guest:[email protected]:5672"],
        "disable_host_sanitize": true,
        "extra_config": {
            "backend/amqp/consumer": {
                "name": "queue-1",
                "exchange": "some-exchange",
                "durable": true,
                "delete": false,
                "no_wait": true,
                "no_local": false,
                "routing_key": ["#"],
                "prefetch_count": 10,
                "prefetch_size": 1024,
                "auto_ack": false
            }
        }
    }]
}

• name - string as the queue name
• exchange - string the exchange name (must have a topic type if already exists).
• routing_key - list: The list of routing keys you will use to consume messages.
• durable - bool true is recommended, but depends on the use case. Durable queues will survive server restarts and remain when there are no remaining consumers or bindings.
• delete - bool false is recommended to avoid deletions when the consumer is disconnected
• no_wait - bool: When true, do not wait for the server to confirm the request and immediately begin deliveries. If it is not possible to consume, a channel exception will be raised and the channel will be closed.
• prefetch_count - int (optional): Is the number of messages you want to prefetch prior to consume them.
• prefetch_size - int (optional): Is the number of bytes you want to use to prefetch messages.
• no_local - bool (optional) - The no_local flag is not supported by RabbitMQ.
• auto_ack - bool. When KrakenD retrieves the messages, regardless of the success or failure of the operation, it marks them as ACK. Defaults to false.