AMQP requests

An AMQP region publishes to an AMQP 0-9-1 broker and reads what comes to its queues (ADR-171). The URL is amqp://[user:password@]host[:port][/vhost] (port 5672, the virtual host percent-encoded: /%2Fcarpet-express), or amqps:// (5671, over TLS, verified as https://).

### File a declaration: the decision comes to the decisions queue
# @expect 1
# @property delivery-mode 2
# @property correlationId {{$uuid}}
AMQP amqp://localhost:5672/%2Fcarpet-express
exchange: customs
routing-key: customs.GB.filing
subscribe: customs.decisions

{"destinationCountry": "GB"}

### Await what the application publishes to the customs exchange
# @expect 1
AMQP amqp://localhost:5672/%2Fcarpet-express
bind: customs customs.*.filing

Header	Meaning
exchange	The exchange the messages go to; without it, the default exchange (routing keys are queue names)
routing-key	The messages’ routing key
subscribe	Queues consumed, separated by commas; a queue’s messages go to the region, not to the application
bind	EXCHANGE KEY: a queue of the region’s own, bound to the exchange with that binding key (none for fanout); can be repeated
mandatory	false: a message no queue takes isn’t an error (true by default)
username, password	PLAIN credentials; without them the URL’s, then APIGENIE_AMQP_USERNAME and APIGENIE_AMQP_PASSWORD, then guest. They are [redacted] in the output and reports

# @property NAME VALUE lines with the name of a basic property set it: content-type, content-encoding, delivery-mode, priority, correlation-id, reply-to, expiration (milliseconds), message-id, timestamp (seconds since the epoch, or now), type, user-id and app-id. Other names, and # @property user NAME VALUE, are application headers. The region consumes its queues before it publishes, then reads until it has # @expect messages or # @timeout has passed; its own messages coming back are left out. RabbitMQ’s direct reply-to works: subscribe: amq.rabbitmq.reply-to with # @property reply-to amq.rabbitmq.reply-to.

With an AsyncAPI --spec, the channel is the one of the exchange and routing key (a queue channel’s for the default exchange and its queue’s name), and a message read from a queue is that queue’s channel’s. What is published is checked against the channel’s receive operations and what is read against its send operations or as a reply: the body, the headers against the message’s headers, and the properties against the AMQP bindings (message.properties.invalid). A reply is paired with its request by its correlation id in a header or a property: properties are seen by their AMQP and AsyncAPI names (correlation_id and correlationId, reply_to and replyTo), so $message.header#/correlationId finds either.