Connecting to the RabbitMQ web control panel
gds govuk connect rabbitmq -e integration aws/rabbitmq and point your
browser at http://127.0.0.1:15672.
A generic RabbitMQ dashboard shows metrics for queues and exchanges.
How we run RabbitMQ
Producer: an application that publishes messages RabbitMQ. On GOV.UK this could be publishing-api.
Exchanges are AMQP entities where messages are sent. They take a message
and route it into zero or more queues. The routing algorithm used depends on
the exchange type and rules called bindings. When a content change is made
in a publishing application (e.g. Travel Advice Publisher), Publishing API
publishes a message to our main exchange,
Queues are very similar to queues in other message and task-queueing
systems: they store messages that are consumed by applications. An example of a
email_alert_service which is used by
email-alert-service to forward publishing activity to
email-alert-api. Queues are created by consumer applications.
Bindings are rules that exchanges use (among other things) to route
messages to queues. To instruct an exchange E to route messages to a queue Q, Q
has to be bound to E. Bindings may have an optional routing key attribute. An
example of a binding is the
cache_clearing_service-high queue is
bound to the
published_documents exchange with a routing
key matching of
*.major. E.g messages sent to the exchange with a routing key
guide.major will be routed to that queue.
Messages consist of a JSON payload and publish options (we predominantly use content type, routing key and persistant).
- content_type (string) - tells the consumer the type of message. E.g
- routing_key (string) - matches against bindings to filter messages to certain
- persistant (boolean) - tells RabbitMQ whether to save the message to disk.
Message options are set when a message is published. In our use case, the message’s payload is the content item in JSON format. The code in the publishing-api to publish a message is here.
Consumer applications are applications which consume messages from one or more queues. For email-alert-service this is done by running this rake task and using the major change processor to do the processing of the consumed messages. All our consumer applications use the govuk_message_queue_consumer gem to consume messages from RabbitMQ in a standardised way.
You can see live examples of things like queues, exchanges, bindings etc by connecting to the RabbitMQ control panel.