Topic exchange combines multiple message consumers with the filtering, based on the message routing key and wildcards matching. These subscribers might be queues q.order.generate-invoice and q.order.assemble-shipment, which will both receive a copy of the original message. Second subscriber might be a service, which will start a new process in the magazine, a process of collecting all the order items and assembling them in a single shipment. It is going to copy and send the message for all bounded subscribers - one subscriber might be a service which is going to generate the invoice to the customer. Routing key will be simply ignored.Įxample: Your system publishes a message to x.order-created fanout exchange. Message can be processed by different consumers in a different way. It it similar to publish/subscribe model - as a consumer, You subscribe for something, and publisher sends the message to all subscribers. Fanout exchangeįanout exchange is useful when You want to send the message to one or more queues, and it’s ideal for broadcasting. In such case, a producer provides an address for the message where should it be routed.
AUDIOBOOK BUILDER QUEUE PDF
System schedules report generation by sending a message to x.generate-report exchange, and specifies the target destination as a routing key - pdf or docx. A user clicks on a Generate report button and selects the target format- PDF or DOCX file. One example can be a reporting system, which generates reports in a specified format, asynchronously. Direct exchangeĭirect exchange is useful when You want to have a single exchange, and to specify the target “address” of the message, based on a routing key filtering. Because default exchange is a direct exchange, let’s go to the next point. Personally I don’t use it directly at all, and I always provide exchange name in a message producer. Symbol # means matching of zero or more words, like taxi.eco.#, which will match all routing keys starting with taxi.eco. You can use * symbol to match any word at a specific position, like taxi.*.large. Routing key is a list of words separated with. Although routing-key with wildcards is supported, it is not mandatory - You still can provide the routing key implicitly, without any wildcards. Messages are being passed to one or many queues. Topic exchange routes the message based on the the routing-key wildcard matching. It’s worth to mention that in this case, header value may not be a string, so it’s a little more flexible. any - at least one header must match, to route the message to the queue.all - all headers must match in order to route the message to the queue.Headers order does not matter.Īn argument x-match is added to the binding between the exchange and the queue, and it can have two values: Headers exchange routes the message based on… it’s headers ! Routing key is ignored, and if the message headers match binding configuration - the message will be sent to the bounded queue. Provided routing key will be simply ignored. Fanout exchangeįanout exchange copies and sends the received message to all queues bound to it. A routing key in the message must exactly match the routing key specified in the binding - it’s like an address, telling the exchange where a message should go. A routing key is set by the producer, as a message header. Direct exchangeĭirect exchange uses message’s routing key, to route the message to a single queue. Every created queue is automatically bound to the default exchange, with the same routing key as queue name.
When a message is send to the default exchange, then it will be routed to the queue with a queue name equal to the message routing key.
Exchanges Default exchangeĭefault exchange is a pre-declared direct exchange, which name is set to an empty string "". If You want, You can use RabbitMQ with other protocols, e.g. RabbitMQ is a lightweight, scalable message broker, which uses AMQP protocol as a core protocol - supported AMQP version is 0.9.1 natively, and version 1.0.0 via a plugin. If You would like to learn more about AMQP model, see Materials section at the bottom of this article - there You will find links to more articles, which cover AMQP topic with more details.
Important thing to remember is the fact, that messages are not published directly to the queues, but they are always being sent to the exchange. Queue acts like as a buffer for messages, which will be consumed later Message stays in the queue until it’s consumed by the consumer.It contains a set of rules that exchange uses to route the message to the queues Binding - binding links exchanges with the queues.It will copy the message and send it to queue(s) based on the exchange type, message’s routing key and message’s headers Exchange receives the message and is responsible for the routing.Producer publishes a message to an exchange.
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