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AMQP 0-9-1 Overview
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AMQP Bindings
What is a binding?
A binding connects a queue to an exchange, specifying how messages should be routed based on the defined routing keys. It determines which messages a queue receives from an exchange.
What is a routing key?
A routing key is a string that helps the broker route messages to the right queue. Think of it as a label that matches messages with their intended queues.
In order to route messages from an exchange to a queue there needs to be a binding between the two.
- Ensure the exchange and queue exist: The exchange acts as a message router, while the queue stores messages.
- Attach the queue to the exchange: Establish a link between the queue and the exchange. A routing key may be needed for the binding depending on the exchange type.
Example: Bind a queue to an exchange.
import pika
connection = pika.BlockingConnection(pika.ConnectionParameters(host='localhost'))
channel = connection.channel()
exchange_name = 'my_exchange'
channel.exchange_declare(exchange=exchange_name, exchange_type='direct')
queue_name = 'my_queue'
channel.queue_declare(queue=queue_name)
channel.queue_bind(exchange=exchange_name, queue=queue_name)
Routing keys
Bindings can include an optional routing key, while messages have their routing keys. When a message arrives at the exchange, the exchange checks its routing key against the routing keys of the binding. If there’s a match, the message is delivered to the corresponding queue(s).
Example: Bind a queue to an exchange using a defined routing key.
import pika
connection = pika.BlockingConnection(pika.ConnectionParameters(host='localhost'))
channel = connection.channel()
exchange_name = 'my_exchange'
channel.exchange_declare(exchange=exchange_name, exchange_type='direct')
queue_name = 'my_queue'
channel.queue_declare(queue=queue_name)
routing_key = "test"
channel.queue_bind(exchange=exchange_name, queue=queue_name, routing_key=routing_key)
Read more about how different exchanges are using routing keys.
Header attributes
Headers can be added to a message to provide additional context and control how it is routed.
A headers exchange is a type of exchange that routes messages based on these headers instead of the routing key. In a headers exchange, the routing logic is determined by the presence and values of headers in the message.
When using the header exchange, an argument called x-match is used as part of the binding. The message’s headers are matched to the binding’s headers. This header specifies whether all headers must match or just one.
- The
x-matchheader can have two values:allorany.all: The message must match all the headers specified in the binding.any: The message must match at least one of the headers specified in the binding.
Ready to take the next steps? Here are some things you should keep in mind:
Managed LavinMQ instance on CloudAMQP
LavinMQ has been built with performance and ease of use in mind - we've benchmarked a throughput of about 1,000,000 messages/sec. You can try LavinMQ without any installation hassle by creating a free instance on CloudAMQP. Signing up is a breeze.
Help and feedback
We welcome your feedback and are eager to address any questions you may have about this piece or using LavinMQ. Join our Slack channel to connect with us directly. You can also find LavinMQ on GitHub.