Introduction
Configuration
- Publisher Confirms
- Import/Export definitions
- Consumer Cancellation
- Configuration files
- Consumer Acknowledgments
- Prefetch
- Policies
Sample Code
Features
- Dead Letter Exchange
- Consistent Hash Exchange
- Alternate Exchange
- Shovel
- Federation
- RPC
- Direct Reply-to
- Delayed Message Exchange
- Pause Consumers
AMQP 0-9-1 Overview
Queue deep-dive
LavinMQ CLI
Management Interface
Management HTTP API
Tutorials
Security
Monitoring
Development
Support
AMQP Bindings
LavinMQ allows a lot of flexibility. A lot of this flexibility is in the bindings and how it is defined by the routing key, headers, and the type of exchange. A binding is an association or relation between a queue and an exchange. It describes which queue is interested in messages from a given exchange.
What is a binding?
A binding is an association or relation between a queue and an exchange. A queue tells the exchange that it is interested in messages from the given exchange, given some directives in the routing key on the binding and headers.
Bindings between queues and exchanges
Bindings are rules that exchanges use to route messages to queues. A queue must be bound to at least one exchange in order to receive messages from publishers.
Code example in Python, Pika:
channel.queue_bind(exchange=exchange_name, queue=queue_name)Routing keys
Bindings can take an extra parameter called routing key. A routing key can also be sent with a message. The routing key on the binding is sometimes called a binding key. The routing key in the message is what the exchange is looking at while delivering messages.
Code example with routing key in Python, Pika:
channel.queue_bind(exchange=exchange_name, queue=queue_name, routing_key=test)Read more about how different exchanges are using routing keys.
Header attributes
In the header exchange, a special argument named x-match, added in the binding
between exchange and queue, specifies if all headers must match or just one.
Either any common header between the message and the binding count as a match,
or all the headers referenced in the binding need to be present in the message
for it to match.
The x-match property can have two different values: any or all, where
all is the default value. A value of all means all header pairs (key, value)
must match, while a value of any means at least one of the header pairs must
match. Headers can be constructed using a wider range of data types, integer or
hash for example, instead of a string. The headers exchange type (used with the
binding argument any) is useful for directing messages which contain a
subset of known (unordered) criteria.
Code example in Ruby (bunny):
queue = channel.queue("", :exclusive => true).bind(x,
:arguments => {"os" => "linux", "cores" => 8, "x-match" => "all"})