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This document describes the concept, types, and usage of exchange in TDMQ for RabbitMQ.
Concept
Exchange is a message routing agent in TDMQ for RabbitMQ. A producer sends a message to an exchange, which then routes the message to one or more queues based on its attributes or content (or discards it). Then, a consumer pulls it from such queues for consumption.
TDMQ for RabbitMQ currently supports four types of exchange: Direct, Fanout, Topic, and Header.
Direct: a direct exchange will route messages to the queue whose binding key exactly matches the routing key.
Fanout: a fanout exchange will route messages to all queues bound to it.
Topic: a topic exchange supports multi-condition match and fuzzy match; that is, it will route messages to the queues bound to it by using routing key pattern match and string comparison.
Header: A header exchange has nothing to do with routing key and matches messages by the
Headers attribute. When binding a queue to a header exchange, declare a map key-value pair to implement the binding.Direct Exchange
Routing rule: a direct exchange will route messages to the queue whose binding key exactly matches the routing key.
Use case: this type of exchange is suitable for filtering messages by simple character identifiers and is often used for unicast routing.
Example:
Message | Routing Key | Binding Key | Queue |
Message 1 | bizA | bizA | Queue 1 |
Message 2 | bizB | bizB | Queue 2 |
Fanout Exchange
Routing rule: this type of exchange will route messages to all queues bound to it.
Use case: this type of exchange is suitable for broadcast message scenarios. For example, a distribution system can use a fanout exchange to broadcast various status and configuration updates.
Example
Message | Routing Key | Binding Key | Queue |
Message 1 | bazA.wechat_pay | bazA.credit, bazB.credit | Queue 1, Queue 2 |
Message 2 | bazA.alipay | bazA.credit, bazB.credit | Queue 1, Queue 2 |
Message 3 | bazC.credit | bazA.credit, bazB.credit | Queue 1, Queue 2 |
Topic Exchange
Routing rule: this type of exchange supports multi-condition match and fuzzy match; that is, it will route messages to the queues bound to it by using routing key pattern match and string comparison.
The wildcards supported by topic exchanges include asterisk "*" and pound sign "#".
"*" represents a word, such as
sh."#" represents zero, one, or more words separated by period ".", such as
cn.hz.Use case
This type of exchange is often used for multicast routing. For example, you can use a topic exchange to distribute data about specific geographic locations.
Example
Message | Routing Key | Binding Key | Queue |
Message 1 | cn.hz | cn.hz.# | Queue 1 |
Message 2 | cn.hz.store | cn.hz.#, cn.*.store | Queue 1, Queue 2 |
Message 3 | cn.sz.store | cn.*.store | Queue 2 |
Header Exchange
A header exchange has nothing to do with routing key and matches messages by the
Headers attribute. When binding a queue to a header exchange, declare a map key-value pair to implement the binding. When a message is sent to RabbitMQ, the Headers attribute of the message will be obtained to match the key-value pair specified during exchange binding, and the message will be routed to the queue only if there is a full match.The x-match rule has two types:
x-match = all: A message can be received only if all key-value pairs are matched.
x-match = any: A message can be received as long as any key-value pair is matched.
Message | Message Headers Attribute | Binding Headers Attribute | Queue |
Message 1 | key1=value1key2=value2 | x-match = anykey1=value1
key2=value2 | Queue 1 |
Message 2 | key1=value1
key2=value2key3=value3 | x-match = any
key1=value1
key2=value2 x-match = all
key1=value1
key2=value2`key3=value3 | Queue 1, Queue 2 |
Yes
No
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