Topic exchange (pattern matching) in RabbitMQ - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a Topic Exchange in RabbitMQ?

A Topic Exchange routes messages to queues based on matching between a message routing key and the pattern that was used to bind a queue to the exchange. It uses wildcards for flexible routing.

beginner

What wildcard characters are used in Topic Exchange bindings?

The '*' (star) matches exactly one word, and the '#' (hash) matches zero or more words in the routing key.

intermediate

How does the routing key 'stock.usd.nyse' match the binding key 'stock.*.*'?

The routing key 'stock.usd.nyse' matches 'stock.*.*' because '*' matches exactly one word. Here, 'usd' and 'nyse' each match one '*'.

intermediate

Explain the difference between '*' and '#' in Topic Exchange pattern matching.

'*' matches exactly one word in the routing key, while '#' matches zero or more words, allowing more flexible matching.

beginner

What happens if a message's routing key does not match any binding pattern in a Topic Exchange?

The message is discarded or returned to the sender if no queue binding matches the routing key pattern in the Topic Exchange.

Which wildcard in a Topic Exchange matches zero or more words?

A #

B *

C ?

D %

The '#' wildcard matches zero or more words in the routing key pattern.

What does the routing key 'log.error.system' match if the binding key is 'log.*.*'?

A Matches only if '#' is used

B Does not match

C Matches only if '*' is replaced by '#'

D Matches

Each '*' matches exactly one word, so 'error' and 'system' match the two '*' in 'log.*.*'.

If a queue is bound with 'sensor.#', which routing key will NOT match?

A sensor.temperature

B sensor.temperature.outdoor

C device.sensor.temperature

D sensor

'device.sensor.temperature' does not start with 'sensor', so it does not match the binding key 'sensor.#'.

What type of exchange uses pattern matching with wildcards '*' and '#'?

A Direct Exchange

B Topic Exchange

C Fanout Exchange

D Headers Exchange

Topic Exchange uses routing keys with '*' and '#' wildcards for pattern matching.

Which binding key would match routing keys with exactly three words starting with 'app'?

A app.*.*

B app.#

C *.app.*

D #.app

'app.*.*' matches routing keys with three words where the first word is 'app'.

Describe how the '*' and '#' wildcards work in RabbitMQ Topic Exchange pattern matching.

Think about how many words each wildcard can match in the routing key.

Explain what happens when a message is sent to a Topic Exchange with a routing key that does not match any queue binding.

Consider how routing keys and binding keys interact in message delivery.