Understanding RabbitMQ Exchange Types with Go: Default, Direct, Fanout, and Topic

3. Fanout Exchange

Concept

• Sends every message to all queues bound to the exchange.
• Ignores routing keys.
• Good for broadcast scenarios (notifications, pub/sub).

Code Example

fanout/publisher/main.go

ch.ExchangeDeclare("logs_fanout", "fanout", true, false, false, false, nil)
ch.Publish("logs_fanout", "", false, false, amqp.Publishing{
    ContentType: "text/plain",
    Body:        []byte("Broadcast log"),
})

fanout/consumer_1/main.go

q, _ := ch.QueueDeclare("", false, false, true, false, nil) // auto-generated queue
ch.QueueBind(q.Name, "", "logs_fanout", false, nil)

msgs, _ := ch.Consume(q.Name, "", true, false, false, false, nil)
for d := range msgs {
    log.Printf("[fanout consumer] %s", d.Body)
}

Diagram

flowchart LR
  P[Producer] --> F((Fanout Exchange: logs_fanout))
  F --> Q1[Queue: c1] --> C1[Consumer1]
  F --> Q2[Queue: c2] --> C2[Consumer2]
  F --> Q3[Queue: c3] --> C3[Consumer3]

4. Topic Exchange

Concept

• Routes messages based on pattern-matching in the routing key.
• Supports wildcards:
  • * matches one word.
  • # matches zero or more words.
• Good for event-driven systems where events have hierarchical names.

Code Example

topic/publisher/main.go

ch.ExchangeDeclare("logs_topic", "topic", true, false, false, false, nil)
ch.Publish("logs_topic", "order.us.created", false, false, amqp.Publishing{
    ContentType: "text/plain",
    Body:        []byte("Order created in US"),
})

topic/consumer_1/main.go

q, _ := ch.QueueDeclare("us_orders", true, false, false, false, nil)
ch.QueueBind(q.Name, "order.us.*", "logs_topic", false, nil)

msgs, _ := ch.Consume(q.Name, "", true, false, false, false, nil)
for d := range msgs {
    log.Printf("[us_orders] %s", d.Body)
}

Diagram

flowchart LR
  P[Producer] -->|order.us.created| T((Topic Exchange: logs_topic))
  T -->|bind=order.us.*| Q1[Queue: us_orders] --> C1[Consumer1]
  T -->|bind=order.#| Q2[Queue: all_orders] --> C2[Consumer2]