Integration / RabbitMQ Interview Questions
Explain the lifecycle of a consumer connection and channel?
A consumer's path from nothing to actively receiving messages involves several distinct AMQP handshakes layered on top of each other.
sequenceDiagram
participant C as Consumer App
participant B as Broker
C->>B: TCP connect
C->>B: connection.open (negotiate heartbeat, frame_max)
B-->>C: connection.open-ok
C->>B: channel.open
B-->>C: channel.open-ok
C->>B: queue.declare / queue.bind (if needed)
C->>B: basic.qos (prefetch)
C->>B: basic.consume
B-->>C: consumer tag assigned
loop deliveries
B-->>C: basic.deliver (message)
C-->>B: basic.ack / basic.nack
end
C->>B: channel.close
C->>B: connection.close
A channel is a lightweight virtual connection multiplexed over a single TCP connection, which is why applications are encouraged to open one TCP connection per process and many channels within it, rather than a new TCP connection per consumer. If the channel or connection closes unexpectedly, any messages delivered but not yet acked are automatically requeued by the broker.
What is a channel, relative to a connection?
What happens to delivered-but-unacked messages if the channel closes unexpectedly?
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