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1. Message arrives on the Queue
2. The Queue notifies some interested Consumers that there is work to be done
3. The Consumers notify their ConsumerTarget that they would like to do work
4. The ConsumerTargets notify their Session that they would like to do work
5. The Sessions notify their Connections that they would like to do work
6. The Connections schedule themselves. This is the switch from the incoming Thread to the IO-Thread.
   
7. The Scheduler kicks off a IO-Thread to process the work of a Connection
8. The Connection iterates over its Sessions that want to do work
9. The Sessions iterate over its ConsumerTargets that want to do work
10. The ConsumerTargets iterate over its Consumers that want to do work
11. The Consumer tries to pulls a message from the Queue
12. If successful the message is put on the IO-buffer to be sent down the wire

Threading Model

Consumers are The consuming part is always invoked from the consuming connection's IO-Thread whereas the Queue publishing part might be invoked from different threads (producing connection's IO-Thread, Housekeeping thread for held or TTLed messages, a consuming connection's IO-Thread in case for message reject).

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