[rabbitmq]

Thanks for this lengthy reply. I'll try to keep mine short and that means skipping over a bunch of stuff.

First, re "whilst exchanges and bindings survive the loss of individual nodes, queues and their messages do not" -- this needs to be clarified. When queues are replicated, their messages do survive, in order, in the replica. The queue itself may die but the client can get back into context by finding another node in the group. This is observationally similar to DHTs.

Second, "a single logical broker" and "sounds an awful lot like a single element in the system that is responsible for message traffic".... NOOOOOO the point of 'logical' is the opposite of what you say!

Finally the BIG difference between DHTs and something like Rabbit is that in a DHT each datum is replicated around the ring N times, non-uniformly. Whereas in a system like Rabbit each datum is replicated N times in a uniform manner, such that ordered pairs of messages A and B will exist in every queue which has either A or B.