[rabbitmq-discuss] Set 21673 memory limit

[tsuraan]

> vm_memory_high_watermark. See http://www.rabbitmq.com/extensions.html#memsup

I don't think this is what I'm looking for.  I remember seeing some
argument for the disk-based queues that will limit how many messages
rabbit actually keeps in RAM, where the rest of the messages are
stored on disk.  So I'm not thinking of how to trigger the
channel.flow command, but rather how to control the size of the RAM
cache of messages.