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hello,guys,now I want to know the the process of start a new instance,and I
find the code in nova/conductor/rpcapi.py,

cctxt = self.client.prepare(version=version)
 cctxt.cast(context, 'build_instances', **kw)

I know the code do a cast method,send the message to exchange,but which is
the exchange,where can i find the definition of the exchange.Also,the
exchange will send the message to queue,and i can use the command
'rabbitmqctl list_bindings' to find the queue which is binding with the
exchange,but where is the  code of the queue,how does it deal the message
in queue?

anybody can help me?thanks.
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