scripts/rabbitmq-server contains: ERL_ARGS="+K true +A30 -kernel inet_default_listen_options [{sndbuf,16384},{recbuf,4096}]" The erl manpage (http://linux.die.net/man/1/erl) says: +A size: Sets the number of threads in async thread pool, valid range is 0-1024. Default is 0. The default is 0, why does rabbit use 30? Aman