The ActiveMQ broker runs under the
activemq user account by default. Most systems will limit non-root users' usage of resources using the user limit (
ulimit) mechanism. When the broker runs as the
activemq user, the number of open files permissible by the
activemq user will limit the number of open connections that the process can have (each connection consumes an open file handle). Each node in the message queue needs an active connection. The number of nodes connected to the broker will be roughly equal to the number of open files allowed. After running a broker on my EL6 system, the default
ulimit value is 1024, and the number of nodes that I would typically be able to reach via the broker is 1000. You can check ...