Each connection to the Broker consumes resources while it is connected. In order to protect the Broker against malfunctioning (or malicious) client processes, it is possible to limit the number of connections that can be active on any given port.

Connection limits on AMQP ports are controlled by an attribute "maxOpenConnections" on the port. By default this takes the value of the context variable qpid.port.max_open_connections which in itself is defaulted to the value -1 meaning there is no limit.

If the interpolated value of maxOpenConnections on an AMQP port is a positive integer, then when that many active connections have been established no new connections will be allowed (until an existing connection has been closed). Any such rejection of a connection will be accompanied by the operational log message PRT-1005.

The context variable qpid.port.open_connections_warn_percent can be used to control when a warning log message is generated as the number of open connections approaches the limit for the port. The default value of this variable is 80 meaning that if more the number of open connections to the port has exceeded 80% of the given limit then the operatinal log message PRT-1004 will be generated.