A publish/subscribe system is non-disruptively reconfigured, such that
messages are not lost during the reconfiguration. After reconfiguration
is initiated, messages that are to be delivered within the
publish/subscribe system are forwarded using either an old path or a new
path. That is, until the reconfigured system is stabilized, some messages
may be delivered using the old path, while other messages are delivered
using a new path. After the system is stabilized, the new path is used
for delivery of all the messages, until another reconfiguration is
initiated.