A content-based publish/subscribe system for providing gapless message
delivery from a publishing client to a subscribing client, the system
includes a plurality of brokers operatively coupled to one another via a
network. Each of the brokers include at least one processor and are
configured as a publisher-hosting broker, a subscriber-hosting broker or
an intermediate broker. The subscriber-hosting broker is operatively
coupled to the publisher-hosting broker via the network through the
intermediate broker. At least a portion of the plurality of brokers are
configured so as to eliminate a need for persistent storage of messages
at the intermediate broker and to substantially guarantee a gapless
delivery of one or more messages transmitted by the publishing client to
the subscribing client, even in the presence of a failure in the
publish/subscribe system.