1. A system for providing a messaging cluster with hybrid partitions, comprising: a computer environment which includes a processor and memory; a cluster of message brokers operating at the computer environment, which supports a hybrid of one or more fixed type partitions and on-demand type partitions; wherein a message producer can be associated with a configuration that indicates a type of partition to be used for connection with that message producer, and wherein the cluster of message brokers assigns to that connection a partition of the indicated type; and whereupon a load-balancing or failover of a message broker having active connections to message producers, those connections having an indication of fixed type partition are assigned to a same partition at a failed-over message broker, and those connections having an indication of on-demand type partition are assigned to an on-demand partition at the failed-over message broker.