Issue

• In AMQ 6.3 it can be achieved by setting message header JMSXGroupSeq property to "-1" in the next message of the group. In AMQ 7.1 this feature doesn't work. Using AMQ 7.1 grouping handler with the group-timeout configured imposes risk of breaking message group sequencing for long running transactions unless the setting value is aligned with the transaction timeout.

Once first message of a message group is bound to a consumer, AMQ 7.1 will keep delivering all subsequent messages from that group to the consumer. For large and relatively static set of message groups, there should be a way of re-balancing them across all available consumers should number of consumers increase.