Seems like it might be an unintended ordering consequence? or is it covered by the JMS spec? I suspect the latter, but wanted to discuss anyway... Per this JIRA, https://issues.apache.org/jira/browse/AMQ-2790 client-side priority support was created, but also made default. So in this case, a producer sending messages with priority values set on the messages would be reordered in the consumer according to priority regardless of whether priority is enabled on the broker side.
However, the JMS spec says this about priority: "JMS does not require that a provider strictly implement priority ordering of messages; however, it should do its best to deliver expedited messages ahead of normal messages." -- *Christian Posta* http://www.christianposta.com/blog twitter: @christianposta