问题
During configuration of JMS queues on JBoss 7 with HornetQ (based on standalone-full.xml configuration) I noticed an attribute 'durable'.
I browsed several sources and many of them stated queues are always 'durable', meaning the message will be always delivered, even in case of potential receivers being inactive at the time of send.
Does this attribute in JBoss 7 HornetQ refer to temporary queues? Or does this attribute refer to some kind of non-temporary non-durable queues?
回答1:
I feel the word "Durable" is more applicable to Topics than queues. A durable subscription is one where the publications for a subscriber are stored by the messaging provider when that subscriber is not running. Once the subscriber becomes active, these stored messages will be delivered to that subscriber. For non-Durable subscribers will not receive any publications if they are not active.
With respect to Queues, the messages are held in the queue till someone receives them or they expire. The messages can be persistent meaning they will survive restart of messaging provider and non-persistent where the messages are lost when messaging provider goes down.
回答2:
After brief investigation I came up with a few conclusions. All observations are based on JBoss 7.1.1.Final with HornetQ Server 2.2.13.Final.
The non-durable queue is not a temporary queue. It exists until it's manually deleted.
All the messages submitted to non-durable queue vanish upon JMS provider restart/failure (delivery modes, i.e. PERSISTENT / NON_PERSISTENT of the submitted messages are ignored).
The value of JMSDeliveryMode header element of the messages is not modified. In particular, if the message was submitted with PERSISTENT delivery mode to a non-durable queue, the flag is set to PERSISTENT, even though the non-durable queue does not persist the message (it is lost in case of JMS provider restart/failure).
From the client side it seems to be a bit of a disturbing prospect, since the sender has potentially no way of knowing whether the declared delivery mode of the message will not be respected, due to the problematic meaning of 'non-durable' queue.
Furthermore, the term 'durable queue' in this context seems disjointed from the 'durable subscription', as it does not appear to affect delivery of messages to inactive consumers in any way.
回答3:
Durable subscription in JMS means that if subscriber disconnected and then connected again to JMS destination (queue or topic) it will receive all messages that have been sent to the destination so far and have not been expired yet.
来源：https://stackoverflow.com/questions/13816718/what-is-the-meaning-of-durable-attribute-for-jms-queue-in-jboss-7-with-hornetq