Managing Physical Destination Limits

When creating a topic or queue destination, the administrator can specify how the broker should behave when certain memory limits are reached. Specifically, when the number of messages reaching a physical destination exceeds the number specified with the maxNumMsgs property or when the total amount of memory allowed for messages exceeds the number specified with the maxTotalMsgBytes property, the broker takes one of the following actions, depending on the setting of the limitBehavior property:

• Slows message producers (FLOW_CONTROL)

• Throws out the oldest message in memory (REMOVE_OLDEST)

• Throws out the lowest priority message in memory (REMOVE_LOW_PRIORITY)

• Rejects the newest messages (REJECT_NEWEST)

If the default value REJECT_NEWEST is specified for the limitBehavior property, the broker throws out the newest messages received when memory limits are exceeded. If the message discarded is a persistent message, the producing client gets an exception which should be handled by resending the message later.

If any of the other values is selected for the limitBehavior property or if the message is not persistent, the application client is not notified if a message is discarded. Application clients should let the administrator know how they prefer this property to be set for best performance and reliability.