O'Reilly - Java Message Service

Java Message Service
have already processed more recently delivered messages, which would place the
redelivered message out of the original order.
If you would like to see multiple recipients in action, try starting two instances of
QWholesaler and three or more instances of QRetailer, each in a separate command
window:
java chap5.B2B.QWholesaler localhost WHOLESALER1 password
java chap5.B2B.QWholesaler localhost WHOLESALER2 password
java chap5.B2B.QRetailer localhost RETAILER1 password
java chap5.B2B.QRetailer localhost RETAILER2 password
java chap5.B2B.QRetailer localhost RETAILER3 password
In the command window for one of the QWholesaler applications, type the following
command:
Surfboards, 999.99, 499.99
Upon hitting the enter key, each instance of QRetailer will get the price quote, and
respond with a "Buy" order. If you have three QRetailers up and running, you should see
two of the messages going to one of the QWholesalers, and one going to the other.
5.5 Examining a Queue
If you don't see this behavior, load balancing may not be broken. It
may mean that vendor-specific queue settings are preventing load
balancing; you may need to send more than three messages
simultaneously to populate the queue enough to cause the messages
to be delivered to more than one consumer. For example, in SonicMQ
there is a configurable pre-fetch count that determines how many
messages may be batched together as they are delivered to a
consumer. The default is three messages, so the messages get
delivered to each consumer three at a time. The SonicMQ version of
these samples has some code that sets the value to one, which makes
load balancing work properly with only three clients:
...
qReceiver.setPrefetchThreshold(0);
qReceiver.setPrefetchCount(1);
...
It is likely that other vendors have the same kind of optimization, so
you should check that possibility if you are using a vendor other than
SonicMQ and don't see the proper behavior.
A QueueBrowser is a specialized object that allows you to peek ahead at pending messages
on a Queue without actually consuming them. This feature is unique to point-to-point
messaging. Queue browsing can be useful for monitoring the contents of a queue from an
administration tool, or for browsing through multiple messages to locate a message that is
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