On Fri, May 7, 2010 at 3:19 PM, Jamie McCrindle <jamiemccrin...@gmail.com> wrote: > Greetings all, > > After some weeks of scratching my head, I _believe_ I have found the > magic combination that appears to be causing messages to become stuck > in our network of brokers. It's so convoluted that it's entirely > likely that the error isn't what I think it is but I have managed to > create a test case that mirrors the behaviour we're seeing live. And > it goes something like this: > > We have two brokers in a network of brokers. Producers were publishing > to a queue on one of the brokers and consumers reading off the queue > in the other broker. After a short while, messages would suddenly pile > up on the 'producer' broker and not get read off on the 'consumer' > broker. > > Pause for lots of random testing... > > It appeared that the network bridge subscription from the 'consumer' > broker was disappearing from the 'producer' broker, causing the pile > up. > > More testing later... > > And it looks like if we have a DefaultMessageListenerContainer with > the following configuration: > > maxMessagesPerTask: 1 > cacheLevel: CONSUMER > maxConcurrentConsumer: 3 (more than 1, basically) > concurrentConsumers: 1 > sessionAcknowledgeMode: Session.AUTO_ACKNOWLEDGE > > When Spring scales back the dynamic amount of consumers, the network > subscription appears to get lost and messages pile up on the producer > side. > > Workaround: > > Use concurrentConsumers instead of maxConcurrentConsumers so that > there are a static number of consumers (not setting maxMessagesPerTask > also seems to work).
If this is a topology of more than two brokers, you may want to try setting the suppressDuplicateQueueSubscriptions=true on the network connector to improve the dispatching sufficiency. It essentially eliminates some of the duplicate routes to a given consumer. More info is available here: http://activemq.apache.org/networks-of-brokers.html#NetworksofBrokers-NetworkConnectorProperties Also, there is a prefetchSize property on the network connector that is not documented on the ActiveMQ website. You may try setting that to 1 on the network connector. Bruce -- perl -e 'print unpack("u30","D0G)u8...@4vyy9&5R\"F)R=6-E+G-N>61E<D\!G;6%I;\"YC;VT*" );' ActiveMQ in Action: http://bit.ly/2je6cQ Blog: http://bruceblog.org/ Twitter: http://twitter.com/brucesnyder
