Thanks Bruce, It's just the 2 brokers at the moment and prefetchSize is set to 1. It looks like a combination of spring's dynamic connection scaling, having maxMessagesPerTask set to 1 and the the network bridge connection getting lost.
cheers, j. On Sat, May 8, 2010 at 1:16 AM, Bruce Snyder <bruce.sny...@gmail.com> wrote: > 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 >
