What version of ActiveMQ are you using?
Justin On Fri, Nov 25, 2022 at 4:20 AM Mark Johnson <spike.john...@gmail.com> wrote: > Hi, > > We have Apache Camel routes consuming messages and updating a database. Due > to the nature of the business, there will be multiple messages in the queue > that need to update the same row in the db tables. This results in a lot of > db transaction rollbacks as the number of consumers increases. > > We have proved to ourselves that using Message Groups with part of the db > table primary key as the JMSXGroupID resolves the rollback. There will also > be considerably more groups than consumers, so I have no concerns about > consumers being idle because all groups are already serviced. > > We have also proved that we can horizontally scale the Camel deployment > based on queue depth. > > What we can't work out is how to put the two solutions together, as whilst > Message Group will rebalance when a consumer disconnects, it does not > rebalance on new consumers, according to the documentation. > > The documentation suggests that sending in a message with a -1 SeqNr will > force the group to be treated as new, however at the point where we are > scaling up there will already be thousands of messages on the queue. > > Does the reset happen when the broker receives the message or when the > message gets to the head of the queue? If the latter, could I use message > priority to force it to the head? > > If those conditions are met then I thinking that the Camel routes could > process 1k msgs then send in a -1 reset message for their current GroupID > to cause it to be rebalanced. Would also need to set prefetch=1 to ensure > that the client does not have messages buffered, although even if we didn't > do that, this pattern should reduce the number of rollbacks significantly. > > Is there a better way for groups to be moved to new consumers? > > Any suggestions gratefully received. > > Mark Johnson >
