How can I use reliable messaging together with a load balancer?
The point of reliable messaging is to help ensure that messages get from one place to another. This means that the protocol notices when messages that were expected to be delivered go missing. On the other hand, the point of a load balancer is to make sure that messages are spread out and that there aren't too many messages going to the same place. You can see how these two goals might come into conflict at times.
Many load balancers do offer a compromise to make these two goals simultaneously achievable though. A perfect load balancer would take the total sum of messages delivered and divide those messages evenly up among the available processing nodes. However, assume that the number of messages in any one client session is relatively small compared to the total number of messages processed. A load balancer could instead apportion groups of messages among the available processing nodes where the total sum of messages is still split roughly equally. This division according to groups would allow a feature like reliable messaging to work because the same server would be used to process all of the messages in the reliable session. The feature that this division method represents is typically called "sticky sessions" or some other phrase for affinitization in the load balancer.
Next time: Local Settings and Policy