Artemis currently has the ability to configure both a live and a backup server in the same JVM. This is referred to as "colocated" brokers.
The original use-case for this functionality was very early cloud infrastructure where durable, attached storage was not readily available. However, since the development of this feature most (if not all) cloud environments support durable storage separate from the broker so that if the broker goes down a new, identical broker can be spun-up quickly and attached to the same storage. This provides high availability without the need for any idle backups or replication of any kind which functionally nullifies this feature. Aside from this, it turns out that (surprise!) configuring & running multiple brokers in the same JVM is difficult and error-prone not to mention dynamically coordinating the acquisition of backups in a running cluster and protecting against split-brain. I was able to quickly search and find 5 open Jiras for colocated issues (of course, there may be more): ARTEMIS-452 - Scale down with colocated backup failing when using replication ARTEMIS-2165 - Not having backup available after restart in colocated configuration ARTEMIS-2609 - Ha-policy collocated not working. ARTEMIS-2452 - group-name ignored in shared store colocated setup ARTEMIS-1863 - Colocated Replicating Cluster Ends Up in an Infinite Quorum Vote Loop After Failover and Restart At this point I recommend that we deprecate this feature and steer users who want this kind of functionality to either existing cloud infrastructure options or multiple, distinct brokers on the same hardware (i.e. outside the cloud). What are your thoughts? Justin
