Once upon a time, mod_cluster load balancing group functionality was referred to as "domain". This name has its historical links to mod_proxy_balancer and mod_jk origins.

When we had moved from EAP 5 (JBoss Application Server 5) to EAP 6 (JBoss Application Server 7), the name "Domain" started to collide with AS7 Domain controller and Domain management functionality.

In order to prevent this confusion and to avoid adding additional noise to already very much overloaded terms linked to "mod_cluster"; it has been decided to rename all mod_cluster subsystem public references from Domain to Load Balancing Group.

The same took place on Mod_cluster Manager console in Apache HTTP Server mod_manager module.

Unfortunately, due to a high risk of breaking something, internally, the load balancing native code kept the word "domain".

It appears that during the translation of the Apache HTTP Server native mod_cluster load balancing functionality to the new Java implementation in Undertow mod_cluster proxy, the domain label has been kept.

Call to action

Please, replace any references to "Domain" in Undertow mod_cluster proxy related context with "Load Balancing Group" (abbreviated as LBGroup). It will save us from endless conversations explaining users that no, indeed not, Undertow proxy mod_cluster Domain does not have anything in common with your Domain controller settings...
I would like to highlight this concern especially with regard to UNDERTOW-489.