If one uses hostnames and a worker registers itself e.g. as Host=karm.brq.redhat.com the Undertow mod_cluster proxy enforces exact alias matching, which corresponds to Apache HTTP Server mod_cluster module implementation directive UseAlias being set to 1 (enforcing).

Symptoms

Thus registered worker's context:

INFO  [io.undertow] (default task-3) registering context /clusterbench, for node worker-1, 
with aliases [default-host, localhost]

causes HTTP 404 errors both while trying to access the context on IP address or hostname.
This worker:

INFO  [io.undertow] (default task-20) registering context /clusterbench, for node worker-1, 
with aliases [default-host, karm.brq.redhat.com]

, with one of its aliases being karm.brq.redhat.com could be accessed via the Undertow mod_cluster proxy without problems.

Call to action

We need to decide whether this difference in default behaviour is desirable or not and act accordingly.

WDYT?