mod_cluster UDP multicast listener does not honour the proper interface ----------------------------------------------------------------------- Key: MODCLUSTER-495 URL: https://issues.jboss.org/browse/MODCLUSTER-495 Project: mod_cluster Issue Type: Bug Components: Core & Container Integration (Java) Affects Versions: 1.3.1.Final Environment: Linux, multiple NICs Reporter: Michal Karm Babacek Assignee: Radoslav Husar h3. Wrong interface On a multi-interface systems, it is necessary to pick the right interface the balancer should send to and worker should receive from. Merely setting UDP multicast address and port is not enough. * With Apache HTTP Server, this is achieved by {{AdvertiseBindAddress}} directive (though the default is wrong MODCLUSTER-487) * With Undertow mod_cluster proxy in Wildfly, the {{interface}} could be set in socket bindings, e.g.: {code}<socket-binding name="modcluster-adv" port="7637" multicast-address="224.0.1.105" multicast-port="7637" interface="special-public"/>{code} * In the case of Tomcat/JBossWeb, [historical mod_cluster 1.x|http://docs.jboss.org/mod_cluster/1.1.0/html_single/#d0e1113] documentation suggests that it is done "automatically": _interface on which mod_cluster's internal connection was established_. The statement from the historical documentation doesn't make much sense to me -- which internal connection? The actual result is that if you have 2 boxes, 2 interfaces each: h4. Balancer (Undertow or Apache HTTP Server) {{Box 1: enp1s0:10.16.88.186, enp2s0:172.17.71.254}}, all connectors including advertisement bound to {{enp2s0:172.17.71.254}} h4. Worker (Tomcat) {{Box 2: enp1s0:10.16.88.181, enp2s0:172.17.66.254}}, HTTP/AJP connectors bound to {{enp2s0:172.17.66.254}} {code} <Listener className="org.jboss.modcluster.container.catalina.standalone.ModClusterListener" advertise="true" loadMetricClass="org.jboss.modcluster.load.metric.impl.BusyConnectorsLoadMetric" loadMetricCapacity="1" loadHistory="9" loadDecayFactor="2" stickySession="true" stickySessionForce="false" stickySessionRemove="true" excludedContexts="ROOT,manager,docs,examples,host-manager" autoEnableContexts="true" advertiseGroupAddress="224.0.1.105" advertisePort="7637" <Connector address="172.17.66.254" port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" /> <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" address="172.17.66.254"/> <Engine name="Catalina" defaultHost="localhost" jvmRoute="172.17.66.254node"> {code} The worker node *is unable to receive balancer's advertising*. The tomcat actually listens for advertisements on {{enp1s0:10.16.88.181}}, because if I rebind the balancer to {{enp1s0:10.16.88.186}}, the whole setup suddenly works. I also verified it with the Advertize.java utility. h3. Suggestion IMHO, we have to either make it configurable via listener's attribute or fetch the interface from one of the available connectors (sometimes AJP is not configured, sometimes HTTP(S) ain't -- but at least one is always present).