Previously WildFly only supported the ability to encode session affinity information into the JSESSIONID cookie, which is already used to uniquely identify a session. While this works well with the httpd family of load balancer modules (e.g. mod_cluster, mod_proxy_balancer, mod_jk) for which this mechanism was designed, however, the current set of load balancers used in the cloud rely on a separate cookie for implementing sticky sessions (e.g. HAProxy, IIS, etc.), and thus we lack the ability to allow WildFly to guide requests for a given session to the server that can most efficiently handle it.

To resolve this, we need to configure the Undertow subsystem to use a separate cookie to send affinity information.