If the JBoss LogManager was added to the boot classpath, for example for custom Java agents (e.g. Introscope or JMX agent), the JBoss LogManager would be bootstrapped using the default configurator, rather than using the logging subsystem's own configurator.
As the logging subsystem assumed that its own configurator would be used, this resulted in the JBoss EAP 6 failing to start, displaying the following error:
ERROR [org.jboss.as.controller.management-operation] (ServerService Thread Pool -- 5) JBAS014612: Operation ("add") failed - address: ([
("subsystem" => "logging"),
("console-handler" => "CONSOLE")
]): java.lang.ClassCastException: org.jboss.logmanager.PropertyConfigurator cannot be cast to org.jboss.as.logging.logmanager.ConfigurationPersistence
This issue has been fixed in this release of JBoss EAP 6, so that the the logging subsystem no longer assumes that its own configurator is used. If the logging subsystem's own configurator is not used, it replaces the original configurator (usually the default configurator).
As a result of this fix, custom Java agents can now be used without affecting how the JBoss LogManager is initially configured.