Our application uses a non-standard approach of sometimes rendering several JSF pages in response to one request. One main page is sent back as a response, other(s) created with redirected response etc. are sent as notification email. This worked fine in Wildfly 8.2, but breaks in Wildfly 10.1 (only if statistics collection is enabled) in that the secondary pages are not created with internal stacktrace looking like this:

...
Caused by: java.lang.IllegalStateException: UT000139: Exchange already complete
at io.undertow.server.HttpServerExchange.addExchangeCompleteListener(HttpServerExchange.java:916)
at io.undertow.server.handlers.MetricsHandler.handleRequest(MetricsHandler.java:54)
at io.undertow.servlet.core.MetricsChainHandler.handleRequest(MetricsChainHandler.java:59)
at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:274)
at io.undertow.servlet.handlers.ServletInitialHandler.dispatchToPath(ServletInitialHandler.java:209)
at io.undertow.servlet.spec.RequestDispatcherImpl.forwardImpl(RequestDispatcherImpl.java:221)
... 66 more