Improved error message for InvocationTarget/NullPointerExceptions related to terminated requests

Investigations with different servlet containers under load indicate that suspended continuations may be awoken with terminated requests. This yields either null server names/ports (typically in Jetty 6) or InvocationTargetExceptions (in Jetty 7/8 and Tomcat) with underlying IllegalStateExceptions.

Sample stack trace from Tomcat:

java.lang.reflect.InvocationTargetException: null
at sun.reflect.GeneratedMethodAccessor47.invoke(Unknown Source) ~[na:na]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) ~[na:1.6.0_26]
at java.lang.reflect.Method.invoke(Method.java:597) ~[na:1.6.0_26]
at net.liftweb.http.provider.servlet.containers.Servlet30AsyncProvider.resume(Servlet30AsyncProvider.scala:102) ~[lift-webkit_2.8.1-2.4-M4.jar:2.4-M4]
[…]
Caused by: java.lang.IllegalStateException: The request associated with the AsyncContext has already completed processing.
at org.apache.catalina.core.AsyncContextImpl.check(AsyncContextImpl.java:438) ~[catalina.jar:7.0.23]
at org.apache.catalina.core.AsyncContextImpl.getResponse(AsyncContextImpl.java:196) ~[catalina.jar:7.0.23]
... 22 common frames omitted

From Jetty 7/8:

java.lang.reflect.InvocationTargetException: null
at sun.reflect.GeneratedMethodAccessor22.invoke(Unknown Source) ~[na:na]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) ~[na:1.6.0_26]
at java.lang.reflect.Method.invoke(Method.java:597) ~[na:1.6.0_26]
at net.liftweb.http.provider.servlet.containers.Servlet30AsyncProvider.resume(Servlet30AsyncProvider.scala:106) ~[lift-webkit_2.8.1-2.4-M4.jar:2.4-M4]
at net.liftweb.http.provider.servlet.HTTPRequestServlet.resume(HTTPRequestServlet.scala:163) ~[lift-webkit_2.8.1-2.4-M4.jar:2.4-M4]
[…]
Caused by: java.lang.IllegalStateException: IDLE,initial
at org.eclipse.jetty.server.AsyncContinuation.complete(AsyncContinuation.java:534) ~[na:na]
... 22 common frames omitted

From Jetty 6:

java.lang.NullPointerException: null
at org.eclipse.jetty.server.Request.getServerName(Request.java:1008) ~[na:na]
at org.eclipse.jetty.server.Request.getServerPort(Request.java:1071) ~[na:na]
at net.liftweb.http.provider.servlet.HTTPRequestServlet.serverPort(HTTPRequestServlet.scala:92) ~[lift-webkit_2.9.0-1-2.4-M3.jar:2.4-M3]
at net.liftweb.http.Req$$anonfun$hostAndPath$1.apply(Req.scala:968) ~[lift-webkit_2.9.0-1-2.4-M3.jar:2.4-M3]
at net.liftweb.http.Req$$anonfun$hostAndPath$1.apply(Req.scala:968) ~[lift-webkit_2.9.0-1-2.4-M3.jar:2.4-M3]
at net.liftweb.common.Full.map(Box.scala:491) ~[lift-common_2.9.0-1-2.4-M3.jar:2.4-M3]
at net.liftweb.http.Req.hostAndPath(Req.scala:968) ~[lift-webkit_2.9.0-1-2.4-M3.jar:2.4-M3]

Again, the underlying cause for this seems to be continuations that are awoken with requests that were terminated before the continuation was restored.