On both the current 9.0 version and 9.1 beta when the HTTP Service Request Processing Thread Count (Maximum number of request processing threads) is reached NO OTHER deployed http servlet will respond and the App Server is deadlocked. The App Server must be shutdown (often requiring explicitly killing the process). The default Thread Count for 9.0 appears to be 5, and the 9.1 beta appears to be 20. Increasing these numbers does increase the number of concurrent web service calls before deadlock is reached, however this does appear to be a serious problem with the web servlet engine. I have created a trivial 100 line servlet which demonstrates this deadlock behavior which I can provide to anyone interested.
[Message sent by forum member 'steveshell' (steveshell)]
http://forums.java.net/jive/thread.jspa?messageID=225117