I have an intermittent bug that I've been trying to trying to track down
for a long time. The symptom is that the same tomcat request object is
being processed by two different threads. The symptom is a random crash
when one thread returns and recycles the request, and the other thread
access the request object, usually causing an NPE.
Note, there are no background threads going on here. I see my top-most
filter AuthFilter.doFilter() is being called once with a Tomcat
RequestFacade object, and before that thread returns, AuthFilter.doFilter()
is called again on another thread with the exact == RequestFacade object.
Google hasn't given me any leads (beyond "don't pass a request do another
thread". I'm not).
My suspicion at this point centers around this code, though I have not
spent a much time in Tomcat internals. In Tomcat 8.5.8
AbstractProtocol.ConnectionHandler.process() around line 889.
wrapper.registerReadInterest();
} else if (state == SocketState.SENDFILE) {
// Sendfile in progress. If it fails, the socket will be
// closed. If it works, the socket will be re-added to the
// poller
connections.remove(socket);
Thread t = threads.remove(socket); assert t == Thread.currentThread();
release(processor);
} else if (state == SocketState.UPGRADED) {
// Don't add sockets back to the poller if this was a
My reading of this is that when state == SENDFILE, the request is not
complete in some sense. However, the processor is being released to be
recycled. Is this OK for the processor to be picked up by another thread
at this point?
Thanks for any help,
Matt
