Hi, I'm using Apache Bench (ab) to send 1,000 requests with a
concurrency of 500 to a simple servlet on Tomcat trunk (revision 992708,
2010-09-03) which uses request.startAsync() and
Executors.newFixedThreadPool(10) to do the work and return a few bytes
of response and asyncContext.complete().
What I'm noticing is that every once in a while there is an errant
request that takes up to 10 seconds, while the average is around half a
second. I've reproduced this on both Oracle and IBM JVMs. I've looked at
verbosegc and see no anomalies in pause times or heap usage. I've taken
javadumps and I don't see any thread that is obviously "stuck" anywhere.
Most importantly, if I compare this to a servlet that writes the same
bytes but synchronously (i.e. a "classic" servlet service() method),
then I don't see this aberration.
I can see these long requests in my access log by changing
org.apache.catalina.valves.AccessLogValve to "%h %l %u %t "%r"
%s %b %D", e.g.:
127.0.0.1 - - [04/Sep/2010:18:46:20 -0700] "GET /myapp/ HTTP/1.0" 500
207 10986
127.0.0.1 - - [04/Sep/2010:18:46:22 -0700] "GET /myapp/ HTTP/1.0" 500
207 10428
127.0.0.1 - - [04/Sep/2010:18:46:22 -0700] "GET /myapp/ HTTP/1.0" 500
207 10347
My question is: how do I debug these 500 errors?
Thanks.
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