Hi Sam
You jar - does it include any JSP tag files written as JSP fragments? There
are known issues in this area. The dependency management seems to get
confused, resulting in lots of unnecessary compilation of the .tag files
Regards
Ron
----- Original Message -----
From: "Sam Hokin" <s...@ims.net>
To: <users@tomcat.apache.org>
Sent: Friday, February 20, 2009 12:23 PM
Subject: very slow class loading on initial JSP/servlet request after
restart
I've been struggling with a very severe problem on one of my three Tomcat
servers since late December. I'm completely stumped. I'm running 6.0.18
on all three servers, which are all running Fedora Core 9, all currently
running Sun's JDK 1.6.0_12. The only difference is hardware. The server
that's being a problem is a Dell PowerEdge 1950, quad dual core. All three
servers are configured exactly the same, with Apache HTTPD and using
mod_proxy_ajp to pass requests on to Tomcat's AJP connector. All Tomcat
instances are running the tomcat-native APR v1.1.14 that comes bundled
with Tomcat. However, this problem persists on the problematic server if I
don't run tomcat-native APR.
The problem, which spontaneously appeared a few days before Christmas on
this one server, is that the initial request of a JSP or servlet takes
AGES to respond, usually exceeding several minutes. I've found that
compilation of a JSP to a class file is nearly instant, but response from
the resulting compiled class takes forever. Further, I found that this
only happens when the offending JSP (or servlet) imports classes that I
wrote, located in a JAR in Tomcat's /lib directory or inside the web app's
WEB-INF/lib directory, or expanded out under WEB-INF/classes. For
example, the following simple JSP,
<%@ page import="java.util.*, java.io.*, net.ims.jcms.*" %>
<%
java.util.Date endDate = new java.util.Date();
out.println(endDate.toString());
%>
takes AGES to respond, the first time it is requested after a Tomcat
restart (even if the compiled class is present under the /work tree),
while another JSP with the same executable lines:
<%@ page import="java.util.*, java.io.* %>
<%
java.util.Date endDate = new java.util.Date();
out.println(endDate.toString());
%>
responds immediately. The net.ims.jcms package is something I wrote.
After the first time a JSP has been requested, subsequent requests respond
immediately. So, the server still functions, but there is a horribly long
delay before pages respond after a Tomcat restart.
Again, this is not a compilation issue; I've monitored the /work directory
and can see that the class files appear very quickly. In addition, this
problem recurs after a Tomcat restart when the compiled class files
already exist under /work. I've run the JVM with the -verbose:class
option, and, sure enough, the long delay corresponds to a long delay
before the page's class is loaded by the JVM. As soon as the JVM spits
out the line saying it loaded the class, the response is sent.
So, my conclusion is that the class loader simply takes a very long time,
on the first request, if the class imports the package that I wrote.
After the class is loaded into memory by that first request, subsequent
requests respond normally.
I cannot divine any problem with my JAR file or classes within it that
would result in this problem; furthermore, it only occurs on one of three
servers running the exact same everything. I have run MEMTEST86 on the
offending server and memory seems to be fine. It is fine for all other
services, processes, etc. The problem is robust on this specific server -
it has transcended versions of Tomcat, the JVM, the kernel version, etc.
I would greatly appreciate any suggestions for further diagnostics, things
to try, offending things I may have done in my Java package, etc. Thanks!
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