We haven't performed either of those. I will try that.
We did watch the packet flow between the browser and the server using
wireshark in order to rule out something weird with the network. You
could see where Tomcat responded with the partial page, the browser
returns the packet acknowledgement, and then nothing. The server stops
responding.
I will see if strace reveals any clues. Thank you for the suggestion!
Warm regards,
Jordan Michaels
Vivio Technologies
http://www.viviotech.net/
Open BlueDragon Steering Committee
Railo Community Distributions
Jim Cox wrote:
Can you truss/strace Tomcat, or watch the network traffic between
MySQL and Tomcat? Comparing captures from those tools between
successul and hung page generation might show what the issue is, or at
least suggest other areas to look at.
On Wed, Feb 10, 2010 at 2:53 PM, Jordan Michaels <jor...@viviotech.net> wrote:
We have an interesting situation and I'm wondering if anyone has any ideas
on where we could look for possible solutions.
We have a JSP page that performs a large mysql query of product titles (just
the names). The list is then spit out on the page with drill-down links.
Pretty simple really. The problem is that just after a tomcat restart, the
first and occasionally the second and third requests will process all the
way just fine, but most subsequent requests will "hang" on a random record.
Occasionally one will go all the way through, but most will hang.
Let me clarify, we restart tomcat, hit the page, and the page loads fine. We
hit refresh once or twice, and the page will fail to load fully. The page
will hang after a random product title and just stop responding. You can
click on any other page on the site, but this one page with the large
product listing query hangs in random spots.
We've studied this intently. The server this is running on is a CentOS 4,
32-bit box with 1.5 GB RAM, Apache 2, and mod_jk.
Our first thought was memory issues. We increased Tomcat's memory using the
setenv.sh file, which now contains the following line:
JAVA_OPTS="-Xms128m -Xmx1024m -Xss256m -XX:MaxPermSize=256m "; export
JAVA_OPTS
We've verified that the settings are in place by using the "ps ax" command
and making sure the java process includes the updated settings.
Unfortunately, this seems to have no effect at all.
We then reviewed the logs: catalina.out, mod_jk.log, and apache's
error_log, among others. We monitored these logs using "tail" so we
could see if any errors were thrown as we hit the page. No errors were
thrown if the request went through good or it failed. The logs were
completely quiet.
We've updated Tomcat, mod_jk, the JVM, and the MySQL driver to the absolute
latest versions available as of this writing.
Does anyone have any clues as to where we might look for what is happening
to make this one page hang? It still feels like a memory issue, but with
nothing in the logs and no indicators other then the problem itself, we'd
appreciate any suggestions on what to look for at this point.
Thank you in advance!
--
Warm regards,
Jordan Michaels
Vivio Technologies
http://www.viviotech.net/
Open BlueDragon Steering Committee
Railo Community Distributions
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