John Minchuk minchuk.j...@gmail.com wrote:
Quick overview of our setup. Http request
flow from our load
balancers, to
squid proxys, to Apaches, to our Tomcat servers. We migrated to this
setup
from an Oracle App Server.
Apache: 2.2.3
Tomcat: 7.0.11.0
JVM: 1.6.0_22-b04
Linux: 2.6.18-194.17.1.el5
Our production environment has max threads set at 200, the number of
threads usually hovers around 150. About twice a day, at seemingly
unrelated times we get a sudden spike in the number of ajp threads
open.
Eventually this hits our max of 200. At this point Tomcat still seems
responsive, but the number of our httpd processes spikes until Apache
locks
ups. At this point we have monitoring software that kills and restarts
Apache. We then manually restart Tomcat.
Here is a graph of the AJP Threads running. You can see a sudden jump
to
200 threads. The other dips are most likely reloads triggered by our
configuration management software (puppet).
http://sporkit.com/thread_spike/spike.jpg
Also interesting to note, these threads (all 200) appear to be in the
keep
alive state.
http://sporkit.com/thread_spike/threads.jpg
Our access logs don't indicate a high number of visits, or any one
particular page that might cause this issue (that I can see).
At this point we are stumped. Do we spend our time tracking down
memory
leaks? Is there something we could do to at least mitigate the problem
over the holidays? Any input greatly appreciated.
Without any configuration information it is impossible to be sure what the
problem is.
My best guess is that httpd is configured to use persistent connections to
Tomcat and Tomcat is using the BIO AJP connector. When connections ==
maxThreads everthing locks up. A thread dump on Tomcat will confirm this is
what is happening.
If this is the case, possible solutions are (in my order of preference)
- disable connection reuse in https.conf (ignore the warnings about performance
issues in the docs: the risks are overstated)
- switch to APR/native AJP in Tomcat
- switch to NIO AJP (requires Tomcat upgrade)
You also need to consider some upgrades. The versions you are running are
rather old.
Mark
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