Am 27.04.2017 um 22:21 schrieb Mark Thomas:
On 27/04/17 20:08, John Cartwright - NOAA Federal wrote:
Thanks for your reply Mark! My sysadmin tells me just that we're
using "the defaults" for event_mpm. However we are still using the
BIO AJP connector:
<Connector port="8009" protocol="AJP/1.3" redirectPort="8443"
maxThreads="300" minSpareThreads="25"
maxSpareThreads="75" connectionTimeout="20000"/>
Is there a way I can tell from the Tomcat side when there is thread starvation?
You'd need to look at the number of active connections. If it gets to
300 then you likely have a problem.
netstat might be the least invasive way of doing that. Other options
include the Manager app, JMX and thread dumps.
Switching to NIO will allow you to server more connections with the same
number of threads.
I assume you are using the latest mod_jk version?
The current version of mod_jk also counts the total connection number
(sum of connections from all Apache child processes to your Tomcat) and
makes it available via the status worker for monitoring. The counting
was a bit buggy in older versions, but should be correct in the latest one.
Event MPM and mod_jk: the relevant phase in Apache is the handler phase,
where the actual request forwarding is done by mod_jk. Things do not
really need to change in the handler phase for proxying modules with
event MPM. mod_jk does not need to know about the MPM or behave
specific, the forwarding runs synchronously. By default mod_jk uses as
many connections per Apache process as you have worker threads per
Apache process configured. On the Tomcat side with BIO you need as many
threads for the AJP connector as all you Apache fronting that Tomcat
might have threads in total. Using the NIO connector on the Tomcat side
is indeed better than BIO especially when you expect lots of concurrency
(many Apache threads configured). Make sure you also use a recent Tomcat
patch level then.
What messages did you get in your mod_jk error log?
For the mod_jk config, a good starter is the config files we bundle with
the source download of mod_jk. You can also find them under
http://svn.apache.org/viewvc/tomcat/jk/trunk/conf/
These files set timeouts etc.
Regards,
Rainer
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