JNeuhoff wrote:
Yesterday, I indeed upgraded another server box to Apache 2.0.59, mod_jk
1.2.20, Tomcat 5.5.17, and also set the connection_pool_timeout=600 (is that
value 600 seconds, or milliseconds?). I then subjected this server to a
brief stresstest (roughly 50 simultanious HTTP sessions on Tomcat's end) and
noticed the following:
Good, the value is in seconds, and the info has been added to the docs
for 1.2.21 a few days ago and to the online docs also :) Most other
timeouts are milliseconds though, but for the other ones the correct
info is already in the docs.
Of the two 'Apache.exe' processes running under the Apache2 NT service, one
grew in memory usage quickly from an initial 12MB to nearly 65MB, and stayed
at that level overnight, even though there were no further requests made to
that server since yesterday. I also noticed that a simple 'netstat -a'
reported 35 established connections:
<<
TCP DAOHPRW2:1682 DAOHPRW2.essex.ac.uk:8009 ESTABLISHED
TCP DAOHPRW2:4240 DAOHPRW2.essex.ac.uk:8009 ESTABLISHED
TCP DAOHPRW2:4241 DAOHPRW2.essex.ac.uk:8009 ESTABLISHED
.....
and another 35 established connection the opposite direction:
<<
TCP DAOHPRW2:8009 DAOHPRW2.essex.ac.uk:1682 ESTABLISHED
TCP DAOHPRW2:8009 DAOHPRW2.essex.ac.uk:4240 ESTABLISHED
TCP DAOHPRW2:8009 DAOHPRW2.essex.ac.uk:4241 ESTABLISHED
....
So, are the connections managed by mod_jk between Apache2 and Tomcat not
released from the connection pool, despite the connection_pool_timeout=600?
By default apache will use as max number of connections the same value,
as the max number of threads, so that each thread can get it's own
connection. By default it will shrink the connection pool down to half
of the max size. There is a min value you can configure if this doesn't
fit your needs.
Ideally I'd like to set an upper limit of lets say 200 concurrent HTTP
Sessions for Tomcat, but I am not sure how exactly to configure the various
timeout values and limits for mod_jk and Apache accordingly. Our Tomcat
service makes MySQL queries and it can take at times a few seconds for
generating a response. Does Apache2 use just one child process handling all
requests or connections?
Yes, the Windows MPM has one observer process and a second one, that
handles all the requests. If you are really low on server ressources,
you can shrink you connection pool from 250 (equals number of threads
you configured) to 200 and set the minimum to something like 10. You
should also consider a connect_timeout (e.g. 15000) and a
prepost_timeout (e.g. 10000).
Let us know, if your crashes/hangs still show up with the new setup.
Regards,
Rainer
J.Neuhoff
P.S.
At the moment our server is configured like that:
httpd.conf:
<<
....
Timeout 300
KeepAlive On
MaxKeepAliveRequests 100
KeepAliveTimeout 15
# WinNT MPM
# ThreadsPerChild: constant number of worker threads in the server process
# MaxRequestsPerChild: maximum number of requests a server process serves
<IfModule mpm_winnt.c>
ThreadsPerChild 250
MaxRequestsPerChild 0
</IfModule>
....
### mod_jk 1.x configuration for connecting to Tomcat 5.5
LoadModule jk_module modules/mod_jk.so
JkWorkersFile "C:/Program Files/Apache Software Foundation/Tomcat
5.5/conf/workers.properties"
JkLogFile "C:/Program Files/Apache Software Foundation/Tomcat
5.5/logs/mod_jk.log"
JkLogLevel info
JkLogStampFormat "[%a %b %d %H:%M:%S %Y] "
JkOptions +ForwardKeySize +ForwardURICompat -ForwardDirectories
JkRequestLogFormat "%w %V %T %r %s"
JkMount /jsp-examples/* ajp13
JkMount /servletsp-examples/* ajp13
JkMount /manager/* ajp13
JkMount /ohpr/* ajp13
JkMount /demo-b/* ajp13
....
workers.properties:
<<
# Define 1 real worker using ajp13
worker.list=ajp13
# Set properties for worker1 (ajp13)
worker.ajp13.type=ajp13
worker.ajp13.host=localhost
worker.ajp13.port=8009
worker.ajp13.connection_pool_timeout=600
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