On 10/6/2017 5:15 AM, André Warnier (tomcat) wrote:
On 06.10.2017 11:57, Suvendu Sekhar Mondal wrote:
On Fri, Oct 6, 2017 at 2:06 AM, Jerry Malcolm
<techst...@malcolms.com> wrote:
I am running TC 8.0 on WinServer8 on a commercially hosted platform
with a
WAMP environment. I am running around 10 virtual hosts. 2 hosts are
dedicated to JSPWiki. The other 8 are running variations of the
same custom
application with around 10-15 individual webapps each.
When I am running 7 of the 10 hosts, performance is great. I get JSP
response time under a second. But when I add just a couple of more
of the
hosts, my page response time on all of the apps goes from an acceptable
under a second to horrible at around 15-20 seconds per page. It doesn't
seem to be a specific host causing the problem. Reducing overall
hosts in
any order makes the problem go away.
I've looked at the the processor utilization during the good times
and slow
times, and don't see a significant difference. I have 16GB of
memory, and
it consistently shows about 35% utilization. I also checked mySQL
response
time, and the per-query SQL response does not vary. So it doesn't
appear to
be a db problem.
I suspect there is some TC configuration parameter such as heap, etc
that I
need to tweak. (But I'm not getting OutOfMemory errors). But I
don't know
which one, and I don't know a formula to use to figure out what to
set it
to. So I just need a little education. What tools can I use to
help me
figure out what is going south slowing everything to a crawl when
the extra
hosts come online? And what parameters should I be looking at (and how
should I calculate the proper values based on number of hosts)?
Suggestions?
Interesting problem. Couple of questions:
Is the slowness sporadic or persistent? What happens when you again
shutdown some of the hosts? Does response time comes back to normal?
Is all transactions are slow or some of them which are routed to
specific host(s)?
Are you fronting Tomcat instances with Apache? If yes, then please
post BalancerMember configuration of the Tomcat cluster here.
Taking the OP's observations above at face value, I think that first
thing that I would do, is to configure the Java JVM that runs this
tomcat, to do some logging of the Garbage Collection events. And then
I would look at that logfile, and find out if there is some
significant difference (in frequency of GC, or in the mounts of memory
mentioned for each event), depending on the number of Hosts enabled.
You would have to look at the appropriate command-line switches to use
for the particular JVM being used, for how to set this up.
And then (since this seems to be on a Windows platform, running tomcat
as a service), you should use the "tomcat(version)w.exe" program (a
GUI), to set these parameters properly.
See e.g.
https://tomcat.apache.org/tomcat-8.5-doc/windows-service-howto.html#Tomcat_service_application
--> "Tomcat monitor application"
Thanks for the responses. Answers to several questions in responses:
1) The 16GB is physical OS memory, not JVM memory
2) Re: 'balancermember config'.... I am running one instance of Apache
with mod_jk to one one instance of Tomcat containing all of the 10
virtual hosts. I'm not familiar with 'balancermember'. But it sounds
like something to do with a cluster config. If it still applies to my
config, let me know where I can learn more about it.
3) I'll look into turning on garbage collection logging
4) The problem is constant when I have 'too many' hosts. And the
problem is pervasive to all running hosts. I've found the magic number
is 7 hosts. 7 hosts and life is good. 8+ hosts and everything clogs
up big-time.
I failed to mention that none of these host sites are anywhere close to
'high-volume'. When a user hits the site, there will be flurry of page
activity for a few minutes. But I'd say each of the sites averages one
or two user hits per hour on average. So bringing sites 8, 9, and 10
online is not bringing massive additional tomcat/mySQL/network
activity. It's basically bringing 3 more 'effectively dormant' web
sites online. This seems to me that it's got to have something to with
the size of the basic inactive footprint of each host.
Jerry
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