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From André Warnier (tomcat)>
Subject Re: Performance settings for Multiple Hosts
Date Fri, 06 Oct 2017 10:15:51 GMT
On 06.10.2017 11:57, Suvendu Sekhar Mondal wrote:
> On Fri, Oct 6, 2017 at 2:06 AM, Jerry Malcolm <> 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.

--> "Tomcat monitor application"

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