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From André Warnier>
Subject Re: Tomcat 6 - slow response times outside of data center
Date Mon, 29 Mar 2010 16:54:06 GMT

Just a very preliminary guess : could it be that different DNS lookups 
are involved in the delays ? Obviously, "localhost" and IP addresses 
don't need them, but maybe some of the connections between Tomcat(s) and 
database server(s) are specified by name instead of IP, and/or use 
different DNS servers, or in a different order ?

Ian Hubbard wrote:
> Hi all,
> I've got Tomcat 6 running on a few separate internal dedicated test
> machines in a data center, each with their own separate dedicated SQL
> servers.
> The servers themselves don't bat an eye for the tiny load i'm subjecting
> them to.  For testing (using IE 6 or 7) I've been performing the same
> action, loading a simple page that uses simple queries (packet captures
> indicate that total data transferred is in the 200KB range, start to
> finish), with the following results:
> - on the webservers themselves, going to localhost:8754, pages take less
> than 1 second, all told
> - from another server in the same subnet, to tomcat via IP address to 8754,
> 1-2 far, what's generally seen as normal in other environments
> - from a system outside the data center (but still internal, using VPN over
> dual T1's), again by IP, pages will load in ~17 seconds consistently using
> two of the servers in separate subnets, and 12 seconds consistently from a
> third (each server stands alone in its respective environment, hiding in
> its own little VLAN)
> The servers are configured similarly, as are the networks they live in.  For
> a similar setup to other data centers more geographically distant, I can
> usually expect to see loading times of 3-5 seconds, as opposed to the 12/17
> seconds being seen in these cases.  If they were _all_ consistently 17
> seconds, I'd be more inclined to point my finger firmly at the
> network...that one server that's equivalent for all intents and purposes
> completes the same task in 12, though, is a little strange.
> The network config side of things is beyond my direct control.  There are
> likely things there that can be fine-tuned by request, if I can figure out
> what recommendation to make, and have evidence to support the
> recommendation.
> At this point, I'm particularly interested in whether there's anything
> within my control to improve things.  The tomcat conf settings are fairly
> vanilla -- are there any common things I should look at disabling or
> changing which may improve things?  (Such as settings that could result in
> lookups  and so on, which could slow things down notably even if they aren't
> immediately apparent, given that the servers aren't under any notable load,
> and so on.)
> I'll happily post settings that may be of interest...I haven't done so just
> yet, since I don't want to inundate you with irrelevant info.
> Thank you for taking the time to throw any ideas you may have my way!
> Cheers,
> Ian

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