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From Remy Maucherat <remy.mauche...@gmail.com>
Subject Re: Tomcat in a High Traffic Environment
Date Sat, 30 Oct 2004 08:10:15 GMT
On Fri, 29 Oct 2004 16:39:36 -0700 (PDT), David Rees
<drees@greenhydrant.com> wrote:
> Mladen Turk wrote:
> >
> > Yes, but the keepalive is used mainly for making the 'state' out of
> > 'stateless' protocol, and it's main advantage is that you don't need
> > to acquire a new connection all the time. Take a look at RFC2068.
> > Even apache keeps the thread open on keepalive connections (Of course
> > you have a KeepAliveTimeout).
> >
> > Without keepalive your cluster will perhaps work better in the lab,
> > but it will fail in the real-user scenario.
> 
> This is false.  Your cluster will not break in a real-user scenario
> without Keep-Alive turned on.  There are many HTTP servers out there which
> default to Keep-Alive turned off.
> 
> Keep-Alive is not used for keeping "state" of a stateless protocol.  Pure
> and simple, it is used to improve client-side performance when requesting
> multiple resources in a short timespan by reducing the number of TCP/IP
> connection starts and stops.  This is mostly noticable if your website
> design requires the user to download a large number of small resources to
> view a page.
> 
> It is very common to turn off Keep-Alive or significantly reduce it's
> timeout when attempting to scale to a large number of users without
> keeping a large number of usable connections idle.  You can easily double
> the number of concurrent users handled by a server by turning off
> Keep-Alive.  The only drawback is that if your pages have a large number
> of resources to retrieve per page and your users have a high-latency
> connection to the server.

In the setup where images are served by something else, and Tomcat
only handle the (much more complex) dynamic requests, then disabling
keeapalive makes sense.

-- 
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Rémy Maucherat
Developer & Consultant
JBoss Group (Europe) SàRL
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