Hey there,
On Fri, 8 Jun 2001, David Rees wrote:
> > I've been using these settings:
> >
> > SetEnvIf User-Agent "MSIE [1-4]" nokeepalive
> > ssl-unclean-shutdown downgrade-1.0 force-response-1.0
> > SetEnvIf User-Agent "MSIE [5-9]" ssl-unclean-shutdown
> >
> > and it seems to do the trick (keeping the fingers crossed....)
> >
> > The difference for my app is dramatic!
> >
> > My typical scenario is a fat pipe with a long roundtrip. You
> > wouldn't believe
> > how much of an impact keepalive makes!
>
> Cool, I'll give these settings a shot on my development machines and let the
> list know if there's any problems.
It probably goes without saying - but using "KeepAlives on" has some pretty evil
consequences because of Apache's process model. As long as the connection is
kept alive between browser and server, the "httpd" process that owns it is
*dedicated* to that connection, even if nothing is happening with it, and thus
can't serve anything else. If you start to make a mental picture of loads of
browsers holding loads of keepalive connections open for say 30 seconds each,
you'll start to realise where this can come unstuck.
There's also the other angle too: any old x86 with a tcp/ip stack and a modem
can open a few (hundred) connections to your server and keep reconnecting
whenever they're disconnected, the result can be quite annoying. This is the
same reason that the "Timeout" should be kept as low as acceptable, otherwise
the same old x86 can trickle bytes through 1-by-1 to prevent getting timed out,
and tie up a number of your server processes for as long as they see fit.
(If there's Apache developers listening, this is also why threading in 2.0 won't
solve the problems of 1.3, it'll just scale them back a bit - threads aren't
free, they're just a small linear factor cheaper than processes - please support
non-blocking I/O too, please!).
Cheers,
Geoff
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