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From Sander Smeenk <ssmeenk+apache...@freshdot.net>
Subject [users@httpd] Apache 1.3.x as loadbalancer
Date Mon, 26 Apr 2004 19:51:42 GMT
Hello everyone,

I'm curious as to what performance one might expect from an AMD Athlon
1GHz server functioning as a loadbalancer with RewriteMaps, RewriteRules
and the proxymodule. The rewritemap currently uses a perl script that
doesn't do much more than a lookup in memory and printing out a new url.

My loadbalancer in this configuration is averaging at 166 requests a
second when tested with "ab -n 15000 -c 100". I'm curious to know if
this is a normal value for such a server. Especially since the apache
instances on the server cause it to peak to loads of about 8.

All servers involved, the client, the balancer and the balanced servers
are connected on the same 100mbit swith in the same network, and the
'balanced servers' that actually serve the content are of more than
sufficient processing power to serve the requests. All servers run
Apache 1.3.29.

Some questions arise, like:
Would there be a lot of speed-change in wether the RewriteMap program is
written in C instead of perl? I'd expect it not to, because 'perl' only
needs to be started once, and then the processing is such little work
that i'd expect it to be as fast as something in C.

How comparable is the result of ab (166 reqs/sec) to heavy traffic that
normal users would generate. I mean, how comparable is requesting the
same 52kb file 15000 times to requesting various files of various sizes,
with various delays in getting the actual content?

My loadbalancer has the following limit-configuration:

| KeepAlive            on
| MaxKeepAliveRequests 100
| KeepAliveTimeout     15
| MinSpareServers      30
| MaxSpareServers      200
| StartServers         200
| MaxClients           512
| MaxRequestsPerChild  10000
| Port                 80
| IdentityCheck        off
| HostnameLookups      off

Of 15000 requests with 100 concurrent connections, about 200 to 300
requests fail with returncodes of 500 and 302. The loadbalancing server
seems to return these codes, since I can't find them on the serving
servers.

Since I can't see the content, what could I get redirected to?
And are the 500 errors a sign of server-overload?

I just hope that this solution will work out for me, but I am having
trouble interpreting the results I am getting.

Thanks for any help.

Sander.
-- 
| You dig around for a while but you fail to find any treasure.
| 1024D/08CEC94D - 34B3 3314 B146 E13C 70C8  9BDB D463 7E41 08CE C94D

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