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From Jan Abraham <>
Subject [users@httpd] Apache cluster freezes from time to time
Date Wed, 29 Oct 2003 15:06:09 GMT
Hi there,

i have a urgent problem here:

We've a well visited site (about 100 GB per day), PHP based with an
mySQL database. Because a single server was unable to handle the load,
I've installed a cluster (4 Linux based webservers) with loadbalancing
(LVS) and own database server. It went to public use some days ago.

Unfortunately, the web servers are freezing for some seconds from time
to time. The phenomenon occurs in unregular intervals (1-5 minutes)
indepentently on each server.

During these freezes, I can still type commands into the shell, but they
get not executed until the freeze is over. Afterwards, the load
increases rapidly, and some apache threads seem to die.

This makes me believe that something is wrong with my Apache and/or PHP.
Of course, I won't rule out a problem with the kernel, or the
loadbalancer (but my LVS works on ethernet frame level, so I can't
imagine how it may impact the web server)

What I do rule out are both hardware failure and external attacks.

Systems are running on Debian 3.0r1 woody, updated to "testing". I've
tried some combinations of Apache and PHP:
Apache 1.3.28-4 pkg from testing, 
Apache 1.3.28-4 from Debian sources
PHP 4.3.3 pkg from unstable
PHP 4.3.3 pkg from
PHP 4.3.3 from debian sources
Kernel 2.4.20-2-686 from proposed-updates
Kernel 2.4.20 from debian sources

Of course, next things to do are to build Apache and PHP from the
"vanilla" sources. But since I've to interrupt my sites service for
updating, I'll try to gather some information at first. 

Has someone had similar pheonomenons? Or some ideas or hints?

Thank you in advance,

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