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Hi list,
I've a strange behaviour on a cluster of lighttpd which I can't explain.
Here are the facts:
Xeon CPUs (2x Quad Core)
Gentoo Linux
Kernel 2.6.27.7
Glibc 2.6.1
Lighttpd 1.4.20
Cluster using LVS-DR
What happens:
Lighttpd simply doesn't accept connections. In the tcpdump on the realserver I
can see the SYN packets arrive but the connection isn't accepted on the server
socket. There's no SYN-ACK travelling out, neither a RST or something else.
After 3 SYN retries, the browser shows a timeout error.
The strange thing is: If I try to connect again after the timeout, the
connection is established and further connects work as well! At least most of
the time - sometimes it starts working not until the 2nd or 3rd timeout/reload.
After some moments without new connections, lighty again refrains from
accepting new connections...
I have a huge installation of Apache webservers working well with the very same
LVM-DR setup. The only notable difference between these two server types is
that Apache uses traditional blocking I/O with forking processes and lighttpd
uses non-blocking I/O with select()/epoll based multiplexing.
While doing some investigation on this issue, I found a very similar problem
reported on this list, titled "problems with ipvsadm - 3 seconds delay", dated
from February 2008
(http://lists.graemef.net/pipermail/lvs-users/2008-February/020541.html). I
think it describes the very same problem, especially with the problems
occurring on Quad Core Xeons, which makes me think about a timing problem or
race condition in kernel or glibc.
Any ideas 'round here which may help me to track this issue down?
Regards,
Jan
--
Psssst! Schon vom neuen GMX MultiMessenger gehört? Der kann`s mit allen:
http://www.gmx.net/de/go/multimessenger
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