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G'mornin.
Well, I found one. But it is not an LVS bug. Instead I think this
happens on purpose (at least in my case).
So let's just say we have a simple setup:
client -> switch -> director -> switch -> realserver
The client establishes a connection, sends some data, whatever. Then it
does nothing for say 10 minutes. After that it tries to reuse the still
established connection and it works just fine.
Then it does nothing for say 16 minutes and tries again to use the still
established connection. In the meantime, the default timeout for the
connection table (default 15 minutes) runs out and so this connection is
not valid on the director. So the director replies with RST on the PSH
packet from the client and the connection breaks for the client.
The realserver does not know anything about the reset on the director,
so it still considers the connection established.
That's pretty much it. The client can simply open a new connection, but
the old one will still be considered established on the realserver.
That's what made my MySQL server hit the max_connection limit and reject
any new clients.
I will try to set the timeout higher, as it can easily happen that my
clients do nothing for a few hours at night, which will - sooner or
later - hit the max_connection limit again.
One could also think about tweaking tcp settings on the realserver. But
I am not too familiar with that - yet (still learning :) ).
Hope that helps.
Regards
Dominik
Joseph Mack NA3T schrieb:
On Fri, 12 May 2006, Dominik Klein wrote:
I do not use persistence or FTP. Simple NAT setup with as realserver
MySQL.
The client sends a PSH packet which is immediately RST by the
director. So the realserver still "thinks" the connection is
ESTABLISHED. Therefore the max_connection_limit in MySQL is hit within
a few hours so that no new clients can connect.
can you tell us what to do to reproduce this?
So can anyone confirm that 2.6.15 fixes this problem?
I don't think it has been fixed, so this is unlikely.
Here's a link to the thread I am referring to:
http://archive.linuxvirtualserver.org/html/lvs-users/2005-12/msg00213.html
this is a long outstanding bug. The problem is that noone has figured
out a way of reproducing the problem on demand to fix it.
Joe
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