Re: Our LVS/DR backends freezes

To: Olle Ö?stlund <olle@xxxxxxxxxxx>
Subject: Re: Our LVS/DR backends freezes
Cc: " users mailing list." <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
From: Joseph Mack NA3T <jmack@xxxxxxxx>
Date: Wed, 29 Nov 2006 08:21:50 -0800 (PST)
On Wed, 29 Nov 2006, Olle ~Vstlund wrote:

I'm afraid focus has shifted to the ipvs connection-table. As far as I
know it's not causing us any real trouble. Merely showing very rough
figures. Unless it related to our hanging realservers?

It's not related.

It has something to do with LVS though - the problem doesn't occur when the servers run as standalone machines.

If I have understood things correctly, the director's figures for
connections in FIN_WAIT or CLOSE does not correspond to real connections
at the realserver (I have not been able to see them using netstat as far
as I know). Thus, it is not a figure of the connections consumed at the


If all this is true, I see no relation between the odd
figures in the directors connection-table and the hanging realservers

well possibly/possibly not. We don't understand the problem, so we don't know if the director's connection table is a clue or irrelevant.

On the other hand, if the FIN_WAIT/CLOSE connections in the directors
connection table does exist in some form at the relaserver and consume
resources in the realserver's kernel, I guess it could cause a hanging
realserver when all the resources have ben consumed. If this is
possible, it would explain our problems.

well possibly. I would expect you'd be able to have 64,000 open connections (I don't know what the limit is but it must have at least a 16 bit counter). If you hit some standard resource limit, I'd expect you'd see messages in the logs and the machine should just keep working but not accept more connections.

Tonight I will reboot one of our realservers. This would reset the
leaking resources of that server, while the other server has been
leaking for days and will keep on leaking. If the next freeze will hit
just one server (the one which was not rebooted), it is a confirmation
of our "leaking resources" theory. If both freezes, I'm out of


Finally, I'm very impressed by the way you read and answers postings to
this list. By far the best list I've participated in. Keep up the good


Our response goes up and down, depending on the number of people around and how busy they are.


Joseph Mack NA3T EME(B,D), FM05lw North Carolina
jmack (at) wm7d (dot) net - azimuthal equidistant map
generator at
Homepage It's GNU/Linux!

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