Mailing List Archive: Linux Virtual Server: Users

[lvs-users] LVS Logging?

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michaeln at u

Apr 25, 2009, 5:16 AM

Post #1 of 5 (849 views)
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[lvs-users] LVS Logging?

So, I'm in the process of testing LVS as a replacement to our current
hardware load balancer. For now, I'm implementing this for POP/IMAP.
I've run into a couple problems:

1) If I leave the virtual alone for a while and come back and try to
make a connection, the connection times out. If I keep trying, then
eventually a connection will be made and connections will be made
successfully from that point forward. If no further connections are
made to the virtual for a while (maybe 30-60 minutes?) then it happens
again. Does anyone have any idea what might be going on here? The real
servers are fine because they're the exact same servers that are being
load balanced through the hardware load balancer. A tcpdump from the
virtual shows the request coming in but no return packets.

2) Which brings me to my second problem... Where are the logs for
LVS? I felt that the documentation suggested that I should check
local0, but that log is completely silent unless I myself send a syslog
message to local0.

Lastly, I'm trying to get this all going without HA/ldirectord first so
this is just straight LVS. Any pointers would be great.

Michael

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jmack at wm7d

Apr 25, 2009, 9:18 AM

Post #2 of 5 (784 views)
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Re: [lvs-users] LVS Logging? [In reply to]

On Sat, 25 Apr 2009, Michael Nguyen wrote:

> 1) If I leave the virtual alone for a while and come back
> and try to make a connection, the connection times out.
> If I keep trying, then eventually a connection will be
> made and connections will be made successfully from that
> point forward.

what does `ipsvadm` show when it's hung.

> If no further connections are made to the virtual for a
> while (maybe 30-60 minutes?) then it happens again.

have you handled the tcpip timeouts? People fall over these
all the time and I can't see any good reason for them.
(Graeme did come up with a valid counter example, but I've
forgotten what it was.) Horms has said that he'd extend the
timeouts to some really long time, but I don't know if this
has been done.

> 2) Which brings me to my second problem... Where are the
> logs for LVS?

lvs is kernel code. You don't really want it logging.
However you can turn on debugging and that will give you
more info than ever you'd want.

Joe
--
Joseph Mack NA3T EME(B,D), FM05lw North Carolina
jmack (at) wm7d (dot) net - azimuthal equidistant map
generator at http://www.wm7d.net/azproj.shtml
Homepage http://www.austintek.com/ It's GNU/Linux!

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michaeln at u

Apr 25, 2009, 4:03 PM

Post #3 of 5 (792 views)
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Re: [lvs-users] LVS Logging? [In reply to]

Joseph Mack NA3T wrote:
> On Sat, 25 Apr 2009, Michael Nguyen wrote:
>
>
>> 1) If I leave the virtual alone for a while and come back
>> and try to make a connection, the connection times out.
>> If I keep trying, then eventually a connection will be
>> made and connections will be made successfully from that
>> point forward.
>>
>
> what does `ipsvadm` show when it's hung.
>
It shows this:

TCP pop.sandycat.com:pop3 wlc
-> web05.sandycat.com:pop3 Tunnel 100 0 1
-> web04.sandycat.com:pop3 Tunnel 100 0 0
-> web03.sandycat.com:pop3 Tunnel 100 0 0
-> web02.sandycat.com:pop3 Tunnel 100 0 0
-> web01.sandycat.com:pop3 Tunnel 100 0 0

Which looks pretty normal to me. Again, if I keep hammering on it, this
doesn't *seem* to happen but my concern is that I don't understand the
problem (big surprise!) and that that's not the situation at all.

>> If no further connections are made to the virtual for a
>> while (maybe 30-60 minutes?) then it happens again.
>>
>
> have you handled the tcpip timeouts? People fall over these
> all the time and I can't see any good reason for them.
> (Graeme did come up with a valid counter example, but I've
> forgotten what it was.) Horms has said that he'd extend the
> timeouts to some really long time, but I don't know if this
> has been done.
>
Hmm...I don't think so. Did I miss something in the HOW-TO? Can
elaborate or provide a link?
>> 2) Which brings me to my second problem... Where are the
>> logs for LVS?
>>
>
> lvs is kernel code. You don't really want it logging.
> However you can turn on debugging and that will give you
> more info than ever you'd want.
Fair enough, but I'm just so used to looking at logs to troubleshoot
problems. I can go without.

Michael

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Please read the documentation before posting - it's available at:
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jmack at wm7d

Apr 25, 2009, 5:24 PM

Post #4 of 5 (775 views)
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Re: [lvs-users] LVS Logging? [In reply to]

On Sat, 25 Apr 2009, Michael Nguyen wrote:

>> have you handled the tcpip timeouts?

> Hmm...I don't think so. Did I miss something in the HOW-TO? Can
> elaborate or provide a link?

go to the HOWTO,
hit the link to search the LVS documentation
enter "tcpip timeouts"
go to the first match
search for the first hit for "timeouts"

Joe

--
Joseph Mack NA3T EME(B,D), FM05lw North Carolina
jmack (at) wm7d (dot) net - azimuthal equidistant map
generator at http://www.wm7d.net/azproj.shtml
Homepage http://www.austintek.com/ It's GNU/Linux!

_______________________________________________
Please read the documentation before posting - it's available at:
http://www.linuxvirtualserver.org/

LinuxVirtualServer.org mailing list - lvs-users [at] LinuxVirtualServer
Send requests to lvs-users-request [at] LinuxVirtualServer
or go to http://lists.graemef.net/mailman/listinfo/lvs-users

graeme at graemef

Apr 27, 2009, 1:35 AM

Post #5 of 5 (769 views)
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Re: [lvs-users] LVS Logging? [In reply to]

On Sat, 2009-04-25 at 16:03 -0700, Michael Nguyen wrote:
> Fair enough, but I'm just so used to looking at logs to troubleshoot
> problems. I can go without.

I guess the followup question is:

What would you expect the ip_vs code to log?

Please remember that (in the scenario you're using) it's a pretty "dumb"
system - you set it up, and it routes traffic as you asked it to.
There's nothing more to it than that - it's totally unaware of the
sources, the targets, the VIPs, the RIPs and so on as it's simply doing
as it's told.

If you want something more complex, you probably need one of the
management and monitoring applications in front of it.

As there's no real explanation of your tunnel topology, have you read
this:
http://www.austintek.com/LVS/LVS-HOWTO/HOWTO/LVS-HOWTO.LVS-Tun.html#arp_problem_lvs-tun ??

It sounds to me very much like an ARP problem with your realservers,
possibly compounded by netfilter rules preventing traffic arriving on
"real" interfaces (as opposed to tun devices).

Graeme

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