Subject: [lvs-users] Generic UPD "connect" check feature for ldirectord?

From: Christian Balzer <[email-masked]>
Date: Wed, 18 Mar 2009 13:01:34 +0900

Hello,

I'm in exactly the same situation as the fellow here:
http://archive.linuxvirtualserver.org/html/lvs-users/2008-06/msg00042.html

Noting the lack of replies or a native rad-acct check option for
ldirectord I was wondering why not adding a UDP "connect" service check to
it? I know it's not as straightforward or reliable as TCP, but in most
environments it should give much more useful results than "none" or "ping".
Netcat seems to have no problem figuring out if something is listening on
an UDP port:
---
auth01:/etc/heartbeat# nc -v -u -z 10.0.0.2 1813
10.0.0.2: inverse host lookup failed: Unknown host
(UNKNOWN) [10.0.0.2] 1813 (radius-acct) open
auth01:/etc/heartbeat# nc -v -u -z 10.0.0.2 1814
10.0.0.2: inverse host lookup failed: Unknown host
(UNKNOWN) [10.0.0.2] 1814 (?) open
auth01:/etc/heartbeat# nc -v -u -z 10.0.0.2 1815
10.0.0.2: inverse host lookup failed: Unknown host
(UNKNOWN) [10.0.0.2] 1815 (?) : Connection refused
---

It would be really nice to see this in a future version so that any UDP
service can be somewhat monitored. 
While hacking this into the installed ldirectord seems easy enough the
likelihood of it being overwritten by a security update during the
lifetime of these servers is just too high.

So for the here and now, I guess the external "misc_check" of keepalived
might be better suited?

Regards,

Christian
-- 
Christian Balzer        Network/Systems Engineer                NOC
[email-masked]   	Global OnLine Japan/Fusion Network Services
http://www.gol.com/
https://secure3.gol.com/mod-pl/ols/index.cgi/?intr_id=F-2ECXvzcr6656

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---

From: Sebastian Vieira <[email-masked]>
Date: Wed, 18 Mar 2009 09:05:29 +0100

HI,

> Netcat seems to have no problem figuring out if something is listening on

I know this is not exactly what you're asking for, but why not try the new
external check feature?

S.

---

From: Christian Balzer <[email-masked]>
Date: Wed, 18 Mar 2009 18:13:40 +0900

Hello,

On Wed, 18 Mar 2009 09:05:29 +0100 Sebastian Vieira wrote:
> > ldirectord I was wondering why not adding a UDP "connect" service
> > check to it? I know it's not as straightforward or reliable as TCP,
> > but in most environments it should give much more useful results than
> > "none" or "ping". Netcat seems to have no problem figuring out if
> > something is listening on an UDP port:
> 
> 
> I know this is not exactly what you're asking for, but why not try the
> new external check feature?
> 
New... feature....
ARGH, I was looking at an old (Debian etch) manpage.
The new boxes running lenny indeed have a ldirectord with that feature
listed. Now that should make it really easy and without the need to fondle
stuff that is not under my control.

Thanks a lot for bringing this up!

Regards,

Christian