[hobbit] Agentless clients

Henrik Stoerner henrik at hswn.dk
Thu Jan 5 18:31:46 CET 2006

On Thu, Jan 05, 2006 at 07:02:52PM +0200, Buchan Milne wrote:
> On Thursday 05 January 2006 18:21, Charles Jones wrote:
> > *real    0m1.912s*
> > user    0m0.022s
> > sys     0m0.008s
> >
> > Almost 2 seconds there....and just for one command. 
> I keep wondering how long the equivalent snmp query takes ... or in fact 
> gathering all the data asynchronously via snmp ...

Let's see ... Net-SNMP includes an "snmpdf" command:

$ time snmpdf -v 1 -c somepassword somehost
Description        size (kB)         Used       Available Used%
/                    5969124       754896         5214228   12%

real    0m0.201s
user    0m0.154s
sys     0m0.019s

$ time ssh somehost df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/hda1              5969124    754896   4911004  14% /

real    0m0.535s
user    0m0.011s
sys     0m0.004s

So: 0.2 seconds for snmp, 0.5 seconds for ssh. (No, I don't know why
they calculate the available disk size differently - df probably 
leaves out the 5% filesystem space that is reserved for "root" use).

SNMP probably wins because it is UDP based, so you avoid a lot of
overhead from the TCP connection setup. Plus the SNMP daemon is running,
so it doesn't need to start a new process to respond.

But I do agree with Charles - using a "bbfetch" style method of pulling
data from clients to the server only works for a small number of hosts.
On the scale that I work with on a daily basis - 2000 hosts or more -
it is simply not practical to contact all hosts every 5 minutes.

I'm still willing to implement the agent-less data collection in Hobbit,
because sometimes that is just going to be the only way you can get
information about a server. So it is an OK way of doing this, if you
know what it should - and should not - be used for.

(BTW, the issue that was raised about updates being easier if you don't
have to deploy them on all clients - that's a non-issue. It boils down
to whether or not you have an (automated) procedure for software and
patch distribution - if you don't have that, then you're in trouble no 
matter how Hobbit collects data.)


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