"Agentless" monitoring with Nagios?

[Eli Stair]

Bringing up SNMP is a valid point (I'm currently handling ~25% of my active
service checks this way).  However there are a number of scenarios where the
load on both the server/network/client is significantly greater to pull down
a tree that needs processing (process table for instance), as the impact on
the client is fairly large to process its own /proc entries to generate the
values, pull them down sequentially, and parse the tree on the server.  Same
deal with a variety of network tables... Even Cisco/Foundry/etc do a
horrible job of having their devices process & generate ARP tables, etc.

Even executing a remote command over SSH with the crypto overhead is faster
in most situations (for me), and actually consumes less cycles on BOTH
ends... This FSH project looks promising, though hasn't been updated since
2001... A scary prospect for anything that is crypto/authentication based :)

I don't see any reason we couldn't whip up an active check script that runs
a number of commands sequentially over the SSH session that's set up at the
beginning, applies the results as separate passive service checks.  That's
the only way I can think of to handle it, since each service check will
otherwise be initiating a separate connection, at whatever rate is
determined by its schedule in the queue.

Then again, check_by_fsh sounds nice too!  Have to look at SSH4 features now
that you mentioned it Steve.

Just my thoughts.

/eli


On 5/15/06 3:56 PM, "Jason Martin" <jhmartin at toger.us> wrote:

> On Mon, May 15, 2006 at 03:34:53PM -0700, Keller, Steve wrote:
>> a replacement.  One of the issues we have is that we cannot, for various
>> (mostly political) reasons, install an agent on the hosts we monitor.
> By any chance is SNMP already in place on the target hosts? That
> might cut down on the number of agent-on-demand checks you have
> to run.
> 
>> So my question is, does anyone know of a reasonable approach to
>> agentless monitoring using Nagios?  We are planning to try SSH4, which
> Check out FSH (http://freshmeat.net/projects/fsh/) which does a
> similiar thing. That should take care of the SSH overhead problem.
> 
> 
>> this has the problem that a host which is down, or busy, could delay
>> checking other hosts.
> If you are writing this in perl, you can have your plugins
> timeout gracefully to prevent that. Nagios can be configured to
> time out plugins as well.
> 
> -Jason Martin



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