On 08/12/2007, Giuseppe Modugno <[EMAIL PROTECTED]> wrote:
> Thanks Dave, your explanation is very clear, but I can't find a real situation
> where a "watcher" helper could help.

> It's difficult to have a situation where the OID variable is really the 
> variable
> of the agent process... isn't it?

Not really.

For example, the agent (or rather the library) keeps internal statistics for the
number of particular type of request received or sent.   Similarly for certain
error conditions (unknown community, etc).   These are intended to implement
the SNMP group of statistics objects, and could easily be passed to the
watcher for implementing in this way.
   (In fact, they are implemented using the older v4 API, and we
haven't bothered
re-writing the code to use the newer style).


Or if you're loading in the contents of a table (e.g. via the cache helper), it
would be simple enough to include a variable that held the number of entries
in the table, or the time that it was loaded.   Either of these would be ideal
candidates for a watcher-based implementation.



> >   As a fer-instance:
> > Suppose you're monitoring a web server....

> I think that the web server is a different process than the SNMP (module or
> main) agent, so the variable can't be accessed directly from within the agent.

It depend on how the MIB module is implemented.
If you're coding this within the SNMP agent, then yes - you'd be limited
to watching the variables that are actually part of the agent itself.

But if you're using the agent library to embed an AgentX subagent within
the web server process, then you'd have direct access to all of the variables
in the web server code.   So that would be an ideal situation for using the
watcher helper.


Dave

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