Re: mib2c.table_data.conf, cache timeout period does'nt seems to change.

Many Thanks,

Francois

2012/2/15 Dave Shield <[email protected]>

> On 14 February 2012 15:35, Francois Bouchard <[email protected]>
> wrote:
> > Here is the code for a cached snmp table module.
>
> OK - I've tried compiling and running that module.
>
> The timeout specified in the header file is given as
>    #define MPBCRMHALARMTABLE_TIMEOUT  10
> and that's exactly what I'm seeing.
>
> The agent generates a log message whenever the load routine
> is called, so if I run this in one window, I'd expect see a series
> of messages of the form
>    mpbcRMHAlarmTable_load: loaded ....
>    mpbcRMHAlarmTable_free
>    mpbcRMHAlarmTable_load: loaded ....
>    mpbcRMHAlarmTable_free
> whenever the table is loaded or freed.
>
>
> If I run a series of GETNEXT requests on this table in a different
> window, with a few seconds between them, then I see the following
> behaviour:
>
>   snmpgetnext ....  mpbcRMHAlarmTable
>         agent prints "loaded" message
>         client receives response
>   sleep 6
>   snmpgetnext ....  mpbcRMHAlarmTable
>         client receives response - note, nothing printed by the agent
>   sleep 6
>   snmpgetnext ....  mpbcRMHAlarmTable
>         agent prints "free" message
>         agent prints "loaded" message
>         client receives response
>   sleep 60
>         agent prints "free" message
>
>
>
> Note that when the agent receives a request for something in this
> table and the cache is older than the defined timeout (12s > 10s),
> then it *does* re-load the data.   This is the expected behaviour.
>
> However the agent does not automatically release the local cache
> (i.e. call the 'free' routine) as soon as the timeout has expired.
> Instead this is handled by a regular "garbage collection" run
> (once a minute),  which will free any stale caches.
>   In the meantime, a request that tries to use that cache will
> spot that it's expired, and reload the data.
>
> Don't get confused between the granularity of how long the data
> is valid for (and hence when incoming requests will trigger a
> cache reload),  and the granularity of garbage collection.
>
> Hope this helps
>
> Dave
>
> PS:  Please note that I'll be off-line for the next week or so,
>  so if you have any further questions on this, you'll have to
>  rely on someone else, or wait for me to get back!
>

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