Rate of change - of - rate of change


14-03-2005 10:03:14

I'm looking to put thresholds on uplinks and would like to include when a link suddenly drops in utilization at a point in time. Like, if a link drops more than 10Mb/sec on an interval. On guages, this would be the rate of change, but on octet counters, the rate of change is the bandwidth (First derivative of the octets counter?). So I'd like to do the rate of change of the bandwidth (the second derivative of the octets counter?). Any ideas?


14-03-2005 18:28:33

There isn't functionality for this currently in NetMRG. You could probably write a script to do this, by pulling values out of the database to make your own calculations. I do think that this would be a good feature, though, so I'm starting bug#397 to address it.


14-03-2005 18:39:40

Looks like you could simply add last_delta_value to the monitors table and track it similar to how last_value is being tracked.


14-03-2005 18:52:19

yes, that should probably work. unfortunately, our release schedule is up in the air at the moment as all of the developers are being kept busy with other things... I'm not sure when we can expect to have this done. Feel free to create a mantis account to monitor the bug, or sending a patch would be even better ;).



16-03-2005 09:07:32

Looks like, if we had the id in the monitors table available, you could create a SQL query

select ( delta_val / delta_time ) from monitors where id = %netmrg_dev_id%

Then graph this on the particular interface and it would get the bandwidth from last time, then graph it, and calculate another delta_val for this.

I think adding acceleration as option for thresholding is still valid, what do you think?


17-03-2005 21:26:03

I do think this is something we should build in. The workaround method you describe has one notable detractor data returned from the query could be that from before or after the current gathering cycle, which isn't ideal.