[ovs-dev] RFC for database statistics interface.

[Keith Amidon]

On Tue, 08 Jun 2010 18:43:59 -0700, Jeremy Stribling <strib at nicira.com> wrote:
> The only use case I know is for the controller to poll the stats at a 
> given interval, but monitor the statistics for delete events (so it can 
> receive the last known value for the statistics).  So as long as there's 
> an understanding that the stats provider will update it one last time 
> before deleting, what you propose will be fine.

This is the primary use case I've heard discussed as well.  In
generally, I've been thinking that we need to do everything we can to
minimize the amount of polling the controllers have to do.  

For normal rx/tx stats the monitoring for delete case is probably
sufficient given 64-bit counters.  For error stats however the
controller may want to know about relatively small changes without
waiting for what could be a very long polling interval.  A monitor with
a threshold seems like it would solve this problem nicely.

All this is a long-winded way of saying that associating a local polling
interval with each stat and then using that to trigger monitors is
something I think we should strongly consider.  If the controller could
set the local polling interval as well as read it (e.g. reduce it from a
relatively long default) that would be ideal.  

       --- Keith