Open Stack

> -----Original Message-----
> From: Julien Danjou [mailto:julien at danjou.info]
> Sent: Friday, November 16, 2012 9:37 PM
> To: OpenStack Development Mailing List
> Cc: Jiang, Yunhong
> Subject: Re: [openstack-dev] [ceilometer] The periodic task on openstack
> 
> On Fri, Nov 16 2012, Eoghan Glynn wrote:
> 
> > So could we at least address issue (a) by simply subtracting
> > the duration of the last tasks run from the next sleep interval?
> 
> […]
> 
> +1

Eoghan, thanks for your quick patch.

> 
> > But I'm not sure that we can always address (b) or (c) even with a
> > special thread for high-priority/time-sensitive tasks.
> 
> We can't do anything about (b), except starting the task again while the
> previous one is not finished. Is that desirable?
> - Yes if your task is taking much time because of blocked I/O (i.e. long
>   round-trip);
> - No if your task is taking much time because of system load.

For nova's periodic task implementation, it's a bit different to. In nova, all periodic_task are organized as a list and are executed in one timer (nova/service.py) through one Looping call
So in nova, (b) is "summary (all periodic task execute time) < periodic_interval", and which will be easier to fulfill, after all,  if this happen, it means the periodic_interval should be adjusted . 

--jyh


> 
> Don't know about (c)
> 
> --
> Julien Danjou
> -- Free Software hacker & freelance
> -- http://julien.danjou.info