Open Stack

On Fri, 2014-02-14 at 15:29 +0000, sahid wrote:
> Greetings,
> 
> I would like to add a new filter based on the load averages.
> 
> This filter will use the command uptime and will provides an option to choice a
> period between 1, 5, and 15 minutes and an option to choice the max load
> average (a float between 0 and 1).
> 
> Why:
>   During a scheduling it could be useful to exclude a host that have a too
> heavy load and the command uptime (available in all linux system) 
> can return a load average of the system in different periods.
> 
> About the implementation:
>   Currently 'all' drivers (libvirt, xenapi, vmware) supports a method
> get_host_uptime that returns the output of the command 'uptime'. We have to add
> in compute/stats.py a new method calculate_loadavg() that returns based on the
> output of driver.get_host_uptime() from compute/ressource_tracker.py a well
> formatted tuple of load averages for each periods. We also need to update
> api/openstack/compute/contrib/hypervisors.py to take care of this new
> field.
> 
>   The implementation will be divided in several parts:
>     * Add to host_manager the possibility to get the loads_averages
>     * Implement the filter based on this new property
>     * Implement the filter with a per-aggregate configuration
> 
> The blueprint: https://blueprints.launchpad.net/nova/+spec/filter-based-uptime
> 
> I will be happy to get any comments about this filter, perharps it is not implemented
> yet because of something I didn't see or my thinking of the implementation is wrong.
> 
> PS: I have checked metrics and cpu_resource but It does not get an averages of the
> system load or perhaps I have not understand all.
> 
> Thanks a lot,
> s.
> 
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I think load average has more than CPU, you need consider like I/O
usage, or even other metrics. Maybe you can have a look at the
https://blueprints.launchpad.net/nova/+spec/utilization-aware-scheduling ?

Also IMHO the policy of "exclude a host that have a too heavy load" is
not so clean, would it be better to keep the usage as a scheduler
weight?

Thanks
--jyh