[ovirt-devel] Chaning the statistics monitoring interval to 30s

[Arik Hadas]

On Wed, Jul 5, 2017 at 9:36 PM, Shirly Radco <sradco at redhat.com> wrote:

>
>
> --
>
> SHIRLY RADCO
>
> BI SOFTWARE ENGINEER,
>
> Red Hat Israel <https://www.redhat.com/>
>
> sradco at redhat.com
>  <https://red.ht/sig>
>  <https://redhat.com/summit>
>
>
> On Wed, Jul 5, 2017 at 6:35 PM, Arik Hadas <ahadas at redhat.com> wrote:
>
>>
>>
>> On Wed, Jul 5, 2017 at 5:57 PM, Roy Golan <rgolan at redhat.com> wrote:
>>
>>> Hi all,
>>>
>>> I would like to get feedback on $subject and see if I'm missing
>>> something. The impact of this is simply less resource consumption and by
>>> that we can support even greater number of hosts [1] and vms in the system.
>>>
>>
>>> If you think more relaxed statistics collection will affect a core flow
>>> let me know - as far as I see I didn't spot anything critical.
>>>
>>
>>> The overhead of a cycle per host something like that: 2 roundtrips per
>>> host in a cycle, (vm + host stats) and tons of memory allocation for char[]
>>> -> json-> maps of maps -> VM/Vds statistics -> Maps -> serialiazing to DB.
>>>
>>> To minimize the effect of this change we can leave a call to 'list' verb
>>> to at least detect vms existence in the same rate as today.
>>>
>>
>> +1
>>
>>
>>>
>>> Pros
>>> - Engine has rore resources to support more hosts/vms/other activities
>>> of the engine
>>> - Vdsm will have more resources as well (need to tweak vdsm to collect
>>> in the same
>>> frequency)
>>> - less DB writes and reads, approx half of what the system will do in
>>> the in its lifefpan (cause this is what is mainly does all the time)
>>>
>>> Cons
>>> - DWH/Dashboard will have less entries, I'm not sure what is graphical
>>> affect given our hourly resolution (cmiiw here)
>>>
>>
>> What's the frequency of the queries done by DWH/Dashboard? Do they count
>> on the _update_date column of the queried data?
>>
>
> Current frequency is 20 seconds.
> The configurations are queried based on the _update_date, but  statistics
> are queried every interval.
>
> The affect will be less accuracy in the hourly calculations.
>

Ack. So if the proposed change is done, it would probably make sense to
increase the inverval of those queries to be higher than 30 sec, or at
least taking into consideration the _update_date of vm_statistics as well.


>
>
>> I'm asking because if they query the database every minute and say "the
>> time now is 10:30 and the queried data is ..." then there should not be
>> less entries.
>>
>>
>>>
>>>
>>> [1] https://bugzilla.redhat.com/show_bug.cgi?id=1430876
>>>
>>
>>>
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>>>
>>
>>
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