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

[Roy Golan]

Action items:
- Demonstrate the effect of the reduction of stats collection on the system
- WIP
- Code changes:
  - config item change: NumberVmRefreshesBeforeSave from 5 to 10
  - make the 'poll' vms job to fire at NumberVmRefreshesBeforeSave / 2 (or
just make the code to support explicit time interval)
  - VDSM should get a config set with the sampling inteval - to support
back-compat




On Thu, Jul 6, 2017 at 11:00 AM Yaniv Kaul <ykaul at redhat.com> wrote:

> On Thu, Jul 6, 2017 at 10:04 AM, Oved Ourfali <oourfali at redhat.com> wrote:
>
>>
>>
>> On Thu, Jul 6, 2017 at 9:38 AM, Arik Hadas <ahadas at redhat.com> wrote:
>>
>>>
>>>
>>> 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.
>>>
>>>
>>
>> Note that it will cause issues with cloudforms to change those queries to
>> 30 seconds, so I guess we'll still query it every 20 seconds (although the
>> data won't change in some of those queries).
>>
>
> I thought it was configurable in ManageIQ how often to query, but in any
> case even if we query every 20 seconds, we'll get updated VM stats, which
> is fine, and not as updated hosts stats, which is fine as well, from my
> perspective.
> Y.
>
>
>>
>>
>>
>>>>
>>>>> 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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>>>>
>>>
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