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

[Oved Ourfali]

On Thu, Jul 6, 2017 at 12:19 PM, Roy Golan <rgolan at redhat.com> wrote:

>
>
> On Thu, Jul 6, 2017 at 12:18 PM Roy Golan <rgolan at redhat.com> wrote:
>
>> 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
>>
>> - Chages to DWH sampling and ManageIQ?
>

I think manageIQ can cope with either 60 seconds or 20 seconds intervals
(after a change we've made when we moved to 20 seconds).
Put an action item indeed to check that with us if we'll decide to do so.


>
>>
>>
>> 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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>>>>
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