openstack team mailing list archive

[Nick Barcet <nick.barcet@xxxxxxxxxxxxx>]

On 05/01/2012 02:23 AM, Loic Dachary wrote:
> On 04/30/2012 11:39 PM, Doug Hellmann wrote:
>>
>>
>> On Mon, Apr 30, 2012 at 3:43 PM, Loic Dachary <loic@xxxxxxxxxxxx
>> <mailto:loic@xxxxxxxxxxxx>> wrote:
>>
>>     On 04/30/2012 08:03 PM, Doug Hellmann wrote:
>>>
>>>
>>>     On Mon, Apr 30, 2012 at 11:43 AM, Loic Dachary <loic@xxxxxxxxxxxx
>>>     <mailto:loic@xxxxxxxxxxxx>> wrote:
>>>
>>>         On 04/30/2012 03:49 PM, Doug Hellmann wrote:
>>>>
>>>>
>>>>         On Mon, Apr 30, 2012 at 6:46 AM, Loic Dachary
>>>>         <loic@xxxxxxxxxxxx <mailto:loic@xxxxxxxxxxxx>> wrote:
>>>>
>>>>             On 04/30/2012 12:15 PM, Loic Dachary wrote:
>>>>             > We could start a discussion from the content of the
>>>>             following sections:
>>>>             >
>>>>             > http://wiki.openstack.org/EfficientMetering#Counters
>>>>             I think the rationale of the counter aggregation needs
>>>>             to be explained. My understanding is that the metering
>>>>             system will be able to deliver the following
>>>>             information: 10 floating IPv4 addresses were allocated
>>>>             to the tenant during three months and were leased from
>>>>             provider NNN. From this, the billing system could add a
>>>>             line to the invoice : 10 IPv4, $N each = $10xN because
>>>>             it has been configured to invoice each IPv4 leased from
>>>>             provider NNN for $N.
>>>>
>>>>             It is not the purpose of the metering system to display
>>>>             each IPv4 used, therefore it only exposes the aggregated
>>>>             information. The counters define how the information
>>>>             should be aggregated. If the idea was to expose each
>>>>             resource usage individually, defining counters would be
>>>>             meaningless as they would duplicate the activity log
>>>>             from each OpenStack component.
>>>>
>>>>             What do you think ?
>>>>
>>>>
>>>>         At DreamHost we are going to want to show each individual
>>>>         resource (the IPv4 address, the instance, etc.) along with
>>>>         the charge information. Having the metering system aggregate
>>>>         that data will make it difficult/impossible to present the
>>>>         bill summary and detail views that we want. It would be much
>>>>         more useful for us if it tracked the usage details for each
>>>>         resource, and let us aggregate the data ourselves.
>>>>
>>>>         If other vendors want to show the data differently, perhaps
>>>>         we should provide separate APIs for retrieving the detailed
>>>>         and aggregate data.
>>>>
>>>>         Doug
>>>>
>>>         Hi,
>>>
>>>         For the record, here is the unfinished conversation we had on IRC
>>>
>>>         (04:29:06 PM) dhellmann: dachary, did you see my reply about
>>>         counter definitions on the list today?
>>>         (04:39:05 PM) dachary: It means some counters must not be
>>>         aggregated. Only the amount associated with it is but there
>>>         is one counter per IP.
>>>         (04:55:01 PM) dachary: dhellmann: what about this :the id of
>>>         the ressource controls the agregation of all counters : if it
>>>         is missing, all resources of the same kind and their measures
>>>         are aggregated. Otherwise only the measures are agreggated.
>>>         http://wiki.openstack.org/EfficientMetering?action=diff&rev2=40&rev1=39
>>>         <http://wiki.openstack.org/EfficientMetering?action=diff&rev2=40&rev1=39>
>>>         (04:55:58 PM) dachary: it makes me a little unconfortable to
>>>         define such an "ad-hoc" grouping
>>>         (04:56:53 PM) dachary: i.e. you actuall control the
>>>         aggregation by chosing which value to put in the id column
>>>         (04:58:43 PM) dachary: s/actuall/actually/
>>>         (05:05:38 PM) ***dachary reading
>>>         http://www.ogf.org/documents/GFD.98.pdf
>>>         (05:05:54 PM) dachary: I feel like we're trying to resolve a
>>>         non problem here
>>>         (05:08:42 PM) dachary: values need to be aggregated. The raw
>>>         input is a full description of the resource and a value (
>>>         gauge ). The question is how to control the aggregation in a
>>>         reasonably flexible way.
>>>         (05:11:34 PM) dachary: The definition of a counter could
>>>         probably be described as : the id of a resource and code to
>>>         fill each column associated with it.
>>>
>>>         I tried to append the following, but the wiki kept failing.
>>>
>>>         Propose that the counters are defined by a function instead
>>>         of being fixed. That helps addressing the issue of
>>>         aggregating the bandwidth associated to a given IP into a
>>>         single counter.
>>>
>>>         Alternate idea :
>>>          * a counter is defined by
>>>           * a name ( o1, n2, etc. ) that uniquely identifies the
>>>         nature of the measure ( outbound internet transit, amount of
>>>         RAM, etc. )
>>>           * the component in which it can be found ( nova, swift etc.)
>>>          * and by columns, each one is set with the result of
>>>         aggregate(find(record),record) where
>>>           * find() looks for the existing column as found by
>>>         selecting with the unique key ( maybe the name and the
>>>         resource id )
>>>           * record is a detailed description of the metering event to
>>>         be aggregated (
>>>         http://wiki.openstack.org/SystemUsageData#compute.instance.exists:
>>>         )
>>>           * the aggregate() function returns the updated row. By
>>>         default it just += the counter value with the old row
>>>         returned by find()
>>>
>>>
>>>     Would we want aggregation to occur within the database where we
>>>     are collecting events, or should that move somewhere else?
>>     I assume the events collected by the metering agents will all be
>>     archived for auditing (or re-building the database)
>>     http://wiki.openstack.org/EfficientMetering?action=diff&rev2=45&rev1=44
>>     <http://wiki.openstack.org/EfficientMetering?action=diff&rev2=45&rev1=44>
>>
>>     Therefore the aggregation should occur when the database is
>>     updated to account for a new event.
>>
>>     Does this make sense ? I may have misunderstood part of your question.
>>
>>
>> I guess what I don't understand is why the aggregated data is written
>> back to the metering database at all. If it's in the same database, it
>> seems like it should be in a different "table" (or equivalent) so the
>> original data is left alone.
> In my view the events are not stored in a database, they are merely
> appended to a log file. The database is built from the events with
> aggregated data. I now understand that you (and Joshua Harlow) think
> it's better to not aggregate the data and let the billing system do this
> job.

My intent when writing the blueprint was that each event would be
recorded atomically in the database, as it is the only way to control
that we have not missed any. Aggregation, should be done at the external
API level if the request is to get the sum of a given counter.

What I missed in the blueprint and seems to be appearing clearly now, is
that an event need to be able to carry the "object-reference" for which
it was collected, and this would seem highly necessary looking at the
messages in this thread. A metering event would essentially be defined
by (who, what, which) instead of a simple (who, what).  As a consequence
we would need to extend the DB schema to add this [which/object
reference], and make sure that we carry it as well when we will work on
the message API format definition.

How does this sound?

Nick

>> Maybe it's time to start focusing these discussions on user stories?
>>
> I agree. Would you like to go first ?
> 
> Cheers
> 
> -- 
> Loïc Dachary         Chief Research Officer
> // eNovance labs   http://labs.enovance.com
> // ✉ loic@xxxxxxxxxxxx  ☎ +33 1 49 70 99 82
> 
> 
> 
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