Code review comment for lp:~al-maisan/launchpad/duration-485524

Muharem Hrnjadovic wrote:
> Jonathan Lange wrote:
>> Review: Needs Information
>> Hello Muharem,
>>
>> I've tried to find you at UDS, but in any case it might be good to
>> talk about this so that folks at home can play along too.
> Very true.
>
>> On IRC earlier, we talked a little about possibly moving this column
>> to the Job table -- something that I thought was a sensible sounding
>> idea but wanted a use case. Here, you move the estimated_duration
>> column to the BuildQueue instead.
> Hmm .. I was suggesting to move it to the Job table but others (bigjools,
> mwhudson) were not unsure whether an estimated job duration and/or
s/not unsure/unsure/
*sigh*
> dispatch time is something that applies to any infrastructure that
> utilises the Job table or to the (Soyuz) build farm only.
> Due to that we thought it's best to contain the change to the
> (Soyuz) build farm. Since the `BuildQueue` table is used by all build
> farm jobs it was the natural place to put that property.
>
>> This, as I understand it, makes the estimated duration a property of a
>> build a property of how it is scheduled, rather than an intrinsic part
>> of the definition of the task. However, I feel my understanding is
>> uncertain.
> This is about the estimation of job dispatch times only. The question
> this answers is: "when will my waiting job start executing on a build
> farm machine"?
>
>> In your original comment, you say that this patch is supposed to make
>> it possible to get job dispatch times irrespective of job type.
>> However, given that you've almost certainly thought about this more
>> than I have, I'd really appreciate it if you could add some
>> information about how this achieves that goal, why it's the best
>> solution, what trade-offs this makes (if any), and maybe give me a
>> hint as to why the column placed onto the Build table in the first
>> place.
> Right. Putting the 'estimated_build_duration' on the `Build` table was a
> design mistake that was exposed by the necessity to support the
> estimation of job dispatch times irrespective of job type i.e. for
> source package builds, recipe builds etc.
>
> The job dispatch times for a given build farm job BFJ are calculated
> based on 2 ingredients: the
>
> 1 - sum of the estimated durations of the jobs that are ahead of BFJ in
> the queue.
> 2 - time span until the next build machine becomes available
> (= min(estimated_duration - (now - job.date_started)) across the
> build machine pool that could run BFJ)
>
> As you can see having a somewhat realistic 'estimated_duration' is
> crucial to the quality of the job dispatch time estimation.
>
> Also, in order to be able to formulate less than nightmarish database
> queries for the 2 ingredients above we need the 'estimated_duration' to
> be in some common place for all build farm job types and that would be
> the `BuildQueue` table in this case.
>
> I hope this helps.
>
> Best regards
>

Best regards

--
Muharem Hrnjadovic <email address hidden>
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