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From Kaxil Naik <kaxiln...@gmail.com>
Subject Re: Setting to add choice of schedule at end or schedule at start of interval
Date Thu, 26 Sep 2019 00:33:14 GMT
I agree with Dan to change the default execution at start of the interval.

How about adding this for 2.0 ??

Don't want to keep delaying this if we have a consensus already.

Regards,
Kaxil


On Fri, Aug 23, 2019, 15:39 Dan Davydov <ddavydov@twitter.com.invalid>
wrote:

> What are people's feelings on changing the default execution to schedule
> interval start and communicating this to existing users in the Updating
> notes so that they can preserve the old behavior? Could potentially cause
> headaches for users who don't read the notes but I think it might make
> sense to bite the bullet at some point for more intuitive behavior overall
> for new users.
>
> On Fri, Aug 23, 2019 at 10:29 AM Dan Davydov <ddavydov@twitter.com> wrote:
>
> > I am for this change, since I feel like in general the start of the
> > interval is more intuitive (I have been working on Airflow for 3 years
> and
> > this still trips me up). That being said I'm not sure how I feel about
> > allowing customization at DAG level instead of cluster level as it makes
> it
> > harder to make assumptions about DAGs on the cluster for ops, though
> maybe
> > this isn't a huge deal given there are tools available that show you why
> > tasks aren't running.
> >
> > I agree with Bole that we should communicate recommended migration
> > strategies if they can't be done automatically.
> >
> > I don't think I'm a fan for arbitrary customization of the interval via a
> > callback, my feeling is this would not provide significant value and
> could
> > be an ops nightmare.
> >
> > On Fri, Aug 23, 2019 at 9:11 AM Jarek Potiuk <Jarek.Potiuk@polidea.com>
> > wrote:
> >
> >> DST: I recall problems with DST especially when the hour goes back and
> the
> >> daily schedule time technically occurs twice the same day or does not
> >> occur
> >> at all. We have some code that chooses arbitrary the first occurence in
> >> the
> >> latter case (there was a problem that it worked differently python 3.6
> vs
> >> 3.5 (!). But also the case when we move forward is an interesting one. I
> >> am
> >> not 100% it will work correctly after changing the scheduling mechanisms
> >> but it's rather easy to test and there is no harm adding it.
> >> There is a DST-specific logic implemented in our next/previous run
> >> calculation and I imagine it could get wrong.
> >>
> >> The tests I am talking about:
> >>
> >>
> DagTest.test_following_previous_schedule_daily_dag_CEST_to_CET/DagTest.test_following_previous_schedule_daily_dag_CET_to_CEST.
> >>
> >> Re: arbitrary customisation/converting DAGs. I think there is no need to
> >> convert existing dags - the default behaviour remains as it is as far
> as I
> >> understand. And this flag is much simpler to understand and reason about
> >> than arbitrary function and it corresponds to real business cases:
> >>
> >> 1) schedule_at_interval_end = True -> wait for the data to be ready for
> >> the
> >> interval (current/default behaviour related to processing batches of
> data)
> >> 2) schedule_at_interval_end = False -> CRON-like behaviour where we
> simply
> >> run arbitrary operation in regular intervals (more intuitive for people
> >> who
> >> are used to CRON-like jobs)
> >>
> >> You can always build your schedule differently if you need something
> >> "in-between" IMHO.
> >>
> >> J.
> >>
> >>
> >>
> >>
> >> On Fri, Aug 23, 2019 at 8:44 AM James Meickle
> >> <jmeickle@quantopian.com.invalid> wrote:
> >>
> >> > This is a change to one of Airflow's core concepts, and it would
> >> require a
> >> > lot of work for existing DAGs to cut over to it. Given that, my
> personal
> >> > preference would be to allow arbitrary customization rather than just
> a
> >> bit
> >> > toggle. Such as allowing passing in a mapping function: given an
> >> interval's
> >> > start date and end date, when should it be executed?
> >> >
> >> > On Fri, Aug 23, 2019 at 8:24 AM Jarek Potiuk <
> Jarek.Potiuk@polidea.com>
> >> > wrote:
> >> >
> >> > > Happy for it as well. There are a number of cases where scheduling
> at
> >> > start
> >> > > makes more sense and as we see Airflow is used now in multiple cases
> >> > where
> >> > > there is no need to process data from an interval and wait until
> that
> >> > data
> >> > > is ready.
> >> > > But indeed some more tests would be great - especially for edge
> cases.
> >> > > Changig mid-air is one but I think there should be test about
> Daylight
> >> > > Saving Time changing.
> >> > > There are some tests for DST so they just need to be extended to
> cover
> >> > > those two different cases.
> >> > >
> >> > >
> >> > > J.
> >> > >
> >> > > On Fri, Aug 23, 2019 at 7:37 AM Kaxil Naik <kaxilnaik@gmail.com>
> >> wrote:
> >> > >
> >> > > > Happy for this feature to merged
> >> > > >
> >> > > > On Fri, Aug 23, 2019, 11:49 Ash Berlin-Taylor <ash@apache.org>
> >> wrote:
> >> > > >
> >> > > > > This has come up a few times before, someone has now opened
a PR
> >> that
> >> > > > > makes this a global+per-dag setting:
> >> > > > > https://github.com/apache/airflow/pull/5787 and it also
> includes
> >> > docs
> >> > > > > that I think does a good job of illustrating the two modes.
> >> > > > >
> >> > > > > Does anyone object to this being merged? If no one says
anything
> >> by
> >> > > > midday
> >> > > > > on Tuesday I will take that as assent and will merge it.
> >> > > > >
> >> > > > > The docs from the PR included below.
> >> > > > >
> >> > > > > Thanks,
> >> > > > > Ash
> >> > > > >
> >> > > > > Scheduled Time vs Execution Time
> >> > > > > ''''''''''''''''''''''''''''''''
> >> > > > >
> >> > > > > A DAG with a ``schedule_interval`` will execute once per
> >> interval. By
> >> > > > > default, the execution of a DAG will occur at the **end**
of the
> >> > > > > schedule interval.
> >> > > > >
> >> > > > > A few examples:
> >> > > > >
> >> > > > > - A DAG with ``schedule_interval='@hourly'``: The DAG run
that
> >> > > processes
> >> > > > > 2019-08-16 17:00 will start running just after 2019-08-16
> >> 17:59:59,
> >> > > > > i.e. once that hour is over.
> >> > > > > - A DAG with ``schedule_interval='@daily'``: The DAG run
that
> >> > processes
> >> > > > > 2019-08-16 will start running shortly after 2019-08-17 00:00.
> >> > > > >
> >> > > > > The reasoning behind this execution vs scheduling behaviour
is
> >> that
> >> > > > > data for the interval to be processed won't be fully available
> >> until
> >> > > > > the interval has elapsed.
> >> > > > >
> >> > > > > In cases where you wish the DAG to be executed at the **start**
> of
> >> > the
> >> > > > > interval, specify ``schedule_at_interval_end=False``, either
in
> >> > > > > ``airflow.cfg``, or on a per-DAG basis.
> >> > > >
> >> > >
> >> > >
> >> > > --
> >> > >
> >> > > Jarek Potiuk
> >> > > Polidea <https://www.polidea.com/> | Principal Software Engineer
> >> > >
> >> > > M: +48 660 796 129 <+48660796129>
> >> > > [image: Polidea] <https://www.polidea.com/>
> >> > >
> >> >
> >>
> >>
> >> --
> >>
> >> Jarek Potiuk
> >> Polidea <https://www.polidea.com/> | Principal Software Engineer
> >>
> >> M: +48 660 796 129 <+48660796129>
> >> [image: Polidea] <https://www.polidea.com/>
> >>
> >
>

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