I think if the mission of Airflow is to be a generic Workflow engine, the
current semantics of execution date aren't a good default. This might be an
unpopular opinion given past threads on this topic :).
The execution_date = end_date semantics make sense for the ETL use case but
not for other use cases I think Cron syntax is more intuitive to users,
i.e. start_date should match execution_date (although I don't have data to
back this up). This is especially prevalent in ML, it's almost a rite of
passage for users to get confused by execution date semantics. I think a
flag to support different execution date semantics makes sense, even at the
cost of being a headache to support both and the complexity increase could
lead to bugs and trickier mailing list support.
On Wed, Apr 10, 2019 at 9:00 PM Gabriel Silk <gs...@dropbox.com.invalid>
wrote:
> My two cents:
>
> "execution_date" is definitely confusing to newcomers, and it's partly the
> ambiguity of the wording, and partly the UI's fault. When I first saw
> execution date, I assumed it meant *the earliest time at which the task
> will execute*, which is wrong. I was confused when no tasks appeared for
> 3pm until 4pm.
>
> My proposal to fix that:
> 1) Always show the *next* task to be executed in the UI, but explain to the
> user that it's not running because its interval has not yet completed.
> Indicate this state visually, perhaps by using some transparency or another
> color.
> 2) Instead of just showing execution date in the UI, show the low/high
> range of the time period it covers (for periodic jobs).
>
> As for what we call the low/high timestamps, I like these two options:
> - low_ts, high_ts
> - interval_start, interval_end
>
> On Wed, Apr 10, 2019 at 6:43 AM James Meickle
> <jmeic...@quantopian.com.invalid> wrote:
>
> > Strictly tying execution start to interval end doesn't work for some
> > workflows (my guess, 1-5% of them?):
> >
> > - You need to start performing tasks before the interval is over
> > - You have tasks that reference a single interval, but can't be completed
> > until several intervals later (due to data latency)
> > - The frequency you need to run the task on is different than the
> frequency
> > of the interval you need to process (like processing all records from the
> > last five days, every day)
> >
> > Airflow doesn't handle any of these situations gracefully and I've seen
> > people attempt all sorts of workarounds for them. Probably even more
> people
> > would try, if we provided decent idioms for doing it rather than those
> > workarounds.
> >
> > On Wed, Apr 10, 2019 at 9:30 AM Driesprong, Fokko <fo...@driesprong.frl>
> > wrote:
> >
> > > I see what you mean. I don't really like the `period_{start,end}` name,
> > but
> > > something such as `interval_{start,end}` might do it for me.
> > >
> > > Personally, I think running the job after the interval closes (since
> then
> > > you have all the data over the interval), makes complete sense for ETL
> > > jobs. I agree it requires some time to get used to. Maybe we're lacking
> > on
> > > documentation here.
> > >
> > > Cheers, Fokko
> > >
> > > Op wo 10 apr. 2019 om 10:08 schreef Flo Rance <troura...@gmail.com>:
> > >
> > > > I didn't expect to participate at any debate on that software, as
> I'm a
> > > > complete newcomer. But I'm almost forced as I am the target audience,
> > > too.
> > > >
> > > > To answer your initial question, after reading a lot of
> documentation I
> > > > find the term execution_date really counterintuitive, so yes maybe
> > > > period_start and period_end might be a better naming to help to
> > > understand
> > > > how all the initial scheduling works. Because even after reading the
> > > > scheduling section of the doc and the FAQ, it was still not clear in
> my
> > > > mind. Btw, I find some ideas exposed by James Meickle in the
> [DISCUSS]
> > > > AIRFLOW-4192 very interesting and I share his opinion that there's
> > still
> > > > room for improvement.
> > > > But a mode to change from "run at end of period, I need all the data
> > > > available for this period" (the current) to "run at _this_ time on
> the
> > > > schedule_interval would be awesome.
> > > >
> > > > Regards,
> > > > Flo
> > > >
> > > > On Tue, Apr 9, 2019 at 4:41 PM Ash Berlin-Taylor <a...@apache.org>
> > wrote:
> > > >
> > > > > Yeah, that's the other thing that has been talked about from
> > > > time-to-time,
> > > > > which is a mode to change from "run at end of period, I need all
> the
> > > data
> > > > > available for this period" (the current) to "run at _this_ time on
> > the
> > > > > schedule_interval, don't wait for the period to end".
> > > > >
> > > > > (No such flag exists right now, before you go looking.)
> > > > >
> > > > > > On 9 Apr 2019, at 15:31, Shaw, Damian P. <
> > > > > damian.sha...@credit-suisse.com> wrote:
> > > > > >
> > > > > > Hi all,
> > > > > >
> > > > > > I'm new to this Airflow Dev mailing list so I wasn't expecting to
> > > reply
> > > > > to anything but I feel I am the target audience for this question.
> I
> > am
> > > > > quite new to airflow and have been setting up an airflow
> environment
> > > for
> > > > my
> > > > > business this last month.
> > > > > >
> > > > > > I find the current "execution_date" a small technical burden and
> a
> > > > large
> > > > > cognitive burden. Our workflow is based on DAGs running at a
> > specified
> > > > time
> > > > > in a specified timezone using the same date as the current calendar
> > > date.
> > > > > >
> > > > > > I have worked around this by creating my own macro and context
> > > > > variables, with the logic looking like this:
> > > > > > airflow_execution_date = context['execution_date']
> > > > > > dag_timezone = context['dag'].timezone
> > > > > > local_execution_date =
> > > > > dag_timezone.convert(airflow_execution_date)
> > > > > > local_cal_date = local_execution_date +
> > > > datetime.timedelta(days=1)
> > > > > >
> > > > > > As you can see this isn't a lot of technical effort, but having a
> > > date
> > > > > that 1) is in the timezone the business users are working in, and
> 2)
> > Is
> > > > the
> > > > > same calendar date the business users are working in it
> significantly
> > > > > reduces the cognitive effort required to set-up tasks. Of course
> this
> > > > > doesn't help with cron format scheduling which I just let the
> > business
> > > > give
> > > > > me the requirements for and I set it up myself as the date logic
> > there
> > > is
> > > > > still confusing as it doesn't work like real cron scheduling which
> > > > everyone
> > > > > is familiar with.
> > > > > >
> > > > > > Maybe "period_start" and "period_end" might help people on Day 0
> of
> > > > > understanding Airflow get that the dates you are dealing with are
> not
> > > > what
> > > > > you expect, but Day 1+ there's still a lot of cognitive overhead if
> > you
> > > > > don't have the exact same model as AirBnb for running DAGs and
> tasks.
> > > > > >
> > > > > > My 2 cents anyway,
> > > > > > Damian Shaw
> > > > > >
> > > > > >
> > > > > > -----Original Message-----
> > > > > > From: Ash Berlin-Taylor [mailto:a...@apache.org]
> > > > > > Sent: Tuesday, April 09, 2019 10:08 AM
> > > > > > To: dev@airflow.apache.org
> > > > > > Subject: [DISCUSS] period_start/period_end instead of
> > > > > execution_date/next_execution_date
> > > > > >
> > > > > > (trying to break this out in to another thread)
> > > > > >
> > > > > > The ML doesn't allow images, but I can guess that it is the deps
> > > > > section of a task instance details screen?
> > > > > >
> > > > > > I'm not saying it's not clear once you know to look there, but
> I'm
> > > > > trying remove/reduce the confusion in the first place. And I think
> we
> > > as
> > > > > committers aren't best placed to know what makes sense as we have
> > > > > internalised how Airflow works :)
> > > > > >
> > > > > > So I guess this is a question to the newest people on the list:
> > Would
> > > > > `period_start` and `period_end` be more or less confusing for you
> > when
> > > > you
> > > > > were first getting started with Airflow?
> > > > > >
> > > > > > -ash
> > > > > >
> > > > > >> On 9 Apr 2019, at 14:47, Driesprong, Fokko <fo...@driesprong.frl
> >
> > > > > wrote:
> > > > > >>
> > > > > >> Ash,
> > > > > >>
> > > > > >> Personally, I think this is quite clear, there is a list of
> > reasons
> > > > why
> > > > > the job isn't being scheduled:
> > > > > >>
> > > > > >>
> > > > > >> Coming back to the question of Bas, I believe that yesterday_ds
> > does
> > > > > not make sense since we cannot assume that the schedule is daily. I
> > > don't
> > > > > see any usage of this variable. Personally, I do use
> > > next_execution_date
> > > > > quite extensively. When you have a job that runs daily, but you
> want
> > to
> > > > > change this to an hourly job. In such a case you don't want to
> change
> > > {{
> > > > > (execution_date + macros.timedelta(days=1)) }} to {{
> (execution_date
> > +
> > > > > macros.timedelta(hours=1)) }} everywhere.
> > > > > >>
> > > > > >> I'm just not sure if the aggressive deprecation of is really
> worth
> > > it.
> > > > > I don't see too much harm in letting them stay.
> > > > > >>
> > > > > >> Cheers, Fokko
> > > > > >>
> > > > > >> Op di 9 apr. 2019 om 12:17 schreef Ash Berlin-Taylor <
> > > a...@apache.org
> > > > > <mailto:a...@apache.org>>:
> > > > > >> To (slightly) hijack this thread:
> > > > > >>
> > > > > >> On the subject of execuction_date: as I'm sure we're all aware
> the
> > > > > concept of execution_date is confusing to new-commers to Airflow
> > (there
> > > > are
> > > > > many questions about "why hasn't my DAG run yet"? "Why is my dag a
> > day
> > > > > behind?" etc.) and although we mention this in the docs it's a
> > > confusing
> > > > > concept.
> > > > > >>
> > > > > >> What to people think about adding two new parameters:
> > `period_start`
> > > > > and `period_end` and making these the preferred terms in place of
> > > > > execution_date and next_execution_date?
> > > > > >>
> > > > > >> This hopefully avoids any ambitious terms like "execution" or
> > "run"
> > > > > which is understandably easy to conflate with the time the task is
> > > being
> > > > > run (i.e. `now()`)
> > > > > >>
> > > > > >> If people think this naming is better and less confusing I would
> > > > > suggest we update all the docs and examples to use these terms (but
> > > still
> > > > > mention the old names somewhere, probably in the macros docs)
> > > > > >>
> > > > > >> Thoughts?
> > > > > >>
> > > > > >> -ash
> > > > > >>
> > > > > >>
> > > > > >>> On 8 Apr 2019, at 16:20, Arthur Wiedmer <
> > arthur.wied...@gmail.com
> > > > > <mailto:arthur.wied...@gmail.com>> wrote:
> > > > > >>>
> > > > > >>> Hi Bas,
> > > > > >>>
> > > > > >>> 1) I am aware of a few places where those parameters are used
> in
> > > > > production
> > > > > >>> in a few hundred jobs. I highly recommend we don't deprecate
> them
> > > > > unless we
> > > > > >>> do it in a major version.
> > > > > >>>
> > > > > >>> 2) As James mentioned, inlets and outlets are a lineage
> > annotation
> > > > > feature
> > > > > >>> which is still under development. Let's leave them in, but we
> can
> > > > guard
> > > > > >>> them behind a feature flag if you prefer.
> > > > > >>>
> > > > > >>> 3) the yesterday*/tomorrow* params are convenience ones if you
> > use
> > > a
> > > > > daily
> > > > > >>> ETL. I agree with you that they are simple to compute, but not
> > > > everyone
> > > > > >>> using Apache Airflow is amazing with Python. Some users are
> only
> > > > > trying to
> > > > > >>> get a query scheduled and rely on a couple of niceties like
> these
> > > to
> > > > > get by.
> > > > > >>>
> > > > > >>> 4) latest_date, end_date (I feel like there used to be
> > start_date,
> > > > but
> > > > > >>> maybe it got lost) were a blend of things which were used by a
> > > > backfill
> > > > > >>> framework used internally at Airbnb. Latest date was used if
> you
> > > > > needed to
> > > > > >>> join to a dimension for which you only wanted the latest
> version
> > of
> > > > the
> > > > > >>> attributes in you backfill. end_date was used for time ranges
> > where
> > > > > several
> > > > > >>> days were processed together in a range to save on compute. I
> > don't
> > > > > see an
> > > > > >>> issue with removing them.
> > > > > >>>
> > > > > >>> Best regards,
> > > > > >>> Arthur
> > > > > >>>
> > > > > >>>
> > > > > >>>
> > > > > >>> On Mon, Apr 8, 2019 at 5:37 AM Bas Harenslak <
> > > > > basharens...@godatadriven.com <mailto:
> basharens...@godatadriven.com
> > >>
> > > > > >>> wrote:
> > > > > >>>
> > > > > >>>> Hi all,
> > > > > >>>>
> > > > > >>>> Following Tao Feng’s question to discuss this PR<
> > > > > >>>> https://github.com/apache/airflow/pull/5010 <
> > > > > https://github.com/apache/airflow/pull/5010>> (AIRFLOW-4192<
> > > > > >>>> https://issues.apache.org/jira/browse/AIRFLOW-4192 <
> > > > > https://issues.apache.org/jira/browse/AIRFLOW-4192>>), please
> > discuss
> > > > here
> > > > > >>>> if you agree/disagree/would change.
> > > > > >>>>
> > > > > >>>> -----------
> > > > > >>>>
> > > > > >>>> The summary of the PR:
> > > > > >>>>
> > > > > >>>> I was confused by the task context values and suggest to clean
> > up
> > > > and
> > > > > >>>> clarify these variables. Some are derivations from other
> > > variables,
> > > > > some
> > > > > >>>> are undocumented and unused, some are wrong (name doesn’t
> match
> > > the
> > > > > value).
> > > > > >>>> Please discuss what you think of the removal of these
> variables:
> > > > > >>>>
> > > > > >>>>
> > > > > >>>> * Removed yesterday_ds, yesterday_ds_nodash, tomorrow_ds,
> > > > > >>>> tomorrow_ds_nodash. IMO the next_* and previous_* variables
> are
> > > > useful
> > > > > >>>> since these require complex logic to compute the next
> execution
> > > > date,
> > > > > >>>> however would leave computing the yesterday* and tomorrow*
> > > variables
> > > > > up to
> > > > > >>>> the user since they are simple one-liners and don't relate to
> > the
> > > > DAG
> > > > > >>>> interval.
> > > > > >>>> * Removed tables. This is a field in params, and is thus
> also
> > > > > >>>> accessible by the user ({{ params.tables }}). Also, it was
> > > > > undocumented.
> > > > > >>>> * Removed latest_date. It's the same as ds and was also
> > > > > undocumented.
> > > > > >>>> * Removed inlets and outlets. Also undocumented, and have
> the
> > > > > >>>> inlets/outlets ever worked/ever been used by anybody?
> > > > > >>>> * Removed end_date and END_DATE. Both have the same value,
> so
> > it
> > > > > >>>> doesn't make sense to have both variables. Also, the value is
> ds
> > > > which
> > > > > >>>> contains the start date of the interval, so the naming didn't
> > make
> > > > > sense to
> > > > > >>>> me. However, if anybody argues in favour of adding
> "start_date"
> > > and
> > > > > >>>> "end_date" to provide the start and end datetime of task
> > instance
> > > > > >>>> intervals, I'd be happy to add them.
> > > > > >>>>
> > > > > >>>> Cheers,
> > > > > >>>> Bas
> > > > > >>>>
> > > > > >>
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
> ===============================================================================
> > > > >
> > > > > > Please access the attached hyperlink for an important electronic
> > > > > communications disclaimer:
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> > > > > >
> > > > >
> > > >
> > >
> >
> ===============================================================================
> > > > >
> > > > >
> > > > >
> > > >
> > >
> >
>
