From my perspective the confusion is twofold:
1. A DAG run starts at the end of an interval. At first this is confusing to people but after some time it starts to make sense. Some visual change in the UI would be helpful though. 2. execution_date in the TI context - the name is confusing to everybody and should be changed IMO. My suggestion is to leave execution_date as is since many users depend on it, and add two new variables “interval_start” and “interval_end” to denote the start and end of the DAG run interval. Bas On 15 Apr 2019, at 15:52, Dan Davydov <ddavy...@twitter.com.INVALID<mailto:ddavy...@twitter.com.INVALID>> wrote: You could start a [VOTE][PMC ONLY] thread on this topic ( https://www.apache.org/foundation/voting.html). Not sure if that's the best Apache way of doing things, but seems fine to me. My PMC vote personally would maybe be to switch the semantics to the opposite of what they are now without having an additional config value, but since that's not very realistic given the migration effort required by users I think a flag would probably be worth the costs I mentioned in my previous email although it's definitely a trade-off. Some kinds of new user/existing survey would probably help collect data to support a decision but could be tough to conduct. On Mon, Apr 15, 2019 at 4:34 PM James Meickle <jmeic...@quantopian.com.invalid<mailto:jmeic...@quantopian.com.invalid>> wrote: Personally I would be very interested in working on a flexible schedule window/window projection patch. But it would be a big undertaking so it doesn't make sense to start it unless there's a lot of community buy-in to the idea that we aren't just for day-after ETL systems. On Mon, Apr 15, 2019 at 8:52 AM airflowuser <airflowu...@protonmail.com.invalid<mailto:airflowu...@protonmail.com.invalid>> wrote: To quote my user-experience professor from ages ago: "If too many people misuse something you wrote it means that YOU are doing something wrong". Something can be well documented but if it's not intuitive it's likely that people will get it wrong. Say someone ask "When did you execute the code?" Your answer will be direct - the time the code started to run. This is why so many people misunderstand the execution_date in the terms of Airflow. Airflow took a word that is well defined in our conscious and replaced it's meaning. ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ On Monday, April 15, 2019 3:35 PM, Dan Davydov <ddavy...@twitter.com.INVALID<mailto:ddavy...@twitter.com.INVALID>> wrote: 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<mailto: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 for3pm 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<mailto: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<mailto: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<mailto: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<mailto: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: http://www.credit-suisse.com/legal/en/disclaimer_email_ib.html ===============================================================================
