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Re: Fundamental change - Separate DAG name and id.


> On 24 Sep 2018, at 23:12, Alex Tronchin-James 949-412-7220 <alex.n.james@xxxxxxxxx> wrote:
> 
> Re: [Brian Greene] "How does filename matter?  Frankly I wish the filename
> was REQUIRED to be the dag name so people would quit confusing themselves
> by mismatching them !"
> 
> FWIW in the Facebook predecessor to airflow, the file path/name WAS the dag
> name. E.g. if your dag resided in best_team/new_project/sweet_dag.py then
> the dag name would be best_team.new_project.sweet_dag
> All tasks were identified by their variable name after that prefix: E.g. if
> best_team.new_project.sweet_dag defines an operator in a variable named
> task1, then the respective task_id is best_team.new_project.sweet_dag.task1.
> 
> Airflow provides additional flexibility to specify DAG and task names to
> avoid the sometimes annoyingly long task names this resulted in and allow
> DAG/task names without forcing a code directory structure and python's
> variable naming restrictions, and I think this is a Good Thing.
> 
> It seems like airflowuser is trying to provide additional metadata beyond
> the DAG/task names (so far, a DAG 'title' distinct from the ID). I've
> provided this through a README.md included in the DAG source directory, but
> maybe it would be a win to instead add a DAG parameter named 'readme' of
> string type which can include a docstring or even markdown to provide any
> desired additional metadata? This could then be displayed by the UI to
> simplify access to any such provided DAG documentation.

You mean like https://airflow.apache.org/concepts.html#documentation-notes <https://airflow.apache.org/concepts.html#documentation-notes> ? ✨
> 
> 🍿
> 
> 
> 
> On Thu, Sep 20, 2018 at 10:45 PM Brian Greene <
> brian@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> 
>> Prior to using airflow for much, on first inspection, I think I may have
>> agreed with you.
>> 
>> After a bit of use I’d agree with Fokko and others - this isn’t really a
>> problem, and separating them seems to do more harm than good related to
>> deployment.
>> 
>> I was gonna stop there, but why?
>> 
>> You can add a task to a dag that’s deployed and has run and still view
>> history.  The “new” task shows up white Squares in the old dags.  nobody
>> said you’re required to also rename the dag when you do so this.  If your
>> process or desire or design determines you need to rename it, well then by
>> definition... isn’t it a new thing without a history?  Airflow is
>> implementing exactly that.
>> 
>> One could argue that renaming to reflect exact purpose is good practice.
>> Yes, I’d agree, but again following that logic if it’s a small enough
>> change to “slip in” then the name likely shouldn’t change.  If it’s big
>> enough I want to change the name then it’s a big enough change that I’m
>> functionally running something “new”, and I expect to need to account for
>> that.  Airflow is enforcing that logic by coupling the name to the
>> deployment of what you said was a new process.
>> 
>> One might put forth that changing the name to be more descriptive In the
>> ui makes it easier for support staff.  I think perhaps if that’s your
>> challenge it’s not airflow that’s a problem.  Dags are of course documented
>> elsewhere besides their name, right?  Yeah it’s self documenting (and the
>> graphs are cool), but I have to assume there’s something besides the NAME
>> to tell people what it does.  Additionally, far more than the name is
>> required for even an operator or monitor watcher to take action - you don’t
>> expect them to know which tasks to rerun or how to troubleshoot failures
>> just based on your “now most descriptive name in the UI” do you?
>> 
>> I spent time In an informatica shop where all the jobs were numbered.
>> Numbered.  Let’s be more exact... their NAMES were NUMBERS like 56709.
>> Terrible, but 100% worked, because while a descriptive name would have been
>> useful, the name is the thing that’s supposed to NOT CHANGE (see code of
>> Abibarshim), and all the other information can attach to that in places
>> where you write... other information.  People would curse a number “F’ing
>> 6291 failed again” - everyone knew what they were talking about.. I digress.
>> 
>> You might decide to document “dag ID 12” or just “12” on your wiki - I’m
>> going to document “daily_sales_import”.  And when things start failing at
>> 3am it’s not my dag “56” that’s failing, it’s the sales_export dag.  But if
>> you document “12”, that’s still it’s name, and it’d better be 12 in all
>> your environments and documents.  This also means the actual db IDs from
>> your proposal are almost certainly NOT the same across your environments,
>> making the 12 unchangeable name!
>> 
>> There are lots of languages (most of them) where the name of a thing is
>> important and hard to change.  It’s not a bad thing, and I’d assume that
>> deploying a thing by name has some significance in many systems.  Go rename
>> a class in... pick a language... tell me how that should be easier to do
>> willy-nilly so it’s easier In the UI.
>> 
>> I suppose you could view it as a limitation, But i don’t think you’ve
>> illuminated a single use case where it’s an actual technical constraint or
>> limitation.
>> 
>> The BEST argument against the current implementation is db performance.
>> It’s a hogwash argument.  Basic key indexes on low cardinality string
>> columns are plenty fast for the airflow workload, and if your task load is
>> so high airflow can’t keep up or your seeing super-fast tasks and airflow
>> db/tracking latency is too much... perhaps a messaging or queue processing
>> solution is better suited to those workloads.  We see scheduler bottlenecks
>> long before the database for our “quick task” scenarios.  Additionally,
>> reading through this list you’ll find people running airflow at substantial
>> scale - I’ve not seen anyone complaining of production performance issues
>> based on this design decision.   At first I hated it.  String keys are
>> dirty, we’re all taught that as good little programmers.  Except when
>> performance won’t be a huge consideration since it’s not OLTP and easy of
>> queryabilty is more important because it’s a growing system... good
>> decision - whoever made it.
>> 
>> How does filename matter?  Frankly I wish the filename was REQUIRED to be
>> the dag name so people would quit confusing themselves by mismatching them
>> !   We’ve renamed dag files with no issue as long as the content doesn’t
>> change, so again, not a real use case.  And really - name your stuff
>> careful before you get to prod man.
>> 
>> I gotta ask - airflowuser - are you gonna use airflow for anything, or
>> just poke it with a stick from a distance and ask semi-inane questions of
>> these fine folks that wrote and spend time working on this cool piece of
>> kit?
>> 
>> B
>> 
>> Sent from a device with less than stellar autocorrect
>> 
>>> On Sep 20, 2018, at 3:12 PM, Driesprong, Fokko <fokko@xxxxxxxxxxxxxx>
>> wrote:
>>> 
>>> I like the dag_id for both the name and as an unique identifier. If you
>>> change the dag in such a way, that it deserves a new name, you probably
>>> want to create a new dag anyway. If you want to give some additional
>>> context, you can use the description field:
>>> 
>> https://github.com/apache/incubator-airflow/blob/master/airflow/models.py#L3131-L3132
>>> 
>>> The name of the file of dag does not have any influence.
>>> 
>>> My 2¢
>>> 
>>> Cheers, Fokko
>>> 
>>> Op do 20 sep. 2018 om 19:40 schreef James Meickle
>>> <jmeickle@xxxxxxxxxxxxxx.invalid>:
>>> 
>>>> I'm personally against having some kind of auto-increment numeric ID for
>>>> DAGs. While this makes a lot of sense for systems where creation is a
>>>> database activity (like a POST request), in Airflow, DAG creation is
>>>> actually a code ship activity. There are all kinds of complex scenarios
>>>> around that:
>>>> 
>>>> - I revert a commit and a DAG disappears or is renamed
>>>> - I run the same file, twice, with multiple parameters to create two
>> DAGs
>>>> - I create the DAG in both staging and prod, but they wind up with
>>>> different IDs
>>>> 
>>>> It's just too hard to automatically track these scenarios.
>>>> 
>>>> If we really wanted to put something like this in place, it would first
>>>> make more sense to decouple DAG creation from code shipping, and instead
>>>> prefer creation of a DAG outside of code (but with a definition that
>>>> references which git repo/committish/file/arguments/etc. to use). Then
>> if
>>>> you do something like rename a file, the DAG breaks, but at least still
>>>> exists in the db with that ID and history still makes sense once you
>> update
>>>> the DAG definition with the new code location.
>>>> 
>>>> On Thu, Sep 20, 2018 at 4:52 AM airflowuser
>>>> <airflowuser@xxxxxxxxxxxxxx.invalid> wrote:
>>>> 
>>>>> Hi,
>>>>> though this could have been explained on Jira I think this should be
>>>>> discussed first.
>>>>> 
>>>>> The problem:
>>>>> Airflow mixes DAG name with id. It uses same filed for both purposes.
>>>>> 
>>>>> I assume that most of you use the dag_id to describe what the DAG
>>>> actually
>>>>> does.
>>>>> For example:
>>>>> 
>>>>> dag = DAG(
>>>>>   dag_id='cost_report_daily',
>>>>> ...
>>>>> )
>>>>> 
>>>>> This dag_id is reflected to the dag id column in the UI.
>>>>> Now, lets say that you want to add another task to this specific dag -
>>>> You
>>>>> are to be extremely careful when you change the dag_id to represent the
>>>> new
>>>>> functionality for example : dag_id='cost_expenses_reports_daily' . This
>>>>> will break the history of the DAG.
>>>>> 
>>>>> Or even with simpler use case.. the user just want to change the name
>> he
>>>>> sees on the UI.
>>>>> 
>>>>> I suggest to have a discussion if the dag_id should be split into id
>> (an
>>>>> actual id) and name to reflect what it does. When the "connection" is
>>>> done
>>>>> by id's  - names can change as much as you want without breaking
>>>> anything.
>>>>> essentially it becomes a field uses for display purpose  only.
>>>>> 
>>>>> * I didn't mention also the issue of DAG file name which can also cause
>>>>> trouble if someone wants to change it.
>>>>> 
>>>>> Sent with [ProtonMail](https://protonmail.com) Secure Email.
>>>> 
>>