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. 🍿 On Thu, Sep 20, 2018 at 10:45 PM Brian Greene < br...@heisenbergwoodworking.com> 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 <fo...@driesprong.frl> > 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 > > <jmeic...@quantopian.com.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 > >> <airflowu...@protonmail.com.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. > >> >
