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Re: hooks & operators improvement proposal


Right I see where you're at, I looked through some of our operators and I
do see some logic that's repeated (converting to JSON and writing to temp
files). We also do what looks like pipes.clear_keys with some of the files
we get using the SSHHook. Now that I notice that, I'm tempted to pull it
and put it with some of our other utils which is what it looks like pipes
is doing. I think if some common things like that existed, we'd consider
using them. I know we burned a lot of time getting tempfiles working right
since we're not all experienced software engineers over here.

On Thu, Sep 27, 2018 at 1:48 PM Daniel Cohen <daniel.cohen@xxxxxxxxxxxxxx>
wrote:

> Hi Michael, thank you for your comment.
> XCom is for sharing state between tasks , and you are right in stating that
> it won't be wise to pass datasets via it.
> I'm suggesting to refactor already exists code in operators (that  each
> operator implemented separately) . if we move some logic to hooks (or other
> construct) we can build more robust operators faster.
>
> 10x
> d
>
> On Thu, Sep 27, 2018 at 4:54 PM Michael Ghen <mike@xxxxxxxxxxxx> wrote:
>
> > I see what your looking for and I think this is the purpose of XCom.
> We've
> > used  xcom in some of our custom operators to get this type of
> > functionality.
> >
> > Though, we tend to avoid putting a lot of data into xcom, I believe
> > somewhere in the docs it talks about how that's an anti pattern. The
> > pattern was to lean on external systems for exchanging data.
> >
> > On Wed, Sep 26, 2018 at 4:26 PM Jeff Payne <jpayne@xxxxxxxxxxx> wrote:
> >
> > > Ah, OK. Thanks for the clarification.
> > >
> > > Get Outlook for Android<https://aka.ms/ghei36>
> > >
> > > ________________________________
> > > From: Daniel Cohen <daniel.cohen@xxxxxxxxxxxxxx>
> > > Sent: Wednesday, September 26, 2018 1:15:16 PM
> > > To: dev@xxxxxxxxxxxxxxxxxxxxxxxxxxxx
> > > Subject: Re: hooks & operators improvement proposal
> > >
> > > Hi Jeff,
> > > seems that I was a bit unclear
> > > The DAG ETL spans across multiple tasks. and usually looks like kickoff
> > >>
> > > source_to_staging >> staging_to_warehouse >> warehouse_post_process.
> > > I'm not proposing changes to operators they are gr8 , what i am
> proposing
> > > is to borrow the same concept to the smaller building blocks.
> > >
> > > I argue that the task anatomy (in ETL flows) is usually comprised of
> > > 'mini' flows that usually looks like read source > serialize > dump
> > > (example
> > > 1
> > > <
> > >
> >
> https://github.com/apache/incubator-airflow/blob/7cd9a26418ce9cb120f1cacd9fdcfe43fe5c0254/airflow/operators/mysql_to_hive.py#L124
> > > >
> > > , example 2
> > > <
> > >
> >
> https://github.com/apache/incubator-airflow/blob/7cd9a26418ce9cb120f1cacd9fdcfe43fe5c0254/airflow/contrib/hooks/salesforce_hook.py#L201
> > > >)
> > > .   you can see that sometimes its written in the operator and
> sometimes
> > in
> > > the hook , the code is not shared and handles same cases each time.
> > >
> > > thanks,
> > > d
> > >
> > >
> > >
> > > On Wed, Sep 26, 2018 at 10:43 PM Jeff Payne <jpayne@xxxxxxxxxxx>
> wrote:
> > >
> > > > So, in your scenario, the ETL pipeline happens inside the single
> > > > operator/task?
> > > >
> > > > If so, would it not make sense for the pipeline to span multiple
> tasks
> > > and
> > > > provide a standard set of functions/decorators/etc for defining the
> > > > input/output to/from each task? That way you would leverage the
> ability
> > > to
> > > > rerun the DAG from a particular step of the ETL pipeline in case of a
> > > > recoverable failure. Or am I misunderstanding...
> > > >
> > > > Get Outlook for Android<https://aka.ms/ghei36>
> > > >
> > > > ________________________________
> > > > From: Daniel Cohen <daniel.cohen@xxxxxxxxxxxxxx>
> > > > Sent: Wednesday, September 26, 2018 12:27:29 PM
> > > > To: dev@xxxxxxxxxxxxxxxxxx
> > > > Subject: hooks & operators improvement proposal
> > > >
> > > > Some thoughts about operators / hooks:
> > > > Operators are composable,  typical ETL flow  looks like `kickoff >>
> > > > source_to_staging >> staging_to_warehouse >> warehouse_post_process`
> > > where
> > > > tasks use shared state (like s3) or naming conventions to continue
> work
> > > > where upstream task left off.
> > > >
> > > > hooks on the other hand are not composable and a lot of ETL logic is
> > > > written ad hoc in the operator each time.
> > > >
> > > > i propose a lightweight, in process, ETL framework that allows
> > > > - hook composition
> > > > - shared general utilities (compression  / file management /
> > > serialization)
> > > > - simplifies operator building
> > > >
> > > > how it looks from the operator's side
> > > > def execute(self, context):
> > > >         # initialize hooks
> > > >         self.s3 = S3Hook...
> > > >         self.mysql = MySqlHook...
> > > >
> > > >         # setup operator state
> > > >         query = 'select * from somewhere'
> > > >
> > > >         # declare your ETL process
> > > >         self.mysql.yield_query(query) >> \
> > > >         pipes.clear_keys(keys=self.scrubbed_columns) >> \
> > > >         pipes.ndjson_dumps() >> \
> > > >         pipes.batch(size=1024) >> \
> > > >         pipes.gzip() >> \
> > > >         pipes.tempfile() >> \
> > > >         self.s3.file_writer(s3_key=self.s3_key,
> > > >                                 bucket_name=self.s3_bucket,
> > > >                                 replace=True)
> > > >
> > > >
> > > > how it looks from the hook's side
> > > >
> > > > @pipes.producer # decorate
> > > > def yield_query(self, query):
> > > >         cursor.execute(query)
> > > >         for row in cursor:
> > > >             yield row
> > > >
> > > >
> > > > *pipes is a module with a set of operations that are generic and
> > > > potentially reused between hooks / operators
> > > >
> > > > the idea inspired by 'bonobo'  and 'python-pipes'  (lightwait etl
> > > packsges)
> > > > and implementation based on on generators and  decorators.
> > > >
> > > > we (cloudinary.com) are planning to open source it , is it something
> > > that
> > > > would be interesting to integrate into airflow ,or as a 3rd party  ?
> or
> > > not
> > > > at all ? any thoughts suggestions ?
> > > >
> > > > thanks ,
> > > > d
> > > >
> > > >
> > > > --
> > > > daniel cohen
> > > > +972-(0)54-4799-147
> > > >
> > >
> > >
> > > --
> > > daniel cohen
> > > +972-(0)54-4799-147
> > >
> >
>
>
> --
> daniel cohen
> +972-(0)54-4799-147
>