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From Mich Talebzadeh <mich.talebza...@gmail.com>
Subject Re: [Spark Structured Streaming] retry/replay failed messages
Date Fri, 09 Jul 2021 15:13:02 GMT
Can you please clarify if you are reading these two topics separately or
within the same scala or python script in Spark Structured Streaming?

HTH


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On Fri, 9 Jul 2021 at 13:44, Bruno Oliveira <bruno.ariev@gmail.com> wrote:

> Hello guys,
>
> I've been struggling with this for some days now, without success, so I
> would highly appreciate any enlightenment. The simplified scenario is the
> following:
>
>    - I've got 2 topics in Kafka (it's already like that in production,
>    can't change it)
>       - transactions-created,
>       - transaction-processed
>    - Even though the schema is not exactly the same, they all share a
>    correlation_id, which is their "transaction_id"
>
> So, long story short, I've got 2 consumers, one for each topic, and all I
> wanna do is sink them in a chain order. I'm writing them w/ Spark
> Structured Streaming, btw
>
> So far so good, the caveat here is:
>
> - I cannot write a given "*processed" *transaction unless there is an
> entry of that same transaction with the status "*created*".
>
> - There is *no* guarantee that any transactions in the topic "transaction-
> *processed*" have a match (same transaction_id) in the "transaction-
> *created*" at the moment the messages are fetched.
>
> So the workflow so far is:
> - Msgs from the "transaction-created" just get synced to postgres, no
> questions asked
>
> - As for the "transaction-processed", it goes as follows:
>
>    - a) Messages are fetched from the Kafka topic
>    - b) Select the transaction_id of those...
>    - c) Fetch all the rows w/ the corresponding id from a Postgres table
>    AND that have the status "CREATED"
>    - d) Then, a pretty much do a intersection between the two datasets,
>    and sink only on "processed" ones that have with step c
>    - e) Persist the resulting dataset
>
> But the rows (from the 'processed') that were not part of the intersection
> get lost afterwards...
>
> So my question is:
> - Is there ANY way to reprocess/replay them at all WITHOUT restarting the
> app?
> - For this scenario, should I fall back to Spark Streaming, instead of
> Structured Streaming?
>
> PS: I was playing around with Spark Streaming (legacy) and managed to
> commit only the ones in the microbatches that were fully successful (still
> failed to find a way to "poll" for the uncommitted ones without restarting,
> though).
>
> Thank you very much in advance!
>
>

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