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From Sergii Mikhtoniuk <mikhton...@gmail.com>
Subject Process available data and stop with savepoint
Date Sun, 17 May 2020 21:46:43 GMT
Hello,

I'm migrating my Spark-based stream processing application to Flink
(Calcite SQL and temporal tables look too attractive to resist).

My Spark app works as follows:
- application is started periodically
- it reads a directory of Parquet files as a stream
- SQL transformations are applied
- resulting append stream is written to another directory
- it runs until all available data is processed
- checkpoints its state
- and **exits**
- upon next run it resumes where it left off, processing only new data

I'm having difficulties replicating this start-stop-resume behavior with
Flink.

When I setup my input stream using:

    env.readFile[Row](..., FileProcessingMode.PROCESS_CONTINUOUSLY)

... I get an infinite stream, but the application will naturally keep
running until aborted manually.

When I use FileProcessingMode.PROCESS_ONCE - the application exits after
exhausting all inputs, but it seems that Flink also treats the end of the
stream as max watermark so, for example, it will close all tumbling windows
that I don't want to be closed yet since more data will arrive upon next
run.

Is there a way not to emit a max watermark with PROCESS_ONCE? If so, can I
still trigger a savepoint when env.execute() returns?

Alternatively, if I use PROCESS_CONTINUOUSLY along with env.executeAsync()
is there a way for me to detect when file stream was exhausted to call
job.stopWithSavepoint()?

Thanks for your help!
- Sergii

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