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From Robert Metzger <rmetz...@apache.org>
Subject Re: Breaking changes in the Streaming API
Date Thu, 11 Feb 2016 09:19:02 GMT
big +1 on reworking the timestamp extractor. There were too many users
stumbling across this. I also misunderstood it when trying it out the first

On Tue, Feb 9, 2016 at 4:54 PM, Stephan Ewen <sewen@apache.org> wrote:

> Hi everyone!
> There are two remaining issues right now pending for 1.0 that will cause
> breaking API changes in the Streaming API.
> 1)
> [FLINK-3379]
> The Timestamp Extractor needs to be changed. That really seems necessary,
> based on the user feedback, because a lot of people mentioned that they are
> getting confused about the TimestampExtractor's mixed two-way system of
> generating watermarks.
> The issue suggests to pull the two different modes of generating watermarks
> into two different classes.
> 2)
> [FLINK-3371] makes the "Trigger" an abstract class (currently interface)
> and moves the "TriggerResult" to a dedicated class. This is necessary for
> avoiding breaking changes in the future, after the release.
> The reason why for these changes are "aligned windows", which have one
> Trigger for the entire window across all keys (
> https://issues.apache.org/jira/browse/FLINK-3370)
> Aligned windows are for example most sliding/tumbling time windows, while
> unaligned windows (with a trigger per key) are for example session and
> count windows. For aligned windows, we can implement an optimized
> representation that uses less memory and is more lightweight to checkpoint.
> Also, the Trigger class may evolve a bit, and and with an abstract class we
> can add methods without breaking user-defined Triggers in the future.
> Greetings,
> Stephan

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