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From Nico Kruber <n...@data-artisans.com>
Subject Re: Event-time and first watermark
Date Thu, 03 Aug 2017 14:29:50 GMT
Hi Gwenhael,
"A Watermark(t) declares that event time has reached time t in that stream, 
meaning that there should be no more elements from the stream with a timestamp 
t’ <= t (i.e. events with timestamps older or equal to the watermark)." [1]

Therefore, they should be behind the actual event with timestamp t.

What is it that you want to achieve in the end? What do you want to use the 
watermark for? They are basically a means to defining when an event time window 
ends.


Nico

[1] https://ci.apache.org/projects/flink/flink-docs-release-1.2/dev/
event_time.html#event-time-and-watermarks

On Thursday, 3 August 2017 10:24:35 CEST Gwenhael Pasquiers wrote:
> Hi,
> 
> From my tests it seems that the initial watermark value is Long.MIN_VALUE
> even though my first data passed through the timestamp extractor before
> arriving into my ProcessFunction. It looks like the watermark "lags" behind
> the data by one message.
> 
> Is there a way to have a watermark more "up to date" ? Or is the only way to
> compute it myself into my ProcessFunction ?
> 
> Thanks.


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