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From "Elias Levy (JIRA)" <j...@apache.org>
Subject [jira] [Created] (FLINK-6472) BoundedOutOfOrdernessTimestampExtractor does not bound out of orderliness
Date Sat, 06 May 2017 16:07:04 GMT
Elias Levy created FLINK-6472:

             Summary: BoundedOutOfOrdernessTimestampExtractor does not bound out of orderliness
                 Key: FLINK-6472
                 URL: https://issues.apache.org/jira/browse/FLINK-6472
             Project: Flink
          Issue Type: Bug
          Components: Streaming
    Affects Versions: 1.3.0
            Reporter: Elias Levy

{{BoundedOutOfOrdernessTimestampExtractor}} attempts to emit watermarks that lag behind the
largest observed timestamp by a configurable time delta.  It fails to so in some circumstances.

The class extends {{AssignerWithPeriodicWatermarks}}, which generates watermarks in periodic
intervals.  The timer for this intervals is a processing time timer.

In circumstances where there is a rush of events (restarting Flink, unpausing an upstream
producer, loading events from a file, etc), many events with timestamps much larger that what
the configured bound would normally allow will be sent downstream without a watermark.  This
can have negative effects downstream, as operators may be buffering the events waiting for
a watermark to process them, thus leading the memory growth and possible out-of-memory conditions.

It is probably best to have a bounded out of orderliness extractor that is based on the punctuated
timestamp extractor, so we can ensure that watermarks are generated in a timely fashion in
event time, with the addition of process time timer to generate a watermark if there has been
a lull in events, thus also bounding the delay of generating a watermark in processing time.

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