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https://issues.apache.org/jira/browse/FLINK-5719?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15857797#comment-15857797
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Robert Metzger commented on FLINK-5719:
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Yes, changing from PublicEvolving to Internal is good!
I don't care so much about changing this, if you think its necessary.
One thing to consider however is the following: If we ever want to add a
functionality that allows operators to "add" latency, we need to expose the
latency markers to the operator.
One way to implement this feature would be adding an additional field to the
marker "addedLatency", where operators can add the milliseconds delay the
operator is adding.
> Let LatencyMarkers completely bypass operators / chains
> -------------------------------------------------------
>
> Key: FLINK-5719
> URL: https://issues.apache.org/jira/browse/FLINK-5719
> Project: Flink
> Issue Type: Improvement
> Components: DataStream API, Streaming
> Reporter: Tzu-Li (Gordon) Tai
>
> Currently, {{LatencyMarker}} s are forwarded through operators via the
> operator interfaces and methods, i.e.
> {{AbstractStreamOperator#processLatencyMarker()}},
> {{Output#emitLatencyMarker()}},
> {{OneInputStreamOperator#processLatencyMarker()}} etc.
> The main issue with this is that {{LatencyMarker}} s are essentially internal
> elements, and the implementation on how to handle them should be final.
> Exposing them through operator interfaces will allow the user to override the
> implementation, and also makes the user interface for operators
> over-complicated.
> [~aljoscha] suggested to bypass such internal stream elements from the
> operator to keep the operator interfaces minimal, in FLINK-5017.
> We propose a similar approach here for {{LatencyMarker}} as well. Since the
> chaining output calls contribute very little to the measured latency and can
> be ignored, instead of passing it through operator chains, latency markers
> can simply be passed downstream once tasks receive them.
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