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https://issues.apache.org/jira/browse/FLINK-4796?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16166443#comment-16166443
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Erik van Oosten commented on FLINK-4796:
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I am not sure why this is marked as a duplicate. The problem here is 
inconsistent handling of the runtime context inside the different layers under 
FlinkKafkaProducer: method {{getRuntimeContext}} gives {{null}} even though 
{{setRuntimeContext}} was called.

How does that relate to the addition of a new interface?

> Add new Sink interface with access to more meta data
> ----------------------------------------------------
>
>                 Key: FLINK-4796
>                 URL: https://issues.apache.org/jira/browse/FLINK-4796
>             Project: Flink
>          Issue Type: Improvement
>          Components: DataStream API
>    Affects Versions: 1.2.0
>            Reporter: Robert Metzger
>            Assignee: Aljoscha Krettek
>
> The current {{SinkFunction}} cannot access the timestamps of elements which 
> resulted in the (somewhat hacky) {{FlinkKafkaProducer010}}. Due to other 
> limitations {{GenericWriteAheadSink}} is currently also a {{StreamOperator}} 
> and not a {{SinkFunction}}.
> We should add a new interface for sinks that takes a context parameter, 
> similar to {{ProcessFunction}}. This will allow sinks to query additional 
> meta data about the element that they're receiving. 
> This is one ML thread where a user ran into a problem caused by this: 
> http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/Why-I-am-getting-Null-pointer-exception-while-accessing-RuntimeContext-in-FlinkKafkaProducer010-td12633.html#a12635
> h3. Original Text (that is still valid but not general)
> The Kafka 0.10 connector supports writing event timestamps to Kafka.
> Currently, the regular DataStream APIs don't allow user code to access the 
> event timestamp easily. That's why the Kafka connector is using a custom 
> operator ({{transform()}}) to access the event time.
> With this JIRA, I would like to provide the event timestamp in the regular 
> DataStream APIs.
> Once I'll look into the issue, I'll post some proposals how to add the 
> timestamp. 



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