[jira] [Created] (FLINK-3375) Allow Watermark Generation in the Kafka Source

["Stephan Ewen (JIRA)" <ji...@apache.org>]

Stephan Ewen created FLINK-3375:
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             Summary: Allow Watermark Generation in the Kafka Source
                 Key: FLINK-3375
                 URL: https://issues.apache.org/jira/browse/FLINK-3375
             Project: Flink
          Issue Type: Improvement
          Components: Kafka Connector
    Affects Versions: 1.0.0
            Reporter: Stephan Ewen
             Fix For: 1.0.0


It is a common case that event timestamps are ascending inside one Kafka Partition. Ascending timestamps are easy for users, because they are handles by ascending timestamp extraction.

If the Kafka source has multiple partitions per source task, then the records become out of order before timestamps can be extracted and watermarks can be generated.

If we make the FlinkKafkaConsumer an event time source function, it can generate watermarks itself. It would internally implement the same logic as the regular operators that merge streams, keeping track of event time progress per partition and generating watermarks based on the current guaranteed event time progress.



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