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https://issues.apache.org/jira/browse/KAFKA-3821?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15323429#comment-15323429
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Randall Hauch commented on KAFKA-3821:
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Source tasks produce records by returning them from their {{poll()}} method,
and the records in the resulting list are ordered, and the lists of records are
ordered based upon the sequence of calls to {{poll()}}. Therefore, a
straightforward way to update the offset explicitly while maintaining this
order is to request it via inclusion of a special {{SourceRecord}} within the
list returned by {{poll()}}. Some ideas include:
* a {{SourceRecord}} object with a null (or special) topic, or a null key and
value; or
* a {{SourceRecord}} object with a null key and value; or
* a subclass of {{SourceRecord}} that denotes this particular kind of request.
Neither is clean or elegant. The first two are very implicit, while the second
requires more processing overhead and logic for every {{SourceRecord}} (though
there are ways around this that may be acceptable).
Any other thoughts?
> Allow Kafka Connect source tasks to produce offset without writing to topics
> ----------------------------------------------------------------------------
>
> Key: KAFKA-3821
> URL: https://issues.apache.org/jira/browse/KAFKA-3821
> Project: Kafka
> Issue Type: Improvement
> Components: KafkaConnect
> Affects Versions: 0.9.0.1
> Reporter: Randall Hauch
> Assignee: Ewen Cheslack-Postava
>
> Provide a way for a {{SourceTask}} implementation to record a new offset for
> a given partition without necessarily writing a source record to a topic.
> Consider a connector task that uses the same offset when producing an unknown
> number of {{SourceRecord}} objects (e.g., it is taking a snapshot of a
> database). Once the task completes those records, the connector wants to
> update the offsets (e.g., the snapshot is complete) but has no more records
> to be written to a topic. With this change, the task could simply supply an
> updated offset.
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