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https://issues.apache.org/jira/browse/KAFKA-2478?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dmitry Stratiychuk updated KAFKA-2478:
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    Status: Patch Available  (was: Open)

Here's a PR https://github.com/apache/kafka/pull/210

> KafkaConsumer javadoc example seems wrong
> -----------------------------------------
>
>                 Key: KAFKA-2478
>                 URL: https://issues.apache.org/jira/browse/KAFKA-2478
>             Project: Kafka
>          Issue Type: Bug
>          Components: consumer
>    Affects Versions: 0.9.0.0
>            Reporter: Dmitry Stratiychuk
>            Assignee: Neha Narkhede
>
> I was looking at this KafkaConsumer example in the javadoc:
> https://github.com/apache/kafka/blob/trunk/clients/src/main/java/org/apache/kafka/clients/consumer/KafkaConsumer.java#L199
> As I understand, commit() method commits the maximum offsets returned by the 
> most recent invocation of poll() method.
> In this example, there's a danger of losing the data.
> Imagine the case where 300 records are returned by consumer.poll()
> The commit will happen after inserting 200 records into the database.
> But it will also commit the offsets for 100 records that are still 
> unprocessed.
> So if consumer fails before buffer is dumped into the database again,
> then those 100 records will never be processed.
> If I'm wrong, could you please clarify the behaviour of commit() method?



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