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https://issues.apache.org/jira/browse/FLINK-5048?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15927941#comment-15927941
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Stephan Ewen commented on FLINK-5048:
-------------------------------------
Sorry to come late here. The fix did not change user-facing behavior - it is
completely internal to the KafkaConsumer. It also proved pretty good and stable.
On the other hand, I think users can simply use the 1.2.0 kafka consumer with
Flink 1.1.x if there is an issue.
> Kafka Consumer (0.9/0.10) threading model leads problematic cancellation
> behavior
> ---------------------------------------------------------------------------------
>
> Key: FLINK-5048
> URL: https://issues.apache.org/jira/browse/FLINK-5048
> Project: Flink
> Issue Type: Bug
> Components: Kafka Connector
> Affects Versions: 1.1.3
> Reporter: Stephan Ewen
> Assignee: Stephan Ewen
> Priority: Blocker
> Fix For: 1.2.0
>
>
> The {{FLinkKafkaConsumer}} (0.9 / 0.10) spawns a separate thread that
> operates the KafkaConsumer. That thread is shielded from interrupts, because
> the Kafka Consumer has not been handling thread interrupts well.
> Since that thread is also the thread that emits records, it may block in the
> network stack (backpressure) or in chained operators. The later case leads to
> situations where cancellations get very slow unless that thread would be
> interrupted (which it cannot be).
> I propose to change the thread model as follows:
> - A spawned consumer thread pull from the KafkaConsumer and pushes its
> pulled batch of records into a blocking queue (size one)
> - The main thread of the task will pull the record batches from the
> blocking queue and emit the records.
> This allows actually for some additional I/O overlay while limiting the
> additional memory consumption - only two batches are ever held, one being
> fetched and one being emitted.
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