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https://issues.apache.org/jira/browse/FLINK-5701?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15854409#comment-15854409
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ASF GitHub Bot commented on FLINK-5701:
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Github user tzulitai commented on the issue:
https://github.com/apache/flink/pull/3278
@tillrohrmann
Yes, in the condition that you described, then at-least-once doesn't hold.
I said _might_ mainly considering there is chance that for every checkpoint
barrier, the previous events (i.e. `event1` in your example) has been
committed. But yes, essentially this indeterminate behaviour means that it is
not at-least-once, so I'm incorrect in saying that it _might_.
I was trying to point out that this indeterminate behaviour made it hard to
have a stable test for `testAtLeastOnceProducerFailsIfFlushingDisabled()`
without relying on sleeping, which ultimately leads to flaky tests.
> FlinkKafkaProducer should check asyncException on checkpoints
> -------------------------------------------------------------
>
> Key: FLINK-5701
> URL: https://issues.apache.org/jira/browse/FLINK-5701
> Project: Flink
> Issue Type: Bug
> Components: Kafka Connector, Streaming Connectors
> Reporter: Tzu-Li (Gordon) Tai
> Priority: Critical
>
> Reported in ML:
> http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/Fink-KafkaProducer-Data-Loss-td11413.html
> The problem:
> The producer holds a {{pendingRecords}} value that is incremented on each
> invoke() and decremented on each callback, used to check if the producer
> needs to sync on pending callbacks on checkpoints.
> On each checkpoint, we should only consider the checkpoint succeeded iff
> after flushing the {{pendingRecords == 0}} and {{asyncException == null}}
> (currently, we’re only checking {{pendingRecords}}).
> A quick fix for this is to check and rethrow async exceptions in the
> {{snapshotState}} method both before and after flushing and
> {{pendingRecords}} becomes 0.
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