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https://issues.apache.org/jira/browse/FLINK-5701?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15860859#comment-15860859
 ] 

ASF GitHub Bot commented on FLINK-5701:
---------------------------------------

Github user tzulitai commented on a diff in the pull request:

    https://github.com/apache/flink/pull/3278#discussion_r100482362
  
    --- Diff: 
flink-connectors/flink-connector-kafka-base/src/test/java/org/apache/flink/streaming/connectors/kafka/FlinkKafkaProducerBaseTest.java
 ---
    @@ -293,6 +293,61 @@ public void run() {
                testHarness.close();
        }
     
    +   /**
    +    * This test is meant to assure that testAtLeastOnceProducer is valid 
by testing that if flushing is disabled,
    +    * the snapshot method does indeed finishes without waiting for pending 
records;
    +    * we set a timeout because the test will not finish if the logic is 
broken
    +    */
    +   @Test(timeout=5000)
    +   public void testDoesNotWaitForPendingRecordsIfFlushingDisabled() throws 
Throwable {
    +           final OneShotLatch inputLatch = new OneShotLatch();
    +
    +           final DummyFlinkKafkaProducer<String> producer = new 
DummyFlinkKafkaProducer<>(
    --- End diff --
    
    Turns out that we must have an extension of `KafkaProducer` provided to 
`FlinkKafkaProducerBase`. The reason is that the producer base requires 
implementing an abstract `flush` method, which doesn't exist on the 
`KafkaProducer`'s interface. So it'll be more straightforward to extend 
`KafkaProducer` and implement a `flush` method ourselves, and let 
`FlinkKafkaProducerBase` call that.


> 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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