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https://issues.apache.org/jira/browse/FLINK-35749?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17862697#comment-17862697
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Fabian Paul commented on FLINK-35749:
-------------------------------------

[~zjmean] I can assign the ticket to you. Do you have a root cause for what is 
causing the issue?

 

>From the information in the ticket, it's hard to find the reason since it 
>misses critical information.
 * How did you configure your Flink job e.g. checkpointing, boundedness?
 * Which Flink version do you use?
 * Are you using the KafkaSink with exactly once semantics?
 * How do you count the messages in the output topic, e.g., only committed 
records?

> Kafka sink component will lose data when kafka cluster is unavailable for a 
> while
> ---------------------------------------------------------------------------------
>
>                 Key: FLINK-35749
>                 URL: https://issues.apache.org/jira/browse/FLINK-35749
>             Project: Flink
>          Issue Type: Bug
>          Components: Connectors / Kafka
>    Affects Versions: 1.16.2, 1.17.1, 1.20.0
>            Reporter: Jimmy Zhao
>            Priority: Blocker
>
> As the title described, here is the procedure to reproduce the problem:
> 1. develop a simple flink stream job to consume from one kafka topic and sink 
> to anthoer kafka sever and topic
> 2. make amount of kafka message and produce to the source kafka topic, record 
> the message number
> 3. start the flink stream job, and config to cosume from earliest source 
> topic offset
> 4. during the job cosuming the source topic, restart the kafka cluster(we use 
> aws MSK)
> 5. the flink job will not throw any Exception like nothing happened, but only 
> print error log like : [kafka-producer-network-thread | producer-2] INFO  
> org.apache.kafka.clients.NetworkClient  - [Producer clientId=producer-2] Node 
> 2 disconnected.
> 6. wait for the kafka cluster finished restarting and all the source kafka 
> message consumed
> 7. count the target kafka topic message number, compare to the source, there 
> is a high probability of data loss(more than 50%)



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