[jira] [Commented] (KAFKA-14947) Duplicate records are getting created in the topic.

["Yash Mayya (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-14947?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17718513#comment-17718513 ] 

Yash Mayya commented on KAFKA-14947:
------------------------------------

[~krishnendudas] the offset commits for source connectors were asynchronous and periodic even in AK 2.6.2, see [this class|https://github.com/apache/kafka/blob/da65af02e5856e3429259e26eb49986122e34747/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/SourceTaskOffsetCommitter.java#L47].

 
{quote}With our existing connect API code and with the Kafka server (2.6.2), our ingestion mechanism was working fine in the live environment. We checked the Kafka server (2.6.2) WorkerSourceTask::execute() method, and it was following the below-mentioned execution path
 # Poll the task for the new data.
 # If get any data, save the new data into the Kafka topic.
 # Commit the offset.{quote}
 

This isn't exactly accurate as the offset commit part isn't done synchronously with the poll and the produce (to the Kafka topic). Perhaps the *offset.flush.interval.ms* worker configuration (which determines the offset commit interval) is different between your two environments?

 
{quote}But that willn't be persistent. At every start, the object will be reset. Any suggestion, on how we can make it persistent in the new Kafka server (3.1.1) 
{quote}
 

That will always be the case for restarts which is why I mentioned in my previous comment that source offsets are typically queried from the offset storage only during connector / task startup. I'm not sure I follow why the local in-memory offset can't be used during regular running of the connector task?

> Duplicate records are getting created in the topic. 
> ----------------------------------------------------
>
>                 Key: KAFKA-14947
>                 URL: https://issues.apache.org/jira/browse/KAFKA-14947
>             Project: Kafka
>          Issue Type: Bug
>          Components: producer 
>    Affects Versions: 3.1.1
>            Reporter: krishnendu Das
>            Priority: Blocker
>         Attachments: Kafka_server_3.1.1_data_duplication_issue_log
>
>
> We are using Kafka connect API (version 2.3.0) and Kafka  (version 3.1.1) for data ingestion purposes. Previously we were using Kafka (version 2.6.2) and the same Kafka connect API (version 2.3.0). The data ingestion was happening properly. 
>  
> Recently we updated the Kafka version from 2.6.2 to 3.1.1.
> Post update we are facing duplicate data issues from the source connector into the Kafka topic. After debugging the 3.1.1 code, we saw one new function
> {*}updateCommittableOffsets{*}() got added and called inside the {*}WorkerSourceTask::execute{*}() as part of bug fix --"KAFKA-12226: Commit source task offsets without blocking on batch delivery (#11323)"
>  
> Now because of this function, we are observing this scenario
>  # Inside the execute() at the start of the flow, the call goes to updateCommittableOffsets() to check if anything was there to perform the committed offset or not. As the first poll is still not yet happened, this function didn't find anything for commit.
>  # Then Kafka connects API poll() method is called from the WorkerSourceTask::execute(). *---------> 1st poll*
>  # Kafka Connect API (using sleepy policy) reads one source file from the Cloud source directory.
>  # Read the whole content of the file and send the result set Kafka server to write to the Kafka topic.
>  # During the 2nd poll updateCommittableOffsets() found some offset to commit and its updates a reference variable committableOffsets, which will be used further by the WorkerSourceTask::commitOffsets() function to perform actual commit offset.
>  # Then Kafka connects the API poll() method is called from the *WorkerSourceTask::execute().* *---------> 2nd poll*
>  # Kafka Connect API (using sleepy policy) reads the same source file again from the start, as the offsetStrorageReader::offset() didn’t give the latest offset.
>  # Read the whole content of the file and send the result set Kafka server to write to the Kafka topic.---> These create duplicate data into the topic.
> ................................................
> ................................................
>  # WorkerSourceTask::commitOffsets() commits the offset.
> ................................................
> ................................................
>  # Then Kafka connects API poll() method is called from the {*}WorkerSourceTask::execute(){*}. ---------> 3rd poll
>  # This time offsetStrorageReader::offset() will be able to give the latest offset.
>  # Kafka Connect API (using sleepy policy) reads the same source file from the last read position.



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