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https://issues.apache.org/jira/browse/NIFI-9390?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Peter Turcsanyi updated NIFI-9390:
----------------------------------
    Fix Version/s: 1.16.0
       Resolution: Fixed
           Status: Resolved  (was: Patch Available)

> MergeContent does not work properly in Kafka Connect Stateless flows
> --------------------------------------------------------------------
>
>                 Key: NIFI-9390
>                 URL: https://issues.apache.org/jira/browse/NIFI-9390
>             Project: Apache NiFi
>          Issue Type: Bug
>          Components: NiFi Stateless
>            Reporter: Peter Turcsanyi
>            Assignee: Peter Turcsanyi
>            Priority: Major
>              Labels: extensions, stateless
>             Fix For: 1.16.0
>
>          Time Spent: 2h 50m
>  Remaining Estimate: 0h
>
> MergeContent does not work in Kafka Connect Stateless flows if the processor 
> is not the first one in the flow.
> NIFI-8469 solved this issue for flows similar to the ones mentioned in that 
> jira:
> GetFile --> SplitText --> ReplaceText --> MergeContent --> PutS3Object
> In this scenario GetFile reads a file and creates a FF from it. SplitText 
> creates multiple FFs. ReplaceText processes all the FFs first and 
> MergeContent will be triggered only after ReplaceText finished with all FFs. 
> So it is able to merge the FFs (but only splits coming from the same input 
> file read by GetFile).
> A Kafka Connect Stateless Sink flow may look like this:
> Input port --> "Process/Transform messages" --> MergeContent --> PutS3Object
> The Kafka Connect framework polls some messages from the Kafka topic that 
> will be enqueued in the stateless flow. Then the first processor gets 
> triggered with one FF. This FF is sent downstream till the end of the flow. 
> MergeContent can only see one FF at a time so it cannot merge multiple files.
> So the issue is that the first processor gets triggered for each flowfile 
> separately (which is fine for GetFile but not for the KC Stateless flow). 
> Only subsequent processors get triggered in "triggerWhileReady" way:
> [https://github.com/apache/nifi/blob/18fc492e4ce97d2bca4f96df1a1f1eb2b3e80899/nifi-stateless/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/stateless/flow/StandardStatelessFlowCurrent.java#L68-L77]



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