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https://issues.apache.org/jira/browse/NIFI-3860?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16004848#comment-16004848
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Brandon DeVries commented on NIFI-3860:
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Is there an actual use case that this is addressing? This feels like the sort
of thing that could end up with unintended consequences / unanticipated
effects. If there isn't a compelling reason to make a change, I don't know
that I would...
> Consider relaxing the constraint that ProcessSession enforces we give it the
> most recent version of a FlowFile
> --------------------------------------------------------------------------------------------------------------
>
> Key: NIFI-3860
> URL: https://issues.apache.org/jira/browse/NIFI-3860
> Project: Apache NiFi
> Issue Type: Improvement
> Components: Core Framework
> Reporter: Mark Payne
> Assignee: Mark Payne
>
> Currently, when we call methods on ProcessSession to access or modify a
> FlowFile, the ProcessSession will roll itself back and throw a
> FlowFileHandlingException with the message "<FlowFile> is not the most recent
> version of this FlowFile within this session". This was done to ensure that
> Processor developers ensure that they know what they are doing and always
> have the most recent version of a FlowFile. However, this comes with a few
> downsides:
> * It can result in code being complex in error-handling cases when we need to
> ensure that no matter what we hold the most recent version of a FlowFile
> * It's easy to call session.putAttribute and forget to store the most recent
> version of the FlowFile, which gets returned - this is most problematic when
> dealing with a Collection<FlowFile>.
> * We have a method for ProcessSession.read(FlowFile) that returns an
> InputStream. However, we don't have a corresponding write() method. This is
> due to the fact that once we finish writing to the FlowFile, we would have to
> return the most up-to-date version of the FlowFile and there's no way to do
> that if returning an OutputStream.
> We should consider relaxing this constraint and instead just always make use
> of the most recent version of the FlowFile, even if an older version of the
> FlowFile is passed in.
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