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https://issues.apache.org/jira/browse/NIFI-7557?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Bryan Bende resolved NIFI-7557.
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Fix Version/s: 1.13.0
Resolution: Fixed
> Cache large/common FlowFile attributes when restoring FlowFile Repository
> -------------------------------------------------------------------------
>
> Key: NIFI-7557
> URL: https://issues.apache.org/jira/browse/NIFI-7557
> Project: Apache NiFi
> Issue Type: Improvement
> Components: Core Framework
> Reporter: Mark Payne
> Assignee: Mark Payne
> Priority: Major
> Fix For: 1.13.0
>
> Time Spent: 40m
> Remaining Estimate: 0h
>
> When NiFi is restarted, it restores FlowFiles from the repository. Each
> attribute on a FlowFile is read from disk and put into a HashMap. There are
> times when a Processor will add a large attribute to every FlowFile that it
> sees, and this results in using much more heap upon NiFi restart to store
> FlowFiles than it does while NiFi is running. This is because the Processor
> holds the value of that FlowFile as a single String object and adds that
> String to the HashMap of attributes on every FlowFile.
> However, on restart, NiFi deserializes a byte stream to come up with the
> attribute value. As a result, each FlowFile that has that attribute value
> ends up with its own String object, even though the same value is repeated
> many times.
> As a result, a huge amount of heap may be used on restart, causing NiFi to
> encounter OOME when attempting to restore the FlowFile Repository.
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