[jira] [Updated] (NIFI-3376) Implement content repository ResourceClaim compaction

["Michael Moser (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/NIFI-3376?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Michael Moser updated NIFI-3376:
--------------------------------
    Attachment: NIFI-3376_Content_Repo_size_demo.xml

Attached is a template that generates flowfiles that get bundled into a single claim.  Most get deleted but a few are kept in a queue.
Set nifi.content.repository.archive.enabled=false in nifi.properties.  Start NiFi, load template into its graph, and start processors mentioned in the labels.  After several minutes, check the size of the content_repository on disk and observe the content claim files that remain on disk.
It's notable that FileSystemRepository has a thread that runs every 2 minutes to archive or delete (for this test, delete) content claim files that are no longer referenced.  So you can stop the processors and let NiFi chill for > 2 minutes and the content repository will reach a steady state.

> Implement content repository ResourceClaim compaction
> -----------------------------------------------------
>
>                 Key: NIFI-3376
>                 URL: https://issues.apache.org/jira/browse/NIFI-3376
>             Project: Apache NiFi
>          Issue Type: Improvement
>          Components: Core Framework
>    Affects Versions: 0.7.1, 1.1.1
>            Reporter: Michael Moser
>            Assignee: Michael Hogue
>         Attachments: NIFI-3376_Content_Repo_size_demo.xml
>
>
> On NiFi systems that deal with many files whose size is less than 1 MB, we often see that the actual disk usage of the content_repository is much greater than the size of flowfiles that NiFi reports are in its queues.  As an example, NiFi may report "50,000 / 12.5 GB" but the content_repository takes up 240 GB of its file system.  This leads to scenarios where a 500 GB content_repository file system gets 100% full, but "I only had 40 GB of data in my NiFi!"
> When several content claims exist in a single resource claim, and most but not all content claims are terminated, the entire resource claim is still not eligible for deletion or archive.  This could mean that only one 10 KB content claim out of a 1 MB resource claim is counted by NiFi as existing in its queues.
> If a particular flow has a slow egress point where flowfiles could back up and remain on the system longer than expected, this problem is exacerbated.
> A potential solution is to compact resource claim files on disk. A background thread could examine all resource claims, and for those that get "old" and whose active content claim usage drops below a threshold, then rewrite the resource claim file.
> A potential work-around is to allow modification of the FileSystemRepository MAX_APPENDABLE_CLAIM_LENGTH to make it a smaller number.  This would increase the probability that the content claims reference count in a resource claim would reach 0 and the resource claim becomes eligible for deletion/archive.  Let users trade-off performance for more accurate accounting of NiFi queue size to content repository size.



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