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https://issues.apache.org/jira/browse/NIFI-3376?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16097373#comment-16097373
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Joseph Witt commented on NIFI-3376:
-----------------------------------
thinking on it more i'm back to appreciating the comments about locking and
behavior in supporting something like this in the current design of these
repositories. I could get very expensive to implement and maintain the same
level of consistency. I think if we can first be able to monitor/observe that
is step 1. Then I think we determine if reducing the max appendable claim size
offers a sufficient tradeoff. And if not then we probably need to evaluate
alternative designs for the repositories to better help the cases that the
monitoring reveals and that reduced claim sizes dont alter. These would be
things like having designed ability to move data to differing storage options
based on its age, size, loss tolerance, etc..
> 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
>
> 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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