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https://issues.apache.org/jira/browse/OAK-2045?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Chetan Mehrotra updated OAK-2045:
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Attachment: OAK-2045-segment-fault-approach.patch
[patch|^OAK-2045-segment-fault-approach.patch] based on Segment fault approach
which relies on logical linking of SegmentNodeState based on path they refer to
post cleanup.
Each segmentId would records its in memory creationTime. Further each
{{SegmentNodeState}} would maintain a path property if the state is part of
repository tree. While performing cleanup those segmentId would be marked stale
which are considered _old_. Due to this when a SegmentNodeState which refers to
an old revision tries to access any property then it would result in a
{{SegmentStaleException}}. Upon detecting such an exception aka _SegmentFault_
the state would locate the latest nodeState for the given path and update its
segmentId.
SegementNodeState maintains an in memory state of templateId. Once the backing
segment turn stale this state also need to be purged. To manage that each
SegmentNodeState registers itself with the SegementId. Once any SegmentId is
marked stale then each linked SegmentNodeState is refreshed such that they let
go of in memory state.
This should enable JCR session which hold reference to old NodeState upon
startup be linked to latest NodeState and allow collection of revisions from
those states.
Points to consider
* cleanup and lastCreationTime - The time argument passed to cleanup call
should be older than any pending session operation. This can be based on
lastSave from SessionMbeans.
*Cons*
* Need to make the segmentId and offset volatile in Record which does not look
good and might have some effect on access performance
* SegmentId maintains a wekreference list of the SegmentNodeState - This might
need bit more care
[~alexparvulescu] [~jukkaz] [~mduerig] [~tmueller] [~mreutegg] Kindly review
> Long running JCR session prevent live cleanup in Segment FileStore
> ------------------------------------------------------------------
>
> Key: OAK-2045
> URL: https://issues.apache.org/jira/browse/OAK-2045
> Project: Jackrabbit Oak
> Issue Type: Bug
> Components: segmentmk
> Reporter: Chetan Mehrotra
> Assignee: Chetan Mehrotra
> Fix For: 1.1
>
> Attachments: OAK-2045-segment-fault-approach.patch,
> OAK-2045-test-fix.patch
>
>
> Cleanup operation in SegmentNodeStore detects the un referenced garbage and
> clean it up. To determine the reference validity it starts with an initial
> set of SegmentId which have a live java reference.
> This works fine for simple setup but when Oak repository is used in an
> application (like Sling) where application code can create long running
> session (for observation) then such session are bound to old NodeState at
> time of startup. Such references prevent the cleanup logic to remove older
> revisions while system is running. Such revisions can only be removed via an
> offline compaction-> cleanup.
> Need to find out a way where we can _migrate_ such old NodeState references
> to newer revisions
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