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https://issues.apache.org/jira/browse/OAK-2131?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14616440#comment-14616440
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Stefan Egli edited comment on OAK-2131 at 7/7/15 9:49 AM:
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bq. Or do you mean it does actually happen, but when LastRevRecoveryAgent is
triggered, it updates _lastRevs that aren't really necessary?
yes. The root is updated at an earlier stage since {{Commit}} does not filter
out the root (and parents that have no content changes). So as I understand the
rational behind OAK-2131 it tries to reduce the number of {{_lastRev}} changes
by using the fact that if there is a content change that will be visible in the
parent anyway via the commitRoot - so it is using that instead of explicitly
updating {{_lastRev}}. However, the {{LastRevRecoveryAgent}} does not do this
optimization (which I think it is correct to not do) and updates all
{{_lastRev}}s that the {{Commit}} has "optimized-away"
bq. In any case, can you please file a new issue and provide information about
how to reproduce?
yes, I can do that
was (Author: egli):
bq. Or do you mean it does actually happen, but when LastRevRecoveryAgent is
triggered, it updates _lastRevs that aren't really necessary?
yes. The root is updates at an earlier stage since {{Commit}} does not filter
out the root (and parents that have no content changes). So as I understand the
rational behind OAK-2131 it tries to reduce the number of {{_lastRev}} changes
by using the fact that if there is a content change that will be visible in the
parent anyway via the commitRoot - so it is using that instead of explicitly
updating {{_lastRev}}. However, the {{LastRevRecoveryAgent}} does not do this
optimization (which I think it is correct to not do) and updates all
{{_lastRev}}s that the {{Commit}} has "optimized-away"
bq. In any case, can you please file a new issue and provide information about
how to reproduce?
yes, I can do that
> Reduce usage of _lastRev
> ------------------------
>
> Key: OAK-2131
> URL: https://issues.apache.org/jira/browse/OAK-2131
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: core, mongomk
> Reporter: Marcel Reutegger
> Assignee: Marcel Reutegger
> Fix For: 1.1.3
>
> Attachments: OAK-2131.patch
>
>
> As described in OAK-1768 the usage of _lastRev must be reduced to better
> handle large transaction. The short term solution implemented for OAK-1768
> relies on MapDB to temporarily store the pending modifications to a temp
> file. This solution prevents an OOME when there is a large commit, but can
> take quite a while to update the _lastRev fields after the branch is merged.
> This has an impact on the visibility of changes in a cluster because any
> further changes done after the merge only become visible when the large
> update of the _lastRev fields went through.
> Delayed propagation of changes can become a problem in a cluster when some
> components rely on a timely visibility of changes. One example is the Apache
> Sling Topology, which sends heartbeats through the cluster by updating
> properties in the repository. The topology implementation will consider a
> cluster node dead if those updates are not propagated in the cluster within a
> given timeout. Ultimately this may lead to a cluster with multiple leaders.
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