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https://issues.apache.org/jira/browse/OAK-2829?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Julian Sedding updated OAK-2829:
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Attachment: CompareAgainstBaseStateTest.java
A few weeks ago, while testing the migration of a CRX repository to a local
MongoDB, I made some observations that may be related.
I was working with a modified version of oak-upgrade that allows incremental
(or repeated) copying of a JR2 repo into an Oak repo. During the second run,
with an identical source repo, I noticed that a lot of time was spent in the
commit hooks calculating diffs.
In DocumentNodeState#compareAgainstBaseState(), I experimentally skipped the
optimization for DocumentNodeState instances, thus falling back to the generic
implementation in AbstractNodeState. For this specific case, where a large
commit is compared with no or very few changes, this accellerated the commit
hooks by a factor of ~10. I have tried to reproduce this in a synthetic
benchmark, but there I only managed to produce a scenario that had comparable
performance for both.
So while I don't understand the exact parameters, I provide this input in the
hope that it will be helpful in resolving this issue. I'll also attach the
benchmark class.
> Comparing node states for external changes is too slow
> ------------------------------------------------------
>
> Key: OAK-2829
> URL: https://issues.apache.org/jira/browse/OAK-2829
> Project: Jackrabbit Oak
> Issue Type: Bug
> Components: core, mongomk
> Reporter: Marcel Reutegger
> Assignee: Marcel Reutegger
> Priority: Blocker
> Fix For: 1.3.0, 1.2.3
>
> Attachments: CompareAgainstBaseStateTest.java, graph.png
>
>
> Comparing node states for local changes has been improved already with
> OAK-2669. But in a clustered setup generating events for external changes
> cannot make use of the introduced cache and is therefore slower. This can
> result in a growing observation queue, eventually reaching the configured
> limit. See also OAK-2683.
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