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https://issues.apache.org/jira/browse/OAK-591?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13577652#comment-13577652
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Thomas Mueller commented on OAK-591:
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I think it's a more general problem, not so much related to the API.
Let's assume there is only one oak-core writing to the storage backend. In that
case oak-core could use an efficient cache, knowing that a node can only be
changed if the same oak-core update it.
In a cluster, with multiple oak-core instances writing to the same storage
backend, if you want to ensure you read the latest data, you will have to ask
the backend. Unless if you get notified by the storage backend about
modifications. Or if you don't always need to ensure you are working with the
very latest data.
> Improve KernelNodeStore cache efficiency
> ----------------------------------------
>
> Key: OAK-591
> URL: https://issues.apache.org/jira/browse/OAK-591
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: core
> Affects Versions: 0.6
> Reporter: Marcel Reutegger
> Attachments: mk.log.gz, OAK-591.patch
>
>
> The cache in KernelNodeStore references entries with a path+revision combo.
> This mapping quickly becomes inefficient when there are writes on the
> repository. Whenever something is changed, the complete cache basically
> becomes invalid and oak-core needs to re-fetch nodes again, even though they
> didn't change. The attached test shows this behaviour. The test initially
> creates 10 nodes and lets a thread read those nodes repeatedly. To make the
> test somewhat realistic the reader acquires a new session in every run
> through the loop. This is to simulate e.g. a request which acquires a new
> session every time (Apache Sling does it that way). At the same time writes
> occur but in a separate part of the repository. As can be seen in the logs,
> the nodes are read from the MicroKernel whenever something changes anywhere
> in the repository. Obviously this is no limited to the test nodes. The log
> also shows repeated reads to node type, user and index nodes. None of them
> change while the test runs.
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