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https://issues.apache.org/jira/browse/OAK-591?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13577580#comment-13577580
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Michael Dürig commented on OAK-591:
-----------------------------------
Isn't what you describe a problem to any such system, not only for the current
Microkernel/API? After all, the fact that the underlying storage layer can do
more efficient caching relies on an implementation detail: namely that nodes
are shared across revisions (i.e. cheaply copied). Any attempt of leveraging
this for a cache in an upper layer will necessarily break encapsulation.
To me this seems to be a further indication that the cache is in the wrong
place. As [~jukkaz] mentioned yesterday, oak-core does neither know enough
about how the data is stored neither on how it is consumed.
> 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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