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https://issues.apache.org/jira/browse/OAK-2808?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16028030#comment-16028030
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Chetan Mehrotra commented on OAK-2808:
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bq. as discussed earlier, we now instantiate directory factory on each indexing
cycle. But, that required hacky modification of setDirectoryFactory (used in
oak-run for out-of-band indexing feature) - I'm not feeling so good about the
approach :-/
Another approach which can be used here is
* Let DefaultDirectoryFactory implement IndexCommitCallback
* Have a single instance of factory which also refers to
activeDeletedBlobCollector
* Register the factory with IndexingContext if it implements callback interface
bq. I looked at doing it the jmx way we discussed - but afaics we'd have to
depend on sun management package... I want to avoid that
No need for that. You can add a reference to CheckpointMBean in
LuceneIndexProviderService. This can then be passed to
ActiveDeletedBlobCollectorFactory
> Active deletion of 'deleted' Lucene index files from DataStore without
> relying on full scale Blob GC
> ----------------------------------------------------------------------------------------------------
>
> Key: OAK-2808
> URL: https://issues.apache.org/jira/browse/OAK-2808
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: lucene
> Reporter: Chetan Mehrotra
> Assignee: Vikas Saurabh
> Labels: datastore, performance
> Fix For: 1.8
>
> Attachments: copyonread-stats.png, OAK-2808-1.patch
>
>
> With storing of Lucene index files within DataStore our usage pattern
> of DataStore has changed between JR2 and Oak.
> With JR2 the writes were mostly application based i.e. if application
> stores a pdf/image file then that would be stored in DataStore. JR2 by
> default would not write stuff to DataStore. Further in deployment
> where large number of binary content is present then systems tend to
> share the DataStore to avoid duplication of storage. In such cases
> running Blob GC is a non trivial task as it involves a manual step and
> coordination across multiple deployments. Due to this systems tend to
> delay frequency of GC
> Now with Oak apart from application the Oak system itself *actively*
> uses the DataStore to store the index files for Lucene and there the
> churn might be much higher i.e. frequency of creation and deletion of
> index file is lot higher. This would accelerate the rate of garbage
> generation and thus put lot more pressure on the DataStore storage
> requirements.
> Discussion thread http://markmail.org/thread/iybd3eq2bh372zrl
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