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From "Chetan Mehrotra (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (OAK-4180) Use another NodeStore as a local cache for a remote Document store
Date Mon, 01 Aug 2016 05:50:20 GMT

     [ https://issues.apache.org/jira/browse/OAK-4180?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Chetan Mehrotra resolved OAK-4180.
       Resolution: Fixed
    Fix Version/s: 1.5.7

All planned work done. Specific issues can be opened going forward.

To enable this feature one needs to configure a SegmentNodeStore in secondary mode. 

Create OSGi config file {{org.apache.jackrabbit.oak.plugins.segment.SegmentNodeStoreService.cfg}}
with following content


And then configure {{org.apache.jackrabbit.oak.plugins.document.secondary.SecondaryStoreCacheService.config}}
with config
includedPaths=[ \

This determines what all paths are included for storage in secondary node store

> Use another NodeStore as a local cache for a remote Document store
> ------------------------------------------------------------------
>                 Key: OAK-4180
>                 URL: https://issues.apache.org/jira/browse/OAK-4180
>             Project: Jackrabbit Oak
>          Issue Type: New Feature
>          Components: documentmk
>            Reporter: Chetan Mehrotra
>            Assignee: Chetan Mehrotra
>              Labels: docs-impacting
>             Fix For: 1.6, 1.5.7
>         Attachments: OAK-4180-v1.patch
> DocumentNodeStore makes use of persistent cache to speed up its processing and save on
making remote calls for data already present in cache
> In addition to that we can look into make use of Segment NodeStore as kind of "local
copy" for certain paths in repository and route calls to it if possible. As part of this task
I would like to prototype such an approach. At high level it would work as below
> # At start bootstrap the setup and shutdown it down
> # Use a modified "sidegrade" and copy over the NodeStats from Document store to Segment
store. In such a copy we also store some Document specific properties like {{readRevision}}
and {{lastRevision}} as hidden property in Segment NodeStates
> # In DocumentNodeStore we refactor the current code to extract a 
> ## {{AbstractDocumentNodeState}} - Abase class which has some logic move out from {{DocumentNodeState}}
> ## {{SegmentDocumentNodeState}} extends above and delegate calls to a wrapped {{SegmentNodeState}}
> ## {{DocumentNodeState}} would also extend {{AbstractDocumentNodeState}} and hence delegate
to some calls to parent. In this when a call comes for {{getChildNode}} it can check if that
can be served by a local copy of {{SegmentNodeStore}} for given {{rootRevision}} then it delegates
to that
> # For update plan is to make use of {{Observer}} which listens to changes and updates
the local copy for certain configured paths. 
> ## Key aspect to address here is handle the restart case where in a cluster a specific
node restarts after some time then how it refreshes itself there
> *Usage*
> Following 2 OSGi configs would need to be seed
> * org.apache.jackrabbit.oak.plugins.segment.SegmentNodeStoreService.config
> {noformat}
> secondary=B"true"
> {noformat}
> * org.apache.jackrabbit.oak.plugins.document.secondary.SecondaryStoreCacheService.config
> {noformat}
> includedPaths=[ \
>   "/",
>   ]
> {noformat}
> With these settings if DocumentNodeStoreService gets started it would pickup the cache
and use it. Change {{includedPaths}} depending on paths in repository which you want to include
in secondary store t

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