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  1. Jackrabbit Oak
  2. OAK-4180

Use another NodeStore as a local cache for a remote Document store




      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

      1. At start bootstrap the setup and shutdown it down
      2. 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
      3. In DocumentNodeStore we refactor the current code to extract a
        1. AbstractDocumentNodeState - Abase class which has some logic move out from DocumentNodeState
        2. SegmentDocumentNodeState extends above and delegate calls to a wrapped SegmentNodeState
        3. 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
      4. For update plan is to make use of Observer which listens to changes and updates the local copy for certain configured paths.
        1. 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

      Following 2 OSGi configs would need to be seed

      • org.apache.jackrabbit.oak.plugins.segment.SegmentNodeStoreService.config
      • org.apache.jackrabbit.oak.plugins.document.secondary.SecondaryStoreCacheService.config
        includedPaths=[ \

      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.

      Feature Docs


        1. OAK-4180-v1.patch
          110 kB
          Chetan Mehrotra

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              chetanm Chetan Mehrotra
              chetanm Chetan Mehrotra
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