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https://issues.apache.org/jira/browse/OAK-4724?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15451795#comment-15451795
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Marcel Reutegger commented on OAK-4724:
---------------------------------------
With the number of writers increased to 20, the queue again fills up with
ObservationQueueTest (blue line). Enabling the prefetching feature with the
patch keeps the queue size low (orange line) even with increased number of
writers.
!queue.png|width=100%!
> Prefetch external changes
> -------------------------
>
> Key: OAK-4724
> URL: https://issues.apache.org/jira/browse/OAK-4724
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: core, documentmk
> Reporter: Marcel Reutegger
> Assignee: Marcel Reutegger
> Labels: observation
> Fix For: 1.6
>
> Attachments: OAK-4724.patch, queue.png
>
>
> In a cluster with listeners that are registered to receive external changes,
> pulling in external changes can become a bottleneck. While processing those
> external changes, further local changes are put into the observation queue
> leading to a system where the queue eventually fills up.
> Instead of processing external changes one after another, the implementation
> could prefetch them as they come in and if needed pull them in parallel.
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