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From "Stefan Egli (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (OAK-2682) Introduce time difference detection for DocumentNodeStore
Date Tue, 11 Aug 2015 15:40:45 GMT

    [ https://issues.apache.org/jira/browse/OAK-2682?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14681961#comment-14681961
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Stefan Egli commented on OAK-2682:
----------------------------------

[~reschke], not quite sure I follow here. If the {{determineServerTimeDifferenceMillis}} additionally
carries a Collection (that's what you're suggesting, correct?), then how would the DocumentNodeStore
know which collection to pass in? Wouldn't that move the problem just up one level? Can't
the RDBDocumentStore just choose a table and hard code that? (I don't see an advantage of
having this as a parameter)

> Introduce time difference detection for DocumentNodeStore
> ---------------------------------------------------------
>
>                 Key: OAK-2682
>                 URL: https://issues.apache.org/jira/browse/OAK-2682
>             Project: Jackrabbit Oak
>          Issue Type: Improvement
>          Components: core, mongomk
>            Reporter: Stefan Egli
>            Assignee: Stefan Egli
>              Labels: resilience
>             Fix For: 1.3.5
>
>         Attachments: OAK-2682.patch
>
>
> Currently the lease mechanism in DocumentNodeStore/mongoMk is based on the assumption
that the clocks are in perfect sync between all nodes of the cluster. The lease is valid for
60sec with a timeout of 30sec. If clocks are off by too much, and background operations happen
to take couple seconds, you run the risk of timing out a lease. So introducing a check which
WARNs if the clocks in a cluster are off by too much (1st threshold, eg 5sec?) would help
increase awareness. Further drastic measure could be to prevent a startup of Oak at all if
the difference is for example higher than a 2nd threshold (optional I guess, but could be
20sec?).



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