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From "Chetan Mehrotra (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (OAK-2682) Introduce time difference detection for DocumentNodeStore
Date Mon, 10 Aug 2015 03:50:45 GMT

    [ https://issues.apache.org/jira/browse/OAK-2682?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14679525#comment-14679525
] 

Chetan Mehrotra commented on OAK-2682:
--------------------------------------

Changes look fin. Though it would be good to also have RDB one working to avoid the ugly stacktrace
at startup!

[~egli] I understand the reproducing the scenario mentioned in this issue is tricky i.e. potential
problematic case that would arise if clock goes out of sysnc. However would it be possible
to have some testcase say using virtual clock which simulates the case and highlight the problem

> 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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