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From "Stefan Egli (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (OAK-2682) Introduce time difference detection for DocumentNodeStore
Date Mon, 10 Aug 2015 11:54:47 GMT

    [ https://issues.apache.org/jira/browse/OAK-2682?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14679993#comment-14679993
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Stefan Egli commented on OAK-2682:
----------------------------------

[~chetanm], thx for the review!
bq. Though it would be good to also have RDB one working to avoid the ugly stacktrace at startup!
Agreed, though I would appreciate some guidance/help on this as I haven't had a look at RDBDocumentStore
so far - so either that ([~reschke], wdyt?) or it would take me a bit more time perhaps to
do it myself.
bq. However would it be possible to have some testcase say using virtual clock which simulates
the case and highlight the problem
I can try to come up with one, good idea. However, could we also deal with this in a follow-up
ticket or do you see this as blocking this ticket itself?

> 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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