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https://issues.apache.org/jira/browse/HBASE-14070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15378828#comment-15378828
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Sai Teja Ranuva commented on HBASE-14070:
-----------------------------------------
[~enis]
Again, Referring to description in the RB link.
"Undo updates to meta with local clock"
My understanding of why timestamps were assigned by the local clock in the
first place was to guard against the possible network reordering of delete
region, add region which might lead to add region to meta getting eclipsed.
In case my understanding is right, why are we undoing the local timestamps
updates to meta table? and does HLC help in this in any way ?
> Hybrid Logical Clocks for HBase
> -------------------------------
>
> Key: HBASE-14070
> URL: https://issues.apache.org/jira/browse/HBASE-14070
> Project: HBase
> Issue Type: New Feature
> Reporter: Enis Soztutar
> Assignee: Sai Teja Ranuva
> Attachments: HybridLogicalClocksforHBaseandPhoenix.docx,
> HybridLogicalClocksforHBaseandPhoenix.pdf
>
>
> HBase and Phoenix uses systems physical clock (PT) to give timestamps to
> events (read and writes). This works mostly when the system clock is strictly
> monotonically increasing and there is no cross-dependency between servers
> clocks. However we know that leap seconds, general clock skew and clock drift
> are in fact real.
> This jira proposes using Hybrid Logical Clocks (HLC) as an implementation of
> hybrid physical clock + a logical clock. HLC is best of both worlds where it
> keeps causality relationship similar to logical clocks, but still is
> compatible with NTP based physical system clock. HLC can be represented in
> 64bits.
> A design document is attached and also can be found here:
> https://docs.google.com/document/d/1LL2GAodiYi0waBz5ODGL4LDT4e_bXy8P9h6kWC05Bhw/edit#
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