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From "Sai Teja Ranuva (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14070) Hybrid Logical Clocks for HBase
Date Tue, 19 Jul 2016 22:08:20 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15384963#comment-15384963
] 

Sai Teja Ranuva commented on HBASE-14070:
-----------------------------------------

Thank you for your insights and suggestions.
I think it makes sense to drop System time as suggested.

> 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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