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Date: Fri, 10 Mar 2017 02:40:38 +0000 (UTC)
From: "Enis Soztutar (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
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Subject: [jira] [Commented] (HBASE-14070) Hybrid Logical Clocks for HBase
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archived-at: Fri, 10 Mar 2017 02:40:45 -0000


    [ https://issues.apache.org/jira/browse/HBASE-14070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15904295#comment-15904295 ] 

Enis Soztutar commented on HBASE-14070:
---------------------------------------

Yep, this would be pretty good if we can get it in. Last time I've looked at it is some time ago. If you want to pick it up, go for it. 

> 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: HBASE-14070.master.001.patch, 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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