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From "Enis Soztutar (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-14070) Hybrid Logical Clocks for HBase
Date Tue, 14 Jul 2015 02:24:07 GMT

     [ https://issues.apache.org/jira/browse/HBASE-14070?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Enis Soztutar updated HBASE-14070:
----------------------------------
    Description: 
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#


  was:
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. 



> 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: Enis Soztutar
>
> 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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