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From "Enis Soztutar (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-14070) Hybrid Logical Clocks for HBase
Date Tue, 14 Jul 2015 02:23:04 GMT
Enis Soztutar created HBASE-14070:

             Summary: 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. 

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