[
https://issues.apache.org/jira/browse/HBASE-14070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15379899#comment-15379899
]
Sai Teja Ranuva commented on HBASE-14070:
-----------------------------------------
I feel it is better to use HLC time in places where we are interested(like
puts, deletes etc), for places where difference in time is needed rather than
the exact time., physical time can be used.
1. This saves us from some contention as HLC.getCurrentTime is
synchronized(This could be significant because, I see that currentTime is being
called everywhere in the code for setting names of files to finding difference
in time etc)
2. Also clears any fuzziness in time difference(insignificant with TTL in hours)
> 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#
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
