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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (HBASE-4178) Use of Random.nextLong() in HRegionServer.addScanner(...)
Date Tue, 09 Aug 2011 23:41:27 GMT

     [ https://issues.apache.org/jira/browse/HBASE-4178?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Lars Hofhansl resolved HBASE-4178.

    Resolution: Won't Fix

> Use of Random.nextLong() in HRegionServer.addScanner(...)
> ---------------------------------------------------------
>                 Key: HBASE-4178
>                 URL: https://issues.apache.org/jira/browse/HBASE-4178
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.90.3
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>            Priority: Minor
> ScannerIds are currently assigned by getting a random long. While it would be a rare
occurrence that two scanners received the same ids on the same region server the results would
seem to be... Bad.
> A client scanner would get results from a different server scanner, and maybe only from
some of the region servers.
> A safer approach would be using an AtomicLong. We do not have to worry about running
of numbers: If we got 10000 scanners per second it'd take > 2.9m years to reach 2^63.
> Then again the same reasoning would imply that this collisions would be happening too
rarely to be of concern (assuming a good random number generator). So maybe this is a none-issue.
> AtomicLong would also imply a minor performance hit on multi core machines, as it would
force a memory barrier.

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