[jira] [Commented] (HBASE-4178) Use of Random.nextLong() in HRegionServer.addScanner(...)

["Lars Hofhansl (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-4178?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13081306#comment-13081306 ] 

Lars Hofhansl commented on HBASE-4178:
--------------------------------------

It would > 29m years... 

> 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
>            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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