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https://issues.apache.org/jira/browse/HBASE-4178?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13081935#comment-13081935
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stack commented on HBASE-4178:
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We have enough open ones already.
> 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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