[jira] [Updated] (HBASE-13378) RegionScannerImpl synchronized for READ_UNCOMMITTED Isolation Levels

["John Leach (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-13378?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

John Leach updated HBASE-13378:
-------------------------------
    Attachment: HBASE-13378.txt

Added patch HBASE-13378.txt that removes scans with IsolationLevel.READ_UNCOMMITED from synchronization block and from placement and removal from the readPoints ConcurrentHashMap.  

Hotspot is removed from our profiling. 

> RegionScannerImpl synchronized for READ_UNCOMMITTED Isolation Levels
> --------------------------------------------------------------------
>
>                 Key: HBASE-13378
>                 URL: https://issues.apache.org/jira/browse/HBASE-13378
>             Project: HBase
>          Issue Type: New Feature
>            Reporter: John Leach
>            Priority: Minor
>         Attachments: HBASE-13378.txt
>
>   Original Estimate: 2h
>  Remaining Estimate: 2h
>
> This block of code below coupled with the close method could be changed so that READ_UNCOMMITTED does not synchronize.  
> {CODE:JAVA}
>       // synchronize on scannerReadPoints so that nobody calculates
>       // getSmallestReadPoint, before scannerReadPoints is updated.
>       IsolationLevel isolationLevel = scan.getIsolationLevel();
>       synchronized(scannerReadPoints) {
>         this.readPt = getReadpoint(isolationLevel);
>         scannerReadPoints.put(this, this.readPt);
>       }
> {CODE}
> This hotspots for me under heavy get requests.



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