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From "Devin Bayer (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7035) thrift server closes HTable of open Scanners
Date Mon, 15 Jul 2013 07:30:48 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7035?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13708288#comment-13708288
] 

Devin Bayer commented on HBASE-7035:
------------------------------------

If you read [HTable|http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/client/HTable.html]
is says:

{quote}
This class is not thread safe for reads nor write.
...
In case of reads, some fields used by a Scan are shared among all threads. The HTable implementation
can either not contract to be safe in case of a Get
{quote}

That does not inspire confidence that scanners are or will remain threadsafe - in fact it
suggests the opposite.
                
> thrift server closes HTable of open Scanners
> --------------------------------------------
>
>                 Key: HBASE-7035
>                 URL: https://issues.apache.org/jira/browse/HBASE-7035
>             Project: HBase
>          Issue Type: Sub-task
>          Components: Thrift
>    Affects Versions: 0.94.4
>            Reporter: Devin Bayer
>              Labels: thrift2
>         Attachments: old-hbase-thrift-v1.patch
>
>   Original Estimate: 4h
>  Remaining Estimate: 4h
>
> ThriftHBaseServiceHandler.openScanner() does this:
> 1. table = pool.getTable()
> 2. scanner = table.getScanner()
> 3. table.close()
> 4. return scanner
> While back porting the thrift server to 0.92.6, I found that table.close() calls connection.close().
Further calls to scanner.next() raise a ConnectionClosed exception. The unit tests do not
catch this since they reuse an open HConnection instance.
> This might work on trunk, but depends on the implementations of HTablePool, HTable and
HConnectionManager. Even with the pool wrapper, if the pool is full, table.close() may be
called, which may invalidate the table. Also,  HTable is not thread-safe, but they are being
reused since they go back in the pool.
> I suggest storing the table handle along with the scanner.

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