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Date: Sat, 22 Sep 2012 04:02:08 +1100 (NCT)
From: "Hiroshi Ikeda (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
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Subject: [jira] [Updated] (HBASE-6651) Thread safety of HTablePool is
 doubtful
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     [ https://issues.apache.org/jira/browse/HBASE-6651?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Hiroshi Ikeda updated HBASE-6651:
---------------------------------

    Attachment: sharedmap_for_hbaseclient.zip

Added sample implementation which might be used to pool and share Connection instances between threads in HBaseClient. I use the name SharedMap, the old name of PoolMap.

In HBaseClient I think PoolMap with ThreadLocalPool leaks objects. Connection (extending Thead) automatically tries to remove itself from the pool at the end of its life, but its thread is different from the thread which created the instance of Connection and put into the pool.
                
> Thread safety of HTablePool is doubtful
> ---------------------------------------
>
>                 Key: HBASE-6651
>                 URL: https://issues.apache.org/jira/browse/HBASE-6651
>             Project: HBase
>          Issue Type: Bug
>          Components: Client
>    Affects Versions: 0.94.1
>            Reporter: Hiroshi Ikeda
>            Priority: Minor
>         Attachments: sample.zip, sample.zip, sharedmap_for_hbaseclient.zip
>
>
> There are some operations in HTablePool to access to PoolMap in multiple times without any explict synchronization. 
> For example HTablePool.closeTablePool() calles PoolMap.values(), and calles PoolMap.remove(). If other threads add new instances to the pool in the middle of the calls, the new added instances might be dropped. (HTablePool.closeTablePool() also has another problem that calling it by multple threads causes accessing HTable by multiple threads.)
> Moreover, PoolMap is not thread safe for the same reason.
> For example PoolMap.put() calles ConcurrentMap.get() and calles ConcurrentMap.put(). If other threads add a new instance to the concurent map in the middle of the calls, the new instance might be dropped.
> And also implementations of Pool have the same problems.

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