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From "Hiroshi Ikeda (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-6651) Improve thread safety of HTablePool
Date Fri, 28 Mar 2014 03:07:19 GMT

     [ https://issues.apache.org/jira/browse/HBASE-6651?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Hiroshi Ikeda updated HBASE-6651:

    Attachment: HBASE-6651-V14-trunk.patch

Added fixed patches for 0.96, 0.98 and trunk.

I reduced changing of existing codes, which have been quickly changed and too difficult to
aim. I also added new methods to ShardMap to refer its registered objects, which introduced
possibility to invalidly access thread unsafe objects, but I compromised because of applicability
to existing codes, and then I excluded some unused classes that I had created.

This ticket was created about more than a year ago and I already forgot many things, but HBase
still uses PoolMap that violates the contract of Map, inconsistently changes its methods'
behaviors by pool-type, and fails to keep thread-safety, so I hope the patches help.

> Improve thread safety of HTablePool
> -----------------------------------
>                 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
>            Assignee: Hiroshi Ikeda
>         Attachments: HBASE-6651-V10.patch, HBASE-6651-V11.patch, HBASE-6651-V12.patch,
HBASE-6651-V13.patch, HBASE-6651-V14-0.96.patch, HBASE-6651-V14-0.98.patch, HBASE-6651-V14-trunk.patch,
HBASE-6651-V2.patch, HBASE-6651-V3.patch, HBASE-6651-V4.patch, HBASE-6651-V5.patch, HBASE-6651-V6.patch,
HBASE-6651-V7.patch, HBASE-6651-V8.patch, HBASE-6651-V9.patch, HBASE-6651.patch, sample.zip,
sample.zip, sharedmap_for_hbaseclient.zip
> There are some operations in HTablePool accessing PoolMap in multiple places without
any explicit synchronization. 
> For example HTablePool.closeTablePool() calls PoolMap.values(), and calls PoolMap.remove().
If other threads add new instances to the pool in the middle of the calls, the newly added
instances might be dropped. (HTablePool.closeTablePool() also has another problem that calling
it by multiple 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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