[
https://issues.apache.org/jira/browse/HBASE-14268?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14937001#comment-14937001
]
Jingcheng Du commented on HBASE-14268:
--------------------------------------
Just my crazy thoughts.
As I know, an objects only with weak references would be collected when the
collector finds it. If this object is located in young gen, it might be
collected very fast.
If we have several threads to acquire and release the same lock, and we might
have one thread will stay long time in the while loop in get(K key) method of
WeakObjectPool (existingRef.get() will always get a null value) if other
threads acquire and release the same lock very fast?
This might hardly happen, but it might be possible right?
> Improve KeyLocker
> -----------------
>
> Key: HBASE-14268
> URL: https://issues.apache.org/jira/browse/HBASE-14268
> Project: HBase
> Issue Type: Improvement
> Components: util
> Reporter: Hiroshi Ikeda
> Assignee: Hiroshi Ikeda
> Priority: Minor
> Fix For: 2.0.0, 1.3.0
>
> Attachments: 14268-V5.patch, HBASE-14268-V2.patch,
> HBASE-14268-V3.patch, HBASE-14268-V4.patch, HBASE-14268-V5.patch,
> HBASE-14268-V5.patch, HBASE-14268-V6.patch, HBASE-14268-V7.patch,
> HBASE-14268-V7.patch, HBASE-14268-V7.patch, HBASE-14268-V7.patch,
> HBASE-14268.patch, KeyLockerIncrKeysPerformance.java,
> KeyLockerPerformance.java, ReferenceTestApp.java
>
>
> 1. In the implementation of {{KeyLocker}} it uses atomic variables inside a
> synchronized block, which doesn't make sense. Moreover, logic inside the
> synchronized block is not trivial so that it makes less performance in heavy
> multi-threaded environment.
> 2. {{KeyLocker}} gives an instance of {{RentrantLock}} which is already
> locked, but it doesn't follow the contract of {{ReentrantLock}} because you
> are not allowed to freely invoke lock/unlock methods under that contract.
> That introduces a potential risk; Whenever you see a variable of the type
> {{RentrantLock}}, you should pay attention to what the included instance is
> coming from.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
