[jira] [Updated] (HBASE-14268) Improve KeyLocker

["Hiroshi Ikeda (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-14268?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Hiroshi Ikeda updated HBASE-14268:
----------------------------------
    Attachment: HBASE-14268-V7.patch

Added a revised patch.

Removed the condition that the generics type {{K}} must extend {{Comparable}}, and allowed the method {{acquireLocks(Set<? extends K> keys)}} to throw {{ClassCastException}} if the given keys contains elements that are not mutually comparable.

That is because the condition for {{Comparable}} was too strong and it was just used for the method {{acquireLocks(Set<? extends K> keys)}}, and actually, it is enough that the given keys are just mutually comparable, which keys may have a comparable subtype.

> 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
>         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.patch, KeyLockerPerformance.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.



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