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From "Jieshan Bean (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5088) A concurrency issue on SoftValueSortedMap
Date Fri, 23 Dec 2011 03:51:30 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5088?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13175253#comment-13175253
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Jieshan Bean commented on HBASE-5088:
-------------------------------------

Loop into the mothod of TreeMap#fixAfterDeletion(Entry<K,V> x), once the x is null(It
may caused by a concurrency issue), it can't come out of that loop. At that time, CPU usage
is high. 
That's what we saw. All the time, the thread was blocked in that method.
Currently, the patch is made just replace TreeMap with ConcurrentSkipListMap as Anoop and
Lars's suggestion. We're verifying the patch.
@Ted, actually, the heapmap method of ConcurrentSkipListMap is different from TreeMap, it
is also backed by the original thread-safe map. what do you think?
                
> A concurrency issue on SoftValueSortedMap
> -----------------------------------------
>
>                 Key: HBASE-5088
>                 URL: https://issues.apache.org/jira/browse/HBASE-5088
>             Project: HBase
>          Issue Type: Bug
>          Components: client
>    Affects Versions: 0.90.4, 0.94.0
>            Reporter: Jieshan Bean
>            Assignee: Jieshan Bean
>
> SoftValueSortedMap is backed by a TreeMap. All the methods in this class are synchronized.
If we use this method to add/delete elements, it's ok.
> But in HConnectionManager#getCachedLocation, it use headMap to get a view from SoftValueSortedMap#internalMap.
Once we operate 
> on this view map(like add/delete) in other threads, a concurrency issue may occur.

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