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Posted to dev@lucene.apache.org by "Shawn Heisey (JIRA)" <ji...@apache.org> on 2015/05/22 21:45:18 UTC
[jira] [Commented] (SOLR-7585) ConcurrentLFUCache throws
NoSuchElementException under a write-heavy load
[ https://issues.apache.org/jira/browse/SOLR-7585?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14556707#comment-14556707 ]
Shawn Heisey commented on SOLR-7585:
------------------------------------
The LFU cache implementation is my code, but I didn't write it from scratch. I started with the existing LRU code. Now that I look at ConcurrentLRUCache, the markAndSweep method there seems to be quite a bit different, and I can't remember what I actually did or whether the differences came afterwards.
I tried adding just the test so I could see if the test fails without the patch. I did so on branch_5x, which is how I discovered that the test uses a lambda expression -- it won't compile on branch_5x because the build is targeted for a 1.7 compile version, and lamba expressions require 1.8. Since I haven't yet wrestled with lambda expressions, I have no idea what they actually do. Can you rewrite the test so it's compatible with Java 7?
> ConcurrentLFUCache throws NoSuchElementException under a write-heavy load
> -------------------------------------------------------------------------
>
> Key: SOLR-7585
> URL: https://issues.apache.org/jira/browse/SOLR-7585
> Project: Solr
> Issue Type: Bug
> Affects Versions: 5.1
> Reporter: Maciej Zasada
> Priority: Minor
> Attachments: SOLR-7585.patch
>
>
> Under a write-heavy load {{ConcurrentLFUCache}} throws {{NoSuchElementException}}. The problem lies within {{org.apache.solr.util.ConcurrentLFUCache#put}} method, which allows for a race condition between the check and the call to {{markAndSweep}} method. Despite that a thread must acquire a lock to perform sweeping, it's still possible that multiple threads successfully detected a need for calling markAndSweep. If they execute it sequentially, subsequent runs will fail with {{NoSuchElementException}}.
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