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https://issues.apache.org/jira/browse/HADOOP-12412?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14746297#comment-14746297
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Michael Harris commented on HADOOP-12412:
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Yeah I'd love to. I'm not convinced I can write anything that's 100% foolproof
though because the bug is occasional livelock in an area of the code with weak
concurrency semantics. Do you have any experience with unit testing for
livelock? If not, that's fine, I'll put something together that at least
demonstrates the problem.
> Concurrency in FileSystem$Cache is very broken
> ----------------------------------------------
>
> Key: HADOOP-12412
> URL: https://issues.apache.org/jira/browse/HADOOP-12412
> Project: Hadoop Common
> Issue Type: Bug
> Components: fs
> Affects Versions: 2.7.0
> Reporter: Michael Harris
> Assignee: Michael Harris
> Priority: Critical
> Attachments: HADOOP-12412.patch
>
>
> The FileSystem cache uses a mild amount of concurrency to protect the cache
> itself, but does nothing to prevent multiple of the same filesystem from
> being constructed and initialized simultaneously. At best, this leads to
> potentially expensive wasted work. At worst, as is the case for Spark, it
> can lead to deadlocks/livelocks, especially when the same configuration
> object is passed into both calls. This should be refactored to use a results
> cache approach (reference Java Concurrency in Practice chapter 5 section 6
> for an example of how to do this correctly), which will be both
> higher-performance and safer.
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