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Date: Sun, 25 Jan 2015 12:18:35 +0000 (UTC)
From: "Varun Saxena (JIRA)" <jira@apache.org>
To: common-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HADOOP-11209)
 Configuration#updatingResource/finalParameters are not thread-safe
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    [ https://issues.apache.org/jira/browse/HADOOP-11209?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14291074#comment-14291074 ] 

Varun Saxena commented on HADOOP-11209:
---------------------------------------

Thanks [~ozawa] for the review and commit

> Configuration#updatingResource/finalParameters are not thread-safe
> ------------------------------------------------------------------
>
>                 Key: HADOOP-11209
>                 URL: https://issues.apache.org/jira/browse/HADOOP-11209
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: conf
>    Affects Versions: 2.6.0
>            Reporter: Josh Rosen
>            Assignee: Varun Saxena
>             Fix For: 2.7.0
>
>         Attachments: HADOOP-11209.001.patch, HADOOP-11209.002.patch, HADOOP-11209.003.patch, HADOOP-11209.004.patch
>
>
> {{Configuration}} objects are not fully thread-safe, which causes problems in multi-threaded frameworks like Spark that use these configurations to interact with existing Hadoop APIs (such as InputFormats).
> SPARK-2546 is an example of a problem caused by this lack of thread-safety.  In that bug, multiple concurrent modifications of the same Configuration (in third-party code) caused an infinite loop because Configuration's internal {{java.util.HashMap}} is not thread-safe.
> One workaround is for our code to clone Configuration objects; unfortunately, this also suffers from thread-safety issues on older Hadoop versions because Configuration's constructor wasn't thread-safe (HADOOP-10456).
> [Looking at a recent version of Configuration.java|https://github.com/apache/hadoop/blob/d989ac04449dc33da5e2c32a7f24d59cc92de536/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/conf/Configuration.java#L666], it seems that the private {{updatingResource}} HashMap and {{finalParameters}} HashSet fields the only non-thread-safe collections in Configuration (Java's {{Properties}} class is thread-safe), so I don't think that it would be hard to make Configuration fully thread-safe.


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