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From "Manoj Govindassamy (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-11267) Avoid redefinition of storageDirs in NNStorage and cleanup its accessors in Storage
Date Thu, 29 Dec 2016 02:32:58 GMT

    [ https://issues.apache.org/jira/browse/HDFS-11267?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15784306#comment-15784306

Manoj Govindassamy commented on HDFS-11267:

Thanks for the review [~linyiqun].

> Avoid redefinition of storageDirs in NNStorage and cleanup its accessors in Storage
> -----------------------------------------------------------------------------------
>                 Key: HDFS-11267
>                 URL: https://issues.apache.org/jira/browse/HDFS-11267
>             Project: Hadoop HDFS
>          Issue Type: Bug
>    Affects Versions: 3.0.0-alpha1
>            Reporter: Manoj Govindassamy
>            Assignee: Manoj Govindassamy
>         Attachments: HDFS-11267.01.patch, HDFS-11267.02.patch
> In the abstract class {{Storage}}, {{storageDirs}} is a protected variable and all its
derived classes like {{NNStorage}}, {{JNStorage}}, {{DataStorage}}.. are iterating over this
non-thread safe variable without any proper locks. Any parallel modification operation like
add or remove volume can mutate the backing storageDirs list and any iterators on this list
around the  same time can face {{ConcurrentModificationException}}. It would be good to make
the variable private and restrict the access via getters and setters. Any thread safe restriction
need to be done can then be placed on the parent class only.
> Also, {{NNStorage}} redefines parent class Storage's {{storageDirs}}, making it inconsistent
with other derived classes. Would be cleaner if {{NNStorage}} can avoid re-defining it locally.

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