Mailing-List: contact common-issues-help@hadoop.apache.org; run by ezmlm
Precedence: bulk
Reply-To: common-issues@hadoop.apache.org
Date: Tue, 23 Jun 2015 15:51:01 +0000 (UTC)
From: "Sangjin Lee (JIRA)" <jira@apache.org>
To: common-issues@hadoop.apache.org
Message-ID: <JIRA.12839261.1434753157000.149044.1435074661521@Atlassian.JIRA>
In-Reply-To: <JIRA.12839261.1434753157000@Atlassian.JIRA>
References: <JIRA.12839261.1434753157000@Atlassian.JIRA>
 <JIRA.12839261.1434753157492@arcas>
Subject: [jira] [Commented] (HADOOP-12107) long running apps may have a huge
 number of StatisticsData instances under FileSystem
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit


    [ https://issues.apache.org/jira/browse/HADOOP-12107?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14597851#comment-14597851 ] 

Sangjin Lee commented on HADOOP-12107:
--------------------------------------

Thanks for pointing that out [~walter.k.su]. I think you're right in that normally one {{Statistics}} instance is created per {{FileSystem}} class. That said, it is possible to create {{Statistics}} instances in other manners simply via invoking the public constructor.

> long running apps may have a huge number of StatisticsData instances under FileSystem
> -------------------------------------------------------------------------------------
>
>                 Key: HADOOP-12107
>                 URL: https://issues.apache.org/jira/browse/HADOOP-12107
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: fs
>    Affects Versions: 2.7.0
>            Reporter: Sangjin Lee
>            Assignee: Sangjin Lee
>            Priority: Minor
>         Attachments: HADOOP-12107.001.patch, HADOOP-12107.002.patch, HADOOP-12107.003.patch
>
>
> We observed with some of our apps (non-mapreduce apps that use filesystems) that they end up accumulating a huge memory footprint coming from {{FileSystem$Statistics$StatisticsData}} (in the {{allData}} list of {{Statistics}}).
> Although the thread reference from {{StatisticsData}} is a weak reference, and thus can get cleared once a thread goes away, the actual {{StatisticsData}} instances in the list won't get cleared until any of these following methods is called on {{Statistics}}:
> - {{getBytesRead()}}
> - {{getBytesWritten()}}
> - {{getReadOps()}}
> - {{getLargeReadOps()}}
> - {{getWriteOps()}}
> - {{toString()}}
> It is quite possible to have an application that interacts with a filesystem but does not call any of these methods on the {{Statistics}}. If such an application runs for a long time and has a large amount of thread churn, the memory footprint will grow significantly.
> The current workaround is either to limit the thread churn or to invoke these operations occasionally to pare down the memory. However, this is still a deficiency with {{FileSystem$Statistics}} itself in that the memory is controlled only as a side effect of those operations.


--
This message was sent by Atlassian JIRA
(v6.3.4#6332)