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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-8361) avoid out-of-memory problems when deserializing strings
Date Fri, 04 May 2012 22:43:50 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-8361?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13268771#comment-13268771
] 

Todd Lipcon commented on HADOOP-8361:
-------------------------------------

Also, does BlockLocation's Writable implementation get used anywhere anymore? Block locations
aren't serialized in the fsimage, so I don't know if we need to change it at this point -
and perhaps we could file a separate JIRA to remove it entirely if it's unused.
                
> avoid out-of-memory problems when deserializing strings
> -------------------------------------------------------
>
>                 Key: HADOOP-8361
>                 URL: https://issues.apache.org/jira/browse/HADOOP-8361
>             Project: Hadoop Common
>          Issue Type: Bug
>            Reporter: Colin Patrick McCabe
>            Assignee: Colin Patrick McCabe
>            Priority: Minor
>         Attachments: HADOOP-8361.001.patch, HADOOP-8361.002.patch
>
>
> In HDFS, we want to be able to read the edit log without crashing on an OOM condition.
 Unfortunately, we currently cannot do this, because there are no limits on the length of
certain data types we pull from the edit log.  We often read strings without setting any upper
limit on the length we're prepared to accept.
> It's not that we don't have limits on strings-- for example, HDFS limits the maximum
path length to 8000 UCS-2 characters.  Linux limits the maximum user name length to either
64 or 128 bytes, depending on what version you are running.  It's just that we're not exposing
these limits to the deserialization functions that need to be aware of them.

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