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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Reopened] (HDFS-3492) fix some misuses of InputStream#skip
Date Thu, 07 Jun 2012 21:06:23 GMT

     [ https://issues.apache.org/jira/browse/HDFS-3492?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Todd Lipcon reopened HDFS-3492:
-------------------------------


This actually seems to have broken TestShortCircuitLocalRead. Looking more closely at the
QA results above, it didn't even run the HDFS tests (perhaps because of the cmake issues).
I will revert this.
                
> fix some misuses of InputStream#skip
> ------------------------------------
>
>                 Key: HDFS-3492
>                 URL: https://issues.apache.org/jira/browse/HDFS-3492
>             Project: Hadoop HDFS
>          Issue Type: Bug
>            Reporter: Colin Patrick McCabe
>            Assignee: Colin Patrick McCabe
>            Priority: Minor
>             Fix For: 2.0.1-alpha
>
>         Attachments: HDFS-3492.001.patch
>
>
> It seems that we have a few cases where programmers are calling InputStream#skip and
not handling "short skips."  Unfortunately, the skip method is documented and implemented
so that it doesn't actually skip the requested number of bytes, but simply tries to skip at
most that amount of bytes.  A better name probably would have been trySkip or similar.
> It seems like most of the time when the argument to skip is small enough, we'll succeed
almost all of the time.  This is no doubt an implementation artifact of some of the popular
stream implementations.  This tends to hide the bug-- however, it is still waiting to emerge
at some point if those implementations ever change or if buffer sizes are adjusted, etc.
> All of these cases can be fixed by calling IOUtils#skipFully to get the behavior that
the programmer expects-- i.e., skipping by the specified amount.

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