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https://issues.apache.org/jira/browse/HADOOP-9639?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13751400#comment-13751400
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Koji Noguchi commented on HADOOP-9639:
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I'm not comfortable with the proposed design where it almost blindly trust
other users to do the right thing and upload the right file.
(Not that I don't trust my users :)
For example, it's easy for me to corrupt the /sharedcache directories by
creating directories with permission 700.
But what worries me the most is, entire security is based on a checksum.
Qutoing from [wikipedia|http://en.wikipedia.org/wiki/Checksum]
"It is important to not use a checksum in a security related application, as a
checksum does not have the properties required to protect data from intentional
tampering."
> truly shared cache for jars (jobjar/libjar)
> -------------------------------------------
>
> Key: HADOOP-9639
> URL: https://issues.apache.org/jira/browse/HADOOP-9639
> Project: Hadoop Common
> Issue Type: New Feature
> Components: filecache
> Affects Versions: 2.0.4-alpha
> Reporter: Sangjin Lee
> Assignee: Sangjin Lee
> Attachments: shared_cache_design.pdf, shared_cache_design_v2.pdf
>
>
> Currently there is the distributed cache that enables you to cache jars and
> files so that attempts from the same job can reuse them. However, sharing is
> limited with the distributed cache because it is normally on a per-job basis.
> On a large cluster, sometimes copying of jobjars and libjars becomes so
> prevalent that it consumes a large portion of the network bandwidth, not to
> speak of defeating the purpose of "bringing compute to where data is". This
> is wasteful because in most cases code doesn't change much across many jobs.
> I'd like to propose and discuss feasibility of introducing a truly shared
> cache so that multiple jobs from multiple users can share and cache jars.
> This JIRA is to open the discussion.
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