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Posted to common-issues@hadoop.apache.org by "John Carrino (JIRA)" <ji...@apache.org> on 2011/04/14 06:34:05 UTC

[jira] [Commented] (HADOOP-7225) DataNode.setNewStorageID pulls entropy from /dev/random

    [ https://issues.apache.org/jira/browse/HADOOP-7225?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13019688#comment-13019688 ] 

John Carrino commented on HADOOP-7225:
--------------------------------------

I think this may need to get filed under HDFS instead of Hadoop Common.

> DataNode.setNewStorageID pulls entropy from /dev/random
> -------------------------------------------------------
>
>                 Key: HADOOP-7225
>                 URL: https://issues.apache.org/jira/browse/HADOOP-7225
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: fs
>    Affects Versions: 0.17.0
>         Environment: linux
>            Reporter: John Carrino
>            Priority: Minor
>   Original Estimate: 10m
>  Remaining Estimate: 10m
>
> DataNode.setNewStorageID uses SecureRandom.getInstance("SHA1PRNG") which always pulls fresh entropy.  
> It wouldn't be so bad if this were only the 120 bits needed by sha1, but the default impl of SecureRandom actually uses a BufferedInputStream around /dev/random and pulls 1024 bits of entropy for this one call.
> If you are on a system without much entropy coming in, this call can block and block others.
> Can we just change this to use "new SecureRandom().nextInt(Integer.MAX_VALUE)" instead?

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