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From "Dima Spivak (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-13382) IntegrationTestBigLinkedList should use SecureRandom
Date Fri, 03 Apr 2015 18:28:55 GMT

     [ https://issues.apache.org/jira/browse/HBASE-13382?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Dima Spivak updated HBASE-13382:
--------------------------------
    Attachment: HBASE-13382_master_v1.patch

There are a few other places we use rand.nextBytes(), but I think this changes the one place
that the weak hash would hurt us. Can someone with more experience with ITBLL make sure I
didn't miss something?

> IntegrationTestBigLinkedList should use SecureRandom
> ----------------------------------------------------
>
>                 Key: HBASE-13382
>                 URL: https://issues.apache.org/jira/browse/HBASE-13382
>             Project: HBase
>          Issue Type: Bug
>          Components: integration tests
>            Reporter: Todd Lipcon
>            Assignee: Dima Spivak
>         Attachments: HBASE-13382_master_v1.patch
>
>
> IntegrationTestBigLinkedList currently uses java.util.Random to generate its random keys.
The keys are 128 bits long, but we generate them using Random.nextBytes(). The Random implementation
itself only has a 48-bit seed, so even though we have a very long key string, it doesn't have
anywhere near that amount of entropy.
> This means that after a few billion rows, it's quite likely to run into a collision:
 filling in a 16-byte key is equivalent to four calls to rand.nextInt(). So, for 10B rows,
we are cycling through 40B different 'seed' values. With a 48-bit seed, it's quite likely
we'll end up using the same seed twice, after which point any future rows generated by the
colliding mappers are going to be equal. This results in broken chains and a failed verification
job.
> The fix is simple -- we should use SecureRandom to generate the random keys, instead.



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