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From "Andrew Wang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-8779) WebUI can't display randomly generated block ID
Date Thu, 16 Jul 2015 21:07:05 GMT

    [ https://issues.apache.org/jira/browse/HDFS-8779?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14630327#comment-14630327
] 

Andrew Wang commented on HDFS-8779:
-----------------------------------

Upon thinking about it more, I'm worried about compatibility issues with WebHDFS. We're changing
the type of blockId from number to string.

I'm guessing that the Java WebHdfsFileSystem implementation somehow already avoids the JS
MAX_SAFE_INTEGER issue, else we would have seen some issues back when we were using random
block IDs. We need to maintain compatibility both with old WebHdfsFileSystem implementations
as well as out-of-tree WebHDFS clients.

Could you do a little more digging on this front? Thanks Walter.

> WebUI can't display randomly generated block ID
> -----------------------------------------------
>
>                 Key: HDFS-8779
>                 URL: https://issues.apache.org/jira/browse/HDFS-8779
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: webhdfs
>            Reporter: Walter Su
>            Assignee: Walter Su
>            Priority: Minor
>         Attachments: HDFS-8779.01.patch, HDFS-8779.02.patch, after-02-patch.png, before.png
>
>
> Old release use randomly generated block ID(HDFS-4645).
> max value of Long in Java is 2^63-1
> max value of number in Javascript is 2^53-1. ( See [Link|https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER])
> Which means almost every randomly generated block ID exceeds MAX_SAFE_INTEGER.
> A integer which exceeds MAX_SAFE_INTEGER cannot be represented in Javascript.



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