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From "Uma Maheswara Rao G (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5761) DataNode fails to validate integrity for checksum type NULL when DataNode recovers
Date Mon, 13 Jan 2014 17:32:51 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5761?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13869719#comment-13869719

Uma Maheswara Rao G commented on HDFS-5761:

Thanks for filing a JIRA. I noticed this when I was looking the JIRA HDFS-5728.
Actually validate integrity check not necessary when it is set to NULL. It should consider
full file length as is.
I think  the below array becomes 0 length array when checksumSize 0? 
byte[] buf = new byte[lastChunkSize+checksumSize];

So, how about just considering blockFileLength when crc type is NULL? Because crc is null
now, so we need not care about integrity check with CRC file at all right.

> DataNode fails to validate integrity for checksum type NULL when DataNode recovers 
> -----------------------------------------------------------------------------------
>                 Key: HDFS-5761
>                 URL: https://issues.apache.org/jira/browse/HDFS-5761
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode
>    Affects Versions: 3.0.0
>            Reporter: Kousuke Saruta
>            Assignee: Kousuke Saruta
>         Attachments: HDFS-5761.patch
> When DataNode is down during writing blocks, the blocks are not filinalized and the next
time DataNode recovers, integrity validation will run.
> But if we use NULL for checksum algorithm (we can set NULL to dfs.checksum.type), DataNode
will fail to validate integrity and cannot be up. 
> The cause is in BlockPoolSlice#validateIntegrity.
> In the method, there is following code.
> {code}
> long numChunks = Math.min(
>           (blockFileLen + bytesPerChecksum - 1)/bytesPerChecksum, 
>           (metaFileLen - crcHeaderLen)/checksumSize);
> {code}
> When we choose NULL checksum, checksumSize is 0 so ArithmeticException will be thrown
and DataNode cannot be up.

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