[jira] Commented: (HADOOP-1471) seekToNewSource() might not work correctly with Checksum failures.

["Raghu Angadi (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-1471?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12502123 ] 

Raghu Angadi commented on HADOOP-1471:
--------------------------------------

I think this bug existed since HADOOP-893 was commited. 


> seekToNewSource() might not work correctly with Checksum failures.
> ------------------------------------------------------------------
>
>                 Key: HADOOP-1471
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1471
>             Project: Hadoop
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.12.3
>            Reporter: Raghu Angadi
>             Fix For: 0.14.0
>
>
> Patch submitted to HADOOP-893  (by me :( ) seemhave a bug in how it deals with the set {{deadNodes}}. After the patch, the {{seekToNewSource()}} looks like this :
> {code}
>     public synchronized boolean seekToNewSource(long targetPos) throws IOException {
>       boolean markedDead = deadNodes.contains(currentNode);
>       deadNodes.add(currentNode);
>       DatanodeInfo oldNode = currentNode;
>       DatanodeInfo newNode = blockSeekTo(targetPos);
>       if (!markedDead) {
>         /* remove it from deadNodes. blockSeekTo could have cleared 
>          * deadNodes and added currentNode again. Thats ok. */
>         deadNodes.remove(oldNode);
>       }
>       // ...
> {code}
> I guess with the expectation that caller of this function decides before the call whether to put the node in {{deadNodes}} or not. I am not sure whether this was a bug then or not but it certainly seems to be bug now. i.e. when there is a checksum error with replica1, we try replica2 and if there a checksum error again, then we try replica1 again! 
> Note that ChecksumFileSystem.java was created after HADOOP-893 was resolved.

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