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Date: Fri, 1 Feb 2013 23:04:12 +0000 (UTC)
From: "Konstantin Boudnik (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12629766.1359488813390.232450.1359759852953@arcas>
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Subject: [jira] [Commented] (HDFS-4452) getAdditionalBlock() can create
 multiple blocks if the client times out and retries.
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    [ https://issues.apache.org/jira/browse/HDFS-4452?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13569213#comment-13569213 ] 

Konstantin Boudnik commented on HDFS-4452:
------------------------------------------

The patch looks mostly good. A few minor comments:
- the logger in the class should be initialized for {{TestAddBlockRetry}}, not {{TestFSDirectory}}
- formatting only change
{noformat}
   LocatedBlock getAdditionalBlock(String src,
-                                         String clientName,
-                                         ExtendedBlock previous,
-                                         HashMap<Node, Node> excludedNodes
-                                         ) 
+                                  String clientName,
+                                  ExtendedBlock previous,
+                                  HashMap<Node, Node> excludedNodes)
{noformat}

Test is failing without the corresponding change in the code, so it seems right on the money.
+1
                
> getAdditionalBlock() can create multiple blocks if the client times out and retries.
> ------------------------------------------------------------------------------------
>
>                 Key: HDFS-4452
>                 URL: https://issues.apache.org/jira/browse/HDFS-4452
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: 2.0.2-alpha
>            Reporter: Konstantin Shvachko
>            Assignee: Konstantin Shvachko
>            Priority: Critical
>         Attachments: getAdditionalBlock.patch, getAdditionalBlock.patch, TestAddBlockRetry.java
>
>
> HDFS client tries to addBlock() to a file. If NameNode is busy the client can timeout and will reissue the same request again. The two requests will race with each other in {{FSNamesystem.getAdditionalBlock()}}, which can result in creating two new blocks on the NameNode while the client will know of only one of them. This eventually results in {{NotReplicatedYetException}} because the extra block is never reported by any DataNode, which stalls file creation and puts it in invalid state with an empty block in the middle.

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