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https://issues.apache.org/jira/browse/HDFS-4452?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Konstantin Shvachko updated HDFS-4452:
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Status: Patch Available (was: Open)
I tested it locally. It passes all tests including TestDFSClientRetries, which
models the case when the retry happens after the first attempt completes
getAdditionalBlock() fully.
I'll write another test which models simultaneous execution of
getAdditionalBlock() by two threads shortly.
> 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, 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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