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From "sam rash (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1142) Lease recovery doesn't reassign lease when triggered by append()
Date Mon, 24 May 2010 21:48:26 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1142?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12870862#action_12870862
] 

sam rash commented on HDFS-1142:
--------------------------------

There's actually still one problem condition that can occur w/o the Namenode taking ownership
of lease when it starts lease recovery:

1. Client A loses lease due to soft/hard limit at a block boundary
2. NN begins lease recovery and finalizes blocks
3. Client A gets new block, starts writing
4. NN closes the file and frees the lease
5. Client A can continue to write to blocks acquired w/o the lease
6. Client A has an error and the block is left as a blockBeingWritten in the datanode

results:
-clients cannot open the file in append since the last block has no locations
-last block shows up as a missing block
-lease recovery will never cleanup the last block since no lease exists

assigning the lease to the NN for recovery prevents step 3 above and can stop this



> Lease recovery doesn't reassign lease when triggered by append()
> ----------------------------------------------------------------
>
>                 Key: HDFS-1142
>                 URL: https://issues.apache.org/jira/browse/HDFS-1142
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: name-node
>    Affects Versions: 0.21.0
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>         Attachments: hdfs-1142.txt, hdfs-1142.txt
>
>
> If a soft lease has expired and another writer calls append(), it triggers lease recovery
but doesn't reassign the lease to a new owner. Therefore, the old writer can continue to allocate
new blocks, try to steal back the lease, etc. This is for the testRecoveryOnBlockBoundary
case of HDFS-1139

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