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From "sam rash (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1350) make datanodes do graceful shutdown
Date Sun, 22 Aug 2010 03:37:16 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1350?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12901129#action_12901129
] 

sam rash commented on HDFS-1350:
--------------------------------

My understanding of how lease recovery works in 20-append is that on cluster restart, an open
file will be recovered by the Namenode.  Datanodes will send the longest valid length of the
block (ie, if there are 8 bytes of checksum and 1500 data, the valid length is 1024 assuming
512 byte chunk size).   The block is then truncated to a valid length.

20-append seems to have a bug that any block where data + checksum length don't match, the
block isn't use in lease recovery.  the work here might be to fix that?



> make datanodes do graceful shutdown
> -----------------------------------
>
>                 Key: HDFS-1350
>                 URL: https://issues.apache.org/jira/browse/HDFS-1350
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: data-node
>            Reporter: sam rash
>            Assignee: sam rash
>
> we found that the Datanode doesn't do a graceful shutdown and a block can be corrupted
(data + checksum amounts off)
> we can make the DN do a graceful shutdown in case there are open files. if this presents
a problem to a timely shutdown, we can make a it a parameter of how long to wait for the full
graceful shutdown before just exiting

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