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From "Aaron T. Myers (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-4258) Rename of Being Written Files
Date Tue, 12 Feb 2013 01:12:12 GMT

    [ https://issues.apache.org/jira/browse/HDFS-4258?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13576273#comment-13576273
] 

Aaron T. Myers commented on HDFS-4258:
--------------------------------------

bq. As in my comment in HDFS-4437, one concern with rename-breaks-leases semantics is the
client is over-powered. "one random client renames one of the top directories. It basically
revokes all the leases granted to other clients under this directory. That is, for any client
wants to gain a lease of any file, it could just rename it and then open it. Most likely it
could get the lease immediately as long as it has write permission."

If the client has write permission on the file, couldn't it just use the {{DistributedFileSystem#recoverLease()}}
API on the file, and then reopen it for append?
                
> Rename of Being Written Files
> -----------------------------
>
>                 Key: HDFS-4258
>                 URL: https://issues.apache.org/jira/browse/HDFS-4258
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs-client, namenode
>    Affects Versions: 3.0.0
>            Reporter: Tsz Wo (Nicholas), SZE
>            Assignee: Brandon Li
>         Attachments: HDFS-4258.patch, HDFS-4258.patch, HDFS-4258.patch, HDFS-4258.patch
>
>
> When a being written file or it's ancestor directories is renamed, the path in the file
lease is also renamed.  Then the writer of the file usually will fail since the file path
in the writer is not updated.
> Moreover, I think there is a bug as follow:
> # Client writes 0's to F_0="/foo/file" and writes 1's to F_1="/bar/file" at the same
time.
> # Rename /bar to /baz
> # Rename /foo to /bar
> Then, writing to F_0 will fail since /foo/file does not exist anymore but writing to
F_1 may succeed since /bar/file exits as a different file.  In such case, the content of /bar/file
could be partly 0's and partly 1's.

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