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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-5744) Revisit append
Date Tue, 19 May 2009 04:48:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-5744?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12710608#action_12710608
] 

stack commented on HADOOP-5744:
-------------------------------

@ Hairong

.bq ..do you still need to recover the lease?

No. If readers will see data near immediately after its hflushed, there is no need to do the
append, wait-on-lease, close, and then new open sequence.

.bq I might be wrong. But I do not think HADOOP-4379 addresses the problem that I raised.
HADOOP-4379 tries to make flushed data visible to a new reader.

To be clear, this is our use case.  When we notice a process has died, a different process
opens a new reader on the file the dead process had been writing (Later, in your '18/May/09
05:03 PM' comment, you say new readers will see up to the last hflush - - just making sure
you understand our usage).



> Revisit append
> --------------
>
>                 Key: HADOOP-5744
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5744
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: dfs
>    Affects Versions: 0.20.0
>            Reporter: Hairong Kuang
>            Assignee: Hairong Kuang
>             Fix For: 0.21.0
>
>         Attachments: AppendSpec.pdf
>
>
> HADOOP-1700 and related issues have put a lot of efforts to provide the first implementation
of append. However, append is such a complex feature. It turns out that there are issues that
were initially seemed trivial but needs a careful design. This jira revisits append, aiming
for a design and implementation supporting a semantics that are acceptable to its users.

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