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From "Hairong Kuang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-5744) Revisit append
Date Thu, 14 May 2009 23:18:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-5744?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12709624#action_12709624
] 

Hairong Kuang commented on HADOOP-5744:
---------------------------------------

Flush needs to make data visible before a block is completed. This has changed a lot of assumptions
in HDFS. Previous append work has put tremendous amount of great work and set up a foundation
for improvement. However there are issues that seemed trivial initially but it turned out
that they needed a thorough design. HADOOP-4379, 4663, 5027, 5133, and 4692 etc. were filed
as bugs but are indeed caused by a lack of design. This issue aims at a design which solves
them all. It's targeted for 0.21.

If no hflush is called, dfs client pushes data to datanodes when a packet is filled up. The
packet size is configurable with a default size of 64K.

> 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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