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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1700) Append to files in HDFS
Date Sun, 08 Jun 2008 23:21:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1700?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12603453#action_12603453
] 

dhruba borthakur commented on HADOOP-1700:
------------------------------------------

The patch looks good. This patch introduces the changes to the ClientProtocol. More changes
will be required for the data transfer protocol between the client and datanode to implement
the full functionality. I documented one of the major remaining issues in HADOOP-3515. 

Till we develop a patch for HADOOP-3515, we either hold off on this patch or check this patch
in by making appendFileInternal throw an unsupported exception. If vote for creating a new
JIRA to check in this patch but leave HADOOP-1700 open till we get a complete solution for
appends.

> Append to files in HDFS
> -----------------------
>
>                 Key: HADOOP-1700
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1700
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: dfs
>    Affects Versions: 0.15.1
>            Reporter: stack
>         Attachments: 1700_20080606.patch, append.patch, Appends.doc, Appends.doc, Appends.html,
Grid_HadoopRenumberBlocks.pdf
>
>
> Request for being able to append to files in HDFS has been raised a couple of times on
the list of late.   For one example, see http://www.nabble.com/HDFS%2C-appending-writes-status-tf3848237.html#a10916193.
 Other mail describes folks' workarounds because this feature is lacking: e.g. http://www.nabble.com/Loading-data-into-HDFS-tf4200003.html#a12039480
(Later on this thread, Jim Kellerman re-raises the HBase need of this feature).  HADOOP-337
'DFS files should be appendable' makes mention of file append but it was opened early in the
life of HDFS when the focus was more on implementing the basics rather than adding new features.
 Interest fizzled.  Because HADOOP-337 is also a bit of a grab-bag -- it includes truncation
and being able to concurrently read/write -- rather than try and breathe new life into HADOOP-337,
instead, here is a new issue focused on file append.  Ultimately, being able to do as the
google GFS paper describes -- having multiple concurrent clients making 'Atomic Record Append'
to a single file would be sweet but at least for a first cut at this feature, IMO, a single
client appending to a single HDFS file letting the application manage the access would be
sufficent.

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