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https://issues.apache.org/jira/browse/HADOOP-1700?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12525789
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Jim Kellerman commented on HADOOP-1700:
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eric baldeschwieler - 06/Sep/07 01:29 AM
> Jim's request that a file exist if its producer dies before a close sounds
> like it would be easy, but then we
> get to flush semantics... I take it you don't just want the last complete
> 128M block Jim? If you want the
> last "log line" then you need something similar to what I outlined.
Yes, we want to get back the last record we wrote. (unless people think a lossy
database is ok :)
Typically we write multiple records at a time. It would not be a big deal for
us to follow a group of writes with a flush, since if we can't write the whole
group, we'd rather not get a partial group back.
So this means that we don't need every write to be atomic, just every flush.
(Think database transaction with multiple updates: either they all succeed or
they all fail)
> Append to files in HDFS
> -----------------------
>
> Key: HADOOP-1700
> URL: https://issues.apache.org/jira/browse/HADOOP-1700
> Project: Hadoop
> Issue Type: New Feature
> Components: dfs
> Reporter: stack
>
> 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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