[jira] [Updated] (HDFS-3107) HDFS truncate

["Plamen Jeliazkov (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HDFS-3107?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Plamen Jeliazkov updated HDFS-3107:
-----------------------------------
    Attachment: HDFS-3107.patch

Attaching refreshed patch for latest trunk.

> HDFS truncate
> -------------
>
>                 Key: HDFS-3107
>                 URL: https://issues.apache.org/jira/browse/HDFS-3107
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: datanode, namenode
>            Reporter: Lei Chang
>            Assignee: Plamen Jeliazkov
>         Attachments: HDFS-3107.008.patch, HDFS-3107.patch, HDFS-3107.patch, HDFS-3107.patch, HDFS-3107.patch, HDFS-3107.patch, HDFS-3107.patch, HDFS-3107.patch, HDFS-3107.patch, HDFS_truncate.pdf, HDFS_truncate.pdf, HDFS_truncate_semantics_Mar15.pdf, HDFS_truncate_semantics_Mar21.pdf, editsStored, editsStored, editsStored.xml
>
>   Original Estimate: 1,344h
>  Remaining Estimate: 1,344h
>
> Systems with transaction support often need to undo changes made to the underlying storage when a transaction is aborted. Currently HDFS does not support truncate (a standard Posix operation) which is a reverse operation of append, which makes upper layer applications use ugly workarounds (such as keeping track of the discarded byte range per file in a separate metadata store, and periodically running a vacuum process to rewrite compacted files) to overcome this limitation of HDFS.



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