Add a notion of immutable/mutable files
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Key: HDFS-3154
URL: https://issues.apache.org/jira/browse/HDFS-3154
Project: Hadoop HDFS
Issue Type: New Feature
Components: name-node
Reporter: Tsz Wo (Nicholas), SZE
Assignee: Tsz Wo (Nicholas), SZE
The notion of immutable file is useful since it lets the system and tools
optimize certain things as discussed in [this email
thread|http://mail-archives.apache.org/mod_mbox/hadoop-hdfs-dev/201203.mbox/%3CCAPn_vTuZomPmBTypP8_1xTr49Sj0fy7Mjhik4DbcAA+BLH53=g...@mail.gmail.com%3E].
Also, many applications require only immutable files. Here is a proposal:
- Immutable files means that the file content is immutable. Operations such as
append and truncate that change the file content are not allowed to act on
immutable files. However, the meta data such as replication and permission of
an immutable file can be updated. Immutable files can also be deleted or
renamed.
- Users have to pass immutable/mutable as a flag in file creation. This is an
unmodifiable property of the created file.
- If users want to change the data in an immutable file, the file could be
copied to another file which is created as mutable.
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