Samer Al-Kiswany created HDFS-6821:
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Summary: Atomicity of multi file operations
Key: HDFS-6821
URL: https://issues.apache.org/jira/browse/HDFS-6821
Project: Hadoop HDFS
Issue Type: Bug
Reporter: Samer Al-Kiswany
Priority: Minor
Looking how HDFS updates the log files in case of chmod –r or chown –r
operations. In these operations, HDFS name node seems to update each file
separately; consequently the strace of the operation looks as follows.
append(edits)
fsync(edits)
append(edits)
fsync(edits)
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append(edits)
fsync(edits)
append(edits)
fsync(edits)
If a crash happens in the middle of this operation (e.g. at the dashed line in
the trace), the system will end up with part of the files updates with the new
owner or permissions and part still with the old owner.
Isn’t it better to log the whole operations (chown -r) as one entry in the edit
file?
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