Mingliang Liu created HDFS-10201:
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Summary: Implement undo log in parity datanode for hflush
operations
Key: HDFS-10201
URL: https://issues.apache.org/jira/browse/HDFS-10201
Project: Hadoop HDFS
Issue Type: Sub-task
Components: erasure-coding
Reporter: Mingliang Liu
Assignee: Mingliang Liu
According to the current design doc for hflush support in erasure coding (see
[HDFS-7661]), the parity datanode (DN) needs an undo log for flush operations.
After hflush/hsync, the last cell will be overwritten when 1) the current strip
is full, 2) the file is closed, 3) or the hflush/hsync is called again for the
current non-full stripe. To serve new reader client and to tolerate failures
between successful hflush/hsync and overwrite operation, the parity DN should
preserve the old cell in the undo log before overwriting it.
As parities correspond to BG length and parity data of different BG length may
have the same block length, the undo log should also save the respective block
group (BG) length information for the flushed data.
This jira is to track the effort of designing and implementing an undo log in
parity DN to support hflush/hsync operations.
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