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https://issues.apache.org/jira/browse/HDFS-6087?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13936378#comment-13936378
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Guo Ruijing commented on HDFS-6087:
-----------------------------------
It support hflush/hsync:
1) sync all buffer.
2) commit buffer to NN if it is block boundary.
3) copy new block and append buffer to new block and commit to NN if it is not
block boundary
> Unify HDFS write/append/truncate
> --------------------------------
>
> Key: HDFS-6087
> URL: https://issues.apache.org/jira/browse/HDFS-6087
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs-client
> Reporter: Guo Ruijing
> Attachments: HDFS Design Proposal.pdf, HDFS Design Proposal_3_14.pdf
>
>
> In existing implementation, HDFS file can be appended and HDFS block can be
> reopened for append. This design will introduce complexity including lease
> recovery. If we design HDFS block as immutable, it will be very simple for
> append & truncate. The idea is that HDFS block is immutable if the block is
> committed to namenode. If the block is not committed to namenode, it is HDFS
> client’s responsibility to re-added with new block ID.
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