Colin Patrick McCabe created HDFS-4157:
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Summary: libhdfs: hdfsTell could be implemented a smarter than it
is
Key: HDFS-4157
URL: https://issues.apache.org/jira/browse/HDFS-4157
Project: Hadoop HDFS
Issue Type: Improvement
Components: libhdfs
Affects Versions: 2.0.3-alpha
Reporter: Colin Patrick McCabe
Priority: Minor
In libhdfs, {{hdfsTell}} currently makes an RPC to the {{DataNode}} to
determine the position of the stream. However, we could cache this information
easily, since libhdfs controls access to the stream. This would avoid the
double overhead of JNI and the RPC itself.
This would be very helpful for {{fuse_dfs}}, since that program calls
{{hdfsTell}} before every {{write}} or {{read}} operation. This can be quite a
lot of overhead, since writes may be as small as 4kb (depends on FUSE
configuration, kernel version, etc.)
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