Csaba Ringhofer created HDFS-17593:
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Summary: Allow setting block locations when opening streams
Key: HDFS-17593
URL: https://issues.apache.org/jira/browse/HDFS-17593
Project: Hadoop HDFS
Issue Type: Improvement
Reporter: Csaba Ringhofer
The HDFS client seems to always get block locations from the namenode when
opening a file:
https://github.com/apache/hadoop/blob/4525c7e35ea22d7a6350b8af10eb8d2ff68376e7/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSClient.java#L1099
This leads to unnecessary RPCs in Apache Impala when doing remote reads, as the
block locations are cached globally and the executors already have a good guess
about the block locations when opening a stream. Unless the cached block
locations are stale ideally no RPC should be made to the namenode.
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