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Posted to hdfs-dev@hadoop.apache.org by "Rajesh Balamohan (JIRA)" <ji...@apache.org> on 2015/09/28 02:55:04 UTC

[jira] [Created] (HDFS-9150) Consider implementing lazy seek in S3AInputStream

Rajesh Balamohan created HDFS-9150:
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             Summary: Consider implementing lazy seek in S3AInputStream
                 Key: HDFS-9150
                 URL: https://issues.apache.org/jira/browse/HDFS-9150
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: HDFS
            Reporter: Rajesh Balamohan


- Currently, "read(long position, byte[] buffer, int offset, int length)" is not implemented in S3AInputStream (unlike DFSInputStream). So, "readFully(long position, byte[] buffer, int offset, int length)" in S3AInputStream goes through the default implementation of seek(), read(), seek() in FSInputStream. 
- However, seek() in S3AInputStream involves re-opening of connection to S3 everytime (https://github.com/apache/hadoop/blob/trunk/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AInputStream.java#L115).  
- It would be good to consider having a lazy seek implementation to reduce connection overheads to S3. (e.g Presto implements lazy seek. https://github.com/facebook/presto/blob/master/presto-hive/src/main/java/com/facebook/presto/hive/PrestoS3FileSystem.java#L623)




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