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Posted to common-issues@hadoop.apache.org by "Mostafa Mokhtar (JIRA)" <ji...@apache.org> on 2017/10/17 23:47:00 UTC
[jira] [Commented] (HADOOP-12444) Support lazy seek in
S3AInputStream
[ https://issues.apache.org/jira/browse/HADOOP-12444?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16208603#comment-16208603 ]
Mostafa Mokhtar commented on HADOOP-12444:
------------------------------------------
[~sailesh] FYI
> Support lazy seek in S3AInputStream
> -----------------------------------
>
> Key: HADOOP-12444
> URL: https://issues.apache.org/jira/browse/HADOOP-12444
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: fs/s3
> Affects Versions: 2.7.1
> Reporter: Rajesh Balamohan
> Assignee: Rajesh Balamohan
> Fix For: 2.8.0, 3.0.0-alpha1
>
> Attachments: HADOOP-12444-004.patch, HADOOP-12444-005.patch, HADOOP-12444-006.patch, HADOOP-12444-007.patch, HADOOP-12444.1.patch, HADOOP-12444.2.patch, HADOOP-12444.3.patch, HADOOP-12444.WIP.patch, hadoop-aws-test-reports.tar.gz
>
>
> - 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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