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https://issues.apache.org/jira/browse/HADOOP-13047?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15252524#comment-15252524
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Steve Loughran commented on HADOOP-13047:
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I propose
# having a configurable default value
# implementing {{setReadAhead(long)}} to allow code to dynamically tune this
value. It does't quite control the pre-load, but it is tuning how far ahead the
stream can read before triggering an expensive seek.
> S3a Forward seek in stream length to be configurable
> ----------------------------------------------------
>
> Key: HADOOP-13047
> URL: https://issues.apache.org/jira/browse/HADOOP-13047
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: fs/s3
> Affects Versions: 2.8.0
> Reporter: Steve Loughran
>
> Even with lazy seek, tests can show that sometimes a short-distance forward
> seek is triggering a close + reopen, because the threshold for the seek is
> simply available bytes in the inner stream.
> A configurable threshold would allow data to be read and discarded before
> that seek. This should be beneficial over long-haul networks as the time to
> set up the TCP channel is high, and TCP-slow-start means that the ramp up of
> bandwidth is slow. In such deployments, it will better to read forward than
> re-open, though the exact "best" number will vary with client and endpoint.
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