[
https://issues.apache.org/jira/browse/HADOOP-922?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Doug Cutting updated HADOOP-922:
--------------------------------
Status: Open (was: Patch Available)
The call to skipTo() will still, in the worst case, cause an entire block to be
streamed across the wire, using a lot of network bandwidth. Before we commit
this I'd like to see some benchmarks showing that this is faster than closing
and re-opening the connection.
Note also that the stream buffering code already performs a similar
optimization: if a 100k buffer is used, and one seeks within the buffer, then
no i/o is performed on the underlying stream. So seeks of the underlying
stream are generally at least a few k bytes away.
> Optimize small reads and seeks
> ------------------------------
>
> Key: HADOOP-922
> URL: https://issues.apache.org/jira/browse/HADOOP-922
> Project: Hadoop
> Issue Type: Bug
> Components: dfs
> Affects Versions: 0.10.1
> Reporter: dhruba borthakur
> Assigned To: dhruba borthakur
> Attachments: smallreadseek3.patch
>
>
> A seek on a DFSInputStream causes causes the next read to re-open the socket
> connection to the datanode and fetch the remainder of the block all over
> again. This is not optimal.
> A small read followed by a small positive seek could re-utilize the data
> already fetched from the datanode as part of the previous read.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
