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From "Lei (Eddy) Xu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-5353) add progress callback feature to the slow FileUtil operations with ability to cancel the work
Date Mon, 30 Jun 2014 16:54:25 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-5353?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14047841#comment-14047841

Lei (Eddy) Xu commented on HADOOP-5353:

Thank you [~steve_l@iseran.com]! Your comments are a great start point for me to adjust this

I will try to implement a callback to {{IOProgress}} now and see what I can get from there..

> add progress callback feature to the slow FileUtil operations with ability to cancel
the work
> ---------------------------------------------------------------------------------------------
>                 Key: HADOOP-5353
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5353
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: fs
>    Affects Versions: 0.21.0
>            Reporter: Steve Loughran
>            Assignee: Lei (Eddy) Xu
>            Priority: Minor
>         Attachments: HADOOP-5353.000.patch
> This is something only of relevance of people doing front ends to FS operations, and
as they could take the code in FSUtil and add something with this feature, its a blocker to
none of them. 
> Current FileUtil.copy can take a long time to move large files around, but there is no
progress indicator to GUIs, or a way to cancel the operation mid-way, short of interrupting
the thread or closing the filesystem.
> I propose a FileIOProgress interface to the copy ops, one that had a single method to
notify listeners of bytes read and written, and the number of files handled.
> {code}
> interface FileIOProgress {
>  boolean progress(int files, long bytesRead, long bytesWritten);
> }
> The return value would be true to continue the operation, or false to stop the copy and
leave the FS in whatever incomplete state it is in currently. 
> it could even be fancier: have  beginFileOperation and endFileOperation callbacks to
pass in the name of the current file being worked on, though I don't have a personal need
for that.
> GUIs could show progress bars and cancel buttons, other tools could use the interface
to pass any cancellation notice upstream.
> The FileUtil.copy operations would call this interface (blocking) after every block copy,
so the frequency of invocation would depend on block size and network/disk speeds. Which is
also why I don't propose having any percentage done indicators; it's too hard to predict percentage
of time done for distributed file IO with any degree of accuracy.

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