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https://issues.apache.org/jira/browse/HADOOP-5353?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15323082#comment-15323082
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Steve Loughran commented on HADOOP-5353:
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Quick review
* please don't change indentation needlessly, do follow hadoop code layout
rules, import wildcard policy etc.
* {{FileUtil.copy()}} should throw FileNotFoundException when things aren't
there.
* line 482 Have a look inside FileSystem.exists() and you'll see why you could
cut that clause and just go with the else clause
* 499. Exception.toString() over Exception.getMessage
* line 529. I think there should be better handling than "false" if the
destination dir couldn't be created, given its
the complete failure of the operation.
* like 546 & elsewhere. Use try-with-resources now the codebase is Java 7+
{{CommandWithDestination}}: {{TargetFileSystem}} supports try-with-resources
cleanup too. Same for {{writeStreamToFile}}
regarding the test,
# look at [
https://github.com/steveloughran/formality/blob/master/styleguide/styleguide.md
] for how to write good asserts.
# In particular, assertTrue and assertFalse must have messages, and if some
probe of exception value/state fails, just throw that exception again.
# There's lots of code in {{ContractTestUtils}} for writing/reading/probing
filesystems
> 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: Pranav Prakash
> Priority: Minor
> Attachments: HADOOP-5353.000.patch, HADOOP-5353.001.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, j 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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