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https://issues.apache.org/jira/browse/HADOOP-12910?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15303503#comment-15303503
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stack commented on HADOOP-12910:
--------------------------------
bq. Why making the entire async feature unavailable in branch 2?
I'd think a new API on HDFS with a new semantic showing up late in the life of
H2 would come as a surprise to most and seems like a natural H3 differentiator.
But no matter. Sounds like you are targeting H2.
bq. I suggest returning Future (or a sub-interface to support callbacks) in
branch 2 and CompletableFuture (or our own implementation of CompletableFuture)
in trunk. In this way, trunk is backward compatible to branch 2 since
CompletableFuture implements Future.
Suggest it should be same in branch 2 and branch 3 given how much work the spec
and implementation will be. You can't consume the API in a
non-blocking/asynchronous way if you can't register a callback. So a Future
alone is not sufficient, or to put it another way, if H2 returns a Future,
only, and H3 allows registering callbacks, then the implementation and consumer
will have to change going from H2 to H3.
> Add new FileSystem API to support asynchronous method calls
> -----------------------------------------------------------
>
> Key: HADOOP-12910
> URL: https://issues.apache.org/jira/browse/HADOOP-12910
> Project: Hadoop Common
> Issue Type: New Feature
> Components: fs
> Reporter: Tsz Wo Nicholas Sze
> Assignee: Xiaobing Zhou
> Attachments: HADOOP-12910-HDFS-9924.000.patch,
> HADOOP-12910-HDFS-9924.001.patch, HADOOP-12910-HDFS-9924.002.patch
>
>
> Add a new API, namely FutureFileSystem (or AsynchronousFileSystem, if it is a
> better name). All the APIs in FutureFileSystem are the same as FileSystem
> except that the return type is wrapped by Future, e.g.
> {code}
> //FileSystem
> public boolean rename(Path src, Path dst) throws IOException;
> //FutureFileSystem
> public Future<Boolean> rename(Path src, Path dst) throws IOException;
> {code}
> Note that FutureFileSystem does not extend FileSystem.
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