akka流中异步文件IO的当前状态是什么？

Question

Target:

I would like to see Akka's file IO to be as asynchronous and non-blocking as possible.

My status of knowledge so far:

In older project documentation you can read this:

Note

Since the current version of Akka (2.3.x) needs to support JDK6, the currently provided File IO implementations are not able to utilise Asynchronous File IO operations, as these were introduced in JDK7 (and newer). Once Akka is free to require JDK8 (from 2.4.x) these implementations will be updated to make use of the new NIO APIs (ie AsynchronousFileChannel).

The current akka version is '2.5.4'. The current version of akka-stream is '2.11' or '2.12'. In the current documentation the note from abhove is missing and it is only explicitly mentioned that file IO means blocking operations which are processed by a dispatcher dedicated to IO operations.

In the 'MANIFEST.MF' file inside the akka-streams Jar-File there is a line:

Require-Capability: osgi.ee;filter:="(&(osgi.ee=JavaSE)(version=1.8))"

So I guess it requires Java 8.

There is a question related to scala asynchronous file IO but its from January 2015. One of the answers contains:

Akka IO, while not providing file IO in it's core, has a module developed by Dario Rexin, which allows to use AsynchronousFileChannel with Akka IO in a very simple manner. Have a look at this library to make use of it: https://github.com/drexin/akka-io-file

Questions:

1. How asynchronous is the current state of akka streams file IO?
2. Does akka streams file IO use 'AsynchronousFileChannel' from Java's NIO?
3. Do I have to do something to use 'AsynchronousFileChannel' from Java's NIO?

Answer 1

1. How asynchronous is the current state of akka streams file IO?

Perusing the source code shows that Akka Stream's FileIO uses java.nio.ByteBuffer and java.nio.channels.FileChannel . And as the documentation states, the file IO operations run in isolation on a dedicated dispatcher.

There is an open pull request that attempts to use AsynchronousFileChannel . Based on the benchmark results reported in that PR, the PR might be closed in favor of trying a newer approach with synchronous NIO as captured in another PR .

2. Does akka streams file IO use 'AsynchronousFileChannel' from Java's NIO?

No.

3. Do I have to do something to use 'AsynchronousFileChannel' from Java's NIO?

This question is moot, because Akka Streams does not use AsynchronousFileChannel .