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Carl Fredrik Samson
2020-02-03 23:02:48 +01:00
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@@ -154,9 +154,8 @@
<p><strong>Relevant for:</strong></p>
<ul>
<li>High level introduction to concurrency in Rust</li>
<li>Knowing what Rust provides and not when working with async</li>
<li>Knowing what Rust provides and not when working with async code</li>
<li>Understanding why we need runtimes </li>
<li>Knowing that Rust has <code>Futures 1.0</code> and <code>Futures 3.0</code>, and how to deal with them</li>
<li>Getting pointers to further reading on concurrency in general</li>
</ul>
</blockquote>
@@ -168,14 +167,15 @@ pretty simple. I promise.</p>
<p>Let's get some of the common roadblocks out of the way first.</p>
<p>Async in Rust is different from most other languages in the sense that Rust
has a very lightweight runtime.</p>
<p>In languages like C#, JavaScript, Java and GO, already includes a runtime
<p>Languages like C#, JavaScript, Java and GO, already includes a runtime
for handling concurrency. So if you come from one of those languages this will
seem a bit strange to you.</p>
<p>In Rust you will have to make an active choice about which runtime to use.</p>
<h3><a class="header" href="#what-rusts-standard-library-takes-care-of" id="what-rusts-standard-library-takes-care-of">What Rust's standard library takes care of</a></h3>
<ol>
<li>The definition of an interruptible task</li>
<li>An efficient technique to start, suspend, resume and store tasks
which are executed concurrently. </li>
<li>An efficient technique to start, suspend, resume and store tasks which are
executed concurrently.</li>
<li>A defined way to wake up a suspended task</li>
</ol>
<p>That's really what Rusts standard library does. As you see there is no definition
@@ -190,15 +190,15 @@ of non-blocking I/O, how these tasks are created or how they're run.</p>
an event queue and so on.</p>
<p>Executors, accepts one or more asynchronous tasks called <code>Futures</code> and takes
care of actually running the code we write, suspend the tasks when they're
waiting for I/O and resumes them.</p>
waiting for I/O and resume them.</p>
<p>In theory, we could choose one <code>Reactor</code> and one <code>Executor</code> that have nothing
to do with each other besides one creates leaf <code>Futures</code> and one runs them, but
in reality today you'll most often get both in a <code>Runtime</code>.</p>
to do with each other besides that one creates leaf <code>Futures</code> and the other one
runs them, but in reality today you'll most often get both in a <code>Runtime</code>.</p>
<p>There are mainly two such runtimes today <a href="https://github.com/async-rs/async-std">async_std</a> and <a href="https://github.com/tokio-rs/tokio">tokio</a>.</p>
<p>Quite a bit of complexity attributed to <code>Futures</code> are actually complexity rooted
in runtimes. Creating an efficient runtime is hard. Learning how to use one
correctly can be hard as well, but both are excellent and it's just like
learning any new library.</p>
in runtimes. Creating an efficient runtime is hard. </p>
<p>Learning how to use one correctly can require quite a bit of effort as well, but you'll see that there are several similarities between these kind of runtimes so
learning one makes learning the next much easier.</p>
<p>The difference between Rust and other languages is that you have to make an
active choice when it comes to picking a runtime. Most often you'll just use
the one provided for you.</p>
@@ -212,9 +212,10 @@ still. This will get resolved in time, but unfortunately it's not always easy
to know in advance.</p>
<p>A good sign is that if you're required to use combinators like <code>and_then</code> then
you're using <code>Futures 1.0</code>.</p>
<p>While not directly compatible, there is a tool that let's you relatively easily
convert a <code>Future 1.0</code> to a <code>Future 3.0</code> and vice a versa. You can find all you
need in the <a href="https://github.com/rust-lang/futures-rs"><code>futures-rs</code></a> crate and all <a href="https://rust-lang.github.io/futures-rs/blog/2019/04/18/compatibility-layer.html">information you need here</a>.</p>
<p>While they're not directly compatible, there is a tool that let's you relatively
easily convert a <code>Future 1.0</code> to a <code>Future 3.0</code> and vice a versa. You can find
all you need in the <a href="https://github.com/rust-lang/futures-rs"><code>futures-rs</code></a> crate and all
<a href="https://rust-lang.github.io/futures-rs/blog/2019/04/18/compatibility-layer.html">information you need here</a>.</p>
<h2><a class="header" href="#first-things-first" id="first-things-first">First things first</a></h2>
<p>If you find the concepts of concurrency and async programming confusing in
general, I know where you're coming from and I have written some resources to
@@ -226,11 +227,10 @@ try to give a high level overview that will make it easier to learn Rusts
<li><a href="https://cfsamson.github.io/book-exploring-async-basics/5_strategies_for_handling_io.html">Async Basics - Strategies for handling I/O</a></li>
<li><a href="https://cfsamson.github.io/book-exploring-async-basics/6_epoll_kqueue_iocp.html">Async Basics - Epoll, Kqueue and IOCP</a></li>
</ul>
<p>Now learning these concepts by studying futures is making it much harder than
it needs to be, so go on and read these chapters. I'll be right here when
you're back. </p>
<p>However, if you feel that you have the basics covered, then go right on. </p>
<p>Let's get moving!</p>
<p>Learning these concepts by studying futures is making it much harder than
it needs to be, so go on and read these chapters if you feel a bit unsure. </p>
<p>I'll be right here when you're back.</p>
<p>However, if you feel that you have the basics covered, then let's get moving!</p>
</main>