What Async Promised and What It Delivered
35 points
by zdw
7 hours ago
| 4 comments
| causality.blog
| HN
joelwilliamson
2 hours ago
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Function colouring, deadlocks, silent exception swallowing, &c aren’t introduced by the higher levels, they are present in the earlier techniques too.
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littlestymaar
7 minutes ago
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I wish the “Function coloring” died. It made sense in the context of the original blog post (which was about callback hell), but doesn't make sense in the context of async/await. There's litterally nothing special with async, it's just an effect among many others.

As soon as you start using function arguments instead of using a global variable, you are coloring your function in the exact same way. Yet I don't think anyone would make the case that we should stop using function arguments and use global variables instead…

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chmod775
2 hours ago
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Function coloring also only applies to a few select languages. If your runtime allows you can call an async function from a sync function by pausing execution of the current function/thread whenever you're waiting for some async op.

Libraries like Tokio (mentioned in the article) have support for this built-in. Goroutines sidestep the issue completely. C# Tasks are batteries included in that regard. In fact function colors aren't an issue in most languages that have async/await. JavaScript is the odd one out, mostly due to being single-threaded. Can't really be made to work in a clean way in existing JS engines.

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cdaringe
7 hours ago
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Surely by section 7 well be talking (or have talked) about effect systems
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twoodfin
6 minutes ago
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Wasn’t in the prompt.
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paulddraper
2 hours ago
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> This was bad enough that Node.js eventually changed unhandled rejections from a warning to a process crash, and browsers added unhandledrejection events. A feature designed to improve error handling managed to create an entirely new class of silent failures that didn’t exist with callbacks.

Java has this too.

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andrewstuart
3 hours ago
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I like async and await.

I understand that some devs don’t want to learn async programming. It’s unintuitive and hard to learn.

On the other hand I feel like saying “go bloody learn async, it’s awesome and massively rewarding”.

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nottorp
3 hours ago
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> It’s unintuitive and hard to learn.

Funny, because it was supposed to be more intuitive than handling concurrency manually.

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afiori
2 hours ago
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Some come to async from callbacks and others from (green)threads.

If you come from callbacks it is (almost) purely an upgrade, from threads is it more mixed.

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palata
3 hours ago
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It is a tool. Some tools make you more productive after you have learned how to use them.

I find it interesting how in software, I repeatedly hear people saying "I should not have to learn, it should all be intuitive". In every other field, it is a given that experts are experts because they learned first.

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brazzy
1 hour ago
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> I find it interesting how in software, I repeatedly hear people saying "I should not have to learn, it should all be intuitive". In every other field, it is a given that experts are experts because they learned first.

Other fields don't have the same ability to produce unlimited incidental complexity, and therefore not the same need to rein it in. But I don't think there's any field which (as a whole) doesn't value simplicity.

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nottorp
2 hours ago
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Except you're hearing it from someone who doesn't have a problem handling state machines and epoll and manual thread management.
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shakow
2 hours ago
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Frankly, async being non-intuitive does not imply that manual concurrency handling is less so; both are a PITA to do correctly.
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littlestymaar
3 hours ago
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It is. A lot.

But concurrency is hard and there's so much you syntax can do about it.

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andrewstuart
2 hours ago
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It IS intuitive.

After you’ve learned the paradigm and bedded it down with practice.

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tcfhgj
2 hours ago
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I can't follow that it's hard to learn and unintuitive
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brazzy
2 hours ago
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What's awesome or rewarding about it?

It forces programmers to learn completely different ways of doing things, makes the code harder to understand and reason about, purely in order to get better performance.

Which is exactly the wrong thing for language designers to do. Their goal should be to find better ways to get those performance gains.

And the designers of Go and Java did just that.

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tcfhgj
38 minutes ago
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What different way of doing things?

If I want sequential execution, I just call functions like in the synchronous case and append .await. If I want parallel and/or concurrent execution, I spawn futures instead of threads and .await them. If I want to use locks across await points, I use async locks, anything else?

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swiftcoder
2 hours ago
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> It forces programmers to learn completely different ways of doing things, makes the code harder to understand and reason about, purely in order to get better performance.

Technically, promises/futures already did that in all of the mentioned languages. Async/await helped make it more user friendly, but the complexity was already there long before async/await arrived

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brazzy
1 hour ago
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Yes - I was really talking about "asynchronous programming" in general, not the async/await ways to do it in particular.
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