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The thing is, there's a lot more nuance to it than this. Async/await is part of the language syntax in python, but asyncio is only one particular implementation

by nbadg 4y ago

The thing is, there's a lot more nuance to it than this. Async/await is part of the language syntax in python, but asyncio is only one particular implementation of an event loop framework to power it. But really what async/await provides is a general-purpose cooperative multitasking syntax. This allows other libraries to implement their own event loop frameworks, each with their own different semantics and considerations (the two best-known alternatives being Curio and Trio). At a language level, there's nothing even forcing you to use async/await for ascync IO -- you could, if you really wanted, probably write a library that used it to start threads and await their completion. So you have, from highest-level to lowest-level: application code, async/await language syntax, the event loop framework, and then the implementation of the event loop itself. The OP article concerns a peculiar implementation detail in the lowest level that makes it very easy to write bugs at the highest level. But that means that even if you do "async all the things", you'll only encounter this situation if you write your application code in a particular way. It just so happens that "in a particular way" is, in this case, the overwhelming majority of how people write it, which is, of course, why the OP article is relevant.

heavyset_go 4y ago
> The OP article concerns a peculiar implementation detail in the lowest level that makes it very easy to write bugs at the highest level. Are other async implementations using the asyncio.Task abstraction? I haven't looked into it, but I assumed that asyncio.Task was tied to the asyncio implementation and event loop.
- nbadg 4y ago
  asyncio.Task is part of the asyncio event loop framework. So any event loop implementation that conforms to that framework will have to have one (including the default event loop implementation that ships with asyncio). So for example, uvloop, which is an alternative event loop implementation that works with the asyncio event loop framework, also uses asyncio Tasks. Other event loop frameworks can do whatever they want, and presumably, wouldn't be importing from asyncio. Whether they have a similar abstraction is completely up to the framework itself. Trio, for example, doesn't have a concept of a task object at all, because it enforces a strict tree structure for tasks.
LtWorf 4y ago
> This allows other libraries to implement their own event loop frameworks At work someone replaced the default library with another faster implementation. Then the unix socket listener task was not working. A few hours of git bisect later, I found out the offending commit was the 1 line switching the event loop. Seems the fast implementation didn't implement unix sockets and just had "pass" in the function.

by nbadg 4y ago

heavyset_go 4y ago

> The OP article concerns a peculiar implementation detail in the lowest level that makes it very easy to write bugs at the highest level. Are other async implementations using the asyncio.Task abstraction? I haven't looked into it, but I assumed that asyncio.Task was tied to the asyncio implementation and event loop.

nbadg 4y ago
asyncio.Task is part of the asyncio event loop framework. So any event loop implementation that conforms to that framework will have to have one (including the default event loop implementation that ships with asyncio). So for example, uvloop, which is an alternative event loop implementation that works with the asyncio event loop framework, also uses asyncio Tasks. Other event loop frameworks can do whatever they want, and presumably, wouldn't be importing from asyncio. Whether they have a similar abstraction is completely up to the framework itself. Trio, for example, doesn't have a concept of a task object at all, because it enforces a strict tree structure for tasks.

LtWorf 4y ago

> This allows other libraries to implement their own event loop frameworks At work someone replaced the default library with another faster implementation. Then the unix socket listener task was not working. A few hours of git bisect later, I found out the offending commit was the 1 line switching the event loop. Seems the fast implementation didn't implement unix sockets and just had "pass" in the function.