Strange issue with AsyncContext + TweetInvi's Sync. about asyncex HOT 10 CLOSED

The Sync.ExcecuteTaskAsync(...) call seems to imply that TweetInvi has its own sync-to-async wrapper which is possibly making assumptions that don't quite hold in all cases. I only say this because in the TweetInvi wiki none of the examples I've come across so far seems to do anything async and there's no Sync.ExcecuteTaskAsync(...) to be found.

from asyncex.

Here's the awesome code ;)

https://github.com/linvi/tweetinvi/blob/master/Tweetinvi/Sync.cs#L43

I suspect the problem lies in there. Perhaps take that code, or a variant of it, into your own code and then you can step through it more easily. I'd add some logging in there too.

It really sounds like it's doing a sync-over-async style API (search the pfxteam blog for articles about that) which can be tricky.

from asyncex.

Thanks for bringing up those details, @IanYates.

The problem is that the default ITaskFactory.ExecuteTaskAsync implementation is using Task.Factory.StartNew without specifying a TaskScheduler. The default value for TaskScheduler is (unfortunately) TaskScheduler.Current, not TaskSchedler.Default.

Since AsyncContext uses TaskScheduler, this means the ITaskFactory is in fact trying to queue its work on the AsyncContext, not the ThreadPool.

from asyncex.

Thanks, for looking into this so quickly I will read your article and update the library if needed!

from asyncex.

Thanks for taking a look at this, both of you. For now, I have my project working by just waiting on Task.Result (since my project depends on TweetInvi, I can't just remove that), but I would like to be able to use AsyncContext with it. It sounds like the issue is with TweetInvi, then? Is that right?

from asyncex.

Quick question to you. I am well used to threads but I do have less knowledge on the async/await.

Quickly reading your article, would you agree that instead of await Task.Factory.StartNew(action);, I should use await TaskEx.Run(action);, or is defining the TaskCreateOption manually a better option?

from asyncex.

I would say to just call TaskEx.Run. There are several less-than-satisfactory defaults with StartNew. Since you're using Microsoft.Bcl.Async, a proper call would look something like Task.Factory.StartNew(action, CancellationToken.None, TaskCreationOptions.None, TaskScheduler.Default), which is very long compared to TaskEx.Run(() => action()). :)

from asyncex.

The new version of AsyncContext hides the current TaskScheduler.

While I think this is technically incorrect, this kind of bug is found all over the place (almost all uses of StartNew/ContinueWith on the Internet are wrong). As such, the new AsyncContext goes out of its way to hide its TaskScheduler.

from asyncex.

With the new AsyncContext, will Tweetinvi need to upgrade/change some of the code?

from asyncex.

No, Tweetinvi doesn't have to change. The hiding of the TaskScheduler works around that bug.

However, I still do recommend using Task.Run (or at least specifying TaskScheduler.Default). It works with the new AsyncContext, but it may not work with other custom contexts.

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