Hi, Can we pause and resume a coroutine job?

# coroutines

[Deepak Rathi]

Hi, Can we pause and resume a coroutine job?

[louiscad]

No, usually, we use Flow with the xxxLatest operators to stop or start something.

What's your use case?

[uli]

• You can use suspend(Cancelable)Coroutine and hold on to the continuation instead of resuming it. Then, later you can resume it at any time.
• You might also be able to write a pauseable dispatcher.
• In general “no”.

[louiscad]

Pausable dispatchers are often a bad idea, because they can lead to leaks, unused resources held, aka memory or resource leaks

[Deepak Rathi]

My use case is to download a file in background and pause and resume the coroutine intermittently based on certain conditions.

@louiscad could you please share any examples of flow getting paused and resumed ?

[uli]

I assume you are using blocking IO on Dispatchers.IO. For pausing of blocking IO, it will be even harder. I see no way to pause a blocking operation. Either interrupt it or wait till it’s done.
Pausing a coroutine will always work on a suspended coroutine only.

[gildor]

I think for this case, it must be a feature of your downloader, when you can just suspend on particular condition before/after each of buffer reads, you can use mutex or similar primitives to suspend until it unlocked

Attempt to use pausable dispatcher is probably a bad idea, you should be explicit and have some "pause" point in your code

[simon.vergauwen]

I've toyed with this once, since I read an article talking about this topic using promises, and non-blocking/suspension from another language.

Here is a toy implementation, but it works.

[simon.vergauwen]

Untitled.cpp

Untitled.cpp

[Zach Klippenstein (he/him) [MOD]]

+1 to what Andrey said but also because this sounds like business logic, not coroutines plumbing.