Is there a way to run suspending code in blocking ...

# coroutines

[kingsley]

Is there a way to run suspending code in blocking mode reliably? runBlocking seems to give up immediately it encounters an interrupt, leaving the suspending function in a possibly corrupt mode. Or maybe I'm only overthinking this? 🤔

[elizarov]

What do you mean? Can you provide an example?

[kingsley]

Hi @elizarov. I have a setup like:

suspend fun doStuff() {
  // Call suspending API method
  someDb.use {
    // write stuff to db
  }
}

Now, I need to run this function in blocking mode. Currently, I'm simply doing:

fun blockingFun() = runBlocking {
  doStuff()
}

...but there is a time frame after which the thread could be interrupted. Is there a way to guarantee doStuff runs to completion before runBlocking throws interrupted exception?

PS: I was on mobile and didn't get a notification, would have responded to this earlier

[elizarov]

One solution is to do this:

fun blockingFun() = runBlocking {
    run (NonCancellable) { doStuff() }
}

What it does is that runBlocking will throw InterrupedException if interrupted, but it will not cancel the execution of doStuff — it will continue to work even after the runBlocking returns with exception (it will execute as if working with Unconfined dispatcher)

[elizarov]

If that does not solve your problem, then it is quite straightforward to implement some kind of runBlockingUninterruptibly { … } or runBlocking(interruptible=false) { … }

[kingsley]

Yes. I thought about using run(NonCancellable), but I am using some resources that might get closed once runBlocking returns

I am currently using a runSilentBlocking which basically wraps run blocking in a try/catch, but yes, I'll look into tweaking runBlocking to make it run uninterruptibly

[elizarov]

You are welcome to submit a pull request for kotlinx.coroutines project or, at least, create an issue (in its github tracker)