Hi there! I’m working on an open source library I ...

# coroutines

[pgreze]

Hi there! I’m working on an open source library I released few months ago to easily launch external process from Kotlin:
https://github.com/pgreze/kotlin-process/pull/7
I would like to add cancellation support but the way I found so far seems not covering all cases (see PR description).
For example, is it worth having a third async operation actively monitoring the isActive state?

Thank you in advance for any support 🙏

[ephemient]

why not something like

suspend fun process(vararg command: String) = suspendCancellableCoroutine { continuation ->
    val process = ProcessBuilder(*command).start()
    continuation.invokeOnCancellation { process.destroy() }
    continuation.resume(process.waitFor()) { }
}

[Nick Allen]

FYI: runInterruptible can help break out of blocking methods like Process.waitFor

[pgreze]

@ephemient this seems really helpful, let me try it and come back to you if it worked or not 👍

[pgreze]

@Nick Allen could you give me more insights on this function? I found this discussion but I’m wondering what’s happening in case of cancellation

[ephemient]

runInterruptible is pretty similar and also throws a InterruptedException which can help break out of some blocking functions (such as waitFor)

[ephemient]

not exactly needed here because .destroy() will cause .waitFor() to finish anyway

[ephemient]

using runInterruptible would look something like this:

suspend fun process(vararg command: String): Int {
    val process = ProcessBuilder(*command).start()
    try {
        return runInterruptible {
            process.waitFor()
        }
    } finally {
        process.destroy()
    }
}

[pgreze]

@ephemient thanks again for your insights. invokeOnCancellation seems what I need but always good to know the alternatives 🙂

[pgreze]

@ephemient I tried using invokeOnCancellation but I could not use awaitAll inside, and everything I tried were just more verbose alternatives of my runInterruptible experiment.
If you don’t mind reviewing it, here is my current working code: https://github.com/pgreze/kotlin-process/pull/7/files

[Nick Allen]

Perhaps you'd prefer to just destroy the process when the IO related scope is done? Register once the process is created: coroutineContext[Job]!!.invokeOnCompletion { process.destroy()}

[pgreze]

@Nick Allen I was trying to avoid calling destroy unless necessary, but not sure what’s the best practice regarding this function…