Does GraalVM polyglot api support "interuptions"

[walksanatora]

Aka: "can I set execution timeouts before running polyglot code and resume it later"

[chumer]

You can interrupt any execution of polyglot code with Context.interrupt() from any thread (for example a timer). But that will trigger an exception in the polyglot code, so resuming at the same location is not easily possible. You would need to take care of resuming yourself.

Here is a quick example of how to interrupt JavaScript guest execution:

public static void main(String[] args) throws ReflectiveOperationException {
	var timer = new java.util.Timer(true);
	try (Context c = Context.create()) {
		timer.schedule(new TimerTask() {
			@Override
			public void run() {
				// maximum interruption time
				try {
					c.interrupt(Duration.ofMinutes(5));
				} catch (TimeoutException e) {
					// failed to interrupt in time.
					// its possible that the guest application denies an interrupt.
					// only thing you can do is cancel now with:
					// c.close(true) which cannot be denied by the guest application
				}
			}
		}, 500);
		try {
			c.eval("js", "while(true);");
		} catch (PolyglotException e) {
			if (e.isInterrupted()) {
				e.printStackTrace();
				
				// resume evaluation - depends on the use-case what to do here / whether possible
			}
		}
	} finally {
		timer.cancel();
	}
}

If your goal is to implement a workflow engine with continuations, then some language implementations like Espresso have language-specific support for continuations. See here https://github.com/oracle/graal/blob/master/espresso/docs/continuations.md
There is currently nothing on the polyglot level for continuations, but we might support that in the future.

[walksanatora]

so alternitively is there a way to in the polyglot'd code (wasm,llvm,python,js,etc...) to yield saying "I have exited you can run other stuff now"

[sgammon]

Sure, but I think you would need an event loop structure to manage your tasks, and a method to call out to the host to tell it that a context can be shelved while other work is performed. It could in theory be resumed by a guest method which is plucked from the context back to the host.

[sgammon]

(Correct me if I am wrong @chumer which I frequently am. Of course @walksanatora you would be responsible for synchronization in any case, including this one)