How to deal with infinite loops?

[admin-iq-ega]

We are evaluating Jactl and we appreciate its concept of customisation. We want to use Jactl scripts for the backend of a web application based on Spring Boot.

Currently we are thinking of infinite loops, which obviously will never finish:

    @Test
    void testInfiniteScript() {
	Object result = Jactl.eval("while (true) { }");
	// will never finish!!
	assertThat(result).isNull();
    }

As a first approach we tried to abandon long running scripts after a certain timeout. But it seems the script execution cannot be cancelled.

Is there a way to deal with infinite loops introduced accidentally or by malicious users?

[jaccomoc]

There is no current mechanism for detecting and aborting infinite loops but you are not the first to have such a requirement. I don't think it would be too difficult to add such a feature.
I am thinking of something where you can optionally enable infinite loop detection (optional since it will have a slight performance impact). There are different ways that the detection mechanism could work:

1. Maximum iterations for any given loop.
2. Maximum iterations across all loops in a given script (i.e. each time around any for/while etc would increment a counter which would be compared against a configurable max iteration count).
3. A timeout where a script would abort if it is still running after a configurable amount of time.

Option 1 would be the easiest and lowest performance impact but only provides a partial solution since loops could have nested loops or invoke functions that have their own loops inside them, so I think implementing option 2 and 3 is probably the way to go.

I will think a bit more about it and do some investigation to see how easy it would be to implement.

[jaccomoc]

Jactl 2.3.0 which has just been released now has support for infinite loop detection. You can configure a limit for loop iterations or configure and/or configure a timeout. See enhancement #91.