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Validate tick_duration millisecond resolution #178

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sgbalogh
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Hi! I noticed some strange behavior while running a simulation where the tick duration was sub-millisecond, and discovered that tokio::time::sleep apparently uses millisecond resolution.

I added some validation to the builder, to panic whenever a duration with higher than ms resolution is supplied, since it looked like some other validation was already happening here. Let me know if this seems useful.

Love the project btw!

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Thanks for improving this!

src/builder.rs Outdated
@@ -193,6 +193,11 @@ impl Builder {
panic!("Maximum message latency must be greater than minimum.");
}

if self.config.tick.as_nanos() % Duration::from_millis(1).as_nanos() != 0 {
// Tick duration is used for tokio::time::sleep, which requires millisecond resolution.
panic!("Tick duration resolution is in milliseconds, but value provided would require higher.")
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Consider adding the provided value in the panic message to aid in debugging.

@@ -193,6 +193,11 @@ impl Builder {
panic!("Maximum message latency must be greater than minimum.");
}

if self.config.tick.as_nanos() % Duration::from_millis(1).as_nanos() != 0 {
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Would it be simpler to just check < Duration::from_millis(1)?

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I think someone could provide a value that was > 1 ms, but had a higher resolution, e.g. Duration::from_micros(1500), which I believe we would want to disallow still given that comment on tokio::time::sleep.

Though, we might want to disallow Duration::ZERO in addition I suppose?

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I don't think it needs to be this restrictive. Given that the runtime is paused we aren't actually running for the duration, we are simply advancing time by it.

Duration::ZERO is a good callout, and I'm not actually sure what would happen in that case. My guess is that nothing runs.

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2 participants