DirectRaterLimiter::check_all does not error on exceeded cap

[jean-airoldie]

If I correctly understand the DirectRateLimiter::check_all doc, it should error when a n greater than the initial max_burst when creating the Quota is passed. However it is not the case:

#[test]
fn errors_on_exceeded_cap() {
    let lim = RateLimiter::direct(Quota::per_second(nonzero!(10u32)));

    // This does not error even though we exceed the capacity.
    block_on(lim.check(nonzero!(11u32))).unwrap_err();
}

[antifuchs]

Thanks for reporting this issue (and for including a test case - that's really helpful)! I had to adjust it a bit so it would compile & then error:

#[test]
fn errors_on_exceeded_cap() {
    let lim = RateLimiter::direct(Quota::per_second(nonzero!(10u32)));

    // This does not error even though we exceed the capacity.
    assert_eq!(
        Err(NegativeMultiDecision::InsufficientCapacity(10)),
        lim.check_all(nonzero!(11u32))
    );
}

I guess we're seeing an off-by-one error somewhere!

[antifuchs]

Yeppppp, this is definitely an off-by-one error in the weight > tau check in test_n_all_and_update. I'll think about this some more.