Confusion about ErrTooManyRequests error

[bigunyak]

Hi,

Thanks a lot for your library, it's simple, yet powerful! :)
Could you please clarify one confusion I have about ErrTooManyRequests error? I don't quite understand from the code when this error could happen.
I see the if state == StateHalfOpen && cb.counts.Requests >= cb.maxRequests condition in the beforeRequest() method but from the rest of the code it doesn't look like it could ever be met. This is because we either get enough consecutive requests to trip circuit to close with this condition if cb.counts.ConsecutiveSuccesses >= cb.maxRequests { cb.setState(StateClosed, now) } or we go back to open state because of a single failure in onFailure(). Or did I misunderstand something?

[YoshiyukiMineo]

If you call cb.Execute in parallel, you can call too many beforeRequest before afterRequest.

[tegaralaga]

If you call cb.Execute in parallel, you can call too many beforeRequest before afterRequest.

AFAIK beforeRequest will not executed in parallel since it has mutex. I try to get ErrTooManyRequests just last night, but couldn't get it.

[chiendo97]

Hi @tegaralaga

You can reproduce the ErrToManyRequests by this test case.

func TestTooManyRequests(t *testing.T) {
	customCB.setState(StateHalfOpen, time.Now())

	// 3 consecutive successes
	succeedLater(customCB, time.Duration(1000)*time.Millisecond) 
	succeedLater(customCB, time.Duration(1000)*time.Millisecond)
	succeedLater(customCB, time.Duration(1000)*time.Millisecond)

	time.Sleep(time.Duration(100) * time.Millisecond)

	assert.Equal(t, Counts{3, 0, 0, 0, 0}, customCB.counts)
	assert.Equal(t, succeed(customCB), ErrTooManyRequests)
}

[rthier]

I'm using the "two steps" circuit breaker and is very easy to get the ErrTooManyRequests.
The problem is that after this error the state half open never change!

The state machine stuck by the condition mentioned in this issue:
if state == StateHalfOpen && cb.counts.Requests >= cb.maxRequests

Maybe this is a issue when use the "two steps" feature, but probably a public function to force a state or reset the counters would be helpful to handle this behavior.