@Willy, since 1.8 (I think), the DNS task is autonomous and not triggered by the check anymore.
Second, HAProxy never ever follows up TTLs. Third, I "fixed" a bug in 2.0.10 which triggers this change of behavior. Basically, "timeout resolve" which is supposed to be the interval between 2 DNS resolutions was not applied when the response was valid. (f50e1ac4442be41ed8b9b7372310d1d068b85b33) So to recover from previous behavior, just increase this value, which is by default 1s. Baptiste