Some embodiments provide a novel method for dynamically adjusting sampling rates of a middlebox service. In some embodiments, the method is performed by the controller. The method configures the forwarding element to collect samples from packets processed by the forwarding element at a first sampling rate. The method analyzes the samples in order to collect information regarding the packets processed by the forwarding element. Based on the analysis, the method detects a new traffic pattern in the packets processed by the forwarding element. The method then configures the forwarding element to collect samples from packets processed by the forwarding element at a second sampling rate different than the first sampling rate.