EXHIBIT 2

JOINT FILING AGREEMENT

The undersigned hereby agree to the joint filing of the Amendment No. 1 to Schedule 13D to which this Agreement is attached.

Dated:  December 19, 2017

DISCOVERY EQUITY PARTNERS, L.P.
By	Michael R. Murphy*
	Michael R. Murphy
	Manager
DISCOVERY GROUP I, LLC
By	Michael R. Murphy *
	Michael R. Murphy
	Manager
*By:	/s/ Mark Buckley
	Mark Buckley
	Attorney-in-Fact for Michael R. Murphy