Edge computing is a promising infrastructure evolution to reduce traffic loads and support low-latency communications. Furthermore, content-centric networks provide a natural solution to cache contents at edge nodes. However, it is a challenge for edge nodes to handle massive and highly dynamic content requests by users, and if without an efficient content caching strategy, the edge nodes will encounter high traffic load and latency due to increasing retrieval from content providers. This paper formulates a proactive edge caching problem to minimize the content retrieval cost at edge nodes. We exploit the inherent content caching and request aggregation mechanism in the content-centric networks to jointly minimize traffic load and content retrieval delay cost generated by the massive and dynamic content requests. We develop a Q-learning algorithm, which is an online optimal caching strategy, as it is adaptable to dynamic content popularity and content request intensity, and derive the long-term minimization of the content retrieval cost. Simulation results illustrate that the proposed algorithm can achieve a lower content retrieval cost compared with several baseline caching schemes. INDEX TERMS Content-centric networks, dynamic content requests, edge computing, proactive caching, Q-learning. XIAOGENG XU (Student Member, IEEE) received the B.S. degree in communications engineering from the Beijing University of Technology, China, in 2005, the M.S. degree in digital communication systems and technology from the Chalmers University of Technology, Sweden, in 2007. She is currently pursuing the Ph.D. degree in communication and information systems from the Beijing University of Posts and Telecommunications. Her current researches focus on caching performance analysis and optimization in content-centric networks. CHUNYAN FENG (Senior Member, IEEE) received the B.S. degree in communications engineering and the M.S. and Ph.D. degrees in communication and information systems from the Beijing University of Posts and Telecommunications (BUPT), Beijing, China. She is currently a Professor with the School of Information and Communication Engineering, BUPT. Her research interests are in the areas of broadband networks and wireless communication systems. Her current research focuses on cognitive radio and green wireless communications.