1. A computer-executable method for ranking content popularity in a content-centric network (CCN) content cache, the method comprising: receiving, by a CCN node, an interest in a piece of content stored in the content cache; servicing the interest by accessing the piece of content; in response to the piece of content being accessed, updating an object-specific service rate associated with the piece of content by calculating an exponentially weighted moving average (EWMA) of numbers of accesses to the piece of content over a time constant, wherein calculating the EWMA involves applying a weight coefficient that is a function of a time interval between consecutive accesses to the content piece and performing a table lookup to obtain pre-calculated exponential weight functions, and wherein the object-specific service rate indicates a frequency that the piece of content is accessed; updating system-wide service rate statistics, which involves calculating a per-object service rate averaged over a set of pieces of content stored in the content cache; and determining a popularity level associated with the piece of content based on the updated object-specific service rate and the updated system-wide service rate statistics.