A simple implementation of consitant hashing in Clojure

consistent-hashing.clj

(defprotocol ConsistentHashRing
  (add-node [this node] "add node to the ring")
  (remove-node [this node] "remove node and its replicas of the ring")
  (find-node [this data] "find the node responsible of data"))

(defn- find-closest-key [xs h]
  (or (first (drop-while #(> h %) xs))
      (first xs)))

(extend-protocol ConsistentHashRing
  PersistentTreeMap
  (add-node [this node] (assoc this (.hashCode node) node))
  (remove-node [this node] (dissoc this (.hashCode node)))
  (find-node [this data] (this (find-closest-key (keys this) (.hashCode data)))))