Exception in thread "main" java.lang.ClassCastException: Cannot cast clojure.lang.PersistentList to storm.kafka.KafkaConfig$BrokerHosts, compiling:(word_count_kafka.clj:26)

word_count_kafka.clj

(ns storm.starter.clj.word-count-kafka
  (:import ;[backtype.storm StormSubmitter LocalCluster]
            [storm.kafka KafkaConfig  HostPort KafkaSpout SpoutConfig StringScheme])
  (:use [backtype.storm clojure config])
  (:gen-class))

(def ^{:private true}
  host (list "localhost:9092"))

(def ^{:private true
       :doc "List of Kafka hosts"}
  ZkHosts host )

(def ^{:private true
       :doc "Topic Name"}
  topic "bidder")

(def ^{:private true
       :doc "root path of Zookeeper for the spout to store the consumer offsets"}
  zkRoot "/kafkastorm")

(def ^{:private true
       :doc "id for this consumer for storing the consumer offsets in zookeeper"}
  id "discovery")

(def ^{:private true
       :doc "kafka spout config definition"}
  spout-config (SpoutConfig. ZkHosts topic zkRoot id))

(def kafka-spout
  (KafkaSpout. spout-config
    )
  )

(defbolt split-sentence ["word"] [tuple collector]
  (let [words (.split (.getString tuple 0) " ")]
    (doseq [w words]
      (emit-bolt! collector [w] :anchor tuple))
    (ack! collector tuple)
    ))

(defbolt word-count ["word" "count"] {:prepare true}
  [conf context collector]
  (let [counts (atom {})]
    (bolt
     (execute [tuple]
       (let [word (.getString tuple 0)]
         (swap! counts (partial merge-with +) {word 1})
         (emit-bolt! collector [word (@counts word)] :anchor tuple)
         (ack! collector tuple)
         )))))

(defn mk-topology []

  (topology
   {"1" (spout-spec kafka-spout)
   {"2" (bolt-spec {"1" :shuffle "2" :shuffle}
                   split-sentence
                   :p 5)
    "3" (bolt-spec {"3" ["word"]}
                   word-count
                   :p 6)}))

(defn run-local! []
  (let [cluster (LocalCluster.)]
    (.submitTopology cluster "word-count-kafka" {TOPOLOGY-DEBUG true} (mk-topology))
    (Thread/sleep 10000)
    (.shutdown cluster)
    ))

(defn submit-topology! [name]
  (StormSubmitter/submitTopology
   name
   {TOPOLOGY-DEBUG true
    TOPOLOGY-WORKERS 3}
   (mk-topology)))

(defn -main
  ([]
   (run-local!))
  ([name]
   (submit-topology! name)))