leaks_memory.clj

(import '(java.net InetAddress
                   InetSocketAddress
                   DatagramPacket
                   DatagramSocket))

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; networking

(defrecord UDPServer [dgram-socket connected closed])

(defn create-udp-server
  "Uses parameters local-ip and local-port and returns a udp-server record."
  [^String local-ip, local-port]
  (let [sa (InetSocketAddress. (InetAddress/getByName local-ip) local-port)]
    (UDPServer. (DatagramSocket. sa)
                true
                false)))

(defn udp-listen
  [udp-server]
  (let [buf-len 1500
        datagram-packet (DatagramPacket. (byte-array buf-len) buf-len)
        listen (fn [] (do
          (.receive (:dgram-socket udp-server) datagram-packet)
          (String. (.getData datagram-packet))))]
    (do (listen))))

(defn udp-send
  [udp-server ^String message]
  (comment The message will be padded on the right side with null bytes.
           Location of first null + 1 is length of string)
  (let [length (.length (.trim message))]
    (.send (:dgram-socket udp-server) (DatagramPacket. (.getBytes message) length))))

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;
; Creates two UDP sockets, a listener and a sender.  Simply collect packet
;   data from the listener and send data via the sender.
; Leaks memory even when just the listener is listening but the sender is
;   not being called.


(def listener (create-udp-server "127.0.0.1" 514 running))
(def sender (create-udp-server "10.0.0.1" 514 running))
(def process (agent nil))

(loop []
  (send-off process (fn [_] (udp-send sender (udp-listen listener))))
  (recur))

Problem solved by amalloy on IRC (at this time the code above is still broken, though). Calling send-off on an agent without letting the agent finish things first was causing the memory "leak" or the inability for the queue list of things the agent was working on to get gc'ed.