Clojurians Log v2

something like this maybe?

(def ^:private RETRY_FIELD (get-bytes "retry: "))

(defn- event->bytes
  [name data id retry]
  (let [bab (ByteArrayBuilder.)]
    (when name
      (.write bab ^bytes EVENT_FIELD)
      (.write bab ^bytes (get-bytes name))
      (.write bab ^bytes EOL))

    (when data
      (doseq [part (string/split-lines data)]
        (.write bab ^bytes DATA_FIELD)
        (.write bab ^bytes (get-bytes part))
        (.write bab ^bytes EOL)))

    (when id
      (.write bab ^bytes ID_FIELD)
      (.write bab ^bytes (get-bytes id))
      (.write bab ^bytes EOL))

    (when retry
      (.write bab ^bytes RETRY_FIELD)
      (.write bab ^bytes (get-bytes (str retry)))
      (.write bab ^bytes EOL))

    (.write bab ^bytes EOL)
    (.toByteArray bab)))

code currently doesn't check that anything other than EOL is actually written to the buffer (since I make data optional here)