Make random-fodder-seq thread safe

- The details of the bug and fix are in the docstring of
`hyperion.key/random-fodder-seq`.

api/spec/hyperion/key_spec.clj

@@ -47,6 +47,15 @@
  (should= true (seq? (random-fodder-seq)))
  (should= 10 (count (set (map (fn [_] (take 5 (random-fodder-seq))) (range 10))))))
 
+ (it "random-fodder-seq is threadsafe"
+ (should= 250
+ (reduce +
+ (map
+ (fn[_] (count (set (pmap
+ (fn [_] (take 10 (random-fodder-seq)))
+ (range 50)))))
+ (range 5)))))
+
 ; (it "generate key times"
 ; (prn (take 100 (iterate (fn [_] (generate-id)) nil)))
 ; (prn (take 100 (iterate (fn [_] (generate-id2)) nil)))

api/src/hyperion/key.clj

@@ -23,7 +23,13 @@
 (def fodder-count (count key-fodder))
 
 (defn random-fodder-seq
- ([] (random-fodder-seq (java.util.Random. (System/nanoTime))))
+ "The default generator for `random-fodder-seq` is threadsafe for JDK 1.6b73
+ or greater (http://bugs.java.com/view_bug.do?bug_id=6379897). Calls to this on
+ multiple threads (i.e. `(pmap (fn [_] (take 10 random-fodder-seq)) (range 10))`)
+ will have a different seed for each instance of `java.util.Random`. If on a JDK
+ earlier than JDK 1.6b73 there is a chance that there will be multiple instances
+ of `java.util.Random` with the same seed causing collisions"
+ ([] (random-fodder-seq (java.util.Random.)))
  ([generator]
  (cons
  (aget key-fodder (.nextInt generator fodder-count))