Merge pull request #15 from sungjuc/master

Concurrency issues of atomicCreateIfAbsent function
jhartman · May 15, 2013 · 50b42ca · 50b42ca
2 parents 1c08f3f + f0ddf5f
commit 50b42ca
Showing 1 changed file with 6 additions and 6 deletions.
diff --git a/cluster/src/main/scala/com/linkedin/norbert/norbertutils/package.scala b/cluster/src/main/scala/com/linkedin/norbert/norbertutils/package.scala
@@ -43,15 +43,15 @@ package object norbertutils {
 
   // TODO: Put this into a utility somewhere? Scala's concurrent getOrElseUpdate is not atomic, unlike this guy
   def atomicCreateIfAbsent[K, V](map: ConcurrentMap[K, V], key: K)(fn: K => V): V = {
-    val oldValue = map.get(key)
-    if(oldValue == null) {
-      map.synchronized {
+    map.synchronized {
+      val oldValue = map.get(key)
+      if(oldValue == null) {
         val newValue = fn(key)
         map.putIfAbsent(key, newValue)
         map.get(key)
+      } else {
+        oldValue
       }
-    } else {
-      oldValue
     }
   }
 
@@ -99,4 +99,4 @@ package object norbertutils {
       case e : Exception => // nothing
     }
   }
-}
+}