Merge pull request #157 from rxin/kryo

3 Kryo related changes.

1. Call Kryo setReferences before calling user specified Kryo registrator. This is done so the user specified registrator can override the default setting.

2. Register more internal classes (MapStatus, BlockManagerId).

3. Slightly refactored the internal class registration to allocate less memory.

core/src/main/scala/org/apache/spark/serializer/KryoSerializer.scala

@@ -27,13 +27,17 @@ import com.twitter.chill.{EmptyScalaKryoInstantiator, AllScalaRegistrar}
 
 import org.apache.spark.{SerializableWritable, Logging}
 import org.apache.spark.broadcast.HttpBroadcast
-import org.apache.spark.storage.{GetBlock,GotBlock, PutBlock, StorageLevel, TestBlockId}
+import org.apache.spark.scheduler.MapStatus
+import org.apache.spark.storage._
 
 /**
- * A Spark serializer that uses the [[http://code.google.com/p/kryo/wiki/V1Documentation Kryo 1.x library]].
+ * A Spark serializer that uses the [[https://code.google.com/p/kryo/ Kryo serialization library]].
  */
 class KryoSerializer extends org.apache.spark.serializer.Serializer with Logging {
-  private val bufferSize = System.getProperty("spark.kryoserializer.buffer.mb", "2").toInt * 1024 * 1024
+
+  private val bufferSize = {
+    System.getProperty("spark.kryoserializer.buffer.mb", "2").toInt * 1024 * 1024
+  }
 
   def newKryoOutput() = new KryoOutput(bufferSize)
 
@@ -42,21 +46,11 @@ class KryoSerializer extends org.apache.spark.serializer.Serializer with Logging
     val kryo = instantiator.newKryo()
     val classLoader = Thread.currentThread.getContextClassLoader
 
-    val blockId = TestBlockId("1")
-    // Register some commonly used classes
-    val toRegister: Seq[AnyRef] = Seq(
-      ByteBuffer.allocate(1),
-      StorageLevel.MEMORY_ONLY,
-      PutBlock(blockId, ByteBuffer.allocate(1), StorageLevel.MEMORY_ONLY),
-      GotBlock(blockId, ByteBuffer.allocate(1)),
-      GetBlock(blockId),
-      1 to 10,
-      1 until 10,
-      1L to 10L,
-      1L until 10L
-    )
-
-    for (obj <- toRegister) kryo.register(obj.getClass)
+    // Allow disabling Kryo reference tracking if user knows their object graphs don't have loops.
+    // Do this before we invoke the user registrator so the user registrator can override this.
+    kryo.setReferences(System.getProperty("spark.kryo.referenceTracking", "true").toBoolean)
+
+    for (cls <- KryoSerializer.toRegister) kryo.register(cls)
 
     // Allow sending SerializableWritable
     kryo.register(classOf[SerializableWritable[_]], new KryoJavaSerializer())
@@ -78,10 +72,6 @@ class KryoSerializer extends org.apache.spark.serializer.Serializer with Logging
     new AllScalaRegistrar().apply(kryo)
 
     kryo.setClassLoader(classLoader)
-
-    // Allow disabling Kryo reference tracking if user knows their object graphs don't have loops
-    kryo.setReferences(System.getProperty("spark.kryo.referenceTracking", "true").toBoolean)
-
     kryo
   }
 
@@ -165,3 +155,21 @@ private[spark] class KryoSerializerInstance(ks: KryoSerializer) extends Serializ
 trait KryoRegistrator {
   def registerClasses(kryo: Kryo)
 }
+
+private[serializer] object KryoSerializer {
+  // Commonly used classes.
+  private val toRegister: Seq[Class[_]] = Seq(
+    ByteBuffer.allocate(1).getClass,
+    classOf[StorageLevel],
+    classOf[PutBlock],
+    classOf[GotBlock],
+    classOf[GetBlock],
+    classOf[MapStatus],
+    classOf[BlockManagerId],
+    classOf[Array[Byte]],
+    (1 to 10).getClass,
+    (1 until 10).getClass,
+    (1L to 10L).getClass,
+    (1L until 10L).getClass
+  )
+}