[SPARK-3019] Pluggable block transfer interface (BlockTransferService)

This pull request creates a new BlockTransferService interface for block fetch/upload and refactors the existing ConnectionManager to implement BlockTransferService (NioBlockTransferService).

Most of the changes are simply moving code around. The main class to inspect is ShuffleBlockFetcherIterator.

Review guide:
- Most of the ConnectionManager code is now in network.cm package
- ManagedBuffer is a new buffer abstraction backed by several different implementations (file segment, nio ByteBuffer, Netty ByteBuf)
- BlockTransferService is the main internal interface introduced in this PR
- NioBlockTransferService implements BlockTransferService and replaces the old BlockManagerWorker
- ShuffleBlockFetcherIterator replaces the told BlockFetcherIterator to use the new interface

TODOs that should be separate PRs:
- Implement NettyBlockTransferService
- Finalize the API/semantics for ManagedBuffer.release()

Author: Reynold Xin <rxin@apache.org>

Closes #2240 from rxin/blockTransferService and squashes the following commits:

64cd9d7 [Reynold Xin] Merge branch 'master' into blockTransferService
1dfd3d7 [Reynold Xin] Limit the length of the FileInputStream.
1332156 [Reynold Xin] Fixed style violation from refactoring.
2960c93 [Reynold Xin] Added ShuffleBlockFetcherIteratorSuite.
e29c721 [Reynold Xin] Updated comment for ShuffleBlockFetcherIterator.
8a1046e [Reynold Xin] Code review feedback:
2c6b1e1 [Reynold Xin] Removed println in test cases.
2a907e4 [Reynold Xin] Merge branch 'master' into blockTransferService-merge
07ccf0d [Reynold Xin] Added init check to CMBlockTransferService.
98c668a [Reynold Xin] Added failure handling and fixed unit tests.
ae05fcd [Reynold Xin] Updated tests, although DistributedSuite is hanging.
d8d595c [Reynold Xin] Merge branch 'master' of github.com:apache/spark into blockTransferService
9ef279c [Reynold Xin] Initial refactoring to move ConnectionManager to use the BlockTransferService.

38 files changed, 1129 insertions, 1273 deletions

diff --git a/core/src/main/scala/org/apache/spark/SparkEnv.scala b/core/src/main/scala/org/apache/spark/SparkEnv.scala
index 20a7444cfc..dd95e406f2 100644
--- a/core/src/main/scala/org/apache/spark/SparkEnv.scala
+++ b/core/src/main/scala/org/apache/spark/SparkEnv.scala
@@ -31,7 +31,8 @@ import org.apache.spark.annotation.DeveloperApi
 import org.apache.spark.api.python.PythonWorkerFactory
 import org.apache.spark.broadcast.BroadcastManager
 import org.apache.spark.metrics.MetricsSystem
-import org.apache.spark.network.ConnectionManager
+import org.apache.spark.network.BlockTransferService
+import org.apache.spark.network.nio.NioBlockTransferService
 import org.apache.spark.scheduler.LiveListenerBus
 import org.apache.spark.serializer.Serializer
 import org.apache.spark.shuffle.{ShuffleMemoryManager, ShuffleManager}
@@ -59,8 +60,8 @@ class SparkEnv (
     val mapOutputTracker: MapOutputTracker,
     val shuffleManager: ShuffleManager,
     val broadcastManager: BroadcastManager,
+    val blockTransferService: BlockTransferService,
     val blockManager: BlockManager,
-    val connectionManager: ConnectionManager,
     val securityManager: SecurityManager,
     val httpFileServer: HttpFileServer,
     val sparkFilesDir: String,
@@ -88,6 +89,8 @@ class SparkEnv (
     // down, but let's call it anyway in case it gets fixed in a later release
     // UPDATE: In Akka 2.1.x, this hangs if there are remote actors, so we can't call it.
     // actorSystem.awaitTermination()
+
+    // Note that blockTransferService is stopped by BlockManager since it is started by it.
   }
 
   private[spark]
@@ -223,14 +226,14 @@ object SparkEnv extends Logging {
 
     val shuffleMemoryManager = new ShuffleMemoryManager(conf)
 
+    val blockTransferService = new NioBlockTransferService(conf, securityManager)
+
     val blockManagerMaster = new BlockManagerMaster(registerOrLookup(
       "BlockManagerMaster",
       new BlockManagerMasterActor(isLocal, conf, listenerBus)), conf, isDriver)
 
     val blockManager = new BlockManager(executorId, actorSystem, blockManagerMaster,
-      serializer, conf, securityManager, mapOutputTracker, shuffleManager)
-
-    val connectionManager = blockManager.connectionManager
+      serializer, conf, mapOutputTracker, shuffleManager, blockTransferService)
 
     val broadcastManager = new BroadcastManager(isDriver, conf, securityManager)
 
@@ -278,8 +281,8 @@ object SparkEnv extends Logging {
       mapOutputTracker,
       shuffleManager,
       broadcastManager,
+      blockTransferService,
       blockManager,
-      connectionManager,
       securityManager,
       httpFileServer,
       sparkFilesDir,
diff --git a/core/src/main/scala/org/apache/spark/network/ReceiverTest.scala b/core/src/main/scala/org/apache/spark/network/BlockDataManager.scala
index 53a6038a9b..e0e9172427 100644
--- a/core/src/main/scala/org/apache/spark/network/ReceiverTest.scala
+++ b/core/src/main/scala/org/apache/spark/network/BlockDataManager.scala
@@ -17,21 +17,20 @@
 
 package org.apache.spark.network
 
-import java.nio.ByteBuffer
-import org.apache.spark.{SecurityManager, SparkConf}
+import org.apache.spark.storage.StorageLevel
 
-private[spark] object ReceiverTest {
-  def main(args: Array[String]) {
-    val conf = new SparkConf
-    val manager = new ConnectionManager(9999, conf, new SecurityManager(conf))
-    println("Started connection manager with id = " + manager.id)
 
-    manager.onReceiveMessage((msg: Message, id: ConnectionManagerId) => {
-      /* println("Received [" + msg + "] from [" + id + "] at " + System.currentTimeMillis) */
-      val buffer = ByteBuffer.wrap("response".getBytes("utf-8"))
-      Some(Message.createBufferMessage(buffer, msg.id))
-    })
-    Thread.currentThread.join()
-  }
-}
+trait BlockDataManager {
+
+  /**
+   * Interface to get local block data.
+   *
+   * @return Some(buffer) if the block exists locally, and None if it doesn't.
+   */
+  def getBlockData(blockId: String): Option[ManagedBuffer]
 
+  /**
+   * Put the block locally, using the given storage level.
+   */
+  def putBlockData(blockId: String, data: ManagedBuffer, level: StorageLevel): Unit
+}
diff --git a/core/src/main/scala/org/apache/spark/network/BlockFetchingListener.scala b/core/src/main/scala/org/apache/spark/network/BlockFetchingListener.scala
new file mode 100644
index 0000000000..34acaa563c
--- /dev/null
+++ b/core/src/main/scala/org/apache/spark/network/BlockFetchingListener.scala
@@ -0,0 +1,37 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.network
+
+import java.util.EventListener
+
+
+/**
+ * Listener callback interface for [[BlockTransferService.fetchBlocks]].
+ */
+trait BlockFetchingListener extends EventListener {
+
+  /**
+   * Called once per successfully fetched block.
+   */
+  def onBlockFetchSuccess(blockId: String, data: ManagedBuffer): Unit
+
+  /**
+   * Called upon failures. For each failure, this is called only once (i.e. not once per block).
+   */
+  def onBlockFetchFailure(exception: Throwable): Unit
+}
diff --git a/core/src/main/scala/org/apache/spark/network/BlockTransferService.scala b/core/src/main/scala/org/apache/spark/network/BlockTransferService.scala
new file mode 100644
index 0000000000..84d991fa68
--- /dev/null
+++ b/core/src/main/scala/org/apache/spark/network/BlockTransferService.scala
@@ -0,0 +1,131 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.network
+
+import scala.concurrent.{Await, Future}
+import scala.concurrent.duration.Duration
+
+import org.apache.spark.storage.StorageLevel
+
+
+abstract class BlockTransferService {
+
+  /**
+   * Initialize the transfer service by giving it the BlockDataManager that can be used to fetch
+   * local blocks or put local blocks.
+   */
+  def init(blockDataManager: BlockDataManager)
+
+  /**
+   * Tear down the transfer service.
+   */
+  def stop(): Unit
+
+  /**
+   * Port number the service is listening on, available only after [[init]] is invoked.
+   */
+  def port: Int
+
+  /**
+   * Host name the service is listening on, available only after [[init]] is invoked.
+   */
+  def hostName: String
+
+  /**
+   * Fetch a sequence of blocks from a remote node asynchronously,
+   * available only after [[init]] is invoked.
+   *
+   * Note that [[BlockFetchingListener.onBlockFetchSuccess]] is called once per block,
+   * while [[BlockFetchingListener.onBlockFetchFailure]] is called once per failure (not per block).
+   *
+   * Note that this API takes a sequence so the implementation can batch requests, and does not
+   * return a future so the underlying implementation can invoke onBlockFetchSuccess as soon as
+   * the data of a block is fetched, rather than waiting for all blocks to be fetched.
+   */
+  def fetchBlocks(
+      hostName: String,
+      port: Int,
+      blockIds: Seq[String],
+      listener: BlockFetchingListener): Unit
+
+  /**
+   * Upload a single block to a remote node, available only after [[init]] is invoked.
+   */
+  def uploadBlock(
+      hostname: String,
+      port: Int,
+      blockId: String,
+      blockData: ManagedBuffer,
+      level: StorageLevel): Future[Unit]
+
+  /**
+   * A special case of [[fetchBlocks]], as it fetches only one block and is blocking.
+   *
+   * It is also only available after [[init]] is invoked.
+   */
+  def fetchBlockSync(hostName: String, port: Int, blockId: String): ManagedBuffer = {
+    // A monitor for the thread to wait on.
+    val lock = new Object
+    @volatile var result: Either[ManagedBuffer, Throwable] = null
+    fetchBlocks(hostName, port, Seq(blockId), new BlockFetchingListener {
+      override def onBlockFetchFailure(exception: Throwable): Unit = {
+        lock.synchronized {
+          result = Right(exception)
+          lock.notify()
+        }
+      }
+      override def onBlockFetchSuccess(blockId: String, data: ManagedBuffer): Unit = {
+        lock.synchronized {
+          result = Left(data)
+          lock.notify()
+        }
+      }
+    })
+
+    // Sleep until result is no longer null
+    lock.synchronized {
+      while (result == null) {
+        try {
+          lock.wait()
+        } catch {
+          case e: InterruptedException =>
+        }
+      }
+    }
+
+    result match {
+      case Left(data) => data
+      case Right(e) => throw e
+    }
+  }
+
+  /**
+   * Upload a single block to a remote node, available only after [[init]] is invoked.
+   *
+   * This method is similar to [[uploadBlock]], except this one blocks the thread
+   * until the upload finishes.
+   */
+  def uploadBlockSync(
+      hostname: String,
+      port: Int,
+      blockId: String,
+      blockData: ManagedBuffer,
+      level: StorageLevel): Unit = {
+    Await.result(uploadBlock(hostname, port, blockId, blockData, level), Duration.Inf)
+  }
+}
diff --git a/core/src/main/scala/org/apache/spark/network/ConnectionManagerTest.scala b/core/src/main/scala/org/apache/spark/network/ConnectionManagerTest.scala
deleted file mode 100644
index 4894ecd41f..0000000000
--- a/core/src/main/scala/org/apache/spark/network/ConnectionManagerTest.scala
+++ /dev/null
@@ -1,103 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *    http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.apache.spark.network
-
-import java.nio.ByteBuffer
-
-import scala.concurrent.Await
-import scala.concurrent.duration._
-import scala.io.Source
-
-import org.apache.spark._
-
-private[spark] object ConnectionManagerTest extends Logging{
-  def main(args: Array[String]) {
-    // <mesos cluster> - the master URL <slaves file> - a list slaves to run connectionTest on
-    // [num of tasks] - the number of parallel tasks to be initiated default is number of slave
-    // hosts [size of msg in MB (integer)] - the size of messages to be sent in each task,
-    // default is 10 [count] - how many times to run, default is 3 [await time in seconds] :
-    // await time (in seconds), default is 600
-    if (args.length < 2) {
-      println("Usage: ConnectionManagerTest <mesos cluster> <slaves file> [num of tasks] " +
-        "[size of msg in MB (integer)] [count] [await time in seconds)] ")
-      System.exit(1)
-    }
-
-    if (args(0).startsWith("local")) {
-      println("This runs only on a mesos cluster")
-    }
-
-    val sc = new SparkContext(args(0), "ConnectionManagerTest")
-    val slavesFile = Source.fromFile(args(1))
-    val slaves = slavesFile.mkString.split("\n")
-    slavesFile.close()
-
-    /* println("Slaves") */
-    /* slaves.foreach(println) */
-    val tasknum = if (args.length > 2) args(2).toInt else slaves.length
-    val size = ( if (args.length > 3) (args(3).toInt) else 10 ) * 1024 * 1024
-    val count = if (args.length > 4) args(4).toInt else 3
-    val awaitTime = (if (args.length > 5) args(5).toInt else 600 ).second
-    println("Running " + count + " rounds of test: " + "parallel tasks = " + tasknum + ", " +
-      "msg size = " + size/1024/1024 + " MB, awaitTime = " + awaitTime)
-    val slaveConnManagerIds = sc.parallelize(0 until tasknum, tasknum).map(
-        i => SparkEnv.get.connectionManager.id).collect()
-    println("\nSlave ConnectionManagerIds")
-    slaveConnManagerIds.foreach(println)
-    println
-
-    (0 until count).foreach(i => {
-      val resultStrs = sc.parallelize(0 until tasknum, tasknum).map(i => {
-        val connManager = SparkEnv.get.connectionManager
-        val thisConnManagerId = connManager.id
-        connManager.onReceiveMessage((msg: Message, id: ConnectionManagerId) => {
-          logInfo("Received [" + msg + "] from [" + id + "]")
-          None
-        })
-
-        val buffer = ByteBuffer.allocate(size).put(Array.tabulate[Byte](size)(x => x.toByte))
-        buffer.flip
-
-        val startTime = System.currentTimeMillis
-        val futures = slaveConnManagerIds.filter(_ != thisConnManagerId).map{ slaveConnManagerId =>
-          {
-            val bufferMessage = Message.createBufferMessage(buffer.duplicate)
-            logInfo("Sending [" + bufferMessage + "] to [" + slaveConnManagerId + "]")
-            connManager.sendMessageReliably(slaveConnManagerId, bufferMessage)
-          }
-        }
-        val results = futures.map(f => Await.result(f, awaitTime))
-        val finishTime = System.currentTimeMillis
-        Thread.sleep(5000)
-
-        val mb = size * results.size / 1024.0 / 1024.0
-        val ms = finishTime - startTime
-        val resultStr = thisConnManagerId + " Sent " + mb + " MB in " + ms + " ms at " + (mb / ms *
-          1000.0) + " MB/s"
-        logInfo(resultStr)
-        resultStr
-      }).collect()
-
-      println("---------------------")
-      println("Run " + i)
-      resultStrs.foreach(println)
-      println("---------------------")
-    })
-  }
-}
-
diff --git a/core/src/main/scala/org/apache/spark/network/ManagedBuffer.scala b/core/src/main/scala/org/apache/spark/network/ManagedBuffer.scala
new file mode 100644
index 0000000000..dcecb6beee
--- /dev/null
+++ b/core/src/main/scala/org/apache/spark/network/ManagedBuffer.scala
@@ -0,0 +1,107 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.network
+
+import java.io.{FileInputStream, RandomAccessFile, File, InputStream}
+import java.nio.ByteBuffer
+import java.nio.channels.FileChannel.MapMode
+
+import com.google.common.io.ByteStreams
+import io.netty.buffer.{ByteBufInputStream, ByteBuf}
+
+import org.apache.spark.util.ByteBufferInputStream
+
+
+/**
+ * This interface provides an immutable view for data in the form of bytes. The implementation
+ * should specify how the data is provided:
+ *
+ * - FileSegmentManagedBuffer: data backed by part of a file
+ * - NioByteBufferManagedBuffer: data backed by a NIO ByteBuffer
+ * - NettyByteBufManagedBuffer: data backed by a Netty ByteBuf
+ */
+sealed abstract class ManagedBuffer {
+  // Note that all the methods are defined with parenthesis because their implementations can
+  // have side effects (io operations).
+
+  /** Number of bytes of the data. */
+  def size: Long
+
+  /**
+   * Exposes this buffer's data as an NIO ByteBuffer. Changing the position and limit of the
+   * returned ByteBuffer should not affect the content of this buffer.
+   */
+  def nioByteBuffer(): ByteBuffer
+
+  /**
+   * Exposes this buffer's data as an InputStream. The underlying implementation does not
+   * necessarily check for the length of bytes read, so the caller is responsible for making sure
+   * it does not go over the limit.
+   */
+  def inputStream(): InputStream
+}
+
+
+/**
+ * A [[ManagedBuffer]] backed by a segment in a file
+ */
+final class FileSegmentManagedBuffer(val file: File, val offset: Long, val length: Long)
+  extends ManagedBuffer {
+
+  override def size: Long = length
+
+  override def nioByteBuffer(): ByteBuffer = {
+    val channel = new RandomAccessFile(file, "r").getChannel
+    channel.map(MapMode.READ_ONLY, offset, length)
+  }
+
+  override def inputStream(): InputStream = {
+    val is = new FileInputStream(file)
+    is.skip(offset)
+    ByteStreams.limit(is, length)
+  }
+}
+
+
+/**
+ * A [[ManagedBuffer]] backed by [[java.nio.ByteBuffer]].
+ */
+final class NioByteBufferManagedBuffer(buf: ByteBuffer) extends ManagedBuffer {
+
+  override def size: Long = buf.remaining()
+
+  override def nioByteBuffer() = buf.duplicate()
+
+  override def inputStream() = new ByteBufferInputStream(buf)
+}
+
+
+/**
+ * A [[ManagedBuffer]] backed by a Netty [[ByteBuf]].
+ */
+final class NettyByteBufManagedBuffer(buf: ByteBuf) extends ManagedBuffer {
+
+  override def size: Long = buf.readableBytes()
+
+  override def nioByteBuffer() = buf.nioBuffer()
+
+  override def inputStream() = new ByteBufInputStream(buf)
+
+  // TODO(rxin): Promote this to top level ManagedBuffer interface and add documentation for it.
+  def release(): Unit = buf.release()
+}
diff --git a/core/src/main/scala/org/apache/spark/network/SenderTest.scala b/core/src/main/scala/org/apache/spark/network/SenderTest.scala
deleted file mode 100644
index ea2ad104ec..0000000000
--- a/core/src/main/scala/org/apache/spark/network/SenderTest.scala
+++ /dev/null
@@ -1,76 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *    http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.apache.spark.network
-
-import java.nio.ByteBuffer
-import org.apache.spark.{SecurityManager, SparkConf}
-
-import scala.concurrent.Await
-import scala.concurrent.duration.Duration
-import scala.util.Try
-
-private[spark] object SenderTest {
-  def main(args: Array[String]) {
-
-    if (args.length < 2) {
-      println("Usage: SenderTest <target host> <target port>")
-      System.exit(1)
-    }
-
-    val targetHost = args(0)
-    val targetPort = args(1).toInt
-    val targetConnectionManagerId = new ConnectionManagerId(targetHost, targetPort)
-    val conf = new SparkConf
-    val manager = new ConnectionManager(0, conf, new SecurityManager(conf))
-    println("Started connection manager with id = " + manager.id)
-
-    manager.onReceiveMessage((msg: Message, id: ConnectionManagerId) => {
-      println("Received [" + msg + "] from [" + id + "]")
-      None
-    })
-
-    val size =  100 * 1024  * 1024
-    val buffer = ByteBuffer.allocate(size).put(Array.tabulate[Byte](size)(x => x.toByte))
-    buffer.flip
-
-    val targetServer = args(0)
-
-    val count = 100
-    (0 until count).foreach(i => {
-      val dataMessage = Message.createBufferMessage(buffer.duplicate)
-      val startTime = System.currentTimeMillis
-      /* println("Started timer at " + startTime) */
-      val promise = manager.sendMessageReliably(targetConnectionManagerId, dataMessage)
-      val responseStr: String = Try(Await.result(promise, Duration.Inf))
-        .map { response =>
-          val buffer = response.asInstanceOf[BufferMessage].buffers(0)
-          new String(buffer.array, "utf-8")
-        }.getOrElse("none")
-
-      val finishTime = System.currentTimeMillis
-      val mb = size / 1024.0 / 1024.0
-      val ms = finishTime - startTime
-      // val resultStr = "Sent " + mb + " MB " + targetServer + " in " + ms + " ms at " + (mb / ms
-      //  * 1000.0) + " MB/s"
-      val resultStr = "Sent " + mb + " MB " + targetServer + " in " + ms + " ms (" +
-        (mb / ms * 1000.0).toInt + "MB/s) | Response = " + responseStr
-      println(resultStr)
-    })
-  }
-}
-
diff --git a/core/src/main/scala/org/apache/spark/storage/BlockMessage.scala b/core/src/main/scala/org/apache/spark/network/nio/BlockMessage.scala
index a2bfce7b4a..b573f1a8a5 100644
--- a/core/src/main/scala/org/apache/spark/storage/BlockMessage.scala
+++ b/core/src/main/scala/org/apache/spark/network/nio/BlockMessage.scala
@@ -15,20 +15,20 @@
  * limitations under the License.
  */
 
-package org.apache.spark.storage
+package org.apache.spark.network.nio
 
 import java.nio.ByteBuffer
 
-import scala.collection.mutable.ArrayBuffer
-import scala.collection.mutable.StringBuilder
+import org.apache.spark.storage.{BlockId, StorageLevel, TestBlockId}
 
-import org.apache.spark.network._
+import scala.collection.mutable.{ArrayBuffer, StringBuilder}
 
+// private[spark] because we need to register them in Kryo
 private[spark] case class GetBlock(id: BlockId)
 private[spark] case class GotBlock(id: BlockId, data: ByteBuffer)
 private[spark] case class PutBlock(id: BlockId, data: ByteBuffer, level: StorageLevel)
 
-private[spark] class BlockMessage() {
+private[nio] class BlockMessage() {
   // Un-initialized: typ = 0
   // GetBlock: typ = 1
   // GotBlock: typ = 2
@@ -159,7 +159,7 @@ private[spark] class BlockMessage() {
   }
 }
 
-private[spark] object BlockMessage {
+private[nio] object BlockMessage {
   val TYPE_NON_INITIALIZED: Int = 0
   val TYPE_GET_BLOCK: Int = 1
   val TYPE_GOT_BLOCK: Int = 2
@@ -194,16 +194,4 @@ private[spark] object BlockMessage {
     newBlockMessage.set(putBlock)
     newBlockMessage
   }
-
-  def main(args: Array[String]) {
-    val B = new BlockMessage()
-    val blockId = TestBlockId("ABC")
-    B.set(new PutBlock(blockId, ByteBuffer.allocate(10), StorageLevel.MEMORY_AND_DISK_SER_2))
-    val bMsg = B.toBufferMessage
-    val C = new BlockMessage()
-    C.set(bMsg)
-
-    println(B.getId + " " + B.getLevel)
-    println(C.getId + " " + C.getLevel)
-  }
 }
diff --git a/core/src/main/scala/org/apache/spark/storage/BlockMessageArray.scala b/core/src/main/scala/org/apache/spark/network/nio/BlockMessageArray.scala
index 973d85c0a9..a1a2c00ed1 100644
--- a/core/src/main/scala/org/apache/spark/storage/BlockMessageArray.scala
+++ b/core/src/main/scala/org/apache/spark/network/nio/BlockMessageArray.scala
@@ -15,16 +15,16 @@
  * limitations under the License.
  */
 
-package org.apache.spark.storage
+package org.apache.spark.network.nio
 
 import java.nio.ByteBuffer
 
-import scala.collection.mutable.ArrayBuffer
-
 import org.apache.spark._
-import org.apache.spark.network._
+import org.apache.spark.storage.{StorageLevel, TestBlockId}
+
+import scala.collection.mutable.ArrayBuffer
 
-private[spark]
+private[nio]
 class BlockMessageArray(var blockMessages: Seq[BlockMessage])
   extends Seq[BlockMessage] with Logging {
 
@@ -102,7 +102,7 @@ class BlockMessageArray(var blockMessages: Seq[BlockMessage])
   }
 }
 
-private[spark] object BlockMessageArray {
+private[nio] object BlockMessageArray {
 
   def fromBufferMessage(bufferMessage: BufferMessage): BlockMessageArray = {
     val newBlockMessageArray = new BlockMessageArray()
diff --git a/core/src/main/scala/org/apache/spark/network/BufferMessage.scala b/core/src/main/scala/org/apache/spark/network/nio/BufferMessage.scala
index af35f1fc3e..3b245c5c7a 100644
--- a/core/src/main/scala/org/apache/spark/network/BufferMessage.scala
+++ b/core/src/main/scala/org/apache/spark/network/nio/BufferMessage.scala
@@ -15,7 +15,7 @@
  * limitations under the License.
  */
 
-package org.apache.spark.network
+package org.apache.spark.network.nio
 
 import java.nio.ByteBuffer
 
@@ -23,7 +23,8 @@ import scala.collection.mutable.ArrayBuffer
 
 import org.apache.spark.storage.BlockManager
 
-private[spark]
+
+private[nio]
 class BufferMessage(id_ : Int, val buffers: ArrayBuffer[ByteBuffer], var ackId: Int)
   extends Message(Message.BUFFER_MESSAGE, id_) {
 
diff --git a/core/src/main/scala/org/apache/spark/network/Connection.scala b/core/src/main/scala/org/apache/spark/network/nio/Connection.scala
index 5285ec82c1..74074a8dcb 100644
--- a/core/src/main/scala/org/apache/spark/network/Connection.scala
+++ b/core/src/main/scala/org/apache/spark/network/nio/Connection.scala
@@ -15,17 +15,17 @@
  * limitations under the License.
  */
 
-package org.apache.spark.network
+package org.apache.spark.network.nio
 
 import java.net._
 import java.nio._
 import java.nio.channels._
 
-import scala.collection.mutable.{ArrayBuffer, HashMap, Queue}
-
 import org.apache.spark._
 
-private[spark]
+import scala.collection.mutable.{ArrayBuffer, HashMap, Queue}
+
+private[nio]
 abstract class Connection(val channel: SocketChannel, val selector: Selector,
     val socketRemoteConnectionManagerId: ConnectionManagerId, val connectionId: ConnectionId)
   extends Logging {
@@ -190,7 +190,7 @@ abstract class Connection(val channel: SocketChannel, val selector: Selector,
 }
 
 
-private[spark]
+private[nio]
 class SendingConnection(val address: InetSocketAddress, selector_ : Selector,
     remoteId_ : ConnectionManagerId, id_ : ConnectionId)
   extends Connection(SocketChannel.open, selector_, remoteId_, id_) {
diff --git a/core/src/main/scala/org/apache/spark/network/ConnectionId.scala b/core/src/main/scala/org/apache/spark/network/nio/ConnectionId.scala
index d579c165a1..764dc5e550 100644
--- a/core/src/main/scala/org/apache/spark/network/ConnectionId.scala
+++ b/core/src/main/scala/org/apache/spark/network/nio/ConnectionId.scala
@@ -15,13 +15,13 @@
  * limitations under the License.
  */
 
-package org.apache.spark.network
+package org.apache.spark.network.nio
 
-private[spark] case class ConnectionId(connectionManagerId: ConnectionManagerId, uniqId: Int) {
+private[nio] case class ConnectionId(connectionManagerId: ConnectionManagerId, uniqId: Int) {
   override def toString = connectionManagerId.host + "_" + connectionManagerId.port + "_" + uniqId
 }
 
-private[spark] object ConnectionId {
+private[nio] object ConnectionId {
 
   def createConnectionIdFromString(connectionIdString: String): ConnectionId = {
     val res = connectionIdString.split("_").map(_.trim())
diff --git a/core/src/main/scala/org/apache/spark/network/ConnectionManager.scala b/core/src/main/scala/org/apache/spark/network/nio/ConnectionManager.scala
index 578d806263..09d3ea3065 100644
--- a/core/src/main/scala/org/apache/spark/network/ConnectionManager.scala
+++ b/core/src/main/scala/org/apache/spark/network/nio/ConnectionManager.scala
@@ -15,32 +15,27 @@
  * limitations under the License.
  */
 
-package org.apache.spark.network
+package org.apache.spark.network.nio
 
 import java.io.IOException
+import java.net._
 import java.nio._
 import java.nio.channels._
 import java.nio.channels.spi._
-import java.net._
-import java.util.{Timer, TimerTask}
 import java.util.concurrent.atomic.AtomicInteger
+import java.util.concurrent.{LinkedBlockingDeque, ThreadPoolExecutor, TimeUnit}
+import java.util.{Timer, TimerTask}
 
-import java.util.concurrent.{LinkedBlockingDeque, TimeUnit, ThreadPoolExecutor}
-
-import scala.collection.mutable.ArrayBuffer
-import scala.collection.mutable.HashMap
-import scala.collection.mutable.HashSet
-import scala.collection.mutable.SynchronizedMap
-import scala.collection.mutable.SynchronizedQueue
-
-import scala.concurrent.{Await, ExecutionContext, Future, Promise}
+import scala.collection.mutable.{ArrayBuffer, HashMap, HashSet, SynchronizedMap, SynchronizedQueue}
 import scala.concurrent.duration._
+import scala.concurrent.{Await, ExecutionContext, Future, Promise}
 import scala.language.postfixOps
 
 import org.apache.spark._
 import org.apache.spark.util.{SystemClock, Utils}
 
-private[spark] class ConnectionManager(
+
+private[nio] class ConnectionManager(
     port: Int,
     conf: SparkConf,
     securityManager: SecurityManager,
@@ -904,7 +899,7 @@ private[spark] class ConnectionManager(
 
 
 private[spark] object ConnectionManager {
-  import ExecutionContext.Implicits.global
+  import scala.concurrent.ExecutionContext.Implicits.global
 
   def main(args: Array[String]) {
     val conf = new SparkConf
diff --git a/core/src/main/scala/org/apache/spark/network/ConnectionManagerId.scala b/core/src/main/scala/org/apache/spark/network/nio/ConnectionManagerId.scala
index 57f7586883..cbb37ec5ce 100644
--- a/core/src/main/scala/org/apache/spark/network/ConnectionManagerId.scala
+++ b/core/src/main/scala/org/apache/spark/network/nio/ConnectionManagerId.scala
@@ -15,13 +15,13 @@
  * limitations under the License.
  */
 
-package org.apache.spark.network
+package org.apache.spark.network.nio
 
 import java.net.InetSocketAddress
 
 import org.apache.spark.util.Utils
 
-private[spark] case class ConnectionManagerId(host: String, port: Int) {
+private[nio] case class ConnectionManagerId(host: String, port: Int) {
   // DEBUG code
   Utils.checkHost(host)
   assert (port > 0)
@@ -30,7 +30,7 @@ private[spark] case class ConnectionManagerId(host: String, port: Int) {
 }
 
 
-private[spark] object ConnectionManagerId {
+private[nio] object ConnectionManagerId {
   def fromSocketAddress(socketAddress: InetSocketAddress): ConnectionManagerId = {
     new ConnectionManagerId(socketAddress.getHostName, socketAddress.getPort)
   }
diff --git a/core/src/main/scala/org/apache/spark/network/Message.scala b/core/src/main/scala/org/apache/spark/network/nio/Message.scala
index 04ea50f629..0b874c2891 100644
--- a/core/src/main/scala/org/apache/spark/network/Message.scala
+++ b/core/src/main/scala/org/apache/spark/network/nio/Message.scala
@@ -15,14 +15,15 @@
  * limitations under the License.
  */
 
-package org.apache.spark.network
+package org.apache.spark.network.nio
 
 import java.net.InetSocketAddress
 import java.nio.ByteBuffer
 
 import scala.collection.mutable.ArrayBuffer
 
-private[spark] abstract class Message(val typ: Long, val id: Int) {
+
+private[nio] abstract class Message(val typ: Long, val id: Int) {
   var senderAddress: InetSocketAddress = null
   var started = false
   var startTime = -1L
@@ -42,7 +43,7 @@ private[spark] abstract class Message(val typ: Long, val id: Int) {
 }
 
 
-private[spark] object Message {
+private[nio] object Message {
   val BUFFER_MESSAGE = 1111111111L
 
   var lastId = 1
diff --git a/core/src/main/scala/org/apache/spark/network/MessageChunk.scala b/core/src/main/scala/org/apache/spark/network/nio/MessageChunk.scala
index d0f986a12b..278c5ac356 100644
--- a/core/src/main/scala/org/apache/spark/network/MessageChunk.scala
+++ b/core/src/main/scala/org/apache/spark/network/nio/MessageChunk.scala
@@ -15,13 +15,13 @@
  * limitations under the License.
  */
 
-package org.apache.spark.network
+package org.apache.spark.network.nio
 
 import java.nio.ByteBuffer
 
 import scala.collection.mutable.ArrayBuffer
 
-private[network]
+private[nio]
 class MessageChunk(val header: MessageChunkHeader, val buffer: ByteBuffer) {
 
   val size = if (buffer == null) 0 else buffer.remaining
diff --git a/core/src/main/scala/org/apache/spark/network/MessageChunkHeader.scala b/core/src/main/scala/org/apache/spark/network/nio/MessageChunkHeader.scala
index f3ecca5f99..6e20f291c5 100644
--- a/core/src/main/scala/org/apache/spark/network/MessageChunkHeader.scala
+++ b/core/src/main/scala/org/apache/spark/network/nio/MessageChunkHeader.scala
@@ -15,13 +15,12 @@
  * limitations under the License.
  */
 
-package org.apache.spark.network
+package org.apache.spark.network.nio
 
-import java.net.InetAddress
-import java.net.InetSocketAddress
+import java.net.{InetAddress, InetSocketAddress}
 import java.nio.ByteBuffer
 
-private[spark] class MessageChunkHeader(
+private[nio] class MessageChunkHeader(
     val typ: Long,
     val id: Int,
     val totalSize: Int,
@@ -57,7 +56,7 @@ private[spark] class MessageChunkHeader(
 }
 
 
-private[spark] object MessageChunkHeader {
+private[nio] object MessageChunkHeader {
   val HEADER_SIZE = 45
 
   def create(buffer: ByteBuffer): MessageChunkHeader = {
diff --git a/core/src/main/scala/org/apache/spark/network/nio/NioBlockTransferService.scala b/core/src/main/scala/org/apache/spark/network/nio/NioBlockTransferService.scala
new file mode 100644
index 0000000000..59958ee894
--- /dev/null
+++ b/core/src/main/scala/org/apache/spark/network/nio/NioBlockTransferService.scala
@@ -0,0 +1,205 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.network.nio
+
+import java.nio.ByteBuffer
+
+import scala.concurrent.Future
+
+import org.apache.spark.{SparkException, Logging, SecurityManager, SparkConf}
+import org.apache.spark.network._
+import org.apache.spark.storage.{BlockId, StorageLevel}
+import org.apache.spark.util.Utils
+
+
+/**
+ * A [[BlockTransferService]] implementation based on [[ConnectionManager]], a custom
+ * implementation using Java NIO.
+ */
+final class NioBlockTransferService(conf: SparkConf, securityManager: SecurityManager)
+  extends BlockTransferService with Logging {
+
+  private var cm: ConnectionManager = _
+
+  private var blockDataManager: BlockDataManager = _
+
+  /**
+   * Port number the service is listening on, available only after [[init]] is invoked.
+   */
+  override def port: Int = {
+    checkInit()
+    cm.id.port
+  }
+
+  /**
+   * Host name the service is listening on, available only after [[init]] is invoked.
+   */
+  override def hostName: String = {
+    checkInit()
+    cm.id.host
+  }
+
+  /**
+   * Initialize the transfer service by giving it the BlockDataManager that can be used to fetch
+   * local blocks or put local blocks.
+   */
+  override def init(blockDataManager: BlockDataManager): Unit = {
+    this.blockDataManager = blockDataManager
+    cm = new ConnectionManager(
+      conf.getInt("spark.blockManager.port", 0),
+      conf,
+      securityManager,
+      "Connection manager for block manager")
+    cm.onReceiveMessage(onBlockMessageReceive)
+  }
+
+  /**
+   * Tear down the transfer service.
+   */
+  override def stop(): Unit = {
+    if (cm != null) {
+      cm.stop()
+    }
+  }
+
+  override def fetchBlocks(
+      hostName: String,
+      port: Int,
+      blockIds: Seq[String],
+      listener: BlockFetchingListener): Unit = {
+    checkInit()
+
+    val cmId = new ConnectionManagerId(hostName, port)
+    val blockMessageArray = new BlockMessageArray(blockIds.map { blockId =>
+      BlockMessage.fromGetBlock(GetBlock(BlockId(blockId)))
+    })
+
+    val future = cm.sendMessageReliably(cmId, blockMessageArray.toBufferMessage)
+
+    // Register the listener on success/failure future callback.
+    future.onSuccess { case message =>
+      val bufferMessage = message.asInstanceOf[BufferMessage]
+      val blockMessageArray = BlockMessageArray.fromBufferMessage(bufferMessage)
+
+      for (blockMessage <- blockMessageArray) {
+        if (blockMessage.getType != BlockMessage.TYPE_GOT_BLOCK) {
+          listener.onBlockFetchFailure(
+            new SparkException(s"Unexpected message ${blockMessage.getType} received from $cmId"))
+        } else {
+          val blockId = blockMessage.getId
+          val networkSize = blockMessage.getData.limit()
+          listener.onBlockFetchSuccess(
+            blockId.toString, new NioByteBufferManagedBuffer(blockMessage.getData))
+        }
+      }
+    }(cm.futureExecContext)
+
+    future.onFailure { case exception =>
+      listener.onBlockFetchFailure(exception)
+    }(cm.futureExecContext)
+  }
+
+  /**
+   * Upload a single block to a remote node, available only after [[init]] is invoked.
+   *
+   * This call blocks until the upload completes, or throws an exception upon failures.
+   */
+  override def uploadBlock(
+      hostname: String,
+      port: Int,
+      blockId: String,
+      blockData: ManagedBuffer,
+      level: StorageLevel)
+    : Future[Unit] = {
+    checkInit()
+    val msg = PutBlock(BlockId(blockId), blockData.nioByteBuffer(), level)
+    val blockMessageArray = new BlockMessageArray(BlockMessage.fromPutBlock(msg))
+    val remoteCmId = new ConnectionManagerId(hostName, port)
+    val reply = cm.sendMessageReliably(remoteCmId, blockMessageArray.toBufferMessage)
+    reply.map(x => ())(cm.futureExecContext)
+  }
+
+  private def checkInit(): Unit = if (cm == null) {
+    throw new IllegalStateException(getClass.getName + " has not been initialized")
+  }
+
+  private def onBlockMessageReceive(msg: Message, id: ConnectionManagerId): Option[Message] = {
+    logDebug("Handling message " + msg)
+    msg match {
+      case bufferMessage: BufferMessage =>
+        try {
+          logDebug("Handling as a buffer message " + bufferMessage)
+          val blockMessages = BlockMessageArray.fromBufferMessage(bufferMessage)
+          logDebug("Parsed as a block message array")
+          val responseMessages = blockMessages.map(processBlockMessage).filter(_ != None).map(_.get)
+          Some(new BlockMessageArray(responseMessages).toBufferMessage)
+        } catch {
+          case e: Exception => {
+            logError("Exception handling buffer message", e)
+            val errorMessage = Message.createBufferMessage(msg.id)
+            errorMessage.hasError = true
+            Some(errorMessage)
+          }
+        }
+
+      case otherMessage: Any =>
+        logError("Unknown type message received: " + otherMessage)
+        val errorMessage = Message.createBufferMessage(msg.id)
+        errorMessage.hasError = true
+        Some(errorMessage)
+    }
+  }
+
+  private def processBlockMessage(blockMessage: BlockMessage): Option[BlockMessage] = {
+    blockMessage.getType match {
+      case BlockMessage.TYPE_PUT_BLOCK =>
+        val msg = PutBlock(blockMessage.getId, blockMessage.getData, blockMessage.getLevel)
+        logDebug("Received [" + msg + "]")
+        putBlock(msg.id.toString, msg.data, msg.level)
+        None
+
+      case BlockMessage.TYPE_GET_BLOCK =>
+        val msg = new GetBlock(blockMessage.getId)
+        logDebug("Received [" + msg + "]")
+        val buffer = getBlock(msg.id.toString)
+        if (buffer == null) {
+          return None
+        }
+        Some(BlockMessage.fromGotBlock(GotBlock(msg.id, buffer)))
+
+      case _ => None
+    }
+  }
+
+  private def putBlock(blockId: String, bytes: ByteBuffer, level: StorageLevel) {
+    val startTimeMs = System.currentTimeMillis()
+    logDebug("PutBlock " + blockId + " started from " + startTimeMs + " with data: " + bytes)
+    blockDataManager.putBlockData(blockId, new NioByteBufferManagedBuffer(bytes), level)
+    logDebug("PutBlock " + blockId + " used " + Utils.getUsedTimeMs(startTimeMs)
+      + " with data size: " + bytes.limit)
+  }
+
+  private def getBlock(blockId: String): ByteBuffer = {
+    val startTimeMs = System.currentTimeMillis()
+    logDebug("GetBlock " + blockId + " started from " + startTimeMs)
+    val buffer = blockDataManager.getBlockData(blockId).orNull
+    logDebug("GetBlock " + blockId + " used " + Utils.getUsedTimeMs(startTimeMs)
+      + " and got buffer " + buffer)
+    buffer.nioByteBuffer()
+  }
+}
diff --git a/core/src/main/scala/org/apache/spark/network/SecurityMessage.scala b/core/src/main/scala/org/apache/spark/network/nio/SecurityMessage.scala
index 9af9e2e8e9..747a2088a7 100644
--- a/core/src/main/scala/org/apache/spark/network/SecurityMessage.scala
+++ b/core/src/main/scala/org/apache/spark/network/nio/SecurityMessage.scala
@@ -15,15 +15,13 @@
  * limitations under the License.
  */
 
-package org.apache.spark.network
+package org.apache.spark.network.nio
 
 import java.nio.ByteBuffer
 
-import scala.collection.mutable.ArrayBuffer
-import scala.collection.mutable.StringBuilder
+import scala.collection.mutable.{ArrayBuffer, StringBuilder}
 
 import org.apache.spark._
-import org.apache.spark.network._
 
 /**
  * SecurityMessage is class that contains the connectionId and sasl token
@@ -54,7 +52,7 @@ import org.apache.spark.network._
  *   - Length of the token
  *   - Token
  */
-private[spark] class SecurityMessage() extends Logging {
+private[nio] class SecurityMessage extends Logging {
 
   private var connectionId: String = null
   private var token: Array[Byte] = null
@@ -134,7 +132,7 @@ private[spark] class SecurityMessage() extends Logging {
   }
 }
 
-private[spark] object SecurityMessage {
+private[nio] object SecurityMessage {
 
   /**
    * Convert the given BufferMessage to a SecurityMessage by parsing the contents
diff --git a/core/src/main/scala/org/apache/spark/serializer/KryoSerializer.scala b/core/src/main/scala/org/apache/spark/serializer/KryoSerializer.scala
index 87ef9bb0b4..d6386f8c06 100644
--- a/core/src/main/scala/org/apache/spark/serializer/KryoSerializer.scala
+++ b/core/src/main/scala/org/apache/spark/serializer/KryoSerializer.scala
@@ -27,9 +27,9 @@ import com.twitter.chill.{AllScalaRegistrar, EmptyScalaKryoInstantiator}
 
 import org.apache.spark._
 import org.apache.spark.broadcast.HttpBroadcast
+import org.apache.spark.network.nio.{PutBlock, GotBlock, GetBlock}
 import org.apache.spark.scheduler.MapStatus
 import org.apache.spark.storage._
-import org.apache.spark.storage.{GetBlock, GotBlock, PutBlock}
 import org.apache.spark.util.BoundedPriorityQueue
 import org.apache.spark.util.collection.CompactBuffer
 
diff --git a/core/src/main/scala/org/apache/spark/shuffle/FileShuffleBlockManager.scala b/core/src/main/scala/org/apache/spark/shuffle/FileShuffleBlockManager.scala
index 96facccd52..439981d232 100644
--- a/core/src/main/scala/org/apache/spark/shuffle/FileShuffleBlockManager.scala
+++ b/core/src/main/scala/org/apache/spark/shuffle/FileShuffleBlockManager.scala
@@ -26,6 +26,7 @@ import scala.collection.JavaConversions._
 
 import org.apache.spark.{SparkEnv, SparkConf, Logging}
 import org.apache.spark.executor.ShuffleWriteMetrics
+import org.apache.spark.network.{FileSegmentManagedBuffer, ManagedBuffer}
 import org.apache.spark.serializer.Serializer
 import org.apache.spark.shuffle.FileShuffleBlockManager.ShuffleFileGroup
 import org.apache.spark.storage._
@@ -166,34 +167,30 @@ class FileShuffleBlockManager(conf: SparkConf)
     }
   }
 
-  /**
-   * Returns the physical file segment in which the given BlockId is located.
-   */
-  private def getBlockLocation(id: ShuffleBlockId): FileSegment = {
+  override def getBytes(blockId: ShuffleBlockId): Option[ByteBuffer] = {
+    val segment = getBlockData(blockId)
+    Some(segment.nioByteBuffer())
+  }
+
+  override def getBlockData(blockId: ShuffleBlockId): ManagedBuffer = {
     if (consolidateShuffleFiles) {
       // Search all file groups associated with this shuffle.
-      val shuffleState = shuffleStates(id.shuffleId)
+      val shuffleState = shuffleStates(blockId.shuffleId)
       val iter = shuffleState.allFileGroups.iterator
       while (iter.hasNext) {
-        val segment = iter.next.getFileSegmentFor(id.mapId, id.reduceId)
-        if (segment.isDefined) { return segment.get }
+        val segmentOpt = iter.next.getFileSegmentFor(blockId.mapId, blockId.reduceId)
+        if (segmentOpt.isDefined) {
+          val segment = segmentOpt.get
+          return new FileSegmentManagedBuffer(segment.file, segment.offset, segment.length)
+        }
       }
-      throw new IllegalStateException("Failed to find shuffle block: " + id)
+      throw new IllegalStateException("Failed to find shuffle block: " + blockId)
     } else {
-      val file = blockManager.diskBlockManager.getFile(id)
-      new FileSegment(file, 0, file.length())
+      val file = blockManager.diskBlockManager.getFile(blockId)
+      new FileSegmentManagedBuffer(file, 0, file.length)
     }
   }
 
-  override def getBytes(blockId: ShuffleBlockId): Option[ByteBuffer] = {
-    val segment = getBlockLocation(blockId)
-    blockManager.diskStore.getBytes(segment)
-  }
-
-  override def getBlockData(blockId: ShuffleBlockId): Either[FileSegment, ByteBuffer] = {
-    Left(getBlockLocation(blockId.asInstanceOf[ShuffleBlockId]))
-  }
-
   /** Remove all the blocks / files and metadata related to a particular shuffle. */
   def removeShuffle(shuffleId: ShuffleId): Boolean = {
     // Do not change the ordering of this, if shuffleStates should be removed only
diff --git a/core/src/main/scala/org/apache/spark/shuffle/IndexShuffleBlockManager.scala b/core/src/main/scala/org/apache/spark/shuffle/IndexShuffleBlockManager.scala
index 8bb9efc46c..4ab34336d3 100644
--- a/core/src/main/scala/org/apache/spark/shuffle/IndexShuffleBlockManager.scala
+++ b/core/src/main/scala/org/apache/spark/shuffle/IndexShuffleBlockManager.scala
@@ -21,6 +21,7 @@ import java.io._
 import java.nio.ByteBuffer
 
 import org.apache.spark.SparkEnv
+import org.apache.spark.network.{ManagedBuffer, FileSegmentManagedBuffer}
 import org.apache.spark.storage._
 
 /**
@@ -89,10 +90,11 @@ class IndexShuffleBlockManager extends ShuffleBlockManager {
     }
   }
 
-  /**
-   * Get the location of a block in a map output file. Uses the index file we create for it.
-   * */
-  private def getBlockLocation(blockId: ShuffleBlockId): FileSegment = {
+  override def getBytes(blockId: ShuffleBlockId): Option[ByteBuffer] = {
+    Some(getBlockData(blockId).nioByteBuffer())
+  }
+
+  override def getBlockData(blockId: ShuffleBlockId): ManagedBuffer = {
     // The block is actually going to be a range of a single map output file for this map, so
     // find out the consolidated file, then the offset within that from our index
     val indexFile = getIndexFile(blockId.shuffleId, blockId.mapId)
@@ -102,20 +104,14 @@ class IndexShuffleBlockManager extends ShuffleBlockManager {
       in.skip(blockId.reduceId * 8)
       val offset = in.readLong()
       val nextOffset = in.readLong()
-      new FileSegment(getDataFile(blockId.shuffleId, blockId.mapId), offset, nextOffset - offset)
+      new FileSegmentManagedBuffer(
+        getDataFile(blockId.shuffleId, blockId.mapId),
+        offset,
+        nextOffset - offset)
     } finally {
       in.close()
     }
   }
 
-  override def getBytes(blockId: ShuffleBlockId): Option[ByteBuffer] = {
-    val segment = getBlockLocation(blockId)
-    blockManager.diskStore.getBytes(segment)
-  }
-
-  override def getBlockData(blockId: ShuffleBlockId): Either[FileSegment, ByteBuffer] = {
-    Left(getBlockLocation(blockId.asInstanceOf[ShuffleBlockId]))
-  }
-
   override def stop() = {}
 }
diff --git a/core/src/main/scala/org/apache/spark/shuffle/ShuffleBlockManager.scala b/core/src/main/scala/org/apache/spark/shuffle/ShuffleBlockManager.scala
index 4240580250..63863cc025 100644
--- a/core/src/main/scala/org/apache/spark/shuffle/ShuffleBlockManager.scala
+++ b/core/src/main/scala/org/apache/spark/shuffle/ShuffleBlockManager.scala
@@ -19,7 +19,8 @@ package org.apache.spark.shuffle
 
 import java.nio.ByteBuffer
 
-import org.apache.spark.storage.{FileSegment, ShuffleBlockId}
+import org.apache.spark.network.ManagedBuffer
+import org.apache.spark.storage.ShuffleBlockId
 
 private[spark]
 trait ShuffleBlockManager {
@@ -31,8 +32,7 @@ trait ShuffleBlockManager {
    */
   def getBytes(blockId: ShuffleBlockId): Option[ByteBuffer]
 
-  def getBlockData(blockId: ShuffleBlockId): Either[FileSegment, ByteBuffer]
+  def getBlockData(blockId: ShuffleBlockId): ManagedBuffer
 
   def stop(): Unit
 }
-
diff --git a/core/src/main/scala/org/apache/spark/shuffle/hash/BlockStoreShuffleFetcher.scala b/core/src/main/scala/org/apache/spark/shuffle/hash/BlockStoreShuffleFetcher.scala
index 12b475658e..6cf9305977 100644
--- a/core/src/main/scala/org/apache/spark/shuffle/hash/BlockStoreShuffleFetcher.scala
+++ b/core/src/main/scala/org/apache/spark/shuffle/hash/BlockStoreShuffleFetcher.scala
@@ -21,10 +21,9 @@ import scala.collection.mutable.ArrayBuffer
 import scala.collection.mutable.HashMap
 
 import org.apache.spark._
-import org.apache.spark.executor.ShuffleReadMetrics
 import org.apache.spark.serializer.Serializer
 import org.apache.spark.shuffle.FetchFailedException
-import org.apache.spark.storage.{BlockId, BlockManagerId, ShuffleBlockId}
+import org.apache.spark.storage.{BlockId, BlockManagerId, ShuffleBlockFetcherIterator, ShuffleBlockId}
 import org.apache.spark.util.CompletionIterator
 
 private[hash] object BlockStoreShuffleFetcher extends Logging {
@@ -32,8 +31,7 @@ private[hash] object BlockStoreShuffleFetcher extends Logging {
       shuffleId: Int,
       reduceId: Int,
       context: TaskContext,
-      serializer: Serializer,
-      shuffleMetrics: ShuffleReadMetrics)
+      serializer: Serializer)
     : Iterator[T] =
   {
     logDebug("Fetching outputs for shuffle %d, reduce %d".format(shuffleId, reduceId))
@@ -74,7 +72,13 @@ private[hash] object BlockStoreShuffleFetcher extends Logging {
       }
     }
 
-    val blockFetcherItr = blockManager.getMultiple(blocksByAddress, serializer, shuffleMetrics)
+    val blockFetcherItr = new ShuffleBlockFetcherIterator(
+      context,
+      SparkEnv.get.blockTransferService,
+      blockManager,
+      blocksByAddress,
+      serializer,
+      SparkEnv.get.conf.getLong("spark.reducer.maxMbInFlight", 48) * 1024 * 1024)
     val itr = blockFetcherItr.flatMap(unpackBlock)
 
     val completionIter = CompletionIterator[T, Iterator[T]](itr, {
diff --git a/core/src/main/scala/org/apache/spark/shuffle/hash/HashShuffleReader.scala b/core/src/main/scala/org/apache/spark/shuffle/hash/HashShuffleReader.scala
index 7bed97a63f..88a5f1e5dd 100644
--- a/core/src/main/scala/org/apache/spark/shuffle/hash/HashShuffleReader.scala
+++ b/core/src/main/scala/org/apache/spark/shuffle/hash/HashShuffleReader.scala
@@ -36,10 +36,8 @@ private[spark] class HashShuffleReader[K, C](
 
   /** Read the combined key-values for this reduce task */
   override def read(): Iterator[Product2[K, C]] = {
-    val readMetrics = context.taskMetrics.createShuffleReadMetricsForDependency()
     val ser = Serializer.getSerializer(dep.serializer)
-    val iter = BlockStoreShuffleFetcher.fetch(handle.shuffleId, startPartition, context, ser,
-      readMetrics)
+    val iter = BlockStoreShuffleFetcher.fetch(handle.shuffleId, startPartition, context, ser)
 
     val aggregatedIter: Iterator[Product2[K, C]] = if (dep.aggregator.isDefined) {
       if (dep.mapSideCombine) {
diff --git a/core/src/main/scala/org/apache/spark/storage/BlockFetcherIterator.scala b/core/src/main/scala/org/apache/spark/storage/BlockFetcherIterator.scala
deleted file mode 100644
index e35b7fe62c..0000000000
--- a/core/src/main/scala/org/apache/spark/storage/BlockFetcherIterator.scala
+++ /dev/null
@@ -1,254 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *    http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.apache.spark.storage
-
-import java.util.concurrent.LinkedBlockingQueue
-import org.apache.spark.network.netty.client.{BlockClientListener, LazyInitIterator, ReferenceCountedBuffer}
-
-import scala.collection.mutable.ArrayBuffer
-import scala.collection.mutable.HashSet
-import scala.collection.mutable.Queue
-import scala.util.{Failure, Success}
-
-import org.apache.spark.{Logging, SparkException}
-import org.apache.spark.executor.ShuffleReadMetrics
-import org.apache.spark.network.BufferMessage
-import org.apache.spark.network.ConnectionManagerId
-import org.apache.spark.serializer.Serializer
-import org.apache.spark.util.Utils
-
-/**
- * A block fetcher iterator interface for fetching shuffle blocks.
- */
-private[storage]
-trait BlockFetcherIterator extends Iterator[(BlockId, Option[Iterator[Any]])] with Logging {
-  def initialize()
-}
-
-
-private[storage]
-object BlockFetcherIterator {
-
-  /**
-   * A request to fetch blocks from a remote BlockManager.
-   * @param address remote BlockManager to fetch from.
-   * @param blocks Sequence of tuple, where the first element is the block id,
-   *               and the second element is the estimated size, used to calculate bytesInFlight.
-   */
-  class FetchRequest(val address: BlockManagerId, val blocks: Seq[(BlockId, Long)]) {
-    val size = blocks.map(_._2).sum
-  }
-
-  /**
-   * Result of a fetch from a remote block. A failure is represented as size == -1.
-   * @param blockId block id
-   * @param size estimated size of the block, used to calculate bytesInFlight.
-   *             Note that this is NOT the exact bytes.
-   * @param deserialize closure to return the result in the form of an Iterator.
-   */
-  class FetchResult(val blockId: BlockId, val size: Long, val deserialize: () => Iterator[Any]) {
-    def failed: Boolean = size == -1
-  }
-
-  // TODO: Refactor this whole thing to make code more reusable.
-  class BasicBlockFetcherIterator(
-      private val blockManager: BlockManager,
-      val blocksByAddress: Seq[(BlockManagerId, Seq[(BlockId, Long)])],
-      serializer: Serializer,
-      readMetrics: ShuffleReadMetrics)
-    extends BlockFetcherIterator {
-
-    import blockManager._
-
-    if (blocksByAddress == null) {
-      throw new IllegalArgumentException("BlocksByAddress is null")
-    }
-
-    // Total number blocks fetched (local + remote). Also number of FetchResults expected
-    protected var _numBlocksToFetch = 0
-
-    protected var startTime = System.currentTimeMillis
-
-    // BlockIds for local blocks that need to be fetched. Excludes zero-sized blocks
-    protected val localBlocksToFetch = new ArrayBuffer[BlockId]()
-
-    // BlockIds for remote blocks that need to be fetched. Excludes zero-sized blocks
-    protected val remoteBlocksToFetch = new HashSet[BlockId]()
-
-    // A queue to hold our results.
-    protected val results = new LinkedBlockingQueue[FetchResult]
-
-    // Queue of fetch requests to issue; we'll pull requests off this gradually to make sure that
-    // the number of bytes in flight is limited to maxBytesInFlight
-    protected val fetchRequests = new Queue[FetchRequest]
-
-    // Current bytes in flight from our requests
-    protected var bytesInFlight = 0L
-
-    protected def sendRequest(req: FetchRequest) {
-      logDebug("Sending request for %d blocks (%s) from %s".format(
-        req.blocks.size, Utils.bytesToString(req.size), req.address.hostPort))
-      val cmId = new ConnectionManagerId(req.address.host, req.address.port)
-      val blockMessageArray = new BlockMessageArray(req.blocks.map {
-        case (blockId, size) => BlockMessage.fromGetBlock(GetBlock(blockId))
-      })
-      bytesInFlight += req.size
-      val sizeMap = req.blocks.toMap  // so we can look up the size of each blockID
-      val future = connectionManager.sendMessageReliably(cmId, blockMessageArray.toBufferMessage)
-      future.onComplete {
-        case Success(message) => {
-          val bufferMessage = message.asInstanceOf[BufferMessage]
-          val blockMessageArray = BlockMessageArray.fromBufferMessage(bufferMessage)
-          for (blockMessage <- blockMessageArray) {
-            if (blockMessage.getType != BlockMessage.TYPE_GOT_BLOCK) {
-              throw new SparkException(
-                "Unexpected message " + blockMessage.getType + " received from " + cmId)
-            }
-            val blockId = blockMessage.getId
-            val networkSize = blockMessage.getData.limit()
-            results.put(new FetchResult(blockId, sizeMap(blockId),
-              () => dataDeserialize(blockId, blockMessage.getData, serializer)))
-            // TODO: NettyBlockFetcherIterator has some race conditions where multiple threads can
-            // be incrementing bytes read at the same time (SPARK-2625).
-            readMetrics.remoteBytesRead += networkSize
-            readMetrics.remoteBlocksFetched += 1
-            logDebug("Got remote block " + blockId + " after " + Utils.getUsedTimeMs(startTime))
-          }
-        }
-        case Failure(exception) => {
-          logError("Could not get block(s) from " + cmId, exception)
-          for ((blockId, size) <- req.blocks) {
-            results.put(new FetchResult(blockId, -1, null))
-          }
-        }
-      }
-    }
-
-    protected def splitLocalRemoteBlocks(): ArrayBuffer[FetchRequest] = {
-      // Make remote requests at most maxBytesInFlight / 5 in length; the reason to keep them
-      // smaller than maxBytesInFlight is to allow multiple, parallel fetches from up to 5
-      // nodes, rather than blocking on reading output from one node.
-      val targetRequestSize = math.max(maxBytesInFlight / 5, 1L)
-      logInfo("maxBytesInFlight: " + maxBytesInFlight + ", targetRequestSize: " + targetRequestSize)
-
-      // Split local and remote blocks. Remote blocks are further split into FetchRequests of size
-      // at most maxBytesInFlight in order to limit the amount of data in flight.
-      val remoteRequests = new ArrayBuffer[FetchRequest]
-      var totalBlocks = 0
-      for ((address, blockInfos) <- blocksByAddress) {
-        totalBlocks += blockInfos.size
-        if (address == blockManagerId) {
-          // Filter out zero-sized blocks
-          localBlocksToFetch ++= blockInfos.filter(_._2 != 0).map(_._1)
-          _numBlocksToFetch += localBlocksToFetch.size
-        } else {
-          val iterator = blockInfos.iterator
-          var curRequestSize = 0L
-          var curBlocks = new ArrayBuffer[(BlockId, Long)]
-          while (iterator.hasNext) {
-            val (blockId, size) = iterator.next()
-            // Skip empty blocks
-            if (size > 0) {
-              curBlocks += ((blockId, size))
-              remoteBlocksToFetch += blockId
-              _numBlocksToFetch += 1
-              curRequestSize += size
-            } else if (size < 0) {
-              throw new BlockException(blockId, "Negative block size " + size)
-            }
-            if (curRequestSize >= targetRequestSize) {
-              // Add this FetchRequest
-              remoteRequests += new FetchRequest(address, curBlocks)
-              curBlocks = new ArrayBuffer[(BlockId, Long)]
-              logDebug(s"Creating fetch request of $curRequestSize at $address")
-              curRequestSize = 0
-            }
-          }
-          // Add in the final request
-          if (!curBlocks.isEmpty) {
-            remoteRequests += new FetchRequest(address, curBlocks)
-          }
-        }
-      }
-      logInfo("Getting " + _numBlocksToFetch + " non-empty blocks out of " +
-        totalBlocks + " blocks")
-      remoteRequests
-    }
-
-    protected def getLocalBlocks() {
-      // Get the local blocks while remote blocks are being fetched. Note that it's okay to do
-      // these all at once because they will just memory-map some files, so they won't consume
-      // any memory that might exceed our maxBytesInFlight
-      for (id <- localBlocksToFetch) {
-        try {
-          readMetrics.localBlocksFetched += 1
-          results.put(new FetchResult(id, 0, () => getLocalShuffleFromDisk(id, serializer).get))
-          logDebug("Got local block " + id)
-        } catch {
-          case e: Exception => {
-            logError(s"Error occurred while fetching local blocks", e)
-            results.put(new FetchResult(id, -1, null))
-            return
-          }
-        }
-      }
-    }
-
-    override def initialize() {
-      // Split local and remote blocks.
-      val remoteRequests = splitLocalRemoteBlocks()
-      // Add the remote requests into our queue in a random order
-      fetchRequests ++= Utils.randomize(remoteRequests)
-
-      // Send out initial requests for blocks, up to our maxBytesInFlight
-      while (!fetchRequests.isEmpty &&
-        (bytesInFlight == 0 || bytesInFlight + fetchRequests.front.size <= maxBytesInFlight)) {
-        sendRequest(fetchRequests.dequeue())
-      }
-
-      val numFetches = remoteRequests.size - fetchRequests.size
-      logInfo("Started " + numFetches + " remote fetches in" + Utils.getUsedTimeMs(startTime))
-
-      // Get Local Blocks
-      startTime = System.currentTimeMillis
-      getLocalBlocks()
-      logDebug("Got local blocks in " + Utils.getUsedTimeMs(startTime) + " ms")
-    }
-
-    // Implementing the Iterator methods with an iterator that reads fetched blocks off the queue
-    // as they arrive.
-    @volatile protected var resultsGotten = 0
-
-    override def hasNext: Boolean = resultsGotten < _numBlocksToFetch
-
-    override def next(): (BlockId, Option[Iterator[Any]]) = {
-      resultsGotten += 1
-      val startFetchWait = System.currentTimeMillis()
-      val result = results.take()
-      val stopFetchWait = System.currentTimeMillis()
-      readMetrics.fetchWaitTime += (stopFetchWait - startFetchWait)
-      if (! result.failed) bytesInFlight -= result.size
-      while (!fetchRequests.isEmpty &&
-        (bytesInFlight == 0 || bytesInFlight + fetchRequests.front.size <= maxBytesInFlight)) {
-        sendRequest(fetchRequests.dequeue())
-      }
-      (result.blockId, if (result.failed) None else Some(result.deserialize()))
-    }
-  }
-  // End of BasicBlockFetcherIterator
-}
diff --git a/core/src/main/scala/org/apache/spark/storage/BlockManager.scala b/core/src/main/scala/org/apache/spark/storage/BlockManager.scala
index a714142763..d1bee3d2c0 100644
--- a/core/src/main/scala/org/apache/spark/storage/BlockManager.scala
+++ b/core/src/main/scala/org/apache/spark/storage/BlockManager.scala
@@ -20,6 +20,8 @@ package org.apache.spark.storage
 import java.io.{File, InputStream, OutputStream, BufferedOutputStream, ByteArrayOutputStream}
 import java.nio.{ByteBuffer, MappedByteBuffer}
 
+import scala.concurrent.ExecutionContext.Implicits.global
+
 import scala.collection.mutable.{ArrayBuffer, HashMap}
 import scala.concurrent.{Await, Future}
 import scala.concurrent.duration._
@@ -58,18 +60,14 @@ private[spark] class BlockManager(
     defaultSerializer: Serializer,
     maxMemory: Long,
     val conf: SparkConf,
-    securityManager: SecurityManager,
     mapOutputTracker: MapOutputTracker,
-    shuffleManager: ShuffleManager)
-  extends BlockDataProvider with Logging {
+    shuffleManager: ShuffleManager,
+    blockTransferService: BlockTransferService)
+  extends BlockDataManager with Logging {
 
-  private val port = conf.getInt("spark.blockManager.port", 0)
+  blockTransferService.init(this)
 
   val diskBlockManager = new DiskBlockManager(this, conf)
-  val connectionManager =
-    new ConnectionManager(port, conf, securityManager, "Connection manager for block manager")
-
-  implicit val futureExecContext = connectionManager.futureExecContext
 
   private val blockInfo = new TimeStampedHashMap[BlockId, BlockInfo]
 
@@ -89,11 +87,7 @@ private[spark] class BlockManager(
   }
 
   val blockManagerId = BlockManagerId(
-    executorId, connectionManager.id.host, connectionManager.id.port)
-
-  // Max megabytes of data to keep in flight per reducer (to avoid over-allocating memory
-  // for receiving shuffle outputs)
-  val maxBytesInFlight = conf.getLong("spark.reducer.maxMbInFlight", 48) * 1024 * 1024
+    executorId, blockTransferService.hostName, blockTransferService.port)
 
   // Whether to compress broadcast variables that are stored
   private val compressBroadcast = conf.getBoolean("spark.broadcast.compress", true)
@@ -136,11 +130,11 @@ private[spark] class BlockManager(
       master: BlockManagerMaster,
       serializer: Serializer,
       conf: SparkConf,
-      securityManager: SecurityManager,
       mapOutputTracker: MapOutputTracker,
-      shuffleManager: ShuffleManager) = {
+      shuffleManager: ShuffleManager,
+      blockTransferService: BlockTransferService) = {
     this(execId, actorSystem, master, serializer, BlockManager.getMaxMemory(conf),
-      conf, securityManager, mapOutputTracker, shuffleManager)
+      conf, mapOutputTracker, shuffleManager, blockTransferService)
   }
 
   /**
@@ -149,7 +143,6 @@ private[spark] class BlockManager(
    */
   private def initialize(): Unit = {
     master.registerBlockManager(blockManagerId, maxMemory, slaveActor)
-    BlockManagerWorker.startBlockManagerWorker(this)
   }
 
   /**
@@ -212,21 +205,34 @@ private[spark] class BlockManager(
     }
   }
 
-  override def getBlockData(blockId: String): Either[FileSegment, ByteBuffer] = {
+  /**
+   * Interface to get local block data.
+   *
+   * @return Some(buffer) if the block exists locally, and None if it doesn't.
+   */
+  override def getBlockData(blockId: String): Option[ManagedBuffer] = {
     val bid = BlockId(blockId)
     if (bid.isShuffle) {
-      shuffleManager.shuffleBlockManager.getBlockData(bid.asInstanceOf[ShuffleBlockId])
+      Some(shuffleManager.shuffleBlockManager.getBlockData(bid.asInstanceOf[ShuffleBlockId]))
     } else {
       val blockBytesOpt = doGetLocal(bid, asBlockResult = false).asInstanceOf[Option[ByteBuffer]]
       if (blockBytesOpt.isDefined) {
-        Right(blockBytesOpt.get)
+        val buffer = blockBytesOpt.get
+        Some(new NioByteBufferManagedBuffer(buffer))
       } else {
-        throw new BlockNotFoundException(blockId)
+        None
       }
     }
   }
 
   /**
+   * Put the block locally, using the given storage level.
+   */
+  override def putBlockData(blockId: String, data: ManagedBuffer, level: StorageLevel): Unit = {
+    putBytes(BlockId(blockId), data.nioByteBuffer(), level)
+  }
+
+  /**
    * Get the BlockStatus for the block identified by the given ID, if it exists.
    * NOTE: This is mainly for testing, and it doesn't fetch information from Tachyon.
    */
@@ -333,16 +339,10 @@ private[spark] class BlockManager(
    * shuffle blocks. It is safe to do so without a lock on block info since disk store
    * never deletes (recent) items.
    */
-  def getLocalShuffleFromDisk(
-      blockId: BlockId, serializer: Serializer): Option[Iterator[Any]] = {
-
-    val shuffleBlockManager = shuffleManager.shuffleBlockManager
-    val values = shuffleBlockManager.getBytes(blockId.asInstanceOf[ShuffleBlockId]).map(
-      bytes => this.dataDeserialize(blockId, bytes, serializer))
-
-    values.orElse {
-      throw new BlockException(blockId, s"Block $blockId not found on disk, though it should be")
-    }
+  def getLocalShuffleFromDisk(blockId: BlockId, serializer: Serializer): Option[Iterator[Any]] = {
+    val buf = shuffleManager.shuffleBlockManager.getBlockData(blockId.asInstanceOf[ShuffleBlockId])
+    val is = wrapForCompression(blockId, buf.inputStream())
+    Some(serializer.newInstance().deserializeStream(is).asIterator)
   }
 
   /**
@@ -513,8 +513,9 @@ private[spark] class BlockManager(
     val locations = Random.shuffle(master.getLocations(blockId))
     for (loc <- locations) {
       logDebug(s"Getting remote block $blockId from $loc")
-      val data = BlockManagerWorker.syncGetBlock(
-        GetBlock(blockId), ConnectionManagerId(loc.host, loc.port))
+      val data = blockTransferService.fetchBlockSync(
+        loc.host, loc.port, blockId.toString).nioByteBuffer()
+
       if (data != null) {
         if (asBlockResult) {
           return Some(new BlockResult(
@@ -548,22 +549,6 @@ private[spark] class BlockManager(
     None
   }
 
-  /**
-   * Get multiple blocks from local and remote block manager using their BlockManagerIds. Returns
-   * an Iterator of (block ID, value) pairs so that clients may handle blocks in a pipelined
-   * fashion as they're received. Expects a size in bytes to be provided for each block fetched,
-   * so that we can control the maxMegabytesInFlight for the fetch.
-   */
-  def getMultiple(
-      blocksByAddress: Seq[(BlockManagerId, Seq[(BlockId, Long)])],
-      serializer: Serializer,
-      readMetrics: ShuffleReadMetrics): BlockFetcherIterator = {
-    val iter = new BlockFetcherIterator.BasicBlockFetcherIterator(this, blocksByAddress, serializer,
-      readMetrics)
-    iter.initialize()
-    iter
-  }
-
   def putIterator(
       blockId: BlockId,
       values: Iterator[Any],
@@ -816,12 +801,15 @@ private[spark] class BlockManager(
       data.rewind()
       logDebug(s"Try to replicate $blockId once; The size of the data is ${data.limit()} Bytes. " +
         s"To node: $peer")
-      val putBlock = PutBlock(blockId, data, tLevel)
-      val cmId = new ConnectionManagerId(peer.host, peer.port)
-      val syncPutBlockSuccess = BlockManagerWorker.syncPutBlock(putBlock, cmId)
-      if (!syncPutBlockSuccess) {
-        logError(s"Failed to call syncPutBlock to $peer")
+
+      try {
+        blockTransferService.uploadBlockSync(
+          peer.host, peer.port, blockId.toString, new NioByteBufferManagedBuffer(data), tLevel)
+      } catch {
+        case e: Exception =>
+          logError(s"Failed to replicate block to $peer", e)
       }
+
       logDebug("Replicating BlockId %s once used %fs; The size of the data is %d bytes."
         .format(blockId, (System.nanoTime - start) / 1e6, data.limit()))
     }
@@ -1051,7 +1039,7 @@ private[spark] class BlockManager(
   }
 
   def stop(): Unit = {
-    connectionManager.stop()
+    blockTransferService.stop()
     diskBlockManager.stop()
     actorSystem.stop(slaveActor)
     blockInfo.clear()
diff --git a/core/src/main/scala/org/apache/spark/storage/BlockManagerId.scala b/core/src/main/scala/org/apache/spark/storage/BlockManagerId.scala
index b7bcb2d85d..d4487fce49 100644
--- a/core/src/main/scala/org/apache/spark/storage/BlockManagerId.scala
+++ b/core/src/main/scala/org/apache/spark/storage/BlockManagerId.scala
@@ -36,8 +36,8 @@ import org.apache.spark.util.Utils
 class BlockManagerId private (
     private var executorId_ : String,
     private var host_ : String,
-    private var port_ : Int
-  ) extends Externalizable {
+    private var port_ : Int)
+  extends Externalizable {
 
   private def this() = this(null, null, 0)  // For deserialization only
 
diff --git a/core/src/main/scala/org/apache/spark/storage/BlockManagerWorker.scala b/core/src/main/scala/org/apache/spark/storage/BlockManagerWorker.scala
deleted file mode 100644
index bf002a42d5..0000000000
--- a/core/src/main/scala/org/apache/spark/storage/BlockManagerWorker.scala
+++ /dev/null
@@ -1,147 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *    http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.apache.spark.storage
-
-import java.nio.ByteBuffer
-
-import org.apache.spark.Logging
-import org.apache.spark.network._
-import org.apache.spark.util.Utils
-
-import scala.concurrent.Await
-import scala.concurrent.duration.Duration
-import scala.util.{Try, Failure, Success}
-
-/**
- * A network interface for BlockManager. Each slave should have one
- * BlockManagerWorker.
- *
- * TODO: Use event model.
- */
-private[spark] class BlockManagerWorker(val blockManager: BlockManager) extends Logging {
-
-  blockManager.connectionManager.onReceiveMessage(onBlockMessageReceive)
-
-  def onBlockMessageReceive(msg: Message, id: ConnectionManagerId): Option[Message] = {
-    logDebug("Handling message " + msg)
-    msg match {
-      case bufferMessage: BufferMessage => {
-        try {
-          logDebug("Handling as a buffer message " + bufferMessage)
-          val blockMessages = BlockMessageArray.fromBufferMessage(bufferMessage)
-          logDebug("Parsed as a block message array")
-          val responseMessages = blockMessages.map(processBlockMessage).filter(_ != None).map(_.get)
-          Some(new BlockMessageArray(responseMessages).toBufferMessage)
-        } catch {
-          case e: Exception => {
-            logError("Exception handling buffer message", e)
-            val errorMessage = Message.createBufferMessage(msg.id)
-            errorMessage.hasError = true
-            Some(errorMessage)
-          }
-        }
-      }
-      case otherMessage: Any => {
-        logError("Unknown type message received: " + otherMessage)
-        val errorMessage = Message.createBufferMessage(msg.id)
-        errorMessage.hasError = true
-        Some(errorMessage)
-      }
-    }
-  }
-
-  def processBlockMessage(blockMessage: BlockMessage): Option[BlockMessage] = {
-    blockMessage.getType match {
-      case BlockMessage.TYPE_PUT_BLOCK => {
-        val pB = PutBlock(blockMessage.getId, blockMessage.getData, blockMessage.getLevel)
-        logDebug("Received [" + pB + "]")
-        putBlock(pB.id, pB.data, pB.level)
-        None
-      }
-      case BlockMessage.TYPE_GET_BLOCK => {
-        val gB = new GetBlock(blockMessage.getId)
-        logDebug("Received [" + gB + "]")
-        val buffer = getBlock(gB.id)
-        if (buffer == null) {
-          return None
-        }
-        Some(BlockMessage.fromGotBlock(GotBlock(gB.id, buffer)))
-      }
-      case _ => None
-    }
-  }
-
-  private def putBlock(id: BlockId, bytes: ByteBuffer, level: StorageLevel) {
-    val startTimeMs = System.currentTimeMillis()
-    logDebug("PutBlock " + id + " started from " + startTimeMs + " with data: " + bytes)
-    blockManager.putBytes(id, bytes, level)
-    logDebug("PutBlock " + id + " used " + Utils.getUsedTimeMs(startTimeMs)
-        + " with data size: " + bytes.limit)
-  }
-
-  private def getBlock(id: BlockId): ByteBuffer = {
-    val startTimeMs = System.currentTimeMillis()
-    logDebug("GetBlock " + id + " started from " + startTimeMs)
-    val buffer = blockManager.getLocalBytes(id) match {
-      case Some(bytes) => bytes
-      case None => null
-    }
-    logDebug("GetBlock " + id + " used " + Utils.getUsedTimeMs(startTimeMs)
-        + " and got buffer " + buffer)
-    buffer
-  }
-}
-
-private[spark] object BlockManagerWorker extends Logging {
-  private var blockManagerWorker: BlockManagerWorker = null
-
-  def startBlockManagerWorker(manager: BlockManager) {
-    blockManagerWorker = new BlockManagerWorker(manager)
-  }
-
-  def syncPutBlock(msg: PutBlock, toConnManagerId: ConnectionManagerId): Boolean = {
-    val blockManager = blockManagerWorker.blockManager
-    val connectionManager = blockManager.connectionManager
-    val blockMessage = BlockMessage.fromPutBlock(msg)
-    val blockMessageArray = new BlockMessageArray(blockMessage)
-    val resultMessage = Try(Await.result(connectionManager.sendMessageReliably(
-        toConnManagerId, blockMessageArray.toBufferMessage), Duration.Inf))
-    resultMessage.isSuccess
-  }
-
-  def syncGetBlock(msg: GetBlock, toConnManagerId: ConnectionManagerId): ByteBuffer = {
-    val blockManager = blockManagerWorker.blockManager
-    val connectionManager = blockManager.connectionManager
-    val blockMessage = BlockMessage.fromGetBlock(msg)
-    val blockMessageArray = new BlockMessageArray(blockMessage)
-    val responseMessage = Try(Await.result(connectionManager.sendMessageReliably(
-        toConnManagerId, blockMessageArray.toBufferMessage), Duration.Inf))
-    responseMessage match {
-      case Success(message) => {
-        val bufferMessage = message.asInstanceOf[BufferMessage]
-        logDebug("Response message received " + bufferMessage)
-        BlockMessageArray.fromBufferMessage(bufferMessage).foreach(blockMessage => {
-            logDebug("Found " + blockMessage)
-            return blockMessage.getData
-          })
-      }
-      case Failure(exception) => logDebug("No response message received")
-    }
-    null
-  }
-}
diff --git a/core/src/main/scala/org/apache/spark/storage/ShuffleBlockFetcherIterator.scala b/core/src/main/scala/org/apache/spark/storage/ShuffleBlockFetcherIterator.scala
new file mode 100644
index 0000000000..c8e708aa6b
--- /dev/null
+++ b/core/src/main/scala/org/apache/spark/storage/ShuffleBlockFetcherIterator.scala
@@ -0,0 +1,271 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.storage
+
+import java.util.concurrent.LinkedBlockingQueue
+
+import scala.collection.mutable.ArrayBuffer
+import scala.collection.mutable.HashSet
+import scala.collection.mutable.Queue
+
+import org.apache.spark.{TaskContext, Logging, SparkException}
+import org.apache.spark.network.{ManagedBuffer, BlockFetchingListener, BlockTransferService}
+import org.apache.spark.serializer.Serializer
+import org.apache.spark.util.Utils
+
+
+/**
+ * An iterator that fetches multiple blocks. For local blocks, it fetches from the local block
+ * manager. For remote blocks, it fetches them using the provided BlockTransferService.
+ *
+ * This creates an iterator of (BlockID, values) tuples so the caller can handle blocks in a
+ * pipelined fashion as they are received.
+ *
+ * The implementation throttles the remote fetches to they don't exceed maxBytesInFlight to avoid
+ * using too much memory.
+ *
+ * @param context [[TaskContext]], used for metrics update
+ * @param blockTransferService [[BlockTransferService]] for fetching remote blocks
+ * @param blockManager  [[BlockManager]] for reading local blocks
+ * @param blocksByAddress list of blocks to fetch grouped by the [[BlockManagerId]].
+ *                        For each block we also require the size (in bytes as a long field) in
+ *                        order to throttle the memory usage.
+ * @param serializer serializer used to deserialize the data.
+ * @param maxBytesInFlight max size (in bytes) of remote blocks to fetch at any given point.
+ */
+private[spark]
+final class ShuffleBlockFetcherIterator(
+    context: TaskContext,
+    blockTransferService: BlockTransferService,
+    blockManager: BlockManager,
+    blocksByAddress: Seq[(BlockManagerId, Seq[(BlockId, Long)])],
+    serializer: Serializer,
+    maxBytesInFlight: Long)
+  extends Iterator[(BlockId, Option[Iterator[Any]])] with Logging {
+
+  import ShuffleBlockFetcherIterator._
+
+  /**
+   * Total number of blocks to fetch. This can be smaller than the total number of blocks
+   * in [[blocksByAddress]] because we filter out zero-sized blocks in [[initialize]].
+   *
+   * This should equal localBlocks.size + remoteBlocks.size.
+   */
+  private[this] var numBlocksToFetch = 0
+
+  /**
+   * The number of blocks proccessed by the caller. The iterator is exhausted when
+   * [[numBlocksProcessed]] == [[numBlocksToFetch]].
+   */
+  private[this] var numBlocksProcessed = 0
+
+  private[this] val startTime = System.currentTimeMillis
+
+  /** Local blocks to fetch, excluding zero-sized blocks. */
+  private[this] val localBlocks = new ArrayBuffer[BlockId]()
+
+  /** Remote blocks to fetch, excluding zero-sized blocks. */
+  private[this] val remoteBlocks = new HashSet[BlockId]()
+
+  /**
+   * A queue to hold our results. This turns the asynchronous model provided by
+   * [[BlockTransferService]] into a synchronous model (iterator).
+   */
+  private[this] val results = new LinkedBlockingQueue[FetchResult]
+
+  // Queue of fetch requests to issue; we'll pull requests off this gradually to make sure that
+  // the number of bytes in flight is limited to maxBytesInFlight
+  private[this] val fetchRequests = new Queue[FetchRequest]
+
+  // Current bytes in flight from our requests
+  private[this] var bytesInFlight = 0L
+
+  private[this] val shuffleMetrics = context.taskMetrics.createShuffleReadMetricsForDependency()
+
+  initialize()
+
+  private[this] def sendRequest(req: FetchRequest) {
+    logDebug("Sending request for %d blocks (%s) from %s".format(
+      req.blocks.size, Utils.bytesToString(req.size), req.address.hostPort))
+    bytesInFlight += req.size
+
+    // so we can look up the size of each blockID
+    val sizeMap = req.blocks.map { case (blockId, size) => (blockId.toString, size) }.toMap
+    val blockIds = req.blocks.map(_._1.toString)
+
+    blockTransferService.fetchBlocks(req.address.host, req.address.port, blockIds,
+      new BlockFetchingListener {
+        override def onBlockFetchSuccess(blockId: String, data: ManagedBuffer): Unit = {
+          results.put(new FetchResult(BlockId(blockId), sizeMap(blockId),
+            () => serializer.newInstance().deserializeStream(
+              blockManager.wrapForCompression(BlockId(blockId), data.inputStream())).asIterator
+          ))
+          shuffleMetrics.remoteBytesRead += data.size
+          shuffleMetrics.remoteBlocksFetched += 1
+          logDebug("Got remote block " + blockId + " after " + Utils.getUsedTimeMs(startTime))
+        }
+
+        override def onBlockFetchFailure(e: Throwable): Unit = {
+          logError("Failed to get block(s) from ${req.address.host}:${req.address.port}", e)
+          // Note that there is a chance that some blocks have been fetched successfully, but we
+          // still add them to the failed queue. This is fine because when the caller see a
+          // FetchFailedException, it is going to fail the entire task anyway.
+          for ((blockId, size) <- req.blocks) {
+            results.put(new FetchResult(blockId, -1, null))
+          }
+        }
+      }
+    )
+  }
+
+  private[this] def splitLocalRemoteBlocks(): ArrayBuffer[FetchRequest] = {
+    // Make remote requests at most maxBytesInFlight / 5 in length; the reason to keep them
+    // smaller than maxBytesInFlight is to allow multiple, parallel fetches from up to 5
+    // nodes, rather than blocking on reading output from one node.
+    val targetRequestSize = math.max(maxBytesInFlight / 5, 1L)
+    logInfo("maxBytesInFlight: " + maxBytesInFlight + ", targetRequestSize: " + targetRequestSize)
+
+    // Split local and remote blocks. Remote blocks are further split into FetchRequests of size
+    // at most maxBytesInFlight in order to limit the amount of data in flight.
+    val remoteRequests = new ArrayBuffer[FetchRequest]
+
+    // Tracks total number of blocks (including zero sized blocks)
+    var totalBlocks = 0
+    for ((address, blockInfos) <- blocksByAddress) {
+      totalBlocks += blockInfos.size
+      if (address == blockManager.blockManagerId) {
+        // Filter out zero-sized blocks
+        localBlocks ++= blockInfos.filter(_._2 != 0).map(_._1)
+        numBlocksToFetch += localBlocks.size
+      } else {
+        val iterator = blockInfos.iterator
+        var curRequestSize = 0L
+        var curBlocks = new ArrayBuffer[(BlockId, Long)]
+        while (iterator.hasNext) {
+          val (blockId, size) = iterator.next()
+          // Skip empty blocks
+          if (size > 0) {
+            curBlocks += ((blockId, size))
+            remoteBlocks += blockId
+            numBlocksToFetch += 1
+            curRequestSize += size
+          } else if (size < 0) {
+            throw new BlockException(blockId, "Negative block size " + size)
+          }
+          if (curRequestSize >= targetRequestSize) {
+            // Add this FetchRequest
+            remoteRequests += new FetchRequest(address, curBlocks)
+            curBlocks = new ArrayBuffer[(BlockId, Long)]
+            logDebug(s"Creating fetch request of $curRequestSize at $address")
+            curRequestSize = 0
+          }
+        }
+        // Add in the final request
+        if (curBlocks.nonEmpty) {
+          remoteRequests += new FetchRequest(address, curBlocks)
+        }
+      }
+    }
+    logInfo(s"Getting $numBlocksToFetch non-empty blocks out of $totalBlocks blocks")
+    remoteRequests
+  }
+
+  private[this] def fetchLocalBlocks() {
+    // Get the local blocks while remote blocks are being fetched. Note that it's okay to do
+    // these all at once because they will just memory-map some files, so they won't consume
+    // any memory that might exceed our maxBytesInFlight
+    for (id <- localBlocks) {
+      try {
+        shuffleMetrics.localBlocksFetched += 1
+        results.put(new FetchResult(
+          id, 0, () => blockManager.getLocalShuffleFromDisk(id, serializer).get))
+        logDebug("Got local block " + id)
+      } catch {
+        case e: Exception =>
+          logError(s"Error occurred while fetching local blocks", e)
+          results.put(new FetchResult(id, -1, null))
+          return
+      }
+    }
+  }
+
+  private[this] def initialize(): Unit = {
+    // Split local and remote blocks.
+    val remoteRequests = splitLocalRemoteBlocks()
+    // Add the remote requests into our queue in a random order
+    fetchRequests ++= Utils.randomize(remoteRequests)
+
+    // Send out initial requests for blocks, up to our maxBytesInFlight
+    while (fetchRequests.nonEmpty &&
+      (bytesInFlight == 0 || bytesInFlight + fetchRequests.front.size <= maxBytesInFlight)) {
+      sendRequest(fetchRequests.dequeue())
+    }
+
+    val numFetches = remoteRequests.size - fetchRequests.size
+    logInfo("Started " + numFetches + " remote fetches in" + Utils.getUsedTimeMs(startTime))
+
+    // Get Local Blocks
+    fetchLocalBlocks()
+    logDebug("Got local blocks in " + Utils.getUsedTimeMs(startTime) + " ms")
+  }
+
+  override def hasNext: Boolean = numBlocksProcessed < numBlocksToFetch
+
+  override def next(): (BlockId, Option[Iterator[Any]]) = {
+    numBlocksProcessed += 1
+    val startFetchWait = System.currentTimeMillis()
+    val result = results.take()
+    val stopFetchWait = System.currentTimeMillis()
+    shuffleMetrics.fetchWaitTime += (stopFetchWait - startFetchWait)
+    if (!result.failed) {
+      bytesInFlight -= result.size
+    }
+    // Send fetch requests up to maxBytesInFlight
+    while (fetchRequests.nonEmpty &&
+      (bytesInFlight == 0 || bytesInFlight + fetchRequests.front.size <= maxBytesInFlight)) {
+      sendRequest(fetchRequests.dequeue())
+    }
+    (result.blockId, if (result.failed) None else Some(result.deserialize()))
+  }
+}
+
+
+private[storage]
+object ShuffleBlockFetcherIterator {
+
+  /**
+   * A request to fetch blocks from a remote BlockManager.
+   * @param address remote BlockManager to fetch from.
+   * @param blocks Sequence of tuple, where the first element is the block id,
+   *               and the second element is the estimated size, used to calculate bytesInFlight.
+   */
+  class FetchRequest(val address: BlockManagerId, val blocks: Seq[(BlockId, Long)]) {
+    val size = blocks.map(_._2).sum
+  }
+
+  /**
+   * Result of a fetch from a remote block. A failure is represented as size == -1.
+   * @param blockId block id
+   * @param size estimated size of the block, used to calculate bytesInFlight.
+   *             Note that this is NOT the exact bytes.
+   * @param deserialize closure to return the result in the form of an Iterator.
+   */
+  class FetchResult(val blockId: BlockId, val size: Long, val deserialize: () => Iterator[Any]) {
+    def failed: Boolean = size == -1
+  }
+}
diff --git a/core/src/main/scala/org/apache/spark/storage/ThreadingTest.scala b/core/src/main/scala/org/apache/spark/storage/ThreadingTest.scala
deleted file mode 100644
index 7540f0d5e2..0000000000
--- a/core/src/main/scala/org/apache/spark/storage/ThreadingTest.scala
+++ /dev/null
@@ -1,120 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *    http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.apache.spark.storage
-
-import java.util.concurrent.ArrayBlockingQueue
-
-import akka.actor._
-import org.apache.spark.shuffle.hash.HashShuffleManager
-import util.Random
-
-import org.apache.spark.{MapOutputTrackerMaster, SecurityManager, SparkConf}
-import org.apache.spark.scheduler.LiveListenerBus
-import org.apache.spark.serializer.KryoSerializer
-
-/**
- * This class tests the BlockManager and MemoryStore for thread safety and
- * deadlocks. It spawns a number of producer and consumer threads. Producer
- * threads continuously pushes blocks into the BlockManager and consumer
- * threads continuously retrieves the blocks form the BlockManager and tests
- * whether the block is correct or not.
- */
-private[spark] object ThreadingTest {
-
-  val numProducers = 5
-  val numBlocksPerProducer = 20000
-
-  private[spark] class ProducerThread(manager: BlockManager, id: Int) extends Thread {
-    val queue = new ArrayBlockingQueue[(BlockId, Seq[Int])](100)
-
-    override def run() {
-      for (i <- 1 to numBlocksPerProducer) {
-        val blockId = TestBlockId("b-" + id + "-" + i)
-        val blockSize = Random.nextInt(1000)
-        val block = (1 to blockSize).map(_ => Random.nextInt())
-        val level = randomLevel()
-        val startTime = System.currentTimeMillis()
-        manager.putIterator(blockId, block.iterator, level, tellMaster = true)
-        println("Pushed block " + blockId + " in " + (System.currentTimeMillis - startTime) + " ms")
-        queue.add((blockId, block))
-      }
-      println("Producer thread " + id + " terminated")
-    }
-
-    def randomLevel(): StorageLevel = {
-      math.abs(Random.nextInt()) % 4 match {
-        case 0 => StorageLevel.MEMORY_ONLY
-        case 1 => StorageLevel.MEMORY_ONLY_SER
-        case 2 => StorageLevel.MEMORY_AND_DISK
-        case 3 => StorageLevel.MEMORY_AND_DISK_SER
-      }
-    }
-  }
-
-  private[spark] class ConsumerThread(
-      manager: BlockManager,
-      queue: ArrayBlockingQueue[(BlockId, Seq[Int])]
-    ) extends Thread {
-    var numBlockConsumed = 0
-
-    override def run() {
-      println("Consumer thread started")
-      while(numBlockConsumed < numBlocksPerProducer) {
-        val (blockId, block) = queue.take()
-        val startTime = System.currentTimeMillis()
-        manager.get(blockId) match {
-          case Some(retrievedBlock) =>
-            assert(retrievedBlock.data.toList.asInstanceOf[List[Int]] == block.toList,
-              "Block " + blockId + " did not match")
-            println("Got block " + blockId + " in " +
-              (System.currentTimeMillis - startTime) + " ms")
-          case None =>
-            assert(false, "Block " + blockId + " could not be retrieved")
-        }
-        numBlockConsumed += 1
-      }
-      println("Consumer thread terminated")
-    }
-  }
-
-  def main(args: Array[String]) {
-    System.setProperty("spark.kryoserializer.buffer.mb", "1")
-    val actorSystem = ActorSystem("test")
-    val conf = new SparkConf()
-    val serializer = new KryoSerializer(conf)
-    val blockManagerMaster = new BlockManagerMaster(
-      actorSystem.actorOf(Props(new BlockManagerMasterActor(true, conf, new LiveListenerBus))),
-      conf, true)
-    val blockManager = new BlockManager(
-      "<driver>", actorSystem, blockManagerMaster, serializer, 1024 * 1024, conf,
-      new SecurityManager(conf), new MapOutputTrackerMaster(conf), new HashShuffleManager(conf))
-    val producers = (1 to numProducers).map(i => new ProducerThread(blockManager, i))
-    val consumers = producers.map(p => new ConsumerThread(blockManager, p.queue))
-    producers.foreach(_.start)
-    consumers.foreach(_.start)
-    producers.foreach(_.join)
-    consumers.foreach(_.join)
-    blockManager.stop()
-    blockManagerMaster.stop()
-    actorSystem.shutdown()
-    actorSystem.awaitTermination()
-    println("Everything stopped.")
-    println(
-      "It will take sometime for the JVM to clean all temporary files and shutdown. Sit tight.")
-  }
-}
diff --git a/core/src/test/scala/org/apache/spark/DistributedSuite.scala b/core/src/test/scala/org/apache/spark/DistributedSuite.scala
index 41c294f727..81b64c36dd 100644
--- a/core/src/test/scala/org/apache/spark/DistributedSuite.scala
+++ b/core/src/test/scala/org/apache/spark/DistributedSuite.scala
@@ -24,8 +24,7 @@ import org.scalatest.Matchers
 import org.scalatest.time.{Millis, Span}
 
 import org.apache.spark.SparkContext._
-import org.apache.spark.network.ConnectionManagerId
-import org.apache.spark.storage.{BlockManagerWorker, GetBlock, RDDBlockId, StorageLevel}
+import org.apache.spark.storage.{RDDBlockId, StorageLevel}
 
 class NotSerializableClass
 class NotSerializableExn(val notSer: NotSerializableClass) extends Throwable() {}
@@ -136,7 +135,6 @@ class DistributedSuite extends FunSuite with Matchers with BeforeAndAfter
         sc.parallelize(1 to 10, 2).foreach { x => if (x == 1) System.exit(42) }
       }
       assert(thrown.getClass === classOf[SparkException])
-      System.out.println(thrown.getMessage)
       assert(thrown.getMessage.contains("failed 4 times"))
     }
   }
@@ -202,12 +200,13 @@ class DistributedSuite extends FunSuite with Matchers with BeforeAndAfter
     val blockIds = data.partitions.indices.map(index => RDDBlockId(data.id, index)).toArray
     val blockId = blockIds(0)
     val blockManager = SparkEnv.get.blockManager
-    blockManager.master.getLocations(blockId).foreach(id => {
-      val bytes = BlockManagerWorker.syncGetBlock(
-        GetBlock(blockId), ConnectionManagerId(id.host, id.port))
-      val deserialized = blockManager.dataDeserialize(blockId, bytes).asInstanceOf[Iterator[Int]].toList
+    val blockTransfer = SparkEnv.get.blockTransferService
+    blockManager.master.getLocations(blockId).foreach { cmId =>
+      val bytes = blockTransfer.fetchBlockSync(cmId.host, cmId.port, blockId.toString)
+      val deserialized = blockManager.dataDeserialize(blockId, bytes.nioByteBuffer())
+        .asInstanceOf[Iterator[Int]].toList
       assert(deserialized === (1 to 100).toList)
-    })
+    }
   }
 
   test("compute without caching when no partitions fit in memory") {
diff --git a/core/src/test/scala/org/apache/spark/network/ConnectionManagerSuite.scala b/core/src/test/scala/org/apache/spark/network/nio/ConnectionManagerSuite.scala
index e2f4d4c57c..9f49587cdc 100644
--- a/core/src/test/scala/org/apache/spark/network/ConnectionManagerSuite.scala
+++ b/core/src/test/scala/org/apache/spark/network/nio/ConnectionManagerSuite.scala
@@ -15,23 +15,18 @@
  * limitations under the License.
  */
 
-package org.apache.spark.network
+package org.apache.spark.network.nio
 
 import java.io.IOException
 import java.nio._
-import java.util.concurrent.TimeoutException
 
-import org.apache.spark.{SecurityManager, SparkConf}
-import org.scalatest.FunSuite
-
-import org.mockito.Mockito._
-import org.mockito.Matchers._
-
-import scala.concurrent.TimeoutException
-import scala.concurrent.{Await, TimeoutException}
 import scala.concurrent.duration._
+import scala.concurrent.{Await, TimeoutException}
 import scala.language.postfixOps
-import scala.util.{Failure, Success, Try}
+
+import org.scalatest.FunSuite
+
+import org.apache.spark.{SecurityManager, SparkConf}
 
 /**
   * Test the ConnectionManager with various security settings.
diff --git a/core/src/test/scala/org/apache/spark/shuffle/hash/HashShuffleManagerSuite.scala b/core/src/test/scala/org/apache/spark/shuffle/hash/HashShuffleManagerSuite.scala
index 6061e544e7..ba47fe5e25 100644
--- a/core/src/test/scala/org/apache/spark/shuffle/hash/HashShuffleManagerSuite.scala
+++ b/core/src/test/scala/org/apache/spark/shuffle/hash/HashShuffleManagerSuite.scala
@@ -25,6 +25,7 @@ import org.scalatest.FunSuite
 
 import org.apache.spark.{SparkEnv, SparkContext, LocalSparkContext, SparkConf}
 import org.apache.spark.executor.ShuffleWriteMetrics
+import org.apache.spark.network.{FileSegmentManagedBuffer, ManagedBuffer}
 import org.apache.spark.serializer.JavaSerializer
 import org.apache.spark.shuffle.FileShuffleBlockManager
 import org.apache.spark.storage.{ShuffleBlockId, FileSegment}
@@ -32,10 +33,12 @@ import org.apache.spark.storage.{ShuffleBlockId, FileSegment}
 class HashShuffleManagerSuite extends FunSuite with LocalSparkContext {
   private val testConf = new SparkConf(false)
 
-  private def checkSegments(segment1: FileSegment, segment2: FileSegment) {
-    assert (segment1.file.getCanonicalPath === segment2.file.getCanonicalPath)
-    assert (segment1.offset === segment2.offset)
-    assert (segment1.length === segment2.length)
+  private def checkSegments(expected: FileSegment, buffer: ManagedBuffer) {
+    assert(buffer.isInstanceOf[FileSegmentManagedBuffer])
+    val segment = buffer.asInstanceOf[FileSegmentManagedBuffer]
+    assert(expected.file.getCanonicalPath === segment.file.getCanonicalPath)
+    assert(expected.offset === segment.offset)
+    assert(expected.length === segment.length)
   }
 
   test("consolidated shuffle can write to shuffle group without messing existing offsets/lengths") {
@@ -95,14 +98,12 @@ class HashShuffleManagerSuite extends FunSuite with LocalSparkContext {
       writer.commitAndClose()
     }
     // check before we register.
-    checkSegments(shuffle2Segment, shuffleBlockManager.getBlockData(ShuffleBlockId(1, 2, 0)).left.get)
+    checkSegments(shuffle2Segment, shuffleBlockManager.getBlockData(ShuffleBlockId(1, 2, 0)))
     shuffle3.releaseWriters(success = true)
-    checkSegments(shuffle2Segment, shuffleBlockManager.getBlockData(ShuffleBlockId(1, 2, 0)).left.get)
+    checkSegments(shuffle2Segment, shuffleBlockManager.getBlockData(ShuffleBlockId(1, 2, 0)))
     shuffleBlockManager.removeShuffle(1)
-
   }
 
-
   def writeToFile(file: File, numBytes: Int) {
     val writer = new FileWriter(file, true)
     for (i <- 0 until numBytes) writer.write(i)
diff --git a/core/src/test/scala/org/apache/spark/storage/BlockFetcherIteratorSuite.scala b/core/src/test/scala/org/apache/spark/storage/BlockFetcherIteratorSuite.scala
deleted file mode 100644
index 3c86f6bafc..0000000000
--- a/core/src/test/scala/org/apache/spark/storage/BlockFetcherIteratorSuite.scala
+++ /dev/null
@@ -1,237 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *    http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.apache.spark.storage
-
-import java.io.IOException
-import java.nio.ByteBuffer
-
-import scala.collection.mutable.ArrayBuffer
-import scala.concurrent.future
-import scala.concurrent.ExecutionContext.Implicits.global
-
-import org.scalatest.{FunSuite, Matchers}
-
-import org.mockito.Mockito._
-import org.mockito.Matchers.{any, eq => meq}
-import org.mockito.stubbing.Answer
-import org.mockito.invocation.InvocationOnMock
-
-import org.apache.spark.storage.BlockFetcherIterator._
-import org.apache.spark.network.{ConnectionManager, Message}
-import org.apache.spark.executor.ShuffleReadMetrics
-
-class BlockFetcherIteratorSuite extends FunSuite with Matchers {
-
-  test("block fetch from local fails using BasicBlockFetcherIterator") {
-    val blockManager = mock(classOf[BlockManager])
-    val connManager = mock(classOf[ConnectionManager])
-    doReturn(connManager).when(blockManager).connectionManager
-    doReturn(BlockManagerId("test-client", "test-client", 1)).when(blockManager).blockManagerId
-
-    doReturn((48 * 1024 * 1024).asInstanceOf[Long]).when(blockManager).maxBytesInFlight
-
-    val blIds = Array[BlockId](
-      ShuffleBlockId(0,0,0),
-      ShuffleBlockId(0,1,0),
-      ShuffleBlockId(0,2,0),
-      ShuffleBlockId(0,3,0),
-      ShuffleBlockId(0,4,0))
-
-    val optItr = mock(classOf[Option[Iterator[Any]]])
-    val answer = new Answer[Option[Iterator[Any]]] {
-      override def answer(invocation: InvocationOnMock) = Option[Iterator[Any]] {
-        throw new Exception
-      }
-    }
-
-    // 3rd block is going to fail
-    doReturn(optItr).when(blockManager).getLocalShuffleFromDisk(meq(blIds(0)), any())
-    doReturn(optItr).when(blockManager).getLocalShuffleFromDisk(meq(blIds(1)), any())
-    doAnswer(answer).when(blockManager).getLocalShuffleFromDisk(meq(blIds(2)), any())
-    doReturn(optItr).when(blockManager).getLocalShuffleFromDisk(meq(blIds(3)), any())
-    doReturn(optItr).when(blockManager).getLocalShuffleFromDisk(meq(blIds(4)), any())
-
-    val bmId = BlockManagerId("test-client", "test-client", 1)
-    val blocksByAddress = Seq[(BlockManagerId, Seq[(BlockId, Long)])](
-      (bmId, blIds.map(blId => (blId, 1.asInstanceOf[Long])).toSeq)
-    )
-
-    val iterator = new BasicBlockFetcherIterator(blockManager, blocksByAddress, null,
-      new ShuffleReadMetrics())
-
-    iterator.initialize()
-
-    // Without exhausting the iterator, the iterator should be lazy and not call getLocalShuffleFromDisk.
-    verify(blockManager, times(0)).getLocalShuffleFromDisk(any(), any())
-
-    assert(iterator.hasNext, "iterator should have 5 elements but actually has no elements")
-    // the 2nd element of the tuple returned by iterator.next should be defined when fetching successfully
-    assert(iterator.next()._2.isDefined, "1st element should be defined but is not actually defined")
-    verify(blockManager, times(1)).getLocalShuffleFromDisk(any(), any())
-
-    assert(iterator.hasNext, "iterator should have 5 elements but actually has 1 element")
-    assert(iterator.next()._2.isDefined, "2nd element should be defined but is not actually defined")
-    verify(blockManager, times(2)).getLocalShuffleFromDisk(any(), any())
-
-    assert(iterator.hasNext, "iterator should have 5 elements but actually has 2 elements")
-    // 3rd fetch should be failed
-    intercept[Exception] {
-      iterator.next()
-    }
-    verify(blockManager, times(3)).getLocalShuffleFromDisk(any(), any())
-  }
-
-
-  test("block fetch from local succeed using BasicBlockFetcherIterator") {
-    val blockManager = mock(classOf[BlockManager])
-    val connManager = mock(classOf[ConnectionManager])
-    doReturn(connManager).when(blockManager).connectionManager
-    doReturn(BlockManagerId("test-client", "test-client", 1)).when(blockManager).blockManagerId
-
-    doReturn((48 * 1024 * 1024).asInstanceOf[Long]).when(blockManager).maxBytesInFlight
-
-    val blIds = Array[BlockId](
-      ShuffleBlockId(0,0,0),
-      ShuffleBlockId(0,1,0),
-      ShuffleBlockId(0,2,0),
-      ShuffleBlockId(0,3,0),
-      ShuffleBlockId(0,4,0))
-
-    val optItr = mock(classOf[Option[Iterator[Any]]])
- 
-   // All blocks should be fetched successfully
-    doReturn(optItr).when(blockManager).getLocalShuffleFromDisk(meq(blIds(0)), any())
-    doReturn(optItr).when(blockManager).getLocalShuffleFromDisk(meq(blIds(1)), any())
-    doReturn(optItr).when(blockManager).getLocalShuffleFromDisk(meq(blIds(2)), any())
-    doReturn(optItr).when(blockManager).getLocalShuffleFromDisk(meq(blIds(3)), any())
-    doReturn(optItr).when(blockManager).getLocalShuffleFromDisk(meq(blIds(4)), any())
-
-    val bmId = BlockManagerId("test-client", "test-client", 1)
-    val blocksByAddress = Seq[(BlockManagerId, Seq[(BlockId, Long)])](
-      (bmId, blIds.map(blId => (blId, 1.asInstanceOf[Long])).toSeq)
-    )
-
-    val iterator = new BasicBlockFetcherIterator(blockManager, blocksByAddress, null,
-      new ShuffleReadMetrics())
-
-    iterator.initialize()
-
-    // Without exhausting the iterator, the iterator should be lazy and not call getLocalShuffleFromDisk.
-    verify(blockManager, times(0)).getLocalShuffleFromDisk(any(), any())
-
-    assert(iterator.hasNext, "iterator should have 5 elements but actually has no elements")
-    assert(iterator.next._2.isDefined, "All elements should be defined but 1st element is not actually defined") 
-    assert(iterator.hasNext, "iterator should have 5 elements but actually has 1 element")
-    assert(iterator.next._2.isDefined, "All elements should be defined but 2nd element is not actually defined") 
-    assert(iterator.hasNext, "iterator should have 5 elements but actually has 2 elements")
-    assert(iterator.next._2.isDefined, "All elements should be defined but 3rd element is not actually defined") 
-    assert(iterator.hasNext, "iterator should have 5 elements but actually has 3 elements")
-    assert(iterator.next._2.isDefined, "All elements should be defined but 4th element is not actually defined") 
-    assert(iterator.hasNext, "iterator should have 5 elements but actually has 4 elements")
-    assert(iterator.next._2.isDefined, "All elements should be defined but 5th element is not actually defined")
-
-    verify(blockManager, times(5)).getLocalShuffleFromDisk(any(), any())
-  }
-
-  test("block fetch from remote fails using BasicBlockFetcherIterator") {
-    val blockManager = mock(classOf[BlockManager])
-    val connManager = mock(classOf[ConnectionManager])
-    when(blockManager.connectionManager).thenReturn(connManager)
-
-    val f = future {
-      throw new IOException("Send failed or we received an error ACK")
-    }
-    when(connManager.sendMessageReliably(any(),
-      any())).thenReturn(f)
-    when(blockManager.futureExecContext).thenReturn(global)
-
-    when(blockManager.blockManagerId).thenReturn(
-      BlockManagerId("test-client", "test-client", 1))
-    when(blockManager.maxBytesInFlight).thenReturn(48 * 1024 * 1024)
-
-    val blId1 = ShuffleBlockId(0,0,0)
-    val blId2 = ShuffleBlockId(0,1,0)
-    val bmId = BlockManagerId("test-server", "test-server", 1)
-    val blocksByAddress = Seq[(BlockManagerId, Seq[(BlockId, Long)])](
-      (bmId, Seq((blId1, 1L), (blId2, 1L)))
-    )
-
-    val iterator = new BasicBlockFetcherIterator(blockManager,
-      blocksByAddress, null, new ShuffleReadMetrics())
-
-    iterator.initialize()
-    iterator.foreach{
-      case (_, r) => {
-        (!r.isDefined) should be(true)
-      }
-    }
-  }
-
-  test("block fetch from remote succeed using BasicBlockFetcherIterator") {
-    val blockManager = mock(classOf[BlockManager])
-    val connManager = mock(classOf[ConnectionManager])
-    when(blockManager.connectionManager).thenReturn(connManager)
-
-    val blId1 = ShuffleBlockId(0,0,0)
-    val blId2 = ShuffleBlockId(0,1,0)
-    val buf1 = ByteBuffer.allocate(4)
-    val buf2 = ByteBuffer.allocate(4)
-    buf1.putInt(1)
-    buf1.flip()
-    buf2.putInt(1)
-    buf2.flip()
-    val blockMessage1 = BlockMessage.fromGotBlock(GotBlock(blId1, buf1))
-    val blockMessage2 = BlockMessage.fromGotBlock(GotBlock(blId2, buf2))
-    val blockMessageArray = new BlockMessageArray(
-      Seq(blockMessage1, blockMessage2))
-
-    val bufferMessage = blockMessageArray.toBufferMessage
-    val buffer = ByteBuffer.allocate(bufferMessage.size)
-    val arrayBuffer = new ArrayBuffer[ByteBuffer]
-    bufferMessage.buffers.foreach{ b =>
-      buffer.put(b)
-    }
-    buffer.flip()
-    arrayBuffer += buffer
-
-    val f = future {
-      Message.createBufferMessage(arrayBuffer)
-    }
-    when(connManager.sendMessageReliably(any(),
-      any())).thenReturn(f)
-    when(blockManager.futureExecContext).thenReturn(global)
-
-    when(blockManager.blockManagerId).thenReturn(
-      BlockManagerId("test-client", "test-client", 1))
-    when(blockManager.maxBytesInFlight).thenReturn(48 * 1024 * 1024)
-
-    val bmId = BlockManagerId("test-server", "test-server", 1)
-    val blocksByAddress = Seq[(BlockManagerId, Seq[(BlockId, Long)])](
-      (bmId, Seq((blId1, 1L), (blId2, 1L)))
-    )
-
-    val iterator = new BasicBlockFetcherIterator(blockManager,
-      blocksByAddress, null, new ShuffleReadMetrics())
-    iterator.initialize()
-    iterator.foreach{
-      case (_, r) => {
-        (r.isDefined) should be(true)
-      }
-    }
-  }
-}
diff --git a/core/src/test/scala/org/apache/spark/storage/BlockManagerSuite.scala b/core/src/test/scala/org/apache/spark/storage/BlockManagerSuite.scala
index c200654162..e251660dae 100644
--- a/core/src/test/scala/org/apache/spark/storage/BlockManagerSuite.scala
+++ b/core/src/test/scala/org/apache/spark/storage/BlockManagerSuite.scala
@@ -21,15 +21,19 @@ import java.nio.{ByteBuffer, MappedByteBuffer}
 import java.util.Arrays
 import java.util.concurrent.TimeUnit
 
+import org.apache.spark.network.nio.NioBlockTransferService
+
+import scala.collection.mutable.ArrayBuffer
+import scala.concurrent.Await
+import scala.concurrent.duration._
+import scala.language.implicitConversions
+import scala.language.postfixOps
+
 import akka.actor._
 import akka.pattern.ask
 import akka.util.Timeout
-import org.apache.spark.shuffle.hash.HashShuffleManager
 
-import org.mockito.invocation.InvocationOnMock
-import org.mockito.Matchers.any
-import org.mockito.Mockito.{doAnswer, mock, spy, when}
-import org.mockito.stubbing.Answer
+import org.mockito.Mockito.{mock, when}
 
 import org.scalatest.{BeforeAndAfter, FunSuite, PrivateMethodTester}
 import org.scalatest.concurrent.Eventually._
@@ -38,18 +42,12 @@ import org.scalatest.Matchers
 
 import org.apache.spark.{MapOutputTrackerMaster, SecurityManager, SparkConf}
 import org.apache.spark.executor.DataReadMethod
-import org.apache.spark.network.{Message, ConnectionManagerId}
 import org.apache.spark.scheduler.LiveListenerBus
 import org.apache.spark.serializer.{JavaSerializer, KryoSerializer}
+import org.apache.spark.shuffle.hash.HashShuffleManager
 import org.apache.spark.storage.BlockManagerMessages.BlockManagerHeartbeat
 import org.apache.spark.util.{AkkaUtils, ByteBufferInputStream, SizeEstimator, Utils}
 
-import scala.collection.mutable.ArrayBuffer
-import scala.concurrent.Await
-import scala.concurrent.duration._
-import scala.language.implicitConversions
-import scala.language.postfixOps
-import org.apache.spark.shuffle.ShuffleBlockManager
 
 class BlockManagerSuite extends FunSuite with Matchers with BeforeAndAfter
   with PrivateMethodTester {
@@ -74,8 +72,9 @@ class BlockManagerSuite extends FunSuite with Matchers with BeforeAndAfter
   def rdd(rddId: Int, splitId: Int) = RDDBlockId(rddId, splitId)
 
   private def makeBlockManager(maxMem: Long, name: String = "<driver>"): BlockManager = {
-    new BlockManager(name, actorSystem, master, serializer, maxMem, conf, securityMgr,
-      mapOutputTracker, shuffleManager)
+    val transfer = new NioBlockTransferService(conf, securityMgr)
+    new BlockManager(name, actorSystem, master, serializer, maxMem, conf,
+      mapOutputTracker, shuffleManager, transfer)
   }
 
   before {
@@ -793,8 +792,9 @@ class BlockManagerSuite extends FunSuite with Matchers with BeforeAndAfter
 
   test("block store put failure") {
     // Use Java serializer so we can create an unserializable error.
+    val transfer = new NioBlockTransferService(conf, securityMgr)
     store = new BlockManager("<driver>", actorSystem, master, new JavaSerializer(conf), 1200, conf,
-      securityMgr, mapOutputTracker, shuffleManager)
+      mapOutputTracker, shuffleManager, transfer)
 
     // The put should fail since a1 is not serializable.
     class UnserializableClass
@@ -1005,109 +1005,6 @@ class BlockManagerSuite extends FunSuite with Matchers with BeforeAndAfter
     assert(!store.memoryStore.contains(rdd(1, 0)), "rdd_1_0 was in store")
   }
 
-  test("return error message when error occurred in BlockManagerWorker#onBlockMessageReceive") {
-    store = new BlockManager("<driver>", actorSystem, master, serializer, 1200, conf,
-      securityMgr, mapOutputTracker, shuffleManager)
-
-    val worker = spy(new BlockManagerWorker(store))
-    val connManagerId = mock(classOf[ConnectionManagerId])
-
-    // setup request block messages
-    val reqBlId1 = ShuffleBlockId(0,0,0)
-    val reqBlId2 = ShuffleBlockId(0,1,0)
-    val reqBlockMessage1 = BlockMessage.fromGetBlock(GetBlock(reqBlId1))
-    val reqBlockMessage2 = BlockMessage.fromGetBlock(GetBlock(reqBlId2))
-    val reqBlockMessages = new BlockMessageArray(
-      Seq(reqBlockMessage1, reqBlockMessage2))
-    val reqBufferMessage = reqBlockMessages.toBufferMessage
-
-    val answer = new Answer[Option[BlockMessage]] {
-      override def answer(invocation: InvocationOnMock)
-          :Option[BlockMessage]= {
-        throw new Exception
-      }
-    }
-
-    doAnswer(answer).when(worker).processBlockMessage(any())
-
-    // Test when exception was thrown during processing block messages
-    var ackMessage = worker.onBlockMessageReceive(reqBufferMessage, connManagerId)
-    
-    assert(ackMessage.isDefined, "When Exception was thrown in " +
-      "BlockManagerWorker#processBlockMessage, " +
-      "ackMessage should be defined")
-    assert(ackMessage.get.hasError, "When Exception was thown in " +
-      "BlockManagerWorker#processBlockMessage, " +
-      "ackMessage should have error")
-
-    val notBufferMessage = mock(classOf[Message])
-
-    // Test when not BufferMessage was received
-    ackMessage = worker.onBlockMessageReceive(notBufferMessage, connManagerId)
-    assert(ackMessage.isDefined, "When not BufferMessage was passed to " +
-      "BlockManagerWorker#onBlockMessageReceive, " +
-      "ackMessage should be defined")
-    assert(ackMessage.get.hasError, "When not BufferMessage was passed to " +
-      "BlockManagerWorker#onBlockMessageReceive, " +
-      "ackMessage should have error")
-  }
-
-  test("return ack message when no error occurred in BlocManagerWorker#onBlockMessageReceive") {
-    store = new BlockManager("<driver>", actorSystem, master, serializer, 1200, conf,
-      securityMgr, mapOutputTracker, shuffleManager)
-
-    val worker = spy(new BlockManagerWorker(store))
-    val connManagerId = mock(classOf[ConnectionManagerId])
-
-    // setup request block messages
-    val reqBlId1 = ShuffleBlockId(0,0,0)
-    val reqBlId2 = ShuffleBlockId(0,1,0)
-    val reqBlockMessage1 = BlockMessage.fromGetBlock(GetBlock(reqBlId1))
-    val reqBlockMessage2 = BlockMessage.fromGetBlock(GetBlock(reqBlId2))
-    val reqBlockMessages = new BlockMessageArray(
-      Seq(reqBlockMessage1, reqBlockMessage2))
-
-    val tmpBufferMessage = reqBlockMessages.toBufferMessage
-    val buffer = ByteBuffer.allocate(tmpBufferMessage.size)
-    val arrayBuffer = new ArrayBuffer[ByteBuffer]
-    tmpBufferMessage.buffers.foreach{ b =>
-      buffer.put(b)
-    }
-    buffer.flip()
-    arrayBuffer += buffer
-    val reqBufferMessage = Message.createBufferMessage(arrayBuffer)
-
-    // setup ack block messages
-    val buf1 = ByteBuffer.allocate(4)
-    val buf2 = ByteBuffer.allocate(4)
-    buf1.putInt(1)
-    buf1.flip()
-    buf2.putInt(1)
-    buf2.flip()
-    val ackBlockMessage1 = BlockMessage.fromGotBlock(GotBlock(reqBlId1, buf1))
-    val ackBlockMessage2 = BlockMessage.fromGotBlock(GotBlock(reqBlId2, buf2))
-
-    val answer = new Answer[Option[BlockMessage]] {
-      override def answer(invocation: InvocationOnMock)
-          :Option[BlockMessage]= {
-        if (invocation.getArguments()(0).asInstanceOf[BlockMessage].eq(
-          reqBlockMessage1)) {
-          return Some(ackBlockMessage1)
-        } else {
-          return Some(ackBlockMessage2)
-        }
-      }
-    }
-
-    doAnswer(answer).when(worker).processBlockMessage(any())
-
-    val ackMessage = worker.onBlockMessageReceive(reqBufferMessage, connManagerId)
-    assert(ackMessage.isDefined, "When BlockManagerWorker#onBlockMessageReceive " +
-      "was executed successfully, ackMessage should be defined")
-    assert(!ackMessage.get.hasError, "When BlockManagerWorker#onBlockMessageReceive " +
-      "was executed successfully, ackMessage should not have error")
-  }
-
   test("reserve/release unroll memory") {
     store = makeBlockManager(12000)
     val memoryStore = store.memoryStore
diff --git a/core/src/test/scala/org/apache/spark/storage/DiskBlockManagerSuite.scala b/core/src/test/scala/org/apache/spark/storage/DiskBlockManagerSuite.scala
index 26082ded8c..e4522e00a6 100644
--- a/core/src/test/scala/org/apache/spark/storage/DiskBlockManagerSuite.scala
+++ b/core/src/test/scala/org/apache/spark/storage/DiskBlockManagerSuite.scala
@@ -19,6 +19,7 @@ package org.apache.spark.storage
 
 import java.io.{File, FileWriter}
 
+import org.apache.spark.network.nio.NioBlockTransferService
 import org.apache.spark.shuffle.hash.HashShuffleManager
 
 import scala.collection.mutable
@@ -52,7 +53,6 @@ class DiskBlockManagerSuite extends FunSuite with BeforeAndAfterEach with Before
     rootDir1 = Files.createTempDir()
     rootDir1.deleteOnExit()
     rootDirs = rootDir0.getAbsolutePath + "," + rootDir1.getAbsolutePath
-    println("Created root dirs: " + rootDirs)
   }
 
   override def afterAll() {
diff --git a/core/src/test/scala/org/apache/spark/storage/ShuffleBlockFetcherIteratorSuite.scala b/core/src/test/scala/org/apache/spark/storage/ShuffleBlockFetcherIteratorSuite.scala
new file mode 100644
index 0000000000..809bd70929
--- /dev/null
+++ b/core/src/test/scala/org/apache/spark/storage/ShuffleBlockFetcherIteratorSuite.scala
@@ -0,0 +1,183 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.storage
+
+import org.apache.spark.TaskContext
+import org.apache.spark.network.{BlockFetchingListener, BlockTransferService}
+
+import org.mockito.Mockito._
+import org.mockito.Matchers.{any, eq => meq}
+import org.mockito.invocation.InvocationOnMock
+import org.mockito.stubbing.Answer
+
+import org.scalatest.FunSuite
+
+
+class ShuffleBlockFetcherIteratorSuite extends FunSuite {
+
+  test("handle local read failures in BlockManager") {
+    val transfer = mock(classOf[BlockTransferService])
+    val blockManager = mock(classOf[BlockManager])
+    doReturn(BlockManagerId("test-client", "test-client", 1)).when(blockManager).blockManagerId
+
+    val blIds = Array[BlockId](
+      ShuffleBlockId(0,0,0),
+      ShuffleBlockId(0,1,0),
+      ShuffleBlockId(0,2,0),
+      ShuffleBlockId(0,3,0),
+      ShuffleBlockId(0,4,0))
+
+    val optItr = mock(classOf[Option[Iterator[Any]]])
+    val answer = new Answer[Option[Iterator[Any]]] {
+      override def answer(invocation: InvocationOnMock) = Option[Iterator[Any]] {
+        throw new Exception
+      }
+    }
+
+    // 3rd block is going to fail
+    doReturn(optItr).when(blockManager).getLocalShuffleFromDisk(meq(blIds(0)), any())
+    doReturn(optItr).when(blockManager).getLocalShuffleFromDisk(meq(blIds(1)), any())
+    doAnswer(answer).when(blockManager).getLocalShuffleFromDisk(meq(blIds(2)), any())
+    doReturn(optItr).when(blockManager).getLocalShuffleFromDisk(meq(blIds(3)), any())
+    doReturn(optItr).when(blockManager).getLocalShuffleFromDisk(meq(blIds(4)), any())
+
+    val bmId = BlockManagerId("test-client", "test-client", 1)
+    val blocksByAddress = Seq[(BlockManagerId, Seq[(BlockId, Long)])](
+      (bmId, blIds.map(blId => (blId, 1.asInstanceOf[Long])).toSeq)
+    )
+
+    val iterator = new ShuffleBlockFetcherIterator(
+      new TaskContext(0, 0, 0),
+      transfer,
+      blockManager,
+      blocksByAddress,
+      null,
+      48 * 1024 * 1024)
+
+    // Without exhausting the iterator, the iterator should be lazy and not call
+    // getLocalShuffleFromDisk.
+    verify(blockManager, times(0)).getLocalShuffleFromDisk(any(), any())
+
+    assert(iterator.hasNext, "iterator should have 5 elements but actually has no elements")
+    // the 2nd element of the tuple returned by iterator.next should be defined when
+    // fetching successfully
+    assert(iterator.next()._2.isDefined,
+      "1st element should be defined but is not actually defined")
+    verify(blockManager, times(1)).getLocalShuffleFromDisk(any(), any())
+
+    assert(iterator.hasNext, "iterator should have 5 elements but actually has 1 element")
+    assert(iterator.next()._2.isDefined,
+      "2nd element should be defined but is not actually defined")
+    verify(blockManager, times(2)).getLocalShuffleFromDisk(any(), any())
+
+    assert(iterator.hasNext, "iterator should have 5 elements but actually has 2 elements")
+    // 3rd fetch should be failed
+    intercept[Exception] {
+      iterator.next()
+    }
+    verify(blockManager, times(3)).getLocalShuffleFromDisk(any(), any())
+  }
+
+  test("handle local read successes") {
+    val transfer = mock(classOf[BlockTransferService])
+    val blockManager = mock(classOf[BlockManager])
+    doReturn(BlockManagerId("test-client", "test-client", 1)).when(blockManager).blockManagerId
+
+    val blIds = Array[BlockId](
+      ShuffleBlockId(0,0,0),
+      ShuffleBlockId(0,1,0),
+      ShuffleBlockId(0,2,0),
+      ShuffleBlockId(0,3,0),
+      ShuffleBlockId(0,4,0))
+
+    val optItr = mock(classOf[Option[Iterator[Any]]])
+
+    // All blocks should be fetched successfully
+    doReturn(optItr).when(blockManager).getLocalShuffleFromDisk(meq(blIds(0)), any())
+    doReturn(optItr).when(blockManager).getLocalShuffleFromDisk(meq(blIds(1)), any())
+    doReturn(optItr).when(blockManager).getLocalShuffleFromDisk(meq(blIds(2)), any())
+    doReturn(optItr).when(blockManager).getLocalShuffleFromDisk(meq(blIds(3)), any())
+    doReturn(optItr).when(blockManager).getLocalShuffleFromDisk(meq(blIds(4)), any())
+
+    val bmId = BlockManagerId("test-client", "test-client", 1)
+    val blocksByAddress = Seq[(BlockManagerId, Seq[(BlockId, Long)])](
+      (bmId, blIds.map(blId => (blId, 1.asInstanceOf[Long])).toSeq)
+    )
+
+    val iterator = new ShuffleBlockFetcherIterator(
+      new TaskContext(0, 0, 0),
+      transfer,
+      blockManager,
+      blocksByAddress,
+      null,
+      48 * 1024 * 1024)
+
+    // Without exhausting the iterator, the iterator should be lazy and not call getLocalShuffleFromDisk.
+    verify(blockManager, times(0)).getLocalShuffleFromDisk(any(), any())
+
+    assert(iterator.hasNext, "iterator should have 5 elements but actually has no elements")
+    assert(iterator.next()._2.isDefined,
+      "All elements should be defined but 1st element is not actually defined")
+    assert(iterator.hasNext, "iterator should have 5 elements but actually has 1 element")
+    assert(iterator.next()._2.isDefined,
+      "All elements should be defined but 2nd element is not actually defined")
+    assert(iterator.hasNext, "iterator should have 5 elements but actually has 2 elements")
+    assert(iterator.next()._2.isDefined,
+      "All elements should be defined but 3rd element is not actually defined")
+    assert(iterator.hasNext, "iterator should have 5 elements but actually has 3 elements")
+    assert(iterator.next()._2.isDefined,
+      "All elements should be defined but 4th element is not actually defined")
+    assert(iterator.hasNext, "iterator should have 5 elements but actually has 4 elements")
+    assert(iterator.next()._2.isDefined,
+      "All elements should be defined but 5th element is not actually defined")
+
+    verify(blockManager, times(5)).getLocalShuffleFromDisk(any(), any())
+  }
+
+  test("handle remote fetch failures in BlockTransferService") {
+    val transfer = mock(classOf[BlockTransferService])
+    when(transfer.fetchBlocks(any(), any(), any(), any())).thenAnswer(new Answer[Unit] {
+      override def answer(invocation: InvocationOnMock): Unit = {
+        val listener = invocation.getArguments()(3).asInstanceOf[BlockFetchingListener]
+        listener.onBlockFetchFailure(new Exception("blah"))
+      }
+    })
+
+    val blockManager = mock(classOf[BlockManager])
+
+    when(blockManager.blockManagerId).thenReturn(BlockManagerId("test-client", "test-client", 1))
+
+    val blId1 = ShuffleBlockId(0, 0, 0)
+    val blId2 = ShuffleBlockId(0, 1, 0)
+    val bmId = BlockManagerId("test-server", "test-server", 1)
+    val blocksByAddress = Seq[(BlockManagerId, Seq[(BlockId, Long)])](
+      (bmId, Seq((blId1, 1L), (blId2, 1L))))
+
+    val iterator = new ShuffleBlockFetcherIterator(
+      new TaskContext(0, 0, 0),
+      transfer,
+      blockManager,
+      blocksByAddress,
+      null,
+      48 * 1024 * 1024)
+
+    iterator.foreach { case (_, iterOption) =>
+      assert(!iterOption.isDefined)
+    }
+  }
+}