[SPARK-13308] ManagedBuffers passed to OneToOneStreamManager need to be freed in non-error cases

ManagedBuffers that are passed to `OneToOneStreamManager.registerStream` need to be freed by the manager once it's done using them. However, the current code only frees them in certain error-cases and not during typical operation. This isn't a major problem today, but it will cause memory leaks after we implement better locking / pinning in the BlockManager (see #10705).

This patch modifies the relevant network code so that the ManagedBuffers are freed as soon as the messages containing them are processed by the lower-level Netty message sending code.

/cc zsxwing for review.

Author: Josh Rosen <joshrosen@databricks.com>

Closes #11193 from JoshRosen/add-missing-release-calls-in-network-layer.

network/common/src/main/java/org/apache/spark/network/buffer/ManagedBuffer.java

@@ -65,7 +65,11 @@ public abstract class ManagedBuffer {
   public abstract ManagedBuffer release();
 
   /**
-   * Convert the buffer into an Netty object, used to write the data out.
+   * Convert the buffer into an Netty object, used to write the data out. The return value is either
+   * a {@link io.netty.buffer.ByteBuf} or a {@link io.netty.channel.FileRegion}.
+   *
+   * If this method returns a ByteBuf, then that buffer's reference count will be incremented and
+   * the caller will be responsible for releasing this new reference.
    */
   public abstract Object convertToNetty() throws IOException;
 }

network/common/src/main/java/org/apache/spark/network/buffer/NettyManagedBuffer.java

@@ -64,7 +64,7 @@ public final class NettyManagedBuffer extends ManagedBuffer {
 
   @Override
   public Object convertToNetty() throws IOException {
-    return buf.duplicate();
+    return buf.duplicate().retain();
   }
 
   @Override

network/common/src/main/java/org/apache/spark/network/protocol/MessageEncoder.java

@@ -54,6 +54,7 @@ public final class MessageEncoder extends MessageToMessageEncoder<Message> {
         body = in.body().convertToNetty();
         isBodyInFrame = in.isBodyInFrame();
       } catch (Exception e) {
+        in.body().release();
         if (in instanceof AbstractResponseMessage) {
           AbstractResponseMessage resp = (AbstractResponseMessage) in;
           // Re-encode this message as a failure response.
@@ -80,8 +81,10 @@ public final class MessageEncoder extends MessageToMessageEncoder<Message> {
     in.encode(header);
     assert header.writableBytes() == 0;
 
-    if (body != null && bodyLength > 0) {
-      out.add(new MessageWithHeader(header, body, bodyLength));
+    if (body != null) {
+      // We transfer ownership of the reference on in.body() to MessageWithHeader.
+      // This reference will be freed when MessageWithHeader.deallocate() is called.
+      out.add(new MessageWithHeader(in.body(), header, body, bodyLength));
     } else {
       out.add(header);
     }

network/common/src/main/java/org/apache/spark/network/protocol/MessageWithHeader.java

@@ -19,6 +19,7 @@ package org.apache.spark.network.protocol;
 
 import java.io.IOException;
 import java.nio.channels.WritableByteChannel;
+import javax.annotation.Nullable;
 
 import com.google.common.base.Preconditions;
 import io.netty.buffer.ByteBuf;
@@ -26,6 +27,8 @@ import io.netty.channel.FileRegion;
 import io.netty.util.AbstractReferenceCounted;
 import io.netty.util.ReferenceCountUtil;
 
+import org.apache.spark.network.buffer.ManagedBuffer;
+
 /**
  * A wrapper message that holds two separate pieces (a header and a body).
  *
@@ -33,15 +36,35 @@ import io.netty.util.ReferenceCountUtil;
  */
 class MessageWithHeader extends AbstractReferenceCounted implements FileRegion {
 
+  @Nullable private final ManagedBuffer managedBuffer;
   private final ByteBuf header;
   private final int headerLength;
   private final Object body;
   private final long bodyLength;
   private long totalBytesTransferred;
 
-  MessageWithHeader(ByteBuf header, Object body, long bodyLength) {
+  /**
+   * Construct a new MessageWithHeader.
+   *
+   * @param managedBuffer the {@link ManagedBuffer} that the message body came from. This needs to
+   *                      be passed in so that the buffer can be freed when this message is
+   *                      deallocated. Ownership of the caller's reference to this buffer is
+   *                      transferred to this class, so if the caller wants to continue to use the
+   *                      ManagedBuffer in other messages then they will need to call retain() on
+   *                      it before passing it to this constructor. This may be null if and only if
+   *                      `body` is a {@link FileRegion}.
+   * @param header the message header.
+   * @param body the message body. Must be either a {@link ByteBuf} or a {@link FileRegion}.
+   * @param bodyLength the length of the message body, in bytes.
+     */
+  MessageWithHeader(
+      @Nullable ManagedBuffer managedBuffer,
+      ByteBuf header,
+      Object body,
+      long bodyLength) {
     Preconditions.checkArgument(body instanceof ByteBuf || body instanceof FileRegion,
       "Body must be a ByteBuf or a FileRegion.");
+    this.managedBuffer = managedBuffer;
     this.header = header;
     this.headerLength = header.readableBytes();
     this.body = body;
@@ -99,6 +122,9 @@ class MessageWithHeader extends AbstractReferenceCounted implements FileRegion {
   protected void deallocate() {
     header.release();
     ReferenceCountUtil.release(body);
+    if (managedBuffer != null) {
+      managedBuffer.release();
+    }
   }
 
   private int copyByteBuf(ByteBuf buf, WritableByteChannel target) throws IOException {

network/common/src/main/java/org/apache/spark/network/server/OneForOneStreamManager.java

@@ -20,7 +20,6 @@ package org.apache.spark.network.server;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.Random;
-import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.atomic.AtomicLong;
 

network/common/src/test/java/org/apache/spark/network/protocol/MessageWithHeaderSuite.java

@@ -26,9 +26,13 @@ import io.netty.buffer.Unpooled;
 import io.netty.channel.FileRegion;
 import io.netty.util.AbstractReferenceCounted;
 import org.junit.Test;
+import org.mockito.Mockito;
 
 import static org.junit.Assert.*;
 
+import org.apache.spark.network.TestManagedBuffer;
+import org.apache.spark.network.buffer.ManagedBuffer;
+import org.apache.spark.network.buffer.NettyManagedBuffer;
 import org.apache.spark.network.util.ByteArrayWritableChannel;
 
 public class MessageWithHeaderSuite {
@@ -46,20 +50,43 @@ public class MessageWithHeaderSuite {
   @Test
   public void testByteBufBody() throws Exception {
     ByteBuf header = Unpooled.copyLong(42);
-    ByteBuf body = Unpooled.copyLong(84);
-    MessageWithHeader msg = new MessageWithHeader(header, body, body.readableBytes());
+    ByteBuf bodyPassedToNettyManagedBuffer = Unpooled.copyLong(84);
+    assertEquals(1, header.refCnt());
+    assertEquals(1, bodyPassedToNettyManagedBuffer.refCnt());
+    ManagedBuffer managedBuf = new NettyManagedBuffer(bodyPassedToNettyManagedBuffer);
 
+    Object body = managedBuf.convertToNetty();
+    assertEquals(2, bodyPassedToNettyManagedBuffer.refCnt());
+    assertEquals(1, header.refCnt());
+
+    MessageWithHeader msg = new MessageWithHeader(managedBuf, header, body, managedBuf.size());
     ByteBuf result = doWrite(msg, 1);
     assertEquals(msg.count(), result.readableBytes());
     assertEquals(42, result.readLong());
     assertEquals(84, result.readLong());
+
+    assert(msg.release());
+    assertEquals(0, bodyPassedToNettyManagedBuffer.refCnt());
+    assertEquals(0, header.refCnt());
+  }
+
+  @Test
+  public void testDeallocateReleasesManagedBuffer() throws Exception {
+    ByteBuf header = Unpooled.copyLong(42);
+    ManagedBuffer managedBuf = Mockito.spy(new TestManagedBuffer(84));
+    ByteBuf body = (ByteBuf) managedBuf.convertToNetty();
+    assertEquals(2, body.refCnt());
+    MessageWithHeader msg = new MessageWithHeader(managedBuf, header, body, body.readableBytes());
+    assert(msg.release());
+    Mockito.verify(managedBuf, Mockito.times(1)).release();
+    assertEquals(0, body.refCnt());
   }
 
   private void testFileRegionBody(int totalWrites, int writesPerCall) throws Exception {
     ByteBuf header = Unpooled.copyLong(42);
     int headerLength = header.readableBytes();
     TestFileRegion region = new TestFileRegion(totalWrites, writesPerCall);
-    MessageWithHeader msg = new MessageWithHeader(header, region, region.count());
+    MessageWithHeader msg = new MessageWithHeader(null, header, region, region.count());
 
     ByteBuf result = doWrite(msg, totalWrites / writesPerCall);
     assertEquals(headerLength + region.count(), result.readableBytes());
@@ -67,6 +94,7 @@ public class MessageWithHeaderSuite {
     for (long i = 0; i < 8; i++) {
       assertEquals(i, result.readLong());
     }
+    assert(msg.release());
   }
 
   private ByteBuf doWrite(MessageWithHeader msg, int minExpectedWrites) throws Exception {

network/common/src/test/java/org/apache/spark/network/server/OneForOneStreamManagerSuite.java

@@ -0,0 +1,50 @@
+/*
+ * 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.server;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import io.netty.channel.Channel;
+import org.junit.Test;
+import org.mockito.Mockito;
+
+import org.apache.spark.network.TestManagedBuffer;
+import org.apache.spark.network.buffer.ManagedBuffer;
+
+public class OneForOneStreamManagerSuite {
+
+  @Test
+  public void managedBuffersAreFeedWhenConnectionIsClosed() throws Exception {
+    OneForOneStreamManager manager = new OneForOneStreamManager();
+    List<ManagedBuffer> buffers = new ArrayList<>();
+    TestManagedBuffer buffer1 = Mockito.spy(new TestManagedBuffer(10));
+    TestManagedBuffer buffer2 = Mockito.spy(new TestManagedBuffer(20));
+    buffers.add(buffer1);
+    buffers.add(buffer2);
+    long streamId = manager.registerStream("appId", buffers.iterator());
+
+    Channel dummyChannel = Mockito.mock(Channel.class, Mockito.RETURNS_SMART_NULLS);
+    manager.registerChannel(dummyChannel, streamId);
+
+    manager.connectionTerminated(dummyChannel);
+
+    Mockito.verify(buffer1, Mockito.times(1)).release();
+    Mockito.verify(buffer2, Mockito.times(1)).release();
+  }
+}