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From GitBox <...@apache.org>
Subject [GitHub] NicoK closed pull request #6555: [FLINK-10142][network] reduce locking around credit notification
Date Thu, 30 Aug 2018 20:48:07 GMT
NicoK closed pull request #6555: [FLINK-10142][network] reduce locking around credit notification
URL: https://github.com/apache/flink/pull/6555
 
 
   

This is a PR merged from a forked repository.
As GitHub hides the original diff on merge, it is displayed below for
the sake of provenance:

As this is a foreign pull request (from a fork), the diff is supplied
below (as it won't show otherwise due to GitHub magic):

diff --git a/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/netty/PartitionRequestClient.java
b/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/netty/PartitionRequestClient.java
index 27d341aca40..9c9deaa2542 100644
--- a/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/netty/PartitionRequestClient.java
+++ b/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/netty/PartitionRequestClient.java
@@ -171,10 +171,7 @@ public void operationComplete(ChannelFuture future) throws Exception
{
 	}
 
 	public void notifyCreditAvailable(RemoteInputChannel inputChannel) {
-		// We should skip the notification if the client is already closed.
-		if (!closeReferenceCounter.isDisposed()) {
-			clientHandler.notifyCreditAvailable(inputChannel);
-		}
+		clientHandler.notifyCreditAvailable(inputChannel);
 	}
 
 	public void close(RemoteInputChannel inputChannel) throws IOException {
diff --git a/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/RemoteInputChannel.java
b/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/RemoteInputChannel.java
index 28f30209892..6738abd7f9c 100644
--- a/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/RemoteInputChannel.java
+++ b/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/RemoteInputChannel.java
@@ -191,16 +191,16 @@ void retriggerSubpartitionRequest(int subpartitionIndex) throws IOException,
Int
 		checkError();
 
 		final Buffer next;
-		final int remaining;
+		final boolean moreAvailable;
 
 		synchronized (receivedBuffers) {
 			next = receivedBuffers.poll();
-			remaining = receivedBuffers.size();
+			moreAvailable = !receivedBuffers.isEmpty();
 		}
 
 		numBytesIn.inc(next.getSizeUnsafe());
 		numBuffersIn.inc();
-		return Optional.of(new BufferAndAvailability(next, remaining > 0, getSenderBacklog()));
+		return Optional.of(new BufferAndAvailability(next, moreAvailable, getSenderBacklog()));
 	}
 
 	// ------------------------------------------------------------------------
@@ -289,10 +289,7 @@ public String toString() {
 	private void notifyCreditAvailable() {
 		checkState(partitionRequestClient != null, "Tried to send task event to producer before
requesting a queue.");
 
-		// We should skip the notification if this channel is already released.
-		if (!isReleased.get()) {
-			partitionRequestClient.notifyCreditAvailable(this);
-		}
+		partitionRequestClient.notifyCreditAvailable(this);
 	}
 
 	/**
@@ -306,8 +303,8 @@ public void recycle(MemorySegment segment) {
 		int numAddedBuffers;
 
 		synchronized (bufferQueue) {
-			// Important: check the isReleased state inside synchronized block, so there is no
-			// race condition when recycle and releaseAllResources running in parallel.
+			// Similar to notifyBufferAvailable(), make sure that we never add a buffer
+			// after releaseAllResources() released all buffers (see below for details).
 			if (isReleased.get()) {
 				try {
 					inputGate.returnExclusiveSegments(Collections.singletonList(segment));
@@ -354,13 +351,6 @@ boolean isWaitingForFloatingBuffers() {
 	 */
 	@Override
 	public boolean notifyBufferAvailable(Buffer buffer) {
-		// Check the isReleased state outside synchronized block first to avoid
-		// deadlock with releaseAllResources running in parallel.
-		if (isReleased.get()) {
-			buffer.recycleBuffer();
-			return false;
-		}
-
 		boolean recycleBuffer = true;
 		try {
 			boolean needMoreBuffers = false;
@@ -368,8 +358,13 @@ public boolean notifyBufferAvailable(Buffer buffer) {
 				checkState(isWaitingForFloatingBuffers,
 					"This channel should be waiting for floating buffers.");
 
-				// Important: double check the isReleased state inside synchronized block, so there is
no
-				// race condition when notifyBufferAvailable and releaseAllResources running in parallel.
+				// Important: make sure that we never add a buffer after releaseAllResources()
+				// released all buffers. Following scenarios exist:
+				// 1) releaseAllResources() already released buffers inside bufferQueue
+				// -> then isReleased is set correctly
+				// 2) releaseAllResources() did not yet release buffers from bufferQueue
+				// -> we may or may not have set isReleased yet but will always wait for the
+				//    lock on bufferQueue to release buffers
 				if (isReleased.get() || bufferQueue.getAvailableBufferSize() >= numRequiredBuffers)
{
 					isWaitingForFloatingBuffers = false;
 					recycleBuffer = false; // just in case
@@ -385,10 +380,10 @@ public boolean notifyBufferAvailable(Buffer buffer) {
 				} else {
 					needMoreBuffers = true;
 				}
+			}
 
-				if (unannouncedCredit.getAndAdd(1) == 0) {
-					notifyCreditAvailable();
-				}
+			if (unannouncedCredit.getAndAdd(1) == 0) {
+				notifyCreditAvailable();
 			}
 
 			return needMoreBuffers;
@@ -484,8 +479,8 @@ void onSenderBacklog(int backlog) throws IOException {
 		int numRequestedBuffers = 0;
 
 		synchronized (bufferQueue) {
-			// Important: check the isReleased state inside synchronized block, so there is no
-			// race condition when onSenderBacklog and releaseAllResources running in parallel.
+			// Similar to notifyBufferAvailable(), make sure that we never add a buffer
+			// after releaseAllResources() released all buffers (see above for details).
 			if (isReleased.get()) {
 				return;
 			}
@@ -510,33 +505,40 @@ void onSenderBacklog(int backlog) throws IOException {
 	}
 
 	public void onBuffer(Buffer buffer, int sequenceNumber, int backlog) throws IOException
{
-		boolean success = false;
+		boolean recycleBuffer = true;
 
 		try {
+
+			final boolean wasEmpty;
 			synchronized (receivedBuffers) {
-				if (!isReleased.get()) {
-					if (expectedSequenceNumber == sequenceNumber) {
-						int available = receivedBuffers.size();
+				// Similar to notifyBufferAvailable(), make sure that we never add a buffer
+				// after releaseAllResources() released all buffers from receivedBuffers
+				// (see above for details).
+				if (isReleased.get()) {
+					return;
+				}
 
-						receivedBuffers.add(buffer);
-						expectedSequenceNumber++;
+				if (expectedSequenceNumber != sequenceNumber) {
+					onError(new BufferReorderingException(expectedSequenceNumber, sequenceNumber));
+					return;
+				}
 
-						if (available == 0) {
-							notifyChannelNonEmpty();
-						}
+				wasEmpty = receivedBuffers.isEmpty();
+				receivedBuffers.add(buffer);
+				recycleBuffer = false;
+			}
 
-						success = true;
-					} else {
-						onError(new BufferReorderingException(expectedSequenceNumber, sequenceNumber));
-					}
-				}
+			++expectedSequenceNumber;
+
+			if (wasEmpty) {
+				notifyChannelNonEmpty();
 			}
 
-			if (success && backlog >= 0) {
+			if (backlog >= 0) {
 				onSenderBacklog(backlog);
 			}
 		} finally {
-			if (!success) {
+			if (recycleBuffer) {
 				buffer.recycleBuffer();
 			}
 		}
diff --git a/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/SingleInputGate.java
b/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/SingleInputGate.java
index 2e7d076f3f8..f51dc7417ab 100644
--- a/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/SingleInputGate.java
+++ b/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/SingleInputGate.java
@@ -545,7 +545,7 @@ public void requestPartitions() throws IOException, InterruptedException
{
 
 				currentChannel = inputChannelsWithData.remove();
 				enqueuedInputChannelsWithData.clear(currentChannel.getChannelIndex());
-				moreAvailable = inputChannelsWithData.size() > 0;
+				moreAvailable = !inputChannelsWithData.isEmpty();
 			}
 
 			result = currentChannel.getNextBuffer();
diff --git a/flink-runtime/src/test/java/org/apache/flink/runtime/io/network/partition/consumer/RemoteInputChannelTest.java
b/flink-runtime/src/test/java/org/apache/flink/runtime/io/network/partition/consumer/RemoteInputChannelTest.java
index 63054923498..9141b36d445 100644
--- a/flink-runtime/src/test/java/org/apache/flink/runtime/io/network/partition/consumer/RemoteInputChannelTest.java
+++ b/flink-runtime/src/test/java/org/apache/flink/runtime/io/network/partition/consumer/RemoteInputChannelTest.java
@@ -106,10 +106,33 @@ public void testExceptionOnReordering() throws Exception {
 
 	@Test
 	public void testConcurrentOnBufferAndRelease() throws Exception {
-		// Config
-		// Repeatedly spawn two tasks: one to queue buffers and the other to release the channel
-		// concurrently. We do this repeatedly to provoke races.
-		final int numberOfRepetitions = 8192;
+		testConcurrentReleaseAndSomething(8192, (inputChannel, buffer, j) -> {
+			inputChannel.onBuffer(buffer, j, -1);
+			return null;
+		});
+	}
+
+	@Test
+	public void testConcurrentNotifyBufferAvailableAndRelease() throws Exception {
+		testConcurrentReleaseAndSomething(1024, (inputChannel, buffer, j) ->
+			inputChannel.notifyBufferAvailable(buffer)
+		);
+	}
+
+	private interface TriFunction<T, U, V, R> {
+		R apply(T t, U u, V v) throws Exception;
+	}
+
+	/**
+	 * Repeatedly spawns two tasks: one to call <tt>function</tt> and the other
to release the
+	 * channel concurrently. We do this repeatedly to provoke races.
+	 *
+	 * @param numberOfRepetitions how often to repeat the test
+	 * @param function function to call concurrently to {@link RemoteInputChannel#releaseAllResources()}
+	 */
+	private void testConcurrentReleaseAndSomething(
+			final int numberOfRepetitions,
+			TriFunction<RemoteInputChannel, Buffer, Integer, Object> function) throws Exception
{
 
 		// Setup
 		final ExecutorService executor = Executors.newFixedThreadPool(2);
@@ -122,30 +145,23 @@ public void testConcurrentOnBufferAndRelease() throws Exception {
 			for (int i = 0; i < numberOfRepetitions; i++) {
 				final RemoteInputChannel inputChannel = createRemoteInputChannel(inputGate);
 
-				final Callable<Void> enqueueTask = new Callable<Void>() {
-					@Override
-					public Void call() throws Exception {
-						while (true) {
-							for (int j = 0; j < 128; j++) {
-								// this is the same buffer over and over again which will be
-								// recycled by the RemoteInputChannel
-								inputChannel.onBuffer(buffer.retainBuffer(), j, -1);
-							}
+				final Callable<Void> enqueueTask = () -> {
+					while (true) {
+						for (int j = 0; j < 128; j++) {
+							// this is the same buffer over and over again which will be
+							// recycled by the RemoteInputChannel
+							function.apply(inputChannel, buffer.retainBuffer(), j);
+						}
 
-							if (inputChannel.isReleased()) {
-								return null;
-							}
+						if (inputChannel.isReleased()) {
+							return null;
 						}
 					}
 				};
 
-				final Callable<Void> releaseTask = new Callable<Void>() {
-					@Override
-					public Void call() throws Exception {
-						inputChannel.releaseAllResources();
-
-						return null;
-					}
+				final Callable<Void> releaseTask = () -> {
+					inputChannel.releaseAllResources();
+					return null;
 				};
 
 				// Submit tasks and wait to finish
@@ -158,8 +174,8 @@ public Void call() throws Exception {
 					result.get();
 				}
 
-				assertEquals("Resource leak during concurrent release and enqueue.",
-						0, inputChannel.getNumberOfQueuedBuffers());
+				assertEquals("Resource leak during concurrent release and notifyBufferAvailable.",
+					0, inputChannel.getNumberOfQueuedBuffers());
 			}
 		}
 		finally {


 

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