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本文主要研究一下flink的NetworkBufferPool
BufferPoolFactory
flink-release-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/buffer/BufferPoolFactory.java
public interface BufferPoolFactory {
/**
* Tries to create a buffer pool, which is guaranteed to provide at least the number of required
* buffers.
*
* <p>The buffer pool is of dynamic size with at least <tt>numRequiredBuffers</tt> buffers.
*
* @param numRequiredBuffers
* minimum number of network buffers in this pool
* @param maxUsedBuffers
* maximum number of network buffers this pool offers
*/
BufferPool createBufferPool(int numRequiredBuffers, int maxUsedBuffers) throws IOException;
/**
* Tries to create a buffer pool with an optional owner, which is guaranteed to provide at least the
* number of required buffers.
*
* <p>The buffer pool is of dynamic size with at least <tt>numRequiredBuffers</tt> buffers.
*
* @param numRequiredBuffers
* minimum number of network buffers in this pool
* @param maxUsedBuffers
* maximum number of network buffers this pool offers
* @param owner
* the optional owner of this buffer pool to release memory when needed
*/
BufferPool createBufferPool(int numRequiredBuffers, int maxUsedBuffers, Optional<BufferPoolOwner> owner) throws IOException;
/**
* Destroy callback for updating factory book keeping.
*/
void destroyBufferPool(BufferPool bufferPool) throws IOException;
}- BufferPoolFactory定义了createBufferPool、destroyBufferPool方法；其中createBufferPool支持numRequiredBuffers、maxUsedBuffers、owner参数
NetworkBufferPool
flink-release-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/buffer/NetworkBufferPool.java
public class NetworkBufferPool implements BufferPoolFactory {
//......
private static final Logger LOG = LoggerFactory.getLogger(NetworkBufferPool.class);
private final int totalNumberOfMemorySegments;
private final int memorySegmentSize;
private final ArrayBlockingQueue<MemorySegment> availableMemorySegments;
private volatile boolean isDestroyed;
// ---- Managed buffer pools ----------------------------------------------
private final Object factoryLock = new Object();
private final Set<LocalBufferPool> allBufferPools = new HashSet<>();
private int numTotalRequiredBuffers;
/**
* Allocates all {@link MemorySegment} instances managed by this pool.
*/
public NetworkBufferPool(int numberOfSegmentsToAllocate, int segmentSize) {
this.totalNumberOfMemorySegments = numberOfSegmentsToAllocate;
this.memorySegmentSize = segmentSize;
final long sizeInLong = (long) segmentSize;
try {
this.availableMemorySegments = new ArrayBlockingQueue<>(numberOfSegmentsToAllocate);
}
catch (OutOfMemoryError err) {
throw new OutOfMemoryError("Could not allocate buffer queue of length "
+ numberOfSegmentsToAllocate + " - " + err.getMessage());
}
try {
for (int i = 0; i < numberOfSegmentsToAllocate; i++) {
availableMemorySegments.add(MemorySegmentFactory.allocateUnpooledOffHeapMemory(segmentSize, null));
}
}
catch (OutOfMemoryError err) {
int allocated = availableMemorySegments.size();
// free some memory
availableMemorySegments.clear();
long requiredMb = (sizeInLong * numberOfSegmentsToAllocate) >> 20;
long allocatedMb = (sizeInLong * allocated) >> 20;
long missingMb = requiredMb - allocatedMb;
throw new OutOfMemoryError("Could not allocate enough memory segments for NetworkBufferPool " +
"(required (Mb): " + requiredMb +
", allocated (Mb): " + allocatedMb +
", missing (Mb): " + missingMb + "). Cause: " + err.getMessage());
}
long allocatedMb = (sizeInLong * availableMemorySegments.size()) >> 20;
LOG.info("Allocated {} MB for network buffer pool (number of memory segments: {}, bytes per segment: {}).",
allocatedMb, availableMemorySegments.size(), segmentSize);
}
@Override
public BufferPool createBufferPool(int numRequiredBuffers, int maxUsedBuffers) throws IOException {
return createBufferPool(numRequiredBuffers, maxUsedBuffers, Optional.empty());
}
@Override
public BufferPool createBufferPool(int numRequiredBuffers, int maxUsedBuffers, Optional<BufferPoolOwner> owner) throws IOException {
// It is necessary to use a separate lock from the one used for buffer
// requests to ensure deadlock freedom for failure cases.
synchronized (factoryLock) {
if (isDestroyed) {
throw new IllegalStateException("Network buffer pool has already been destroyed.");
}
// Ensure that the number of required buffers can be satisfied.
// With dynamic memory management this should become obsolete.
if (numTotalRequiredBuffers + numRequiredBuffers > totalNumberOfMemorySegments) {
throw new IOException(String.format("Insufficient number of network buffers: " +
"required %d, but only %d available. The total number of network " +
"buffers is currently set to %d of %d bytes each. You can increase this " +
"number by setting the configuration keys '%s', '%s', and '%s'.",
numRequiredBuffers,
totalNumberOfMemorySegments - numTotalRequiredBuffers,
totalNumberOfMemorySegments,
memorySegmentSize,
TaskManagerOptions.NETWORK_BUFFERS_MEMORY_FRACTION.key(),
TaskManagerOptions.NETWORK_BUFFERS_MEMORY_MIN.key(),
TaskManagerOptions.NETWORK_BUFFERS_MEMORY_MAX.key()));
}
this.numTotalRequiredBuffers += numRequiredBuffers;
// We are good to go, create a new buffer pool and redistribute
// non-fixed size buffers.
LocalBufferPool localBufferPool =
new LocalBufferPool(this, numRequiredBuffers, maxUsedBuffers, owner);
allBufferPools.add(localBufferPool);
try {
redistributeBuffers();
} catch (IOException e) {
try {
destroyBufferPool(localBufferPool);
} catch (IOException inner) {
e.addSuppressed(inner);
}
ExceptionUtils.rethrowIOException(e);
}
return localBufferPool;
}
}
@Override
public void destroyBufferPool(BufferPool bufferPool) throws IOException {
if (!(bufferPool instanceof LocalBufferPool)) {
throw new IllegalArgumentException("bufferPool is no LocalBufferPool");
}
synchronized (factoryLock) {
if (allBufferPools.remove(bufferPool)) {
numTotalRequiredBuffers -= bufferPool.getNumberOfRequiredMemorySegments();
redistributeBuffers();
}
}
}
//......
}- NetworkBufferPool实现了BufferPoolFactory接口，它的构造器接收numberOfSegmentsToAllocate、segmentSize两个参数；构造器里头根据numberOfSegmentsToAllocate创建了availableMemorySegments这个ArrayBlockingQueue，然后通过MemorySegmentFactory.allocateUnpooledOffHeapMemory挨个创建MemorySegment添加到availableMemorySegments
- createBufferPool方法创建的是LocalBufferPool(
传递了自身NetworkBufferPool实例进去)，然后添加到allBufferPools这个set中，同时增加numTotalRequiredBuffers；destroyBufferPool方法则从allBufferPools移除该bufferPool，同时减少numTotalRequiredBuffers - createBufferPool方法及destroyBufferPool方法会调用到redistributeBuffers方法，通过调用LocalBufferPool的setNumBuffers方法来调整buffer pool的大小
LocalBufferPool
flink-release-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/buffer/LocalBufferPool.java
class LocalBufferPool implements BufferPool {
private static final Logger LOG = LoggerFactory.getLogger(LocalBufferPool.class);
/** Global network buffer pool to get buffers from. */
private final NetworkBufferPool networkBufferPool;
/** The minimum number of required segments for this pool. */
private final int numberOfRequiredMemorySegments;
/**
* The currently available memory segments. These are segments, which have been requested from
* the network buffer pool and are currently not handed out as Buffer instances.
*
* <p><strong>BEWARE:</strong> Take special care with the interactions between this lock and
* locks acquired before entering this class vs. locks being acquired during calls to external
* code inside this class, e.g. with
* {@link org.apache.flink.runtime.io.network.partition.consumer.RemoteInputChannel#bufferQueue}
* via the {@link #registeredListeners} callback.
*/
private final ArrayDeque<MemorySegment> availableMemorySegments = new ArrayDeque<MemorySegment>();
/**
* Buffer availability listeners, which need to be notified when a Buffer becomes available.
* Listeners can only be registered at a time/state where no Buffer instance was available.
*/
private final ArrayDeque<BufferListener> registeredListeners = new ArrayDeque<>();
/** Maximum number of network buffers to allocate. */
private final int maxNumberOfMemorySegments;
/** The current size of this pool. */
private int currentPoolSize;
/**
* Number of all memory segments, which have been requested from the network buffer pool and are
* somehow referenced through this pool (e.g. wrapped in Buffer instances or as available segments).
*/
private int numberOfRequestedMemorySegments;
private boolean isDestroyed;
private final Optional<BufferPoolOwner> owner;
/**
* Local buffer pool based on the given <tt>networkBufferPool</tt> with a minimal number of
* network buffers being available.
*
* @param networkBufferPool
* global network buffer pool to get buffers from
* @param numberOfRequiredMemorySegments
* minimum number of network buffers
*/
LocalBufferPool(NetworkBufferPool networkBufferPool, int numberOfRequiredMemorySegments) {
this(networkBufferPool, numberOfRequiredMemorySegments, Integer.MAX_VALUE, Optional.empty());
}
/**
* Local buffer pool based on the given <tt>networkBufferPool</tt> with a minimal and maximal
* number of network buffers being available.
*
* @param networkBufferPool
* global network buffer pool to get buffers from
* @param numberOfRequiredMemorySegments
* minimum number of network buffers
* @param maxNumberOfMemorySegments
* maximum number of network buffers to allocate
*/
LocalBufferPool(NetworkBufferPool networkBufferPool, int numberOfRequiredMemorySegments,
int maxNumberOfMemorySegments) {
this(networkBufferPool, numberOfRequiredMemorySegments, maxNumberOfMemorySegments, Optional.empty());
}
/**
* Local buffer pool based on the given <tt>networkBufferPool</tt> and <tt>bufferPoolOwner</tt>
* with a minimal and maximal number of network buffers being available.
*
* @param networkBufferPool
* global network buffer pool to get buffers from
* @param numberOfRequiredMemorySegments
* minimum number of network buffers
* @param maxNumberOfMemorySegments
* maximum number of network buffers to allocate
* @param owner
* the optional owner of this buffer pool to release memory when needed
*/
LocalBufferPool(
NetworkBufferPool networkBufferPool,
int numberOfRequiredMemorySegments,
int maxNumberOfMemorySegments,
Optional<BufferPoolOwner> owner) {
checkArgument(maxNumberOfMemorySegments >= numberOfRequiredMemorySegments,
"Maximum number of memory segments (%s) should not be smaller than minimum (%s).",
maxNumberOfMemorySegments, numberOfRequiredMemorySegments);
checkArgument(maxNumberOfMemorySegments > 0,
"Maximum number of memory segments (%s) should be larger than 0.",
maxNumberOfMemorySegments);
LOG.debug("Using a local buffer pool with {}-{} buffers",
numberOfRequiredMemorySegments, maxNumberOfMemorySegments);
this.networkBufferPool = networkBufferPool;
this.numberOfRequiredMemorySegments = numberOfRequiredMemorySegments;
this.currentPoolSize = numberOfRequiredMemorySegments;
this.maxNumberOfMemorySegments = maxNumberOfMemorySegments;
this.owner = owner;
}
//......
@Override
public void recycle(MemorySegment segment) {
BufferListener listener;
NotificationResult notificationResult = NotificationResult.BUFFER_NOT_USED;
while (!notificationResult.isBufferUsed()) {
synchronized (availableMemorySegments) {
if (isDestroyed || numberOfRequestedMemorySegments > currentPoolSize) {
returnMemorySegment(segment);
return;
} else {
listener = registeredListeners.poll();
if (listener == null) {
availableMemorySegments.add(segment);
availableMemorySegments.notify();
return;
}
}
}
notificationResult = fireBufferAvailableNotification(listener, segment);
}
}
private MemorySegment requestMemorySegment(boolean isBlocking) throws InterruptedException, IOException {
synchronized (availableMemorySegments) {
returnExcessMemorySegments();
boolean askToRecycle = owner.isPresent();
// fill availableMemorySegments with at least one element, wait if required
while (availableMemorySegments.isEmpty()) {
if (isDestroyed) {
throw new IllegalStateException("Buffer pool is destroyed.");
}
if (numberOfRequestedMemorySegments < currentPoolSize) {
final MemorySegment segment = networkBufferPool.requestMemorySegment();
if (segment != null) {
numberOfRequestedMemorySegments++;
return segment;
}
}
if (askToRecycle) {
owner.get().releaseMemory(1);
}
if (isBlocking) {
availableMemorySegments.wait(2000);
}
else {
return null;
}
}
return availableMemorySegments.poll();
}
}
//......
}- LocalBufferPool的构造器要求传入NetworkBufferPool，而其内部的requestMemorySegment方法，在availableMemorySegments为空且numberOfRequestedMemorySegments < currentPoolSize时，会调用networkBufferPool.requestMemorySegment()来申请MemorySegment；而recycle方法在numberOfRequestedMemorySegments > currentPoolSize时会归还MemorySegment到networkBufferPool，否则在BufferListener为null的时候会归还到availableMemorySegments
小结
- BufferPoolFactory定义了createBufferPool、destroyBufferPool方法；其中createBufferPool支持numRequiredBuffers、maxUsedBuffers、owner参数；NetworkBufferPool实现了BufferPoolFactory接口，它的构造器接收numberOfSegmentsToAllocate、segmentSize两个参数；构造器里头根据numberOfSegmentsToAllocate创建了availableMemorySegments这个ArrayBlockingQueue，然后通过MemorySegmentFactory.allocateUnpooledOffHeapMemory挨个创建MemorySegment添加到availableMemorySegments
- NetworkBufferPool的createBufferPool方法创建的是LocalBufferPool(
传递了自身NetworkBufferPool实例进去)，然后添加到allBufferPools这个set中，同时增加numTotalRequiredBuffers；destroyBufferPool方法则从allBufferPools移除该bufferPool，同时减少numTotalRequiredBuffers；createBufferPool方法及destroyBufferPool方法会调用到redistributeBuffers方法，通过调用LocalBufferPool的setNumBuffers方法来调整buffer pool的大小 - LocalBufferPool的构造器要求传入NetworkBufferPool，而其内部的requestMemorySegment方法，在availableMemorySegments为空且numberOfRequestedMemorySegments < currentPoolSize时，会调用networkBufferPool.requestMemorySegment()来申请MemorySegment；而recycle方法在numberOfRequestedMemorySegments > currentPoolSize时会归还MemorySegment到networkBufferPool，否则在BufferListener为null的时候会归还到availableMemorySegments