Java tutorial
/* * 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.flink.runtime.io.network.netty; import io.netty.buffer.ByteBuf; import io.netty.buffer.ByteBufAllocator; import io.netty.buffer.CompositeByteBuf; import io.netty.buffer.PooledByteBufAllocator; import io.netty.util.internal.PlatformDependent; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import scala.Option; import java.lang.reflect.Field; import static com.google.common.base.Preconditions.checkArgument; /** * Wrapper around Netty's {@link PooledByteBufAllocator} with strict control * over the number of created arenas. */ public class NettyBufferPool implements ByteBufAllocator { private static final Logger LOG = LoggerFactory.getLogger(NettyBufferPool.class); /** The wrapped buffer allocator. */ private final PooledByteBufAllocator alloc; /** PoolArena<ByteBuffer>[] via Reflection. */ private final Object[] directArenas; /** Configured number of arenas. */ private final int numberOfArenas; /** Configured chunk size for the arenas. */ private final int chunkSize; /** * Creates Netty's buffer pool with the specified number of direct arenas. * * @param numberOfArenas Number of arenas (recommended: 2 * number of task * slots) */ NettyBufferPool(int numberOfArenas) { checkArgument(numberOfArenas >= 1, "Number of arenas"); this.numberOfArenas = numberOfArenas; if (!PlatformDependent.hasUnsafe()) { LOG.warn("Using direct buffers, but sun.misc.Unsafe not available."); } // We strictly prefer direct buffers and disallow heap allocations. boolean preferDirect = true; // Arenas allocate chunks of pageSize << maxOrder bytes. With these // defaults, this results in chunks of 16 MB. int pageSize = 8192; int maxOrder = 11; this.chunkSize = pageSize << maxOrder; // Number of direct arenas. Each arena allocates a chunk of 16 MB, i.e. // we allocate numDirectArenas * 16 MB of direct memory. This can grow // to multiple chunks per arena during runtime, but this should only // happen with a large amount of connections per task manager. We // control the memory allocations with low/high watermarks when writing // to the TCP channels. Chunks are allocated lazily. int numDirectArenas = numberOfArenas; // No heap arenas, please. int numHeapArenas = 0; this.alloc = new PooledByteBufAllocator(preferDirect, numHeapArenas, numDirectArenas, pageSize, maxOrder); Object[] allocDirectArenas = null; try { Field directArenasField = alloc.getClass().getDeclaredField("directArenas"); directArenasField.setAccessible(true); allocDirectArenas = (Object[]) directArenasField.get(alloc); } catch (Exception ignored) { LOG.warn("Memory statistics not available"); } finally { this.directArenas = allocDirectArenas; } } /** * Returns the number of arenas. * * @return Number of arenas. */ int getNumberOfArenas() { return numberOfArenas; } /** * Returns the chunk size. * * @return Chunk size. */ int getChunkSize() { return chunkSize; } // ------------------------------------------------------------------------ // Direct pool arena stats via Reflection. This is not safe when upgrading // Netty versions, but we are currently bound to the version we have (see // commit d92e422). In newer Netty versions these statistics are exposed. // ------------------------------------------------------------------------ /** * Returns the number of currently allocated bytes. * * <p>The stats are gathered via Reflection and are mostly relevant for * debugging purposes. * * @return Number of currently allocated bytes. * * @throws NoSuchFieldException Error getting the statistics (should not * happen when the Netty version stays the * same). * @throws IllegalAccessException Error getting the statistics (should not * happen when the Netty version stays the * same). */ public Option<Long> getNumberOfAllocatedBytes() throws NoSuchFieldException, IllegalAccessException { if (directArenas != null) { long numChunks = 0; for (Object arena : directArenas) { numChunks += getNumberOfAllocatedChunks(arena, "qInit"); numChunks += getNumberOfAllocatedChunks(arena, "q000"); numChunks += getNumberOfAllocatedChunks(arena, "q025"); numChunks += getNumberOfAllocatedChunks(arena, "q050"); numChunks += getNumberOfAllocatedChunks(arena, "q075"); numChunks += getNumberOfAllocatedChunks(arena, "q100"); } long allocatedBytes = numChunks * chunkSize; return Option.apply(allocatedBytes); } else { return Option.empty(); } } /** * Returns the number of allocated bytes of the given arena and chunk list. * * @param arena Arena to gather statistics about. * @param chunkListFieldName Chunk list to check. * * @return Number of total allocated bytes by this arena. * * @throws NoSuchFieldException Error getting the statistics (should not * happen when the Netty version stays the * same). * @throws IllegalAccessException Error getting the statistics (should not * happen when the Netty version stays the * same). */ private long getNumberOfAllocatedChunks(Object arena, String chunkListFieldName) throws NoSuchFieldException, IllegalAccessException { // Each PoolArena<ByteBuffer> stores its allocated PoolChunk<ByteBuffer> // instances grouped by usage (field qInit, q000, q025, etc.) in // PoolChunkList<ByteBuffer> lists. Each list has zero or more // PoolChunk<ByteBuffer> instances. // Chunk list of arena Field chunkListField = arena.getClass().getSuperclass().getDeclaredField(chunkListFieldName); chunkListField.setAccessible(true); Object chunkList = chunkListField.get(arena); // Count the chunks in the list Field headChunkField = chunkList.getClass().getDeclaredField("head"); headChunkField.setAccessible(true); Object headChunk = headChunkField.get(chunkList); if (headChunk == null) { return 0; } else { int numChunks = 0; Object current = headChunk; while (current != null) { Field nextChunkField = headChunk.getClass().getDeclaredField("next"); nextChunkField.setAccessible(true); current = nextChunkField.get(current); numChunks++; } return numChunks; } } // ------------------------------------------------------------------------ // Delegate calls to the allocated and prohibit heap buffer allocations // ------------------------------------------------------------------------ @Override public ByteBuf buffer() { return alloc.buffer(); } @Override public ByteBuf buffer(int initialCapacity) { return alloc.buffer(initialCapacity); } @Override public ByteBuf buffer(int initialCapacity, int maxCapacity) { return alloc.buffer(initialCapacity, maxCapacity); } @Override public ByteBuf ioBuffer() { return alloc.ioBuffer(); } @Override public ByteBuf ioBuffer(int initialCapacity) { return alloc.ioBuffer(initialCapacity); } @Override public ByteBuf ioBuffer(int initialCapacity, int maxCapacity) { return alloc.ioBuffer(initialCapacity, maxCapacity); } @Override public ByteBuf heapBuffer() { throw new UnsupportedOperationException("Heap buffer"); } @Override public ByteBuf heapBuffer(int initialCapacity) { throw new UnsupportedOperationException("Heap buffer"); } @Override public ByteBuf heapBuffer(int initialCapacity, int maxCapacity) { throw new UnsupportedOperationException("Heap buffer"); } @Override public ByteBuf directBuffer() { return alloc.directBuffer(); } @Override public ByteBuf directBuffer(int initialCapacity) { return alloc.directBuffer(initialCapacity); } @Override public ByteBuf directBuffer(int initialCapacity, int maxCapacity) { return alloc.directBuffer(initialCapacity, maxCapacity); } @Override public CompositeByteBuf compositeBuffer() { return alloc.compositeBuffer(); } @Override public CompositeByteBuf compositeBuffer(int maxNumComponents) { return alloc.compositeBuffer(maxNumComponents); } @Override public CompositeByteBuf compositeHeapBuffer() { throw new UnsupportedOperationException("Heap buffer"); } @Override public CompositeByteBuf compositeHeapBuffer(int maxNumComponents) { throw new UnsupportedOperationException("Heap buffer"); } @Override public CompositeByteBuf compositeDirectBuffer() { return alloc.compositeDirectBuffer(); } @Override public CompositeByteBuf compositeDirectBuffer(int maxNumComponents) { return alloc.compositeDirectBuffer(maxNumComponents); } @Override public boolean isDirectBufferPooled() { return alloc.isDirectBufferPooled(); } }