001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.io;
019
020import java.nio.ByteBuffer;
021import java.util.ArrayList;
022import java.util.List;
023import java.util.Queue;
024import java.util.concurrent.ConcurrentLinkedQueue;
025import java.util.concurrent.atomic.AtomicInteger;
026import java.util.concurrent.atomic.LongAdder;
027import org.apache.hadoop.conf.Configuration;
028import org.apache.hadoop.hbase.HConstants;
029import org.apache.hadoop.hbase.nio.ByteBuff;
030import org.apache.hadoop.hbase.nio.SingleByteBuff;
031import org.apache.hadoop.hbase.util.ReflectionUtils;
032import org.apache.hadoop.hbase.util.UnsafeAccess;
033import org.apache.yetus.audience.InterfaceAudience;
034import org.slf4j.Logger;
035import org.slf4j.LoggerFactory;
036
037import org.apache.hbase.thirdparty.com.google.common.collect.Sets;
038
039/**
040 * ByteBuffAllocator is used for allocating/freeing the ByteBuffers from/to NIO ByteBuffer pool, and
041 * it provide high-level interfaces for upstream. when allocating desired memory size, it will
042 * return {@link ByteBuff}, if we are sure that those ByteBuffers have reached the end of life
043 * cycle, we must do the {@link ByteBuff#release()} to return back the buffers to the pool,
044 * otherwise ByteBuffers leak will happen, and the NIO ByteBuffer pool may be exhausted. there's
045 * possible that the desired memory size is large than ByteBufferPool has, we'll downgrade to
046 * allocate ByteBuffers from heap which meaning the GC pressure may increase again. Of course, an
047 * better way is increasing the ByteBufferPool size if we detected this case. <br/>
048 * <br/>
049 * On the other hand, for better memory utilization, we have set an lower bound named
050 * minSizeForReservoirUse in this allocator, and if the desired size is less than
051 * minSizeForReservoirUse, the allocator will just allocate the ByteBuffer from heap and let the JVM
052 * free its memory, because it's too wasting to allocate a single fixed-size ByteBuffer for some
053 * small objects. <br/>
054 * <br/>
055 * We recommend to use this class to allocate/free {@link ByteBuff} in the RPC layer or the entire
056 * read/write path, because it hide the details of memory management and its APIs are more friendly
057 * to the upper layer.
058 */
059@InterfaceAudience.Private
060public class ByteBuffAllocator {
061
062  private static final Logger LOG = LoggerFactory.getLogger(ByteBuffAllocator.class);
063
064  // The on-heap allocator is mostly used for testing, but also some non-test usage, such as
065  // scanning snapshot, we won't have an RpcServer to initialize the allocator, so just use the
066  // default heap allocator, it will just allocate ByteBuffers from heap but wrapped by an ByteBuff.
067  public static final ByteBuffAllocator HEAP = ByteBuffAllocator.createOnHeap();
068
069  public static final String ALLOCATOR_POOL_ENABLED_KEY = "hbase.server.allocator.pool.enabled";
070
071  public static final String MAX_BUFFER_COUNT_KEY = "hbase.server.allocator.max.buffer.count";
072
073  public static final String BUFFER_SIZE_KEY = "hbase.server.allocator.buffer.size";
074
075  public static final String MIN_ALLOCATE_SIZE_KEY = "hbase.server.allocator.minimal.allocate.size";
076
077  /**
078   * Set an alternate bytebuffallocator by setting this config, e.g. we can config
079   * {@link DeallocateRewriteByteBuffAllocator} to find out prematurely release issues
080   */
081  public static final String BYTEBUFF_ALLOCATOR_CLASS = "hbase.bytebuff.allocator.class";
082
083  /**
084   * @deprecated since 2.3.0 and will be removed in 4.0.0. Use
085   *             {@link ByteBuffAllocator#ALLOCATOR_POOL_ENABLED_KEY} instead.
086   */
087  @Deprecated
088  public static final String DEPRECATED_ALLOCATOR_POOL_ENABLED_KEY =
089    "hbase.ipc.server.reservoir.enabled";
090
091  /**
092   * @deprecated since 2.3.0 and will be removed in 4.0.0. Use
093   *             {@link ByteBuffAllocator#MAX_BUFFER_COUNT_KEY} instead.
094   */
095  @Deprecated
096  static final String DEPRECATED_MAX_BUFFER_COUNT_KEY = "hbase.ipc.server.reservoir.initial.max";
097
098  /**
099   * @deprecated since 2.3.0 and will be removed in 4.0.0. Use
100   *             {@link ByteBuffAllocator#BUFFER_SIZE_KEY} instead.
101   */
102  @Deprecated
103  static final String DEPRECATED_BUFFER_SIZE_KEY = "hbase.ipc.server.reservoir.initial.buffer.size";
104
105  /**
106   * There're some reasons why better to choose 65KB(rather than 64KB) as the default buffer size:
107   * <p>
108   * 1. Almost all of the data blocks have the block size: 64KB + delta, whose delta is very small,
109   * depends on the size of lastKeyValue. If we set buffer.size=64KB, then each block will be
110   * allocated as a MultiByteBuff: one 64KB DirectByteBuffer and delta bytes HeapByteBuffer, the
111   * HeapByteBuffer will increase the GC pressure. Ideally, we should let the data block to be
112   * allocated as a SingleByteBuff, it has simpler data structure, faster access speed, less heap
113   * usage.
114   * <p>
115   * 2. Since the blocks are MultiByteBuff when using buffer.size=64KB, so we have to calculate the
116   * checksum by an temp heap copying (see HBASE-21917), while if it's a SingleByteBuff, we can
117   * speed the checksum by calling the hadoop' checksum in native lib, which is more faster.
118   * <p>
119   * For performance comparison, please see HBASE-22483.
120   */
121  public static final int DEFAULT_BUFFER_SIZE = 65 * 1024;
122
123  public static final Recycler NONE = () -> {
124  };
125
126  public interface Recycler {
127    void free();
128  }
129
130  protected final boolean reservoirEnabled;
131  protected final int bufSize;
132  private final int maxBufCount;
133  private final AtomicInteger usedBufCount = new AtomicInteger(0);
134
135  private boolean maxPoolSizeInfoLevelLogged = false;
136
137  // If the desired size is at least this size, it'll allocated from ByteBufferPool, otherwise it'll
138  // allocated from heap for better utilization. We make this to be 1/6th of the pool buffer size.
139  private final int minSizeForReservoirUse;
140
141  private final Queue<ByteBuffer> buffers = new ConcurrentLinkedQueue<>();
142
143  // Metrics to track the pool allocation bytes and heap allocation bytes. If heap allocation
144  // bytes is increasing so much, then we may need to increase the max.buffer.count .
145  private final LongAdder poolAllocationBytes = new LongAdder();
146  private final LongAdder heapAllocationBytes = new LongAdder();
147  private long lastPoolAllocationBytes = 0;
148  private long lastHeapAllocationBytes = 0;
149
150  /**
151   * Initialize an {@link ByteBuffAllocator} which will try to allocate ByteBuffers from off-heap if
152   * reservoir is enabled and the reservoir has enough buffers, otherwise the allocator will just
153   * allocate the insufficient buffers from on-heap to meet the requirement.
154   * @param conf             which get the arguments to initialize the allocator.
155   * @param reservoirEnabled indicate whether the reservoir is enabled or disabled. NOTICE: if
156   *                         reservoir is enabled, then we will use the pool allocator to allocate
157   *                         off-heap ByteBuffers and use the HEAP allocator to allocate heap
158   *                         ByteBuffers. Otherwise if reservoir is disabled then all allocations
159   *                         will happen in HEAP instance.
160   * @return ByteBuffAllocator to manage the byte buffers.
161   */
162  public static ByteBuffAllocator create(Configuration conf, boolean reservoirEnabled) {
163    int poolBufSize = conf.getInt(BUFFER_SIZE_KEY, DEFAULT_BUFFER_SIZE);
164    if (reservoirEnabled) {
165      // The max number of buffers to be pooled in the ByteBufferPool. The default value been
166      // selected based on the #handlers configured. When it is read request, 2 MB is the max size
167      // at which we will send back one RPC request. Means max we need 2 MB for creating the
168      // response cell block. (Well it might be much lesser than this because in 2 MB size calc, we
169      // include the heap size overhead of each cells also.) Considering 2 MB, we will need
170      // (2 * 1024 * 1024) / poolBufSize buffers to make the response cell block. Pool buffer size
171      // is by default 64 KB.
172      // In case of read request, at the end of the handler process, we will make the response
173      // cellblock and add the Call to connection's response Q and a single Responder thread takes
174      // connections and responses from that one by one and do the socket write. So there is chances
175      // that by the time a handler originated response is actually done writing to socket and so
176      // released the BBs it used, the handler might have processed one more read req. On an avg 2x
177      // we consider and consider that also for the max buffers to pool
178      int bufsForTwoMB = (2 * 1024 * 1024) / poolBufSize;
179      int maxBuffCount =
180        conf.getInt(MAX_BUFFER_COUNT_KEY, conf.getInt(HConstants.REGION_SERVER_HANDLER_COUNT,
181          HConstants.DEFAULT_REGION_SERVER_HANDLER_COUNT) * bufsForTwoMB * 2);
182      int minSizeForReservoirUse = conf.getInt(MIN_ALLOCATE_SIZE_KEY, poolBufSize / 6);
183      Class<?> clazz = conf.getClass(BYTEBUFF_ALLOCATOR_CLASS, ByteBuffAllocator.class);
184      return (ByteBuffAllocator) ReflectionUtils.newInstance(clazz, true, maxBuffCount, poolBufSize,
185        minSizeForReservoirUse);
186    } else {
187      return HEAP;
188    }
189  }
190
191  /**
192   * Initialize an {@link ByteBuffAllocator} which only allocate ByteBuffer from on-heap, it's
193   * designed for testing purpose or disabled reservoir case.
194   * @return allocator to allocate on-heap ByteBuffer.
195   */
196  private static ByteBuffAllocator createOnHeap() {
197    return new ByteBuffAllocator(false, 0, DEFAULT_BUFFER_SIZE, Integer.MAX_VALUE);
198  }
199
200  protected ByteBuffAllocator(boolean reservoirEnabled, int maxBufCount, int bufSize,
201    int minSizeForReservoirUse) {
202    this.reservoirEnabled = reservoirEnabled;
203    this.maxBufCount = maxBufCount;
204    this.bufSize = bufSize;
205    this.minSizeForReservoirUse = minSizeForReservoirUse;
206  }
207
208  public boolean isReservoirEnabled() {
209    return reservoirEnabled;
210  }
211
212  public long getHeapAllocationBytes() {
213    return heapAllocationBytes.sum();
214  }
215
216  public long getPoolAllocationBytes() {
217    return poolAllocationBytes.sum();
218  }
219
220  public int getBufferSize() {
221    return this.bufSize;
222  }
223
224  public int getUsedBufferCount() {
225    return this.usedBufCount.intValue();
226  }
227
228  /**
229   * The {@link ConcurrentLinkedQueue#size()} is O(N) complexity and time-consuming, so DO NOT use
230   * the method except in UT.
231   */
232  public int getFreeBufferCount() {
233    return this.buffers.size();
234  }
235
236  public int getTotalBufferCount() {
237    return maxBufCount;
238  }
239
240  public static long getHeapAllocationBytes(ByteBuffAllocator... allocators) {
241    long heapAllocBytes = 0;
242    for (ByteBuffAllocator alloc : Sets.newHashSet(allocators)) {
243      heapAllocBytes += alloc.getHeapAllocationBytes();
244    }
245    return heapAllocBytes;
246  }
247
248  public static double getHeapAllocationRatio(ByteBuffAllocator... allocators) {
249    double heapDelta = 0.0, poolDelta = 0.0;
250    long heapAllocBytes, poolAllocBytes;
251    // If disabled the pool allocator, then we use the global HEAP allocator. otherwise we use
252    // the pool allocator to allocate offheap ByteBuffers and use the HEAP to allocate heap
253    // ByteBuffers. So here we use a HashSet to remove the duplicated allocator object in disable
254    // case.
255    for (ByteBuffAllocator alloc : Sets.newHashSet(allocators)) {
256      heapAllocBytes = alloc.heapAllocationBytes.sum();
257      poolAllocBytes = alloc.poolAllocationBytes.sum();
258      heapDelta += (heapAllocBytes - alloc.lastHeapAllocationBytes);
259      poolDelta += (poolAllocBytes - alloc.lastPoolAllocationBytes);
260      alloc.lastHeapAllocationBytes = heapAllocBytes;
261      alloc.lastPoolAllocationBytes = poolAllocBytes;
262    }
263    // Calculate the heap allocation ratio.
264    if (Math.abs(heapDelta + poolDelta) < 1e-3) {
265      return 0.0;
266    }
267    return heapDelta / (heapDelta + poolDelta);
268  }
269
270  /**
271   * Allocate an buffer with buffer size from ByteBuffAllocator, Note to call the
272   * {@link ByteBuff#release()} if no need any more, otherwise the memory leak happen in NIO
273   * ByteBuffer pool.
274   * @return an ByteBuff with the buffer size.
275   */
276  public SingleByteBuff allocateOneBuffer() {
277    if (isReservoirEnabled()) {
278      ByteBuffer bb = getBuffer();
279      if (bb != null) {
280        return new SingleByteBuff(() -> putbackBuffer(bb), bb);
281      }
282    }
283    // Allocated from heap, let the JVM free its memory.
284    return (SingleByteBuff) ByteBuff.wrap(allocateOnHeap(bufSize));
285  }
286
287  private ByteBuffer allocateOnHeap(int size) {
288    heapAllocationBytes.add(size);
289    return ByteBuffer.allocate(size);
290  }
291
292  /**
293   * Allocate size bytes from the ByteBufAllocator, Note to call the {@link ByteBuff#release()} if
294   * no need any more, otherwise the memory leak happen in NIO ByteBuffer pool.
295   * @param size to allocate
296   * @return an ByteBuff with the desired size.
297   */
298  public ByteBuff allocate(int size) {
299    if (size < 0) {
300      throw new IllegalArgumentException("size to allocate should >=0");
301    }
302    // If disabled the reservoir, just allocate it from on-heap.
303    if (!isReservoirEnabled() || size == 0) {
304      return ByteBuff.wrap(allocateOnHeap(size));
305    }
306    int reminder = size % bufSize;
307    int len = size / bufSize + (reminder > 0 ? 1 : 0);
308    List<ByteBuffer> bbs = new ArrayList<>(len);
309    // Allocate from ByteBufferPool until the remaining is less than minSizeForReservoirUse or
310    // reservoir is exhausted.
311    int remain = size;
312    while (remain >= minSizeForReservoirUse) {
313      ByteBuffer bb = this.getBuffer();
314      if (bb == null) {
315        break;
316      }
317      bbs.add(bb);
318      remain -= bufSize;
319    }
320    int lenFromReservoir = bbs.size();
321    if (remain > 0) {
322      // If the last ByteBuffer is too small or the reservoir can not provide more ByteBuffers, we
323      // just allocate the ByteBuffer from on-heap.
324      bbs.add(allocateOnHeap(remain));
325    }
326
327    ByteBuff bb;
328    // we only need a recycler if we successfully pulled from the pool
329    // this matters for determining whether to add leak detection in RefCnt
330    if (lenFromReservoir == 0) {
331      bb = ByteBuff.wrap(bbs);
332    } else {
333      bb = ByteBuff.wrap(bbs, () -> {
334        for (int i = 0; i < lenFromReservoir; i++) {
335          this.putbackBuffer(bbs.get(i));
336        }
337      });
338    }
339
340    bb.limit(size);
341    return bb;
342  }
343
344  /**
345   * Free all direct buffers if allocated, mainly used for testing.
346   */
347  public void clean() {
348    while (!buffers.isEmpty()) {
349      ByteBuffer b = buffers.poll();
350      if (b.isDirect()) {
351        UnsafeAccess.freeDirectBuffer(b);
352      }
353    }
354    this.usedBufCount.set(0);
355    this.maxPoolSizeInfoLevelLogged = false;
356    this.poolAllocationBytes.reset();
357    this.heapAllocationBytes.reset();
358    this.lastPoolAllocationBytes = 0;
359    this.lastHeapAllocationBytes = 0;
360  }
361
362  /**
363   * @return One free DirectByteBuffer from the pool. If no free ByteBuffer and we have not reached
364   *         the maximum pool size, it will create a new one and return. In case of max pool size
365   *         also reached, will return null. When pool returned a ByteBuffer, make sure to return it
366   *         back to pool after use.
367   */
368  private ByteBuffer getBuffer() {
369    ByteBuffer bb = buffers.poll();
370    if (bb != null) {
371      // To reset the limit to capacity and position to 0, must clear here.
372      bb.clear();
373      poolAllocationBytes.add(bufSize);
374      return bb;
375    }
376    while (true) {
377      int c = this.usedBufCount.intValue();
378      if (c >= this.maxBufCount) {
379        if (!maxPoolSizeInfoLevelLogged) {
380          LOG.info("Pool already reached its max capacity : {} and no free buffers now. Consider "
381            + "increasing the value for '{}' ?", maxBufCount, MAX_BUFFER_COUNT_KEY);
382          maxPoolSizeInfoLevelLogged = true;
383        }
384        return null;
385      }
386      if (!this.usedBufCount.compareAndSet(c, c + 1)) {
387        continue;
388      }
389      poolAllocationBytes.add(bufSize);
390      return ByteBuffer.allocateDirect(bufSize);
391    }
392  }
393
394  /**
395   * Return back a ByteBuffer after its use. Don't read/write the ByteBuffer after the returning.
396   * @param buf ByteBuffer to return.
397   */
398  protected void putbackBuffer(ByteBuffer buf) {
399    if (buf.capacity() != bufSize || (reservoirEnabled ^ buf.isDirect())) {
400      LOG.warn("Trying to put a buffer, not created by this pool! Will be just ignored");
401      return;
402    }
403    buffers.offer(buf);
404  }
405}