content: /*
   * 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.celeborn.plugin.flink.tiered;
  
  import static org.apache.flink.util.Preconditions.checkNotNull;
  
  import java.util.LinkedList;
  import java.util.Queue;
  
  import javax.annotation.concurrent.GuardedBy;
  
  import org.apache.flink.core.memory.MemorySegment;
  import org.apache.flink.runtime.io.network.buffer.Buffer;
  import org.apache.flink.runtime.io.network.buffer.BufferListener;
  import org.apache.flink.runtime.io.network.buffer.BufferPool;
  import org.apache.flink.runtime.io.network.buffer.BufferRecycler;
  import org.apache.flink.runtime.io.network.partition.hybrid.tiered.storage.TieredStorageMemoryManager;
  import org.apache.flink.util.ExceptionUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  public class CelebornChannelBufferManager implements BufferListener, BufferRecycler {
  
    private static Logger logger = LoggerFactory.getLogger(CelebornChannelBufferManager.class);
  
    /** The queue to hold the available buffer when the reader is waiting for buffers. */
    private final Queue<Buffer> bufferQueue;
  
    private final TieredStorageMemoryManager memoryManager;
  
    private final CelebornChannelBufferReader bufferReader;
  
    /** The tag indicates whether it is waiting for buffers from the buffer pool. */
    @GuardedBy("bufferQueue")
    private boolean isWaitingForFloatingBuffers;
  
    /** The total number of required buffers for the respective input channel. */
    @GuardedBy("bufferQueue")
    private int numRequiredBuffers = 0;
  
    public CelebornChannelBufferManager(
        TieredStorageMemoryManager memoryManager, CelebornChannelBufferReader bufferReader) {
      this.memoryManager = checkNotNull(memoryManager);
      this.bufferReader = checkNotNull(bufferReader);
      this.bufferQueue = new LinkedList<>();
    }
  
    @Override
    public boolean notifyBufferAvailable(Buffer buffer) {
      if (bufferReader.isClosed()) {
        return false;
      }
      int numBuffers = 0;
      boolean isBufferUsed = false;
      try {
        synchronized (bufferQueue) {
          if (!isWaitingForFloatingBuffers) {
            logger.warn("This channel should be waiting for floating buffers.");
            return false;
          }
          isWaitingForFloatingBuffers = false;
          if (bufferReader.isClosed() || bufferQueue.size() >= numRequiredBuffers) {
            return false;
          }
          bufferQueue.add(buffer);
          isBufferUsed = true;
          numBuffers = 1 + tryRequestBuffers();
          decreaseRequiredCredits(numBuffers);
        }
        bufferReader.notifyAvailableCredits(numBuffers);
      } catch (Throwable t) {
        bufferReader.errorReceived(t.getLocalizedMessage());
      }
      return isBufferUsed;
    }
  
    public void decreaseRequiredCredits(int numCredits) {
      synchronized (bufferQueue) {
        numRequiredBuffers -= numCredits;
      }
    }
  
    @Override
    public void notifyBufferDestroyed() {
      // noop
    }
  
    @Override
    public void recycle(MemorySegment segment) {
      try {
        memoryManager.getBufferPool().recycle(segment);
      } catch (Throwable t) {
        ExceptionUtils.rethrow(t);
      }
    }
  
    Buffer requestBuffer() {
      synchronized (bufferQueue) {
        return bufferQueue.poll();
      }
    }
  
    int requestBuffers(int numRequired) {
      int numRequestedBuffers = 0;
      synchronized (bufferQueue) {
        if (bufferReader.isClosed()) {
          return numRequestedBuffers;
        }
        numRequiredBuffers += numRequired;
        numRequestedBuffers = tryRequestBuffers();
      }
      return numRequestedBuffers;
    }
  
    int tryRequestBuffersIfNeeded() {
      synchronized (bufferQueue) {
        if (numRequiredBuffers > 0 && !isWaitingForFloatingBuffers && bufferQueue.isEmpty()) {
          return tryRequestBuffers();
        }
        return 0;
      }
    }
  
    void close() {
      synchronized (bufferQueue) {
        for (Buffer buffer : bufferQueue) {
          buffer.recycleBuffer();
        }
        bufferQueue.clear();
      }
    }
  
    @GuardedBy("bufferQueue")
    private int tryRequestBuffers() {
      assert Thread.holdsLock(bufferQueue);
      int numRequestedBuffers = 0;
      while (bufferQueue.size() < numRequiredBuffers && !isWaitingForFloatingBuffers) {
        BufferPool bufferPool = memoryManager.getBufferPool();
        Buffer buffer = bufferPool.requestBuffer();
        if (buffer != null) {
          bufferQueue.add(buffer);
          numRequestedBuffers++;
        } else if (bufferPool.addBufferListener(this)) {
          isWaitingForFloatingBuffers = true;
          break;
        }
      }
      return numRequestedBuffers;
    }
  }
  