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.spark.network.server;
  
  import java.util.Iterator;
  import java.util.Map;
  import java.util.Random;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.atomic.AtomicLong;
  
  import com.google.common.base.Preconditions;
  import io.netty.channel.Channel;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import org.apache.spark.network.buffer.ManagedBuffer;
  import org.apache.spark.network.client.TransportClient;
  
  /**
   * StreamManager which allows registration of an Iterator&lt;ManagedBuffer&gt;, which are
   * individually fetched as chunks by the client. Each registered buffer is one chunk.
   */
  public class OneForOneStreamManager extends StreamManager {
    private static final Logger logger = LoggerFactory.getLogger(OneForOneStreamManager.class);
  
    private final AtomicLong nextStreamId;
    private final ConcurrentHashMap<Long, StreamState> streams;
  
    /** State of a single stream. */
    private static class StreamState {
      final String appId;
      final Iterator<ManagedBuffer> buffers;
  
      // The channel associated to the stream
      Channel associatedChannel = null;
  
      // Used to keep track of the index of the buffer that the user has retrieved, just to ensure
      // that the caller only requests each chunk one at a time, in order.
      int curChunk = 0;
  
      StreamState(String appId, Iterator<ManagedBuffer> buffers) {
        this.appId = appId;
        this.buffers = Preconditions.checkNotNull(buffers);
      }
    }
  
    public OneForOneStreamManager() {
      // For debugging purposes, start with a random stream id to help identifying different streams.
      // This does not need to be globally unique, only unique to this class.
      nextStreamId = new AtomicLong((long) new Random().nextInt(Integer.MAX_VALUE) * 1000);
      streams = new ConcurrentHashMap<>();
    }
  
    @Override
    public void registerChannel(Channel channel, long streamId) {
      if (streams.containsKey(streamId)) {
        streams.get(streamId).associatedChannel = channel;
      }
    }
  
    @Override
    public ManagedBuffer getChunk(long streamId, int chunkIndex) {
      StreamState state = streams.get(streamId);
      if (chunkIndex != state.curChunk) {
        throw new IllegalStateException(String.format(
          "Received out-of-order chunk index %s (expected %s)", chunkIndex, state.curChunk));
      } else if (!state.buffers.hasNext()) {
        throw new IllegalStateException(String.format(
          "Requested chunk index beyond end %s", chunkIndex));
      }
      state.curChunk += 1;
      ManagedBuffer nextChunk = state.buffers.next();
  
      if (!state.buffers.hasNext()) {
        logger.trace("Removing stream id {}", streamId);
        streams.remove(streamId);
      }
  
      return nextChunk;
    }
  
    @Override
    public void connectionTerminated(Channel channel) {
      // Close all streams which have been associated with the channel.
      for (Map.Entry<Long, StreamState> entry: streams.entrySet()) {
        StreamState state = entry.getValue();
        if (state.associatedChannel == channel) {
          streams.remove(entry.getKey());
  
          // Release all remaining buffers.
          while (state.buffers.hasNext()) {
            state.buffers.next().release();
          }
        }
      }
    }
  
    @Override
    public void checkAuthorization(TransportClient client, long streamId) {
      if (client.getClientId() != null) {
        StreamState state = streams.get(streamId);
        Preconditions.checkArgument(state != null, "Unknown stream ID.");
        if (!client.getClientId().equals(state.appId)) {
          throw new SecurityException(String.format(
            "Client %s not authorized to read stream %d (app %s).",
            client.getClientId(),
            streamId,
            state.appId));
        }
      }
    }
  
    /**
     * Registers a stream of ManagedBuffers which are served as individual chunks one at a time to
     * callers. Each ManagedBuffer will be release()'d after it is transferred on the wire. If a
     * client connection is closed before the iterator is fully drained, then the remaining buffers
     * will all be release()'d.
     *
     * If an app ID is provided, only callers who've authenticated with the given app ID will be
     * allowed to fetch from this stream.
     */
    public long registerStream(String appId, Iterator<ManagedBuffer> buffers) {
      long myStreamId = nextStreamId.getAndIncrement();
      streams.put(myStreamId, new StreamState(appId, buffers));
      return myStreamId;
    }
  
  }
  