text: /*
   * 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 io.netty.channel.Channel;
  
  import org.apache.spark.network.buffer.ManagedBuffer;
  import org.apache.spark.network.client.TransportClient;
  
  /**
   * The StreamManager is used to fetch individual chunks from a stream. This is used in
   * {@link TransportRequestHandler} in order to respond to fetchChunk() requests. Creation of the
   * stream is outside the scope of the transport layer, but a given stream is guaranteed to be read
   * by only one client connection, meaning that getChunk() for a particular stream will be called
   * serially and that once the connection associated with the stream is closed, that stream will
   * never be used again.
   */
  public abstract class StreamManager {
    /**
     * Called in response to a fetchChunk() request. The returned buffer will be passed as-is to the
     * client. A single stream will be associated with a single TCP connection, so this method
     * will not be called in parallel for a particular stream.
     *
     * Chunks may be requested in any order, and requests may be repeated, but it is not required
     * that implementations support this behavior.
     *
     * The returned ManagedBuffer will be release()'d after being written to the network.
     *
     * @param streamId id of a stream that has been previously registered with the StreamManager.
     * @param chunkIndex 0-indexed chunk of the stream that's requested
     */
    public abstract ManagedBuffer getChunk(long streamId, int chunkIndex);
  
    /**
     * Called in response to a stream() request. The returned data is streamed to the client
     * through a single TCP connection.
     *
     * Note the <code>streamId</code> argument is not related to the similarly named argument in the
     * {@link #getChunk(long, int)} method.
     *
     * @param streamId id of a stream that has been previously registered with the StreamManager.
     * @return A managed buffer for the stream, or null if the stream was not found.
     */
    public ManagedBuffer openStream(String streamId) {
      throw new UnsupportedOperationException();
    }
  
    /**
     * Associates a stream with a single client connection, which is guaranteed to be the only reader
     * of the stream. The getChunk() method will be called serially on this connection and once the
     * connection is closed, the stream will never be used again, enabling cleanup.
     *
     * This must be called before the first getChunk() on the stream, but it may be invoked multiple
     * times with the same channel and stream id.
     */
    public void registerChannel(Channel channel, long streamId) { }
  
    /**
     * Indicates that the given channel has been terminated. After this occurs, we are guaranteed not
     * to read from the associated streams again, so any state can be cleaned up.
     */
    public void connectionTerminated(Channel channel) { }
  
    /**
     * Verify that the client is authorized to read from the given stream.
     *
     * @throws SecurityException If client is not authorized.
     */
    public void checkAuthorization(TransportClient client, long streamId) { }
  
  }
  