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.nio.ByteBuffer;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import org.apache.spark.network.client.RpcResponseCallback;
  import org.apache.spark.network.client.TransportClient;
  
  /**
   * Handler for sendRPC() messages sent by {@link org.apache.spark.network.client.TransportClient}s.
   */
  public abstract class RpcHandler {
  
    private static final RpcResponseCallback ONE_WAY_CALLBACK = new OneWayRpcCallback();
  
    /**
     * Receive a single RPC message. Any exception thrown while in this method will be sent back to
     * the client in string form as a standard RPC failure.
     *
     * This method will not be called in parallel for a single TransportClient (i.e., channel).
     *
     * @param client A channel client which enables the handler to make requests back to the sender
     *               of this RPC. This will always be the exact same object for a particular channel.
     * @param message The serialized bytes of the RPC.
     * @param callback Callback which should be invoked exactly once upon success or failure of the
     *                 RPC.
     */
    public abstract void receive(
        TransportClient client,
        ByteBuffer message,
        RpcResponseCallback callback);
  
    /**
     * Returns the StreamManager which contains the state about which streams are currently being
     * fetched by a TransportClient.
     */
    public abstract StreamManager getStreamManager();
  
    /**
     * Receives an RPC message that does not expect a reply. The default implementation will
     * call "{@link #receive(TransportClient, ByteBuffer, RpcResponseCallback)}" and log a warning if
     * any of the callback methods are called.
     *
     * @param client A channel client which enables the handler to make requests back to the sender
     *               of this RPC. This will always be the exact same object for a particular channel.
     * @param message The serialized bytes of the RPC.
     */
    public void receive(TransportClient client, ByteBuffer message) {
      receive(client, message, ONE_WAY_CALLBACK);
    }
  
    /**
     * Invoked when the channel associated with the given client is active.
     */
    public void channelActive(TransportClient client) { }
  
    /**
     * Invoked when the channel associated with the given client is inactive.
     * No further requests will come from this client.
     */
    public void channelInactive(TransportClient client) { }
  
    public void exceptionCaught(Throwable cause, TransportClient client) { }
  
    private static class OneWayRpcCallback implements RpcResponseCallback {
  
      private static final Logger logger = LoggerFactory.getLogger(OneWayRpcCallback.class);
  
      @Override
      public void onSuccess(ByteBuffer response) {
        logger.warn("Response provided for one-way RPC.");
      }
  
      @Override
      public void onFailure(Throwable e) {
        logger.error("Error response provided for one-way RPC.", e);
      }
  
    }
  
  }
  