content: package org.apache.cassandra.service;
  /*
   *
   * 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.
   *
   */
  import org.apache.cassandra.gms.Gossiper;
  import org.apache.cassandra.net.IVerbHandler;
  import org.apache.cassandra.net.Message;
  import org.apache.cassandra.net.MessagingService;
  import org.apache.cassandra.net.NoPayload;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  public class EchoVerbHandler implements IVerbHandler<NoPayload>
  {
      public static final EchoVerbHandler instance = new EchoVerbHandler();
  
      private static final Logger logger = LoggerFactory.getLogger(EchoVerbHandler.class);
  
      public void doVerb(Message<NoPayload> message)
      {
          // only respond if we are not shutdown
          if (!StorageService.instance.isShutdown() && !Gossiper.instance.shutdownAnnounced.get())
          {
              logger.trace("Sending ECHO_RSP to {}", message.from());
              MessagingService.instance().send(message.emptyResponse(), message.from());
          }
          else
          {
              logger.trace("Not sending ECHO_RSP to {} - we are shutting down", message.from());
          }
      }
  }
  