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.cassandra.tcm;
  
  import java.io.IOException;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import org.apache.cassandra.net.IVerbHandler;
  import org.apache.cassandra.net.Message;
  import org.apache.cassandra.net.MessagingService;
  
  // The cluster metadata equivalent of a Gossip PING; used to exchange the current epochs on
  // two peers via a pair of empty messages
  public class CurrentEpochRequestHandler implements IVerbHandler<Epoch>
  {
      private static final Logger logger = LoggerFactory.getLogger(CurrentEpochRequestHandler.class);
      public void doVerb(Message<Epoch> message) throws IOException
      {
          Message<Epoch> response = message.responseWith(ClusterMetadata.current().epoch);
          MessagingService.instance().send(response, message.from());
          // We try to catch up after responding, as watermark request is going to get retried
          ClusterMetadataService.instance().fetchLogFromPeerOrCMSAsync(ClusterMetadata.current(), message.from(), message.payload);
      }
  }
  