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 io.jafka.network.handlers;
  
  import io.jafka.api.FetchRequest;
  import io.jafka.api.RequestKeys;
  import io.jafka.common.ErrorMapping;
  import io.jafka.log.ILog;
  import io.jafka.log.LogManager;
  import io.jafka.message.MessageSet;
  import io.jafka.mx.BrokerTopicStat;
  import io.jafka.network.MessageSetSend;
  import io.jafka.network.Receive;
  import io.jafka.network.Send;
  
  /**
   * handler for fetch request
   * 
   * @author adyliu (imxylz@gmail.com)
   * @since 1.0
   */
  public class FetchHandler extends AbstractHandler {
  
      public FetchHandler(LogManager logManager) {
          super(logManager);
      }
  
      public Send handler(RequestKeys requestType, Receive request) {
          FetchRequest fetchRequest = FetchRequest.readFrom(request.buffer());
          if (logger.isDebugEnabled()) {
              logger.debug("Fetch request " + fetchRequest.toString());
          }
          return readMessageSet(fetchRequest);
      }
  
      protected MessageSetSend readMessageSet(FetchRequest fetchRequest) {
          final String topic = fetchRequest.topic;
          MessageSetSend response = null;
          try {
              ILog log = logManager.getLog(topic, fetchRequest.partition);
              if (logger.isDebugEnabled()) {
                  logger.debug("Fetching log segment for request=" + fetchRequest + ", log=" + log);
              }
              if (log != null) {
                  response = new MessageSetSend(log.read(fetchRequest.offset, fetchRequest.maxSize));
                  BrokerTopicStat.getInstance(topic).recordBytesOut(response.messages.getSizeInBytes());
                  BrokerTopicStat.getBrokerAllTopicStat().recordBytesOut(response.messages.getSizeInBytes());
              } else {
                  response = new MessageSetSend();
              }
          } catch (Exception e) {
              logger.error("error when processing request " + fetchRequest, e);
              BrokerTopicStat.getInstance(topic).recordFailedFetchRequest();
              BrokerTopicStat.getBrokerAllTopicStat().recordFailedFetchRequest();
              response = new MessageSetSend(MessageSet.Empty, ErrorMapping.valueOf(e));
          }
          return response;
      }
  }
  