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.service.paxos.v1;
  
  
  import java.util.concurrent.atomic.AtomicInteger;
  
  import org.apache.cassandra.db.ConsistencyLevel;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import org.apache.cassandra.net.Message;
  import org.apache.cassandra.transport.Dispatcher;
  import org.apache.cassandra.utils.Nemesis;
  
  /**
   * ProposeCallback has two modes of operation, controlled by the failFast parameter.
   *
   * In failFast mode, we will return a failure as soon as a majority of nodes reject
   * the proposal. This is used when replaying a proposal from an earlier leader.
   *
   * Otherwise, we wait for either all replicas to respond or until we achieve
   * the desired quorum. We continue to wait for all replicas even after we know we cannot succeed
   * because we need to know if no node at all have accepted or if at least one has.
   * In the former case, a proposer is guaranteed no-one will
   * replay its value; in the latter we don't, so we must timeout in case another
   * leader replays it before we can; see CASSANDRA-6013
   */
  public class ProposeCallback extends AbstractPaxosCallback<Boolean>
  {
      private static final Logger logger = LoggerFactory.getLogger(ProposeCallback.class);
  
      @Nemesis private final AtomicInteger accepts = new AtomicInteger(0);
      private final int requiredAccepts;
      private final boolean failFast;
  
      public ProposeCallback(int totalTargets, int requiredTargets, boolean failFast, ConsistencyLevel consistency, Dispatcher.RequestTime requestTime)
      {
          super(totalTargets, consistency, requestTime);
          this.requiredAccepts = requiredTargets;
          this.failFast = failFast;
      }
  
      public void onResponse(Message<Boolean> msg)
      {
          logger.trace("Propose response {} from {}", msg.payload, msg.from());
  
          if (msg.payload)
              accepts.incrementAndGet();
  
          latch.decrement();
  
          if (isSuccessful() || (failFast && (latch.count() + accepts.get() < requiredAccepts)))
          {
              while (latch.count() > 0)
                  latch.decrement();
          }
      }
  
      public int getAcceptCount()
      {
          return accepts.get();
      }
  
      public boolean isSuccessful()
      {
          return accepts.get() >= requiredAccepts;
      }
  
      // Note: this is only reliable if !failFast
      public boolean isFullyRefused()
      {
          // We need to check the latch first to avoid racing with a late arrival
          // between the latch check and the accepts one
          return latch.count() == 0 && accepts.get() == 0;
      }
  }
  