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.simulator;
  
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Objects;
  import java.util.concurrent.TimeUnit;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import org.apache.cassandra.distributed.api.IInvokableInstance;
  import org.apache.cassandra.distributed.api.IMessage;
  import org.apache.cassandra.simulator.systems.SimulatedTime;
  import org.apache.cassandra.simulator.utils.ChanceRange;
  import org.apache.cassandra.simulator.utils.KindOfSequence;
  import org.apache.cassandra.simulator.utils.LongRange;
  
  /**
   * A scheduler that allows to configure network loss chance, that applies this chance to
   * _all_ operations. Useful for testing severe loss scenarios to make sure your retry
   * mechanisms work well.
   */
  public class FixedLossNetworkScheduler implements FutureActionScheduler
  {
      private static final Logger logger = LoggerFactory.getLogger(FixedLossNetworkScheduler.class);
      final RandomSource random;
      final SimulatedTime time;
  
      final KindOfSequence.LinkLatency normalLatency;
      final KindOfSequence.LinkLatency delayLatency;
  
      final KindOfSequence.NetworkDecision dropMessage;
      final KindOfSequence.NetworkDecision delayMessage;
  
      final KindOfSequence.Decision delayChance;
      final LongRange delayNanos, longDelayNanos;
  
      public FixedLossNetworkScheduler(int nodes, RandomSource random, SimulatedTime time, KindOfSequence kind, float min, float max)
      {
          this.random = random;
          this.time = time;
          this.normalLatency = kind.linkLatency(nodes,
                                                new LongRange(2, 20, TimeUnit.MILLISECONDS, TimeUnit.NANOSECONDS),
                                                random);
          this.delayLatency = kind.linkLatency(nodes,
                                               new LongRange(20, 40, TimeUnit.MILLISECONDS, TimeUnit.NANOSECONDS),
                                               random);
  
          this.dropMessage = kind.networkDecision(nodes,
                                                  new ChanceRange(randomSource -> randomSource.qlog2uniformFloat(4), min, max),
                                                  random);
  
          this.delayMessage = kind.networkDecision(nodes,
                                                   new ChanceRange(randomSource -> randomSource.qlog2uniformFloat(4), min, max),
                                                   random);
  
          this.delayChance = kind.decision(new ChanceRange(randomSource -> randomSource.qlog2uniformFloat(4), min, max),
                                           random);
  
          this.delayNanos = new LongRange(2, 100, TimeUnit.MILLISECONDS, TimeUnit.NANOSECONDS);
          this.longDelayNanos = new LongRange(2, 100, TimeUnit.MILLISECONDS, TimeUnit.NANOSECONDS);
      }
  
      private static class DeliveryPair
      {
          final int from;
          final int to;
  
          private DeliveryPair(int from, int to)
          {
              this.from = from;
              this.to = to;
          }
  
          public boolean equals(Object o)
          {
              if (this == o) return true;
              if (o == null || getClass() != o.getClass()) return false;
              DeliveryPair that = (DeliveryPair) o;
              return from == that.from && to == that.to;
          }
  
          public int hashCode()
          {
              return Objects.hash(from, to);
          }
  
          public String toString()
          {
              return "" + from +
                     "->" + to;
          }
      }
  
      private Map<DeliveryPair, Integer> pairs = new HashMap<>();
      private static final int TIMEOUTS_IN_A_ROW = 1;
      public DeliverResult shouldDeliver(int from, int to, IInvokableInstance invoker, IMessage message)
      {
          DeliveryPair pair = new DeliveryPair(from, to);
          if (!dropMessage.get(random, from, to))
          {
              pairs.put(pair, 0);
              return DELIVER_UNPROTECTED_RESULT;
          }
  
          int subsequentFailures = pairs.compute(pair, (k, v) -> v == null ? 1 : v+1);
  
          if (subsequentFailures > TIMEOUTS_IN_A_ROW)
          {
              logger.info("Delivering {} after {} failures in a row", pair, TIMEOUTS_IN_A_ROW);
              pairs.put(pair, 0);
              return DELIVER_UNPROTECTED_RESULT;
          }
  
          logger.info("Timing out {} for the {}th time", pair, subsequentFailures);
          return TIMEOUT_RESULT;
      }
  
      public long messageDeadlineNanos(int from, int to, boolean protectedMessage)
      {
          return time.nanoTime() + (delayMessage.get(random, from, to)
                                    ? normalLatency.get(random, from, to)
                                    : delayLatency.get(random, from, to));
      }
  
      public long messageTimeoutNanos(long expiresAfterNanos, long expirationIntervalNanos, boolean protectedMessage)
      {
          return expiresAfterNanos + random.uniform(0, expirationIntervalNanos / 2);
      }
  
      public long messageFailureNanos(int from, int to, boolean protectedMessage)
      {
          return messageDeadlineNanos(from, to, protectedMessage);
      }
  
      public long schedulerDelayNanos()
      {
          return (delayChance.get(random) ? longDelayNanos : delayNanos).select(random);
      }
  }
  