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   * 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.
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  package org.apache.cassandra.net;
  
  import java.net.UnknownHostException;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Map;
  import java.util.Set;
  import java.util.function.BiPredicate;
  
  import org.junit.After;
  import org.junit.Assert;
  import org.junit.Before;
  import org.junit.BeforeClass;
  import org.junit.Test;
  
  import org.apache.cassandra.config.DatabaseDescriptor;
  import org.apache.cassandra.distributed.test.log.ClusterMetadataTestHelper;
  import org.apache.cassandra.gms.EndpointState;
  import org.apache.cassandra.gms.Gossiper;
  import org.apache.cassandra.gms.HeartBeatState;
  import org.apache.cassandra.locator.InetAddressAndPort;
  import org.apache.cassandra.tcm.Epoch;
  import org.apache.cassandra.utils.FBUtilities;
  
  public class StartupClusterConnectivityCheckerTest
  {
      private StartupClusterConnectivityChecker localQuorumConnectivityChecker;
      private StartupClusterConnectivityChecker globalQuorumConnectivityChecker;
      private StartupClusterConnectivityChecker noopChecker;
      private StartupClusterConnectivityChecker zeroWaitChecker;
  
      private static final long TIMEOUT_NANOS = 100;
      private static final int NUM_PER_DC = 6;
      private Set<InetAddressAndPort> peers;
      private Set<InetAddressAndPort> peersA;
      private Set<InetAddressAndPort> peersAMinusLocal;
      private Set<InetAddressAndPort> peersB;
      private Set<InetAddressAndPort> peersC;
  
      private String getDatacenter(InetAddressAndPort endpoint)
      {
          if (peersA.contains(endpoint))
              return "datacenterA";
          if (peersB.contains(endpoint))
              return "datacenterB";
          else if (peersC.contains(endpoint))
              return "datacenterC";
          return null;
      }
  
      @BeforeClass
      public static void before()
      {
          DatabaseDescriptor.daemonInitialization();
          ClusterMetadataTestHelper.setInstanceForTest();
      }
  
      @Before
      public void setUp() throws UnknownHostException
      {
          localQuorumConnectivityChecker = new StartupClusterConnectivityChecker(TIMEOUT_NANOS, false);
          globalQuorumConnectivityChecker = new StartupClusterConnectivityChecker(TIMEOUT_NANOS, true);
          noopChecker = new StartupClusterConnectivityChecker(-1, false);
          zeroWaitChecker = new StartupClusterConnectivityChecker(0, false);
  
          peersA = new HashSet<>();
          peersAMinusLocal = new HashSet<>();
          peersA.add(FBUtilities.getBroadcastAddressAndPort());
  
          for (int i = 0; i < NUM_PER_DC - 1; i ++)
          {
              peersA.add(InetAddressAndPort.getByName("127.0.1." + i));
              peersAMinusLocal.add(InetAddressAndPort.getByName("127.0.1." + i));
          }
  
          peersB = new HashSet<>();
          for (int i = 0; i < NUM_PER_DC; i ++)
              peersB.add(InetAddressAndPort.getByName("127.0.2." + i));
  
  
          peersC = new HashSet<>();
          for (int i = 0; i < NUM_PER_DC; i ++)
              peersC.add(InetAddressAndPort.getByName("127.0.3." + i));
  
          peers = new HashSet<>();
          peers.addAll(peersA);
          peers.addAll(peersB);
          peers.addAll(peersC);
      }
  
      @After
      public void tearDown()
      {
          MessagingService.instance().outboundSink.clear();
      }
  
      @Test
      public void execute_HappyPath()
      {
          Sink sink = new Sink(true, true, peers);
          MessagingService.instance().outboundSink.add(sink);
          Assert.assertTrue(localQuorumConnectivityChecker.execute(peers, this::getDatacenter));
      }
  
      @Test
      public void execute_NotAlive()
      {
          Sink sink = new Sink(false, true, peers);
          MessagingService.instance().outboundSink.add(sink);
          Assert.assertFalse(localQuorumConnectivityChecker.execute(peers, this::getDatacenter));
      }
  
      @Test
      public void execute_NoConnectionsAcks()
      {
          Sink sink = new Sink(true, false, peers);
          MessagingService.instance().outboundSink.add(sink);
          Assert.assertFalse(localQuorumConnectivityChecker.execute(peers, this::getDatacenter));
      }
  
      @Test
      public void execute_LocalQuorum()
      {
          // local peer plus 3 peers from same dc shouldn't pass (4/6)
          Set<InetAddressAndPort> available = new HashSet<>();
          copyCount(peersAMinusLocal, available, NUM_PER_DC - 3);
          checkAvailable(localQuorumConnectivityChecker, available, false);
  
          // local peer plus 4 peers from same dc should pass (5/6)
          available.clear();
          copyCount(peersAMinusLocal, available, NUM_PER_DC - 2);
          checkAvailable(localQuorumConnectivityChecker, available, true);
      }
  
      @Test
      public void execute_GlobalQuorum()
      {
          // local dc passing shouldn't pass globally with two hosts down in datacenterB
          Set<InetAddressAndPort> available = new HashSet<>();
          copyCount(peersAMinusLocal, available, NUM_PER_DC - 2);
          copyCount(peersB, available, NUM_PER_DC - 2);
          copyCount(peersC, available, NUM_PER_DC - 1);
          checkAvailable(globalQuorumConnectivityChecker, available, false);
  
          // All three datacenters should be able to have a single node down
          available.clear();
          copyCount(peersAMinusLocal, available, NUM_PER_DC - 2);
          copyCount(peersB, available, NUM_PER_DC - 1);
          copyCount(peersC, available, NUM_PER_DC - 1);
          checkAvailable(globalQuorumConnectivityChecker, available, true);
  
          // Everything being up should work of course
          available.clear();
          copyCount(peersAMinusLocal, available, NUM_PER_DC - 1);
          copyCount(peersB, available, NUM_PER_DC);
          copyCount(peersC, available, NUM_PER_DC);
          checkAvailable(globalQuorumConnectivityChecker, available, true);
      }
  
      @Test
      public void execute_Noop()
      {
          checkAvailable(noopChecker, new HashSet<>(), true);
      }
  
      @Test
      public void execute_ZeroWaitHasConnections() throws InterruptedException
      {
          Sink sink = new Sink(true, true, new HashSet<>());
          MessagingService.instance().outboundSink.add(sink);
          Assert.assertFalse(zeroWaitChecker.execute(peers, this::getDatacenter));
          MessagingService.instance().outboundSink.clear();
      }
  
      private void checkAvailable(StartupClusterConnectivityChecker checker, Set<InetAddressAndPort> available,
                                  boolean shouldPass)
      {
          Sink sink = new Sink(true, true, available);
          MessagingService.instance().outboundSink.add(sink);
          Assert.assertEquals(shouldPass, checker.execute(peers, this::getDatacenter));
          MessagingService.instance().outboundSink.clear();
      }
  
      private void copyCount(Set<InetAddressAndPort> source, Set<InetAddressAndPort> dest, int count)
      {
          for (InetAddressAndPort peer : source)
          {
              if (count <= 0)
                  break;
  
              dest.add(peer);
              count -= 1;
          }
      }
  
      private static class Sink implements BiPredicate<Message<?>, InetAddressAndPort>
      {
          private final boolean markAliveInGossip;
          private final boolean processConnectAck;
          private final Set<InetAddressAndPort> aliveHosts;
          private final Map<InetAddressAndPort, ConnectionTypeRecorder> seenConnectionRequests;
  
          Sink(boolean markAliveInGossip, boolean processConnectAck, Set<InetAddressAndPort> aliveHosts)
          {
              this.markAliveInGossip = markAliveInGossip;
              this.processConnectAck = processConnectAck;
              this.aliveHosts = aliveHosts;
              seenConnectionRequests = new HashMap<>();
          }
  
          @Override
          public boolean test(Message message, InetAddressAndPort to)
          {
              ConnectionTypeRecorder recorder = seenConnectionRequests.computeIfAbsent(to, inetAddress ->  new ConnectionTypeRecorder());
  
              if (!aliveHosts.contains(to))
                  return false;
  
              if (processConnectAck)
              {
                  Message msgIn = Message.builder(Verb.REQUEST_RSP, message.payload)
                                         .withEpoch(Epoch.EMPTY)
                                         .from(to)
                                         .build();
                  MessagingService.instance().callbacks.get(message.id(), to).callback.onResponse(msgIn);
              }
  
              if (markAliveInGossip)
                  Gossiper.runInGossipStageBlocking(() -> Gossiper.instance.realMarkAlive(to, new EndpointState(new HeartBeatState(1, 1))));
              return false;
          }
      }
  
      private static class ConnectionTypeRecorder
      {
          boolean seenSmallMessageRequest;
          boolean seenLargeMessageRequest;
      }
  }
  