Ejemplo n.º 1
0
        public void DCAwareRoundRobinPolicyCachesLocalNodes()
        {
            var hostList = new List <Host>
            {
                TestHelper.CreateHost("0.0.0.1", "dc1"),
                TestHelper.CreateHost("0.0.0.2", "dc2"),
                TestHelper.CreateHost("0.0.0.3", "dc1"),
                TestHelper.CreateHost("0.0.0.4", "dc2"),
                TestHelper.CreateHost("0.0.0.5", "dc1"),
                TestHelper.CreateHost("0.0.0.6", "dc2"),
                TestHelper.CreateHost("0.0.0.7", "dc1"),
                TestHelper.CreateHost("0.0.0.8", "dc2"),
                TestHelper.CreateHost("0.0.0.9", "dc1"),
                TestHelper.CreateHost("0.0.0.10", "dc2")
            };
            const string localDc = "dc1";

            var clusterMock = new Mock <ICluster>();

            clusterMock
            .Setup(c => c.AllHosts())
            .Returns(hostList);

            //Initialize the balancing policy
            var policy = new DCAwareRoundRobinPolicy(localDc, 1);

            policy.Initialize(clusterMock.Object);

            var    instances = new ConcurrentBag <object>();
            Action action    = () => instances.Add(policy.GetHosts());

            TestHelper.ParallelInvoke(action, 100);
            Assert.AreEqual(1, instances.GroupBy(i => i.GetHashCode()).Count());
        }
Ejemplo n.º 2
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        public void DCAwareRoundRobinPolicyTestInParallel()
        {
            byte hostLength = 6;
            var  hostList   = new List <Host>();

            hostList.AddRange(GetHostList(1, 1, "remote1"));
            hostList.AddRange(GetHostList(1, 1, "remote2"));
            hostList.AddRange(GetHostList((byte)(hostLength - 3)));
            hostList.AddRange(GetHostList(1, 2, "remote1"));

            var clusterMock = new Mock <ICluster>();

            clusterMock
            .Setup(c => c.AllHosts())
            .Returns(hostList);

            //Initialize the balancing policy
            var policy = new DCAwareRoundRobinPolicy("local", 1);

            policy.Initialize(clusterMock.Object);

            Action action = () =>
            {
                var resultingHosts = new List <Host>();
                var hostEnumerator = policy.NewQueryPlan(new SimpleStatement());
                foreach (var h in hostEnumerator)
                {
                    //Slow down to try to execute it at the same time
                    Thread.Sleep(50);
                    resultingHosts.Add(h);
                }
                //The first hosts should be local
                Assert.True(resultingHosts.Take(hostLength - 3).All(h => h.Datacenter == "local"));
                //It should return the local hosts first and then 1 per each dc
                Assert.AreEqual(hostLength - 1, resultingHosts.Count);
                Assert.AreEqual(hostLength - 1, resultingHosts.Distinct().Count());
            };

            var actions = new List <Action>();

            for (var i = 0; i < 100; i++)
            {
                actions.Add(action);
            }

            var parallelOptions = new ParallelOptions();

            parallelOptions.TaskScheduler          = new ThreadPerTaskScheduler();
            parallelOptions.MaxDegreeOfParallelism = 1000;

            Parallel.Invoke(parallelOptions, actions.ToArray());
            clusterMock.Verify();
        }
Ejemplo n.º 3
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        public void DCAwareRoundRobinYieldsRemoteNodesAtTheEnd()
        {
            var hostList = new List <Host>
            {
                //5 local nodes and 4 remote
                TestHelper.CreateHost("0.0.0.1", "dc1"),
                TestHelper.CreateHost("0.0.0.2", "dc2"),
                TestHelper.CreateHost("0.0.0.3", "dc1"),
                TestHelper.CreateHost("0.0.0.4", "dc2"),
                TestHelper.CreateHost("0.0.0.5", "dc1"),
                TestHelper.CreateHost("0.0.0.6", "dc2"),
                TestHelper.CreateHost("0.0.0.7", "dc1"),
                TestHelper.CreateHost("0.0.0.8", "dc2"),
                TestHelper.CreateHost("0.0.0.9", "dc1"),
                TestHelper.CreateHost("0.0.0.10", "dc2")
            };
            var          localHostsLength = hostList.Count(h => h.Datacenter == "dc1");
            const string localDc          = "dc1";

            var clusterMock = new Mock <ICluster>();

            clusterMock
            .Setup(c => c.AllHosts())
            .Returns(hostList);

            //Initialize the balancing policy
            var policy = new DCAwareRoundRobinPolicy(localDc, 1);

            policy.Initialize(clusterMock.Object);
            Action action = () =>
            {
                var hosts = policy.NewQueryPlan(null, null).ToList();
                for (var i = 0; i < hosts.Count; i++)
                {
                    var h = hosts[i];
                    if (i < localHostsLength)
                    {
                        Assert.AreEqual(localDc, h.Datacenter);
                    }
                    else
                    {
                        Assert.AreNotEqual(localDc, h.Datacenter);
                    }
                }
            };

            TestHelper.ParallelInvoke(action, 100);
        }
Ejemplo n.º 4
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        public void DCAwareRoundRobinPolicyTestInParallel()
        {
            byte hostLength = 6;
            var hostList = new List<Host>();
            hostList.AddRange(GetHostList(1, 1, "remote1"));
            hostList.AddRange(GetHostList(1, 1, "remote2"));
            hostList.AddRange(GetHostList((byte)(hostLength - 3)));
            hostList.AddRange(GetHostList(1, 2, "remote1"));

            var clusterMock = new Mock<ICluster>();
            clusterMock
                .Setup(c => c.AllHosts())
                .Returns(hostList);

            //Initialize the balancing policy
            var policy = new DCAwareRoundRobinPolicy("local", 1);
            policy.Initialize(clusterMock.Object);

            Action action = () =>
            {
                var resultingHosts = new List<Host>();
                var hostEnumerator = policy.NewQueryPlan(new SimpleStatement());
                foreach (var h in hostEnumerator)
                {
                    //Slow down to try to execute it at the same time
                    Thread.Sleep(50);
                    resultingHosts.Add(h);
                }
                //The first hosts should be local
                Assert.True(resultingHosts.Take(hostLength-3).All(h => h.Datacenter == "local"));
                //It should return the local hosts first and then 1 per each dc
                Assert.AreEqual(hostLength - 1, resultingHosts.Count);
                Assert.AreEqual(hostLength - 1, resultingHosts.Distinct().Count());
            };

            var actions = new List<Action>();
            for (var i = 0; i < 100; i++)
            {
                actions.Add(action);
            }

            var parallelOptions = new ParallelOptions();
            parallelOptions.TaskScheduler = new ThreadPerTaskScheduler();
            parallelOptions.MaxDegreeOfParallelism = 1000;

            Parallel.Invoke(parallelOptions, actions.ToArray());
            clusterMock.Verify();
        }
Ejemplo n.º 5
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        public void DCAwareRoundRobinInitializeNotMatchingDcThrows()
        {
            var hostList = new List <Host>
            {
                TestHelper.CreateHost("0.0.0.1", "dc1"),
                TestHelper.CreateHost("0.0.0.2", "dc2")
            };
            var clusterMock = new Mock <ICluster>();

            clusterMock
            .Setup(c => c.AllHosts())
            .Returns(hostList);
            var policy = new DCAwareRoundRobinPolicy("not_valid_dc");

            Assert.Throws <ArgumentException>(() => policy.Initialize(clusterMock.Object));
        }
Ejemplo n.º 6
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        public void DCAwareRoundRobinInitializeRetrievesLocalDc()
        {
            var hostList = new List <Host>
            {
                TestHelper.CreateHost("0.0.0.1", null),
                TestHelper.CreateHost("0.0.0.1", "dc1"),
                TestHelper.CreateHost("0.0.0.2", "dc2")
            };
            var clusterMock = new Mock <ICluster>();

            clusterMock
            .Setup(c => c.AllHosts())
            .Returns(hostList);
            var policy = new DCAwareRoundRobinPolicy();

            policy.Initialize(clusterMock.Object);
            Assert.AreEqual(HostDistance.Local, policy.Distance(hostList[1]));
            Assert.AreNotEqual(HostDistance.Local, policy.Distance(hostList[2]));
        }
Ejemplo n.º 7
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        public void DCAwareRoundRobinPolicyNeverHitsRemoteWhenSet()
        {
            byte hostLength = 5;
            var  hostList   = new List <Host>();

            //Add a remote host at the beginning of the list
            hostList.AddRange(GetHostList(2, 1, "remote"));
            //add local hosts
            hostList.AddRange(GetHostList((byte)(hostLength - 2)));
            //Add another remote host at the end
            hostList.AddRange(GetHostList(2, 2, "remote"));

            var clusterMock = new Mock <ICluster>();

            clusterMock
            .Setup(c => c.AllHosts())
            .Returns(hostList);

            //Initialize the balancing policy
            //0 used nodes per remote dc
            var policy = new DCAwareRoundRobinPolicy("local", 0);

            policy.Initialize(clusterMock.Object);
            var balancedHosts = policy.NewQueryPlan(null, new SimpleStatement());
            var firstRound    = balancedHosts.ToList();

            //Returns only local hosts
            Assert.AreEqual(hostLength - 2, firstRound.Count(h => h.Datacenter == "local"));
            Assert.AreEqual(0, firstRound.Count(h => h.Datacenter != "local"));

            //following rounds: test it multiple times
            var followingRounds = new List <Host>();

            for (var i = 0; i < 10; i++)
            {
                followingRounds.AddRange(policy.NewQueryPlan(null, new SimpleStatement()).ToList());
            }
            Assert.AreEqual(10 * (hostLength - 2), followingRounds.Count);

            //Check that there aren't remote nodes.
            Assert.AreEqual(0, followingRounds.Count(h => h.Datacenter != "local"));
        }
Ejemplo n.º 8
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        public void DCAwareRoundRobinPolicyNeverHistsOtherDcWhenNodeUp()
        {
            byte hostLength = 5;
            var hostList = new List<Host>();
            //Add a remote host at the beginning of the list
            hostList.AddRange(GetHostList(2, 1, "remote"));
            //add local hosts
            hostList.AddRange(GetHostList((byte)(hostLength - 2)));
            //Add another remote host at the end
            hostList.AddRange(GetHostList(2, 2, "remote"));

            var clusterMock = new Mock<ICluster>();
            clusterMock
                .Setup(c => c.AllHosts())
                .Returns(hostList);

            //Initialize the balancing policy
            var policy = new DCAwareRoundRobinPolicy("local");
            policy.Initialize(clusterMock.Object);
            var balancedHosts = policy.NewQueryPlan(new SimpleStatement());
            var firstRound = balancedHosts.Take(hostLength - 2).ToList();

            //Returns only local hosts
            Assert.AreEqual(hostLength - 2, firstRound.Where(h => h.Datacenter == "local").Count());
            Assert.AreEqual(0, firstRound.Where(h => h.Datacenter != "local").Count());

            //following rounds: test it multiple times
            var followingRounds = new List<Host>();
            for (var i = 0; i < 10; i++)
            {
                followingRounds.AddRange(policy.NewQueryPlan(new SimpleStatement()).Take(hostLength - 2));
            }
            Assert.AreEqual(10 * (hostLength - 2), followingRounds.Count);

            //Check that there aren't remote nodes.
            Assert.AreEqual(0, followingRounds.Where(h => h.Datacenter != "local").Count());
        }
Ejemplo n.º 9
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        public void DCAwareRoundRobinPolicyWithNodesChanging()
        {
            var hostList = new ConcurrentBag <Host>
            {
                TestHelper.CreateHost("0.0.0.1", "dc1"),
                TestHelper.CreateHost("0.0.0.2", "dc2"),
                TestHelper.CreateHost("0.0.0.3", "dc1"),
                TestHelper.CreateHost("0.0.0.4", "dc2"),
                TestHelper.CreateHost("0.0.0.5", "dc1"),
                TestHelper.CreateHost("0.0.0.6", "dc2"),
                TestHelper.CreateHost("0.0.0.7", "dc1"),
                TestHelper.CreateHost("0.0.0.8", "dc2"),
                TestHelper.CreateHost("0.0.0.9", "dc1"),
                TestHelper.CreateHost("0.0.0.10", "dc2")
            };
            const string localDc = "dc1";
            //to remove the host 3
            var hostToRemove = hostList.First(h => TestHelper.GetLastAddressByte(h) == 3);
            var clusterMock  = new Mock <ICluster>();

            clusterMock
            .Setup(c => c.AllHosts())
            .Returns(() =>
            {
                return(hostList.ToList());
            });
            //Initialize the balancing policy
            var policy = new DCAwareRoundRobinPolicy(localDc, 1);

            policy.Initialize(clusterMock.Object);

            var    hostYielded = new ConcurrentBag <IEnumerable <Host> >();
            Action action      = () => hostYielded.Add(policy.NewQueryPlan(null, null).ToList());

            //Invoke without nodes changing
            TestHelper.ParallelInvoke(action, 100);
            Assert.True(hostYielded.Any(hl => hl.Any(h => h == hostToRemove)));

            var actionList = new List <Action>(Enumerable.Repeat <Action>(action, 1000));


            actionList.Insert(200, () =>
            {
                var host = TestHelper.CreateHost("0.0.0.11", "dc1");
                //raise event and then add
                clusterMock.Raise(c => c.HostAdded += null, host);
                hostList.Add(host);
            });
            actionList.Insert(400, () =>
            {
                var host = TestHelper.CreateHost("0.0.0.12", "dc1");
                //first add and then raise event
                hostList.Add(host);
                clusterMock.Raise(c => c.HostAdded += null, host);
            });

            actionList.Insert(400, () =>
            {
                var host = hostToRemove;
                hostList = new ConcurrentBag <Host>(hostList.Where(h => h != hostToRemove));
                clusterMock.Raise(c => c.HostRemoved += null, host);
            });

            //Invoke it with nodes being modified
            TestHelper.ParallelInvoke(actionList);
            //Clear the host yielded so far
            hostYielded = new ConcurrentBag <IEnumerable <Host> >();
            //Invoke it a some of times more in parallel
            TestHelper.ParallelInvoke(action, 100);
            //The removed node should not be returned
            Assert.False(hostList.Any(h => h == hostToRemove));
            Assert.False(hostYielded.Any(hl => hl.Any(h => h == hostToRemove)));
        }
Ejemplo n.º 10
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        public void DCAwareRoundRobinPolicyTestInParallel()
        {
            var hostList = new List <Host>
            {
                TestHelper.CreateHost("0.0.0.1", "dc1"),
                TestHelper.CreateHost("0.0.0.2", "dc2"),
                TestHelper.CreateHost("0.0.0.3", "dc1"),
                TestHelper.CreateHost("0.0.0.4", "dc2"),
                TestHelper.CreateHost("0.0.0.5", "dc1"),
                TestHelper.CreateHost("0.0.0.6", "dc2"),
                TestHelper.CreateHost("0.0.0.7", "dc1"),
                TestHelper.CreateHost("0.0.0.8", "dc2"),
                TestHelper.CreateHost("0.0.0.9", "dc1"),
                TestHelper.CreateHost("0.0.0.10", "dc2")
            };
            var          localHostsLength = hostList.Count(h => h.Datacenter == "dc1");
            const string localDc          = "dc1";

            var clusterMock = new Mock <ICluster>();

            clusterMock
            .Setup(c => c.AllHosts())
            .Returns(hostList);

            //Initialize the balancing policy
            var policy = new DCAwareRoundRobinPolicy(localDc, 1);

            policy.Initialize(clusterMock.Object);

            var    allHosts   = new ConcurrentBag <Host>();
            var    firstHosts = new ConcurrentBag <Host>();
            Action action     = () =>
            {
                var hosts = policy.NewQueryPlan(null, null).ToList();
                //Check that the value is not repeated
                Assert.AreEqual(0, hosts.GroupBy(x => x)
                                .Where(g => g.Count() > 1)
                                .Select(y => y.Key)
                                .Count());
                firstHosts.Add(hosts[0]);
                //Add to the general list
                foreach (var h in hosts)
                {
                    allHosts.Add(h);
                }
            };

            var       actions = new List <Action>();
            const int times   = 100;

            for (var i = 0; i < times; i++)
            {
                actions.Add(action);
            }
            TestHelper.ParallelInvoke(actions);

            //Check that the first nodes where different
            foreach (var h in hostList)
            {
                if (h.Datacenter == localDc)
                {
                    Assert.AreEqual(times / localHostsLength, firstHosts.Count(hc => hc == h));
                }
                else
                {
                    Assert.AreEqual(0, firstHosts.Count(hc => hc == h));
                }
            }
            clusterMock.Verify();
        }
Ejemplo n.º 11
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        public void DCAwareRoundRobinPolicyWithNodesChanging()
        {
            var hostList = new ConcurrentBag<Host>
            {
                TestHelper.CreateHost("0.0.0.1", "dc1"),
                TestHelper.CreateHost("0.0.0.2", "dc2"),
                TestHelper.CreateHost("0.0.0.3", "dc1"),
                TestHelper.CreateHost("0.0.0.4", "dc2"),
                TestHelper.CreateHost("0.0.0.5", "dc1"),
                TestHelper.CreateHost("0.0.0.6", "dc2"),
                TestHelper.CreateHost("0.0.0.7", "dc1"),
                TestHelper.CreateHost("0.0.0.8", "dc2"),
                TestHelper.CreateHost("0.0.0.9", "dc1"),
                TestHelper.CreateHost("0.0.0.10", "dc2")
            };
            const string localDc = "dc1";
            //to remove the host 3
            var hostToRemove = hostList.First(h => TestHelper.GetLastAddressByte(h) == 3);
            var clusterMock = new Mock<ICluster>();
            clusterMock
                .Setup(c => c.AllHosts())
                .Returns(() =>
                {
                    return hostList.ToList();
                });
            //Initialize the balancing policy
            var policy = new DCAwareRoundRobinPolicy(localDc, 1);
            policy.Initialize(clusterMock.Object);

            var hostYielded = new ConcurrentBag<IEnumerable<Host>>();
            Action action = () => hostYielded.Add(policy.NewQueryPlan(null, null).ToList());

            //Invoke without nodes changing
            TestHelper.ParallelInvoke(action, 100);
            Assert.True(hostYielded.Any(hl => hl.Any(h => h == hostToRemove)));

            var actionList = new List<Action>(Enumerable.Repeat<Action>(action, 1000));


            actionList.Insert(200, () =>
            {
                var host = TestHelper.CreateHost("0.0.0.11", "dc1");
                //raise event and then add
                clusterMock.Raise(c => c.HostAdded += null, host);
                hostList.Add(host);
            });
            actionList.Insert(400, () =>
            {
                var host = TestHelper.CreateHost("0.0.0.12", "dc1");
                //first add and then raise event
                hostList.Add(host);
                clusterMock.Raise(c => c.HostAdded += null, host);
            });
            
            actionList.Insert(400, () =>
            {
                var host = hostToRemove;
                hostList = new ConcurrentBag<Host>(hostList.Where(h => h != hostToRemove));
                clusterMock.Raise(c => c.HostRemoved += null, host);
            });

            //Invoke it with nodes being modified
            TestHelper.ParallelInvoke(actionList);
            //Clear the host yielded so far
            hostYielded = new ConcurrentBag<IEnumerable<Host>>();
            //Invoke it a some of times more in parallel
            TestHelper.ParallelInvoke(action, 100);
            //The removed node should not be returned
            Assert.False(hostList.Any(h => h == hostToRemove));
            Assert.False(hostYielded.Any(hl => hl.Any(h => h == hostToRemove)));
        }
Ejemplo n.º 12
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        public void DCAwareRoundRobinPolicyCachesLocalNodes()
        {
            var hostList = new List<Host>
            {
                TestHelper.CreateHost("0.0.0.1", "dc1"),
                TestHelper.CreateHost("0.0.0.2", "dc2"),
                TestHelper.CreateHost("0.0.0.3", "dc1"),
                TestHelper.CreateHost("0.0.0.4", "dc2"),
                TestHelper.CreateHost("0.0.0.5", "dc1"),
                TestHelper.CreateHost("0.0.0.6", "dc2"),
                TestHelper.CreateHost("0.0.0.7", "dc1"),
                TestHelper.CreateHost("0.0.0.8", "dc2"),
                TestHelper.CreateHost("0.0.0.9", "dc1"),
                TestHelper.CreateHost("0.0.0.10", "dc2")
            };
            const string localDc = "dc1";

            var clusterMock = new Mock<ICluster>();
            clusterMock
                .Setup(c => c.AllHosts())
                .Returns(hostList);

            //Initialize the balancing policy
            var policy = new DCAwareRoundRobinPolicy(localDc, 1);
            policy.Initialize(clusterMock.Object);

            var instances = new ConcurrentBag<object>();
            Action action = () => instances.Add(policy.GetHosts());
            TestHelper.ParallelInvoke(action, 100);
            Assert.AreEqual(1, instances.GroupBy(i => i.GetHashCode()).Count());
        }
Ejemplo n.º 13
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        public void DCAwareRoundRobinPolicyTestInParallel()
        {
            var hostList = new List<Host>
            {
                TestHelper.CreateHost("0.0.0.1", "dc1"),
                TestHelper.CreateHost("0.0.0.2", "dc2"),
                TestHelper.CreateHost("0.0.0.3", "dc1"),
                TestHelper.CreateHost("0.0.0.4", "dc2"),
                TestHelper.CreateHost("0.0.0.5", "dc1"),
                TestHelper.CreateHost("0.0.0.6", "dc2"),
                TestHelper.CreateHost("0.0.0.7", "dc1"),
                TestHelper.CreateHost("0.0.0.8", "dc2"),
                TestHelper.CreateHost("0.0.0.9", "dc1"),
                TestHelper.CreateHost("0.0.0.10", "dc2")
            };
            var localHostsLength = hostList.Count(h => h.Datacenter == "dc1");
            const string localDc = "dc1";

            var clusterMock = new Mock<ICluster>();
            clusterMock
                .Setup(c => c.AllHosts())
                .Returns(hostList);

            //Initialize the balancing policy
            var policy = new DCAwareRoundRobinPolicy(localDc, 1);
            policy.Initialize(clusterMock.Object);

            var allHosts = new ConcurrentBag<Host>();
            var firstHosts = new ConcurrentBag<Host>();
            Action action = () =>
            {
                var hosts = policy.NewQueryPlan(null, null).ToList();
                //Check that the value is not repeated
                Assert.AreEqual(0, hosts.GroupBy(x => x)
                    .Where(g => g.Count() > 1)
                    .Select(y => y.Key)
                    .Count());
                firstHosts.Add(hosts[0]);
                //Add to the general list
                foreach (var h in hosts)
                {
                    allHosts.Add(h);
                }
            };

            var actions = new List<Action>();
            const int times = 100;
            for (var i = 0; i < times; i++)
            {
                actions.Add(action);
            }
            TestHelper.ParallelInvoke(actions);

            //Check that the first nodes where different
            foreach (var h in hostList)
            {
                if (h.Datacenter == localDc)
                {
                    Assert.AreEqual(times/localHostsLength, firstHosts.Count(hc => hc == h));
                }
                else
                {
                    Assert.AreEqual(0, firstHosts.Count(hc => hc == h));
                }
            }
            clusterMock.Verify();
        }
Ejemplo n.º 14
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 public void DCAwareRoundRobinInitializeNotMatchingDcThrows()
 {
     var hostList = new List<Host>
     {
         TestHelper.CreateHost("0.0.0.1", "dc1"),
         TestHelper.CreateHost("0.0.0.2", "dc2")
     };
     var clusterMock = new Mock<ICluster>();
     clusterMock
         .Setup(c => c.AllHosts())
         .Returns(hostList);
     var policy = new DCAwareRoundRobinPolicy("not_valid_dc");
     Assert.Throws<ArgumentException>(() => policy.Initialize(clusterMock.Object));
 }
Ejemplo n.º 15
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 public void DCAwareRoundRobinInitializeRetrievesLocalDc()
 {
     var hostList = new List<Host>
     {
         TestHelper.CreateHost("0.0.0.1", null),
         TestHelper.CreateHost("0.0.0.1", "dc1"),
         TestHelper.CreateHost("0.0.0.2", "dc2")
     };
     var clusterMock = new Mock<ICluster>();
     clusterMock
         .Setup(c => c.AllHosts())
         .Returns(hostList);
     var policy = new DCAwareRoundRobinPolicy();
     policy.Initialize(clusterMock.Object);
     Assert.AreEqual(HostDistance.Local, policy.Distance(hostList[1]));
     Assert.AreNotEqual(HostDistance.Local, policy.Distance(hostList[2]));
 }
Ejemplo n.º 16
0
        public void DCAwareRoundRobinYieldsRemoteNodesAtTheEnd()
        {
            var hostList = new List<Host>
            {
                //5 local nodes and 4 remote
                TestHelper.CreateHost("0.0.0.1", "dc1"),
                TestHelper.CreateHost("0.0.0.2", "dc2"),
                TestHelper.CreateHost("0.0.0.3", "dc1"),
                TestHelper.CreateHost("0.0.0.4", "dc2"),
                TestHelper.CreateHost("0.0.0.5", "dc1"),
                TestHelper.CreateHost("0.0.0.6", "dc2"),
                TestHelper.CreateHost("0.0.0.7", "dc1"),
                TestHelper.CreateHost("0.0.0.8", "dc2"),
                TestHelper.CreateHost("0.0.0.9", "dc1"),
                TestHelper.CreateHost("0.0.0.10", "dc2")
            };
            var localHostsLength = hostList.Count(h => h.Datacenter == "dc1");
            const string localDc = "dc1";

            var clusterMock = new Mock<ICluster>();
            clusterMock
                .Setup(c => c.AllHosts())
                .Returns(hostList);

            //Initialize the balancing policy
            var policy = new DCAwareRoundRobinPolicy(localDc, 1);
            policy.Initialize(clusterMock.Object);
            Action action = () =>
            {
                var hosts = policy.NewQueryPlan(null, null).ToList();
                for (var i = 0; i < hosts.Count; i++)
                {
                    var h = hosts[i];
                    if (i < localHostsLength)
                    {
                        Assert.AreEqual(localDc, h.Datacenter);
                    }
                    else
                    {
                        Assert.AreNotEqual(localDc, h.Datacenter);
                    }
                }
            };
            TestHelper.ParallelInvoke(action, 100);
        }