Added pool for HttpClients to improve performance (see: https://githu…

…b.com/mspnp/performance-optimization/blob/master/ImproperInstantiation/docs/ImproperInstantiation.md)

Source/Platibus.IntegrationTests/LoadTests.cs

@@ -78,10 +78,10 @@ public async Task When_Sending_2000_Test_Messages_2000_Replies_Should_Be_Handled
 
         [Test]
         [Explicit]
-        public async Task When_Sending_10000_Test_Messages_10000_Replies_Should_Be_Handled_Within_120s()
+        public async Task When_Sending_10000_Test_Messages_10000_Replies_Should_Be_Handled_Within_20s()
         {
             var elapsed = await RunTest(10000);
-            Assert.That(elapsed, Is.LessThan(TimeSpan.FromSeconds(120)));
+            Assert.That(elapsed, Is.LessThan(TimeSpan.FromSeconds(20)));
         }
 
         private static async Task<TimeSpan> RunTest(int messageCount, bool durable = false)

Source/Platibus/Http/HttpClientPool.cs

@@ -0,0 +1,107 @@
+using System;
+using System.Collections.Generic;
+using System.Net;
+using System.Net.Http;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Platibus.Http
+{
+    internal class HttpClientPool
+    {
+        private readonly SemaphoreSlim _poolSync = new SemaphoreSlim(1);
+        private readonly IDictionary<PoolKey, HttpClientHandler> _pool = new Dictionary<PoolKey, HttpClientHandler>();
+
+        public async Task<HttpClient> GetClient(Uri uri, IEndpointCredentials credentials, CancellationToken cancellationToken)
+        {
+            var key = new PoolKey(uri, credentials);
+            HttpClientHandler clientHandler;
+            if (_pool.TryGetValue(key, out clientHandler))
+            {
+                return CreateClient(clientHandler, uri);
+            }
+
+            await _poolSync.WaitAsync(cancellationToken);
+            try
+            {
+                if (!_pool.TryGetValue(key, out clientHandler))
+                {
+                    clientHandler = new HttpClientHandler
+                    {
+                        AllowAutoRedirect = true,
+                        UseProxy = false
+                    };
+
+                    if (credentials != null)
+                    {
+                        credentials.Accept(new HttpEndpointCredentialsVisitor(clientHandler));
+                    }
+
+                    _pool[key] = clientHandler;
+
+                    // Make sure DNS TTL is honored
+                    var sp = ServicePointManager.FindServicePoint(uri);
+                    sp.ConnectionLeaseTimeout = (int)TimeSpan.FromMinutes(5).TotalMilliseconds;
+                }
+            }
+            finally
+            {
+                _poolSync.Release();
+            }
+
+            return CreateClient(clientHandler, uri);
+        }
+
+        private HttpClient CreateClient(HttpClientHandler clientHandler, Uri baseAddress)
+        {
+            return new HttpClient(clientHandler, false)
+            {
+                BaseAddress = baseAddress
+            };
+        }
+
+        private class PoolKey : IEquatable<PoolKey>
+        {
+            private readonly Uri _uri;
+            private readonly IEndpointCredentials _credentials;
+
+            public PoolKey(Uri uri, IEndpointCredentials credentials)
+            {
+                _uri = uri;
+                _credentials = credentials;
+            }
+
+            public bool Equals(PoolKey other)
+            {
+                if (ReferenceEquals(null, other)) return false;
+                if (ReferenceEquals(this, other)) return true;
+                return Equals(_uri, other._uri) && Equals(_credentials, other._credentials);
+            }
+
+            public override bool Equals(object obj)
+            {
+                if (ReferenceEquals(null, obj)) return false;
+                if (ReferenceEquals(this, obj)) return true;
+                return obj.GetType() == GetType() && Equals((PoolKey)obj);
+            }
+
+            public override int GetHashCode()
+            {
+                unchecked
+                {
+                    return ((_uri != null ? _uri.GetHashCode() : 0) * 397) ^ (_credentials != null ? _credentials.GetHashCode() : 0);
+                }
+            }
+
+            public static bool operator ==(PoolKey left, PoolKey right)
+            {
+                return Equals(left, right);
+            }
+
+            public static bool operator !=(PoolKey left, PoolKey right)
+            {
+                return !Equals(left, right);
+            }
+        }
+    }
+}

Source/Platibus/Http/HttpTransportService.cs

@@ -51,6 +51,8 @@ public class HttpTransportService : ITransportService, IQueueListener
         private readonly Func<Message, CancellationToken, Task> _handleMessage;
         private readonly QueueName _outboundQueueName;
 
+        private readonly HttpClientPool _clientPool;
+
         /// <summary>
         /// Initializes a new <see cref="HttpTransportService"/>
         /// </summary>
@@ -91,6 +93,8 @@ public HttpTransportService(Uri baseUri, IEndpointCollection endpoints, IMessage
             _bypassTransportLocalDestination = bypassTransportLocalDestination;
             _handleMessage = handleMessage;
             _outboundQueueName = "Outbound";
+
+            _clientPool = new HttpClientPool();
         }
 
         /// <summary>
@@ -199,28 +203,7 @@ public async Task PublishMessage(Message message, TopicName topicName, Cancellat
 
             await Task.WhenAll(transportTasks);
         }
-
-        private static HttpClient GetClient(Uri uri, IEndpointCredentials credentials)
-        {
-            var clientHandler = new HttpClientHandler
-            {
-                AllowAutoRedirect = true,
-                UseProxy = false
-            };
-
-            if (credentials != null)
-            {
-                credentials.Accept(new HttpEndpointCredentialsVisitor(clientHandler));
-            }
-
-            var httpClient = new HttpClient(clientHandler)
-            {
-                BaseAddress = uri
-            };
-
-            return httpClient;
-        }
-
+
         private async Task TransportMessage(Message message, IEndpointCredentials credentials, CancellationToken cancellationToken = default(CancellationToken))
         {
             HttpClient httpClient = null;
@@ -237,7 +220,7 @@ private static HttpClient GetClient(Uri uri, IEndpointCredentials credentials)
                 var httpContent = new StringContent(message.Content);
                 WriteHttpContentHeaders(message, httpContent);
 
-                httpClient = GetClient(endpointBaseUri, credentials);
+                httpClient = await _clientPool.GetClient(endpointBaseUri, credentials, cancellationToken);
                 var messageId = message.Headers.MessageId;
                 var urlEncodedMessageId = HttpUtility.UrlEncode(messageId);
                 var relativeUri = string.Format("message/{0}", urlEncodedMessageId);
@@ -395,7 +378,7 @@ private async Task SendSubscriptionRequest(IEndpoint endpoint, TopicName topic,
             try
             {
                 var endpointBaseUri = endpoint.Address.WithTrailingSlash();
-                httpClient = GetClient(endpointBaseUri, endpoint.Credentials);
+                httpClient = await _clientPool.GetClient(endpointBaseUri, endpoint.Credentials, cancellationToken);
 
                 var urlSafeTopicName = HttpUtility.UrlEncode(topic);
                 var relativeUri = string.Format("topic/{0}/subscriber?uri={1}", urlSafeTopicName, _baseUri);

Source/Platibus/Platibus.csproj

@@ -94,6 +94,7 @@
     <Compile Include="Http\AuthenticationSchemeElement.cs" />
     <Compile Include="Http\AuthenticationSchemesElementCollection.cs" />
     <Compile Include="Http\BasicAuthorizationService.cs" />
+    <Compile Include="Http\HttpClientPool.cs" />
     <Compile Include="ResourceNotFoundException.cs" />
     <Compile Include="Security\IAuthorizationService.cs" />
     <Compile Include="Http\HttpServerConfigurationManager.cs" />