Increase connection pool size limit automatically (#15263)

Author: pakrym

sdk/core/Azure.Core/CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## 1.6.0-beta.1 (Unreleased)
 
+### Changed
+- `ServicePointManager` Connection limit is automatically increased to `50` for Azure endpoints. 
+
 
 ## 1.5.0 (2020-09-03)
 

sdk/core/Azure.Core/src/Pipeline/HttpClientTransport.cs

@@ -86,6 +86,10 @@ private static HttpClient CreateDefaultClient()
                 httpClientHandler.Proxy = webProxy;
             }
 
+#if NETFRAMEWORK
+            ServicePointHelpers.SetLimits(httpClientHandler);
+#endif
+
             return new HttpClient(httpClientHandler);
         }
 

sdk/core/Azure.Core/src/Pipeline/HttpWebRequestTransport.cs

@@ -48,6 +48,9 @@ public override async ValueTask ProcessAsync(HttpMessage message)
         private async ValueTask ProcessInternal(HttpMessage message, bool async)
         {
             var request = CreateRequest(message.Request);
+
+            ServicePointHelpers.SetLimits(request.ServicePoint);
+
             using var registration = message.CancellationToken.Register(state => ((HttpWebRequest) state).Abort(), request);
             try
             {

sdk/core/Azure.Core/src/Pipeline/ServicePointHelpers.cs

@@ -0,0 +1,32 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+using System.Net;
+using System.Net.Http;
+
+namespace Azure.Core.Pipeline
+{
+    internal static class ServicePointHelpers
+    {
+        private const int RuntimeDefaultConnectionLimit = 2;
+        private const int IncreasedConnectionLimit = 50;
+
+        public static void SetLimits(ServicePoint requestServicePoint)
+        {
+            // Only change when the default runtime limit is used
+            if (requestServicePoint.ConnectionLimit == RuntimeDefaultConnectionLimit)
+            {
+                requestServicePoint.ConnectionLimit = IncreasedConnectionLimit;
+            }
+        }
+
+        public static void SetLimits(HttpClientHandler requestServicePoint)
+        {
+            // Only change when the default runtime limit is used
+            if (requestServicePoint.MaxConnectionsPerServer == RuntimeDefaultConnectionLimit)
+            {
+                requestServicePoint.MaxConnectionsPerServer = IncreasedConnectionLimit;
+            }
+        }
+    }
+}

sdk/core/Azure.Core/tests/HttpPipelineFunctionalTests.cs

@@ -8,12 +8,12 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Azure.Core.Pipeline;
+using Azure.Core.TestFramework;
 using Microsoft.AspNetCore.Http;
 using NUnit.Framework;
 
 namespace Azure.Core.Tests
 {
-
     [TestFixture(typeof(HttpClientTransport), true)]
     [TestFixture(typeof(HttpClientTransport), false)]
 #if NETFRAMEWORK
@@ -158,6 +158,82 @@ public async Task NonBufferedFailedResponsesAreDisposedOf()
             Assert.Greater(reqNum, requestCount);
         }
 
+        [Test]
+        public async Task Opens50ParallelConnections()
+        {
+            // Running 50 sync requests on the threadpool would cause starvation
+            // and the test would take 20 sec to finish otherwise
+            ThreadPool.SetMinThreads(100, 100);
+
+            HttpPipeline httpPipeline = HttpPipelineBuilder.Build(GetOptions());
+            int reqNum = 0;
+
+            TaskCompletionSource<object> requestsTcs = new TaskCompletionSource<object>(TaskCreationOptions.RunContinuationsAsynchronously);
+
+            using TestServer testServer = new TestServer(
+                async context =>
+                {
+                    if (Interlocked.Increment(ref reqNum) == 50)
+                    {
+                        requestsTcs.SetResult(true);
+                    }
+
+                    await requestsTcs.Task;
+                });
+
+            var requestCount = 50;
+            List<Task> requests = new List<Task>();
+            for (int i = 0; i < requestCount; i++)
+            {
+                HttpMessage message = httpPipeline.CreateMessage();
+                message.Request.Uri.Reset(testServer.Address);
+
+                requests.Add(Task.Run(() => ExecuteRequest(message, httpPipeline)));
+            }
+
+            await Task.WhenAll(requests);
+        }
+
+        [Test]
+        [Category("Live")]
+        public async Task Opens50ParallelConnectionsLive()
+        {
+            // Running 50 sync requests on the threadpool would cause starvation
+            // and the test would take 20 sec to finish otherwise
+            ThreadPool.SetMinThreads(100, 100);
+
+            HttpPipeline httpPipeline = HttpPipelineBuilder.Build(GetOptions());
+            int reqNum = 0;
+
+            TaskCompletionSource<object> requestsTcs = new TaskCompletionSource<object>(TaskCreationOptions.RunContinuationsAsynchronously);
+
+            async Task Connect()
+            {
+                using HttpMessage message = httpPipeline.CreateMessage();
+                message.Request.Uri.Reset(new Uri("https://www.microsoft.com/"));
+                message.BufferResponse = false;
+
+                await ExecuteRequest(message, httpPipeline);
+
+                if (Interlocked.Increment(ref reqNum) == 50)
+                {
+                    requestsTcs.SetResult(true);
+                }
+
+                await requestsTcs.Task;
+            }
+
+            var requestCount = 50;
+            List<Task> requests = new List<Task>();
+            for (int i = 0; i < requestCount; i++)
+            {
+
+                requests.Add(Task.Run(() => Connect()));
+            }
+
+            await Task.WhenAll(requests);
+        }
+
         [Test]
         public async Task BufferedResponsesReadableAfterMessageDisposed()
         {
@@ -176,7 +252,6 @@ public async Task BufferedResponsesReadableAfterMessageDisposed()
                     }
                 });
 
-            // Make sure we dispose things correctly and not exhaust the connection pool
             var requestCount = 100;
             for (int i = 0; i < requestCount; i++)
             {