Socket exhaustion from reuse of HttpClient

[hyphmongo]

General information

• SDK/Library version: 4.7.0
• Environment: Production
• Language, language version, and OS: .NET Core 2.1.0

Issue description

Under high traffic we are reaching the point where no more connections can be opened to braintree with netstat showing a lot of connections in TIME_WAIT state.

Looking at HttpService.cs a new instance of HttpClient is being created per request. From the docs the recommendation is to instantiate HttpClient once as a static on the class.

HttpClient is intended to be instantiated once and re-used throughout the life of an application. Instantiating an HttpClient class for every request will exhaust the number of sockets available under heavy loads. This will result in SocketException errors.

[crookedneighbor]

Thanks for the report. We're working on a fix for this and doing some testing internally.

Here's what we have so far:

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c44aa5ef..4a9933f7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,6 @@
+## unreleased
+* Fix issue where HttpClient could throw exceptions under heavy traffic (closes #79)
+
 ## 4.7.0
 * Add `AuthorizationExpiresAt` to `Transaction`
 * Add `ProcessorResponseType` to `Transaction`, `AuthorizationAdjustment`, and `CreditCardVerification`
diff --git a/src/Braintree/HttpService.cs b/src/Braintree/HttpService.cs
index d1d326a8..25d85090 100644
--- a/src/Braintree/HttpService.cs
+++ b/src/Braintree/HttpService.cs
@@ -22,6 +22,10 @@ namespace Braintree
         protected static readonly Encoding encoding = Encoding.UTF8;
 
         protected Configuration Configuration;
+#if netcore
+        protected HttpClient HttpClientWithoutProxy;
+        protected HttpClient HttpClientWithProxy;
+#endif
 
         public Environment Environment
         {
@@ -61,6 +65,25 @@ namespace Braintree
         public HttpService(Configuration configuration)
         {
             Configuration = configuration;
+
+#if netcore
+            HttpClientWithoutProxy = new HttpClient(new HttpClientHandler {
+                AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate,
+                UseProxy = false,
+            }, false);
+            HttpClientWithoutProxy.Timeout = TimeSpan.FromMilliseconds(Configuration.Timeout);
+
+            var proxy = GetWebProxy();
+
+            if (proxy != null) {
+                HttpClientWithProxy = new HttpClient(new HttpClientHandler {
+                    AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate,
+                    UseProxy = true,
+                    Proxy = proxy,
+                }, false);
+                HttpClientWithProxy.Timeout = TimeSpan.FromMilliseconds(Configuration.Timeout);
+            }
+#endif
         }
 
 #if netcore
@@ -89,45 +112,27 @@ namespace Braintree
         }
 
         public string GetHttpResponse(HttpRequestMessage request) {
-            var httpClientHandler = new HttpClientHandler
-            {
-                AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate,
-            };
+            HttpClient client = GetHttpClient(request.RequestUri);
 
-            SetWebProxy(httpClientHandler, request.RequestUri);
-
-            using (var client = new HttpClient(httpClientHandler))
+            var response = client.SendAsync(request).GetAwaiter().GetResult();
+            if (response.StatusCode != (HttpStatusCode) 422)
             {
-                client.Timeout = TimeSpan.FromMilliseconds(Configuration.Timeout);
-                var response = client.SendAsync(request).GetAwaiter().GetResult();
-                if (response.StatusCode != (HttpStatusCode) 422)
-                {
-                    ThrowExceptionIfErrorStatusCode(response.StatusCode, null);
-                }
-
-                return ParseResponseStream(response.Content.ReadAsStreamAsync().GetAwaiter().GetResult());
+                ThrowExceptionIfErrorStatusCode(response.StatusCode, null);
             }
+
+            return ParseResponseStream(response.Content.ReadAsStreamAsync().GetAwaiter().GetResult());
         }
 
         public async Task<string> GetHttpResponseAsync(HttpRequestMessage request) {
-            var httpClientHandler = new HttpClientHandler
-            {
-                AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate,
-            };
-
-            SetWebProxy(httpClientHandler, request.RequestUri);
+            HttpClient client = GetHttpClient(request.RequestUri);
 
-            using (var client = new HttpClient(httpClientHandler))
+            var response = client.SendAsync(request).GetAwaiter().GetResult();
+            if (response.StatusCode != (HttpStatusCode) 422)
             {
-                client.Timeout = TimeSpan.FromMilliseconds(Configuration.Timeout);
-                var response = client.SendAsync(request).GetAwaiter().GetResult();
-                if (response.StatusCode != (HttpStatusCode) 422)
-                {
-                    ThrowExceptionIfErrorStatusCode(response.StatusCode, null);
-                }
-
-                return await ParseResponseStreamAsync(response.Content.ReadAsStreamAsync().GetAwaiter().GetResult());
+                ThrowExceptionIfErrorStatusCode(response.StatusCode, null);
             }
+
+            return await ParseResponseStreamAsync(response.Content.ReadAsStreamAsync().GetAwaiter().GetResult());
         }
 #else
         public HttpWebRequest GetHttpRequest(string URL, string method) {
@@ -197,18 +202,12 @@ namespace Braintree
 #endif
 
 #if netcore
-        protected void SetWebProxy(HttpClientHandler httpClientHandler, Uri URL)
-        {
-            var proxy = GetWebProxy();
-            bool useProxy = false;
-
-            if (proxy != null && !proxy.IsBypassed(URL))
-            {
-                useProxy = true;
-                httpClientHandler.Proxy = proxy;
+        protected HttpClient GetHttpClient (Uri URL) {
+            if (HttpClientWithProxy != null && !GetWebProxy().IsBypassed(URL)) {
+                return HttpClientWithProxy;
             }
 
-            httpClientHandler.UseProxy = useProxy;
+            return HttpClientWithoutProxy;
         }
 #else
         protected void SetRequestProxy(WebRequest request)

If you'd like to give it a try, you can save that to a file named httpclient.diff and apply it with: git apply httpclient.diff

[crookedneighbor]

Upon further examination, it looks like a new braintree service is being created in each request, which I didn't realize. 😬

Here's a new diff that uses a static client if configured.

diff --git a/src/Braintree/Configuration.cs b/src/Braintree/Configuration.cs
index 4384f3ba..32b5c560 100644
--- a/src/Braintree/Configuration.cs
+++ b/src/Braintree/Configuration.cs
@@ -59,6 +59,11 @@ namespace Braintree
             get { return timeout == 0 ? 60000 : timeout; }
             set { timeout = value; }
         }
+        private bool useStaticHttpClient;
+        public bool UseStaticHttpClient {
+            get { return useStaticHttpClient ? true : false; }
+            set { useStaticHttpClient = value; }
+        }
 
         public Configuration()
         {
diff --git a/src/Braintree/HttpService.cs b/src/Braintree/HttpService.cs
index d1d326a8..9d8d6d04 100644
--- a/src/Braintree/HttpService.cs
+++ b/src/Braintree/HttpService.cs
@@ -20,6 +20,9 @@ namespace Braintree
     public class HttpService
     {
         protected static readonly Encoding encoding = Encoding.UTF8;
+        protected static HttpClient staticClient = new HttpClient(new HttpClientHandler {
+                AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate,
+        }, false);
 
         protected Configuration Configuration;
 
@@ -88,45 +91,61 @@ namespace Braintree
             return request;
         }
 
-        public string GetHttpResponse(HttpRequestMessage request) {
-            var httpClientHandler = new HttpClientHandler
+        public string GetHttpResponseWithClient(HttpClient client, HttpRequestMessage request) {
+            var response = client.SendAsync(request).GetAwaiter().GetResult();
+            if (response.StatusCode != (HttpStatusCode) 422)
             {
-                AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate,
-            };
+                ThrowExceptionIfErrorStatusCode(response.StatusCode, null);
+            }
 
-            SetWebProxy(httpClientHandler, request.RequestUri);
+            return ParseResponseStream(response.Content.ReadAsStreamAsync().GetAwaiter().GetResult());
+        }
 
-            using (var client = new HttpClient(httpClientHandler))
+        public async Task<string> GetHttpResponseWithClientAsync(HttpClient client, HttpRequestMessage request) {
+            var response = client.SendAsync(request).GetAwaiter().GetResult();
+            if (response.StatusCode != (HttpStatusCode) 422)
             {
-                client.Timeout = TimeSpan.FromMilliseconds(Configuration.Timeout);
-                var response = client.SendAsync(request).GetAwaiter().GetResult();
-                if (response.StatusCode != (HttpStatusCode) 422)
+                ThrowExceptionIfErrorStatusCode(response.StatusCode, null);
+            }
+
+            return await ParseResponseStreamAsync(response.Content.ReadAsStreamAsync().GetAwaiter().GetResult());
+        }
+
+        public string GetHttpResponse(HttpRequestMessage request) {
+            if (Configuration.UseStaticHttpClient == true) {
+                return GetHttpResponseWithClient(staticClient, request);
+            } else {
+                var httpClientHandler = new HttpClientHandler
                 {
-                    ThrowExceptionIfErrorStatusCode(response.StatusCode, null);
-                }
+                    AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate,
+                };
+
+                SetWebProxy(httpClientHandler, request.RequestUri);
 
-                return ParseResponseStream(response.Content.ReadAsStreamAsync().GetAwaiter().GetResult());
+                using (var client = new HttpClient(httpClientHandler))
+                {
+                    client.Timeout = TimeSpan.FromMilliseconds(Configuration.Timeout);
+                    return GetHttpResponseWithClient(client, request);
+                }
             }
         }
 
         public async Task<string> GetHttpResponseAsync(HttpRequestMessage request) {
-            var httpClientHandler = new HttpClientHandler
-            {
-                AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate,
-            };
+            if (Configuration.UseStaticHttpClient == true) {
+                return await GetHttpResponseWithClientAsync(staticClient, request);
+            } else {
+                var httpClientHandler = new HttpClientHandler
+                {
+                    AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate,
+                };
 
-            SetWebProxy(httpClientHandler, request.RequestUri);
+                SetWebProxy(httpClientHandler, request.RequestUri);
 
-            using (var client = new HttpClient(httpClientHandler))
-            {
-                client.Timeout = TimeSpan.FromMilliseconds(Configuration.Timeout);
-                var response = client.SendAsync(request).GetAwaiter().GetResult();
-                if (response.StatusCode != (HttpStatusCode) 422)
+                using (var client = new HttpClient(httpClientHandler))
                 {
-                    ThrowExceptionIfErrorStatusCode(response.StatusCode, null);
+                    client.Timeout = TimeSpan.FromMilliseconds(Configuration.Timeout);
+                    return await GetHttpResponseWithClientAsync(client, request);
                 }
-
-                return await ParseResponseStreamAsync(response.Content.ReadAsStreamAsync().GetAwaiter().GetResult());
             }
         }
 #else

If you'd like, you can try this diff out.

[hyphmongo]

Thanks! Looks like the static HttpClient is working in my test scenarios

Should there also be an #if netcore check when creating staticClient?

[crookedneighbor]

Yes, I think you are right.

[crookedneighbor]

This is out now in 4.8.0