Google Api

Yavsc/GoogleApiSupport/Google.Apis.Core/Http/ExponentialBackOffInitializer.cs

@@ -0,0 +1,76 @@
+/*
+Copyright 2013 Google Inc
+
+Licensed 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.
+*/
+
+using System;
+
+namespace Google.Apis.Http
+{
+    /// <summary>
+    /// Indicates if exponential back-off is used automatically on exceptions in a service requests and \ or when 503 
+    /// responses is returned form the server.
+    /// </summary>
+    [Flags]
+    public enum ExponentialBackOffPolicy
+    {
+        /// <summary>Exponential back-off is disabled.</summary>
+        None = 0,
+        /// <summary>Exponential back-off is enabled only for exceptions.</summary>
+        Exception = 1,
+        /// <summary>Exponential back-off is enabled only for 503 HTTP Status code.</summary>
+        UnsuccessfulResponse503 = 2
+    }
+
+    /// <summary>
+    /// An initializer which adds exponential back-off as exception handler and \ or unsuccessful response handler by
+    /// the given <see cref="ExponentialBackOffPolicy"/>.
+    /// </summary>
+    public class ExponentialBackOffInitializer : IConfigurableHttpClientInitializer
+    {
+        /// <summary>Gets or sets the used back-off policy.</summary>
+        private ExponentialBackOffPolicy Policy { get; set; }
+
+        /// <summary>Gets or sets the back-off handler creation function.</summary>
+        private Func<BackOffHandler> CreateBackOff { get; set; }
+
+        /// <summary>
+        /// Constructs a new back-off initializer with the given policy and back-off handler create function.
+        /// </summary>
+        public ExponentialBackOffInitializer(ExponentialBackOffPolicy policy, Func<BackOffHandler> createBackOff)
+        {
+            Policy = policy;
+            CreateBackOff = createBackOff;
+        }
+
+        /// <inheritdoc/>
+        public void Initialize(ConfigurableHttpClient httpClient)
+        {
+            var backOff = CreateBackOff();
+
+            // Add exception handler and \ or unsuccessful response handler.
+            if ((Policy & ExponentialBackOffPolicy.Exception) == ExponentialBackOffPolicy.Exception)
+            {
+                httpClient.MessageHandler.AddExceptionHandler(backOff);
+            }
+
+            if ((Policy & ExponentialBackOffPolicy.UnsuccessfulResponse503) ==
+                ExponentialBackOffPolicy.UnsuccessfulResponse503)
+            {
+                httpClient.MessageHandler.AddUnsuccessfulResponseHandler(backOff);
+            }
+        }
+    }
+
+}