From 74110bdff6b3072483b6c4e831d826854e205402 Mon Sep 17 00:00:00 2001
From: "Collin M. Barrett" <collinbarrett@users.noreply.github.com>
Date: Fri, 12 Jul 2019 21:57:24 -0500
Subject: [PATCH] use RetryAfter response header in retry policy

---
 .../ServiceCollectionExtensions.cs            |  2 ++
 .../Polly/ServiceCollectionExtensions.cs      | 36 +++++++++++++++++++
 .../Web/ServiceCollectionExtensions.cs        | 24 +++++--------
 3 files changed, 46 insertions(+), 16 deletions(-)
 create mode 100644 src/FilterLists.Agent/Infrastructure/Polly/ServiceCollectionExtensions.cs

diff --git a/src/FilterLists.Agent/Infrastructure/DependencyInjection/ServiceCollectionExtensions.cs b/src/FilterLists.Agent/Infrastructure/DependencyInjection/ServiceCollectionExtensions.cs
index d2b33e021..e544abab1 100644
--- a/src/FilterLists.Agent/Infrastructure/DependencyInjection/ServiceCollectionExtensions.cs
+++ b/src/FilterLists.Agent/Infrastructure/DependencyInjection/ServiceCollectionExtensions.cs
@@ -4,6 +4,7 @@
 using FilterLists.Agent.Infrastructure.Disk;
 using FilterLists.Agent.Infrastructure.FilterListsApi;
 using FilterLists.Agent.Infrastructure.GitHub;
+using FilterLists.Agent.Infrastructure.Polly;
 using FilterLists.Agent.Infrastructure.Web;
 using MediatR;
 using Microsoft.ApplicationInsights;
@@ -23,6 +24,7 @@ public static void ConfigureServices(this IServiceCollection services)
             services.AddLocalization();
             services.AddTransient<Parser>();
             services.AddMediatR(AppDomain.CurrentDomain.GetAssemblies());
+            services.AddPollyPolicyRegistry();
             services.AddDiskServices();
             services.AddFilterListsApiServices();
             services.AddGitHubServices();
diff --git a/src/FilterLists.Agent/Infrastructure/Polly/ServiceCollectionExtensions.cs b/src/FilterLists.Agent/Infrastructure/Polly/ServiceCollectionExtensions.cs
new file mode 100644
index 000000000..52f64a75e
--- /dev/null
+++ b/src/FilterLists.Agent/Infrastructure/Polly/ServiceCollectionExtensions.cs
@@ -0,0 +1,36 @@
+using System;
+using System.Net;
+using System.Net.Http;
+using System.Threading.Tasks;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using Polly;
+using Polly.Registry;
+
+namespace FilterLists.Agent.Infrastructure.Polly
+{
+    public static class ServiceCollectionExtensions
+    {
+        public static void AddPollyPolicyRegistry(this IServiceCollection services)
+        {
+            var registry = services.AddPolicyRegistry();
+
+            IAsyncPolicy<HttpResponseMessage> waitAndRetryTooManyRequests = Policy
+                .HandleResult<HttpResponseMessage>(r => r.StatusCode == HttpStatusCode.TooManyRequests)
+                .WaitAndRetryAsync(3,
+                    (retryCount, response, context) =>
+                        response.Result?.Headers.RetryAfter.Delta ?? TimeSpan.FromMilliseconds(120),
+                    async (response, timespan, retryCount, context) =>
+                    {
+                        await Task.Run(() =>
+                        {
+                            var logger = services.BuildServiceProvider().GetService<ILogger<IPolicyRegistry<string>>>();
+                            logger.LogInformation("Retrying after 429 TooManyRequests",
+                                response.Result.RequestMessage.RequestUri,
+                                response.Result?.Headers.RetryAfter.Delta.ToString(), retryCount);
+                        });
+                    });
+            registry.Add(nameof(waitAndRetryTooManyRequests), waitAndRetryTooManyRequests);
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/FilterLists.Agent/Infrastructure/Web/ServiceCollectionExtensions.cs b/src/FilterLists.Agent/Infrastructure/Web/ServiceCollectionExtensions.cs
index 9e64657ca..860b826b0 100644
--- a/src/FilterLists.Agent/Infrastructure/Web/ServiceCollectionExtensions.cs
+++ b/src/FilterLists.Agent/Infrastructure/Web/ServiceCollectionExtensions.cs
@@ -1,10 +1,7 @@
-using System;
-using System.Net;
-using System.Net.Http;
+using System.Net.Http;
 using FilterLists.Agent.Core.Lists;
 using FilterLists.Agent.Core.Urls;
 using Microsoft.Extensions.DependencyInjection;
-using Polly;
 
 namespace FilterLists.Agent.Infrastructure.Web
 {
@@ -12,18 +9,13 @@ public static class ServiceCollectionExtensions
     {
         public static void AddWebServices(this IServiceCollection services)
         {
-            services.AddHttpClient<IListRepository, ListRepository>().AddTransientHttpErrorPolicy(b =>
-                b.OrResult(r => r.StatusCode == HttpStatusCode.TooManyRequests)
-                    .WaitAndRetryAsync(5, i => i * TimeSpan.FromSeconds(3)));
-            services.AddHttpClient<IUrlValidator, UrlValidator>()
-                .ConfigureHttpMessageHandlerBuilder(b =>
-                {
-                    b.PrimaryHandler = new HttpClientHandler {AllowAutoRedirect = false};
-                    b.Build();
-                })
-                .AddTransientHttpErrorPolicy(b =>
-                    b.OrResult(r => r.StatusCode == HttpStatusCode.TooManyRequests)
-                        .WaitAndRetryAsync(5, i => i * TimeSpan.FromSeconds(3)));
+            services.AddHttpClient<IListRepository, ListRepository>()
+                .AddPolicyHandlerFromRegistry("waitAndRetryTooManyRequests");
+            services.AddHttpClient<IUrlValidator, UrlValidator>().ConfigureHttpMessageHandlerBuilder(b =>
+            {
+                b.PrimaryHandler = new HttpClientHandler {AllowAutoRedirect = false};
+                b.Build();
+            }).AddPolicyHandlerFromRegistry("waitAndRetryTooManyRequests");
         }
     }
 }
\ No newline at end of file