Make resilient policies configurable.

Author: dsrodenas

src/BuildingBlocks/Resilience/HttpResilience/Policies/CircuitBreakerPolicy.cs

@@ -0,0 +1,18 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Microsoft.eShopOnContainers.BuildingBlocks.Resilience.HttpResilience.Policies
+{
+    internal class CircuitBreakerPolicy : ResilientPolicy
+    {
+        public CircuitBreakerPolicy(int exceptionsAllowedBeforeBreaking, int durationOfBreakInMinutes)
+        {
+            ExceptionsAllowedBeforeBreaking = exceptionsAllowedBeforeBreaking;
+            DurationOfBreakInMinutes = durationOfBreakInMinutes;
+        }
+
+        public int ExceptionsAllowedBeforeBreaking { get; }
+        public int DurationOfBreakInMinutes { get; }
+    }
+}

src/BuildingBlocks/Resilience/HttpResilience/Policies/RetryPolicy.cs

@@ -0,0 +1,20 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Microsoft.eShopOnContainers.BuildingBlocks.Resilience.HttpResilience.Policies
+{
+    internal class RetryPolicy : ResilientPolicy
+    {
+        public RetryPolicy(int retries, int backoffSeconds, bool exponentialBackoff)
+        {
+            Retries = retries;
+            BackoffSeconds = backoffSeconds;
+            ExponentialBackoff = exponentialBackoff;
+        }
+
+        public int Retries { get; }
+        public int BackoffSeconds { get; }
+        public bool ExponentialBackoff { get; }
+    }
+}

src/BuildingBlocks/Resilience/HttpResilience/ResilientHttpClient.cs

@@ -1,8 +1,10 @@
-using Microsoft.Extensions.Logging;
+using Microsoft.eShopOnContainers.BuildingBlocks.Resilience.HttpResilience.Policies;
+using Microsoft.Extensions.Logging;
 using Newtonsoft.Json;
 using Polly;
 using Polly.Wrap;
 using System;
+using System.Collections.Generic;
 using System.Net;
 using System.Net.Http;
 using System.Threading.Tasks;
@@ -19,26 +21,58 @@ public class ResilientHttpClient : IHttpClient
         private PolicyWrap _policyWrapper;
         private ILogger<ResilientHttpClient> _logger;
         public HttpClient Inst => _client;
-        public ResilientHttpClient(ILogger<ResilientHttpClient> logger)
+
+        public ResilientHttpClient(List<Policy> policies, ILogger<ResilientHttpClient> logger)
         {
             _client = new HttpClient();
             _logger = logger;
 
             // Add Policies to be applied
-            _policyWrapper = Policy.WrapAsync(
-                CreateRetryPolicy(),
-                CreateCircuitBreakerPolicy()
-            );
+            _policyWrapper = Policy.WrapAsync(policies.ToArray());
+        }
+
+        public ResilientHttpClient(List<ResilientPolicy> policies, ILogger<ResilientHttpClient> logger)
+        {
+            _client = new HttpClient();
+            _logger = logger;
+
+            // Add Policies to be applied
+            _policyWrapper = Policy.WrapAsync(GeneratePolicies(policies));
+        }
+
+        private Policy[] GeneratePolicies(IList<ResilientPolicy> policies)
+        {
+            var pollyPolicies = new List<Policy>();
+
+            foreach (var policy in policies)
+            {
+                switch (policy)
+                {
+                    case RetryPolicy retryPolicy:
+                        pollyPolicies.Add(
+                            CreateRetryPolicy(
+                                retryPolicy.Retries,
+                                retryPolicy.BackoffSeconds,
+                                retryPolicy.ExponentialBackoff));
+                        break;
+
+                    case CircuitBreakerPolicy circuitPolicy:
+                        pollyPolicies.Add(
+                            CreateCircuitBreakerPolicy(
+                                circuitPolicy.ExceptionsAllowedBeforeBreaking,
+                                circuitPolicy.DurationOfBreakInMinutes));
+                        break;
+                }
+            }
+
+            return pollyPolicies.ToArray();
         }
 
-        private Policy CreateRetryPolicy() =>
+        private Policy CreateRetryPolicy(int retries, int backoffSeconds, bool exponentialBackoff) =>            
             Policy.Handle<HttpRequestException>()
-            .WaitAndRetryAsync(
-                // number of retries
-                6,
-                // exponential backofff
-                retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)),
-                // on retry
+                .WaitAndRetryAsync(
+                retries,               
+                retryAttempt => exponentialBackoff ? TimeSpan.FromSeconds(Math.Pow(backoffSeconds, retryAttempt)) : TimeSpan.FromSeconds(backoffSeconds),
                 (exception, timeSpan, retryCount, context) =>
                 {
                     var msg = $"Retry {retryCount} implemented with Polly's RetryPolicy " +
@@ -50,22 +84,20 @@ private Policy CreateRetryPolicy() =>
                 }
             );
 
-        private Policy CreateCircuitBreakerPolicy() =>
+        private Policy CreateCircuitBreakerPolicy(int exceptionsAllowedBeforeBreaking, int durationOfBreakInMinutes) =>
            Policy.Handle<HttpRequestException>()
            .CircuitBreakerAsync(
-               // number of exceptions before breaking circuit
-               5,
-               // time circuit opened before retry
-               TimeSpan.FromMinutes(1),
+               exceptionsAllowedBeforeBreaking,
+               TimeSpan.FromMinutes(durationOfBreakInMinutes),
                (exception, duration) =>
                {
-                    // on circuit opened
-                    _logger.LogTrace("Circuit breaker opened");
+                   // on circuit opened
+                   _logger.LogTrace("Circuit breaker opened");
                },
                () =>
                {
-                    // on circuit closed
-                    _logger.LogTrace("Circuit breaker reset");
+                   // on circuit closed
+                   _logger.LogTrace("Circuit breaker reset");
                }
            );
 

src/BuildingBlocks/Resilience/HttpResilience/ResilientPolicy.cs

@@ -0,0 +1,10 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Microsoft.eShopOnContainers.BuildingBlocks.Resilience.HttpResilience
+{
+    public class ResilientPolicy
+    {
+    }
+}

src/BuildingBlocks/Resilience/HttpResilience/ResilientPolicyFactory.cs

@@ -0,0 +1,20 @@
+using Microsoft.eShopOnContainers.BuildingBlocks.Resilience.HttpResilience.Policies;
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Microsoft.eShopOnContainers.BuildingBlocks.Resilience.HttpResilience
+{
+    public static class ResilientPolicyFactory
+    {
+        public static ResilientPolicy CreateRetryPolicy(int retries, int backoffSeconds, bool exponentialBackoff)
+        {
+            return new RetryPolicy(retries, backoffSeconds, exponentialBackoff); 
+        }
+
+        public static ResilientPolicy CreateCiscuitBreakerPolicy(int exceptionsAllowedBeforeBreaking, int durationOfBreakInMinutes)
+        {
+            return new CircuitBreakerPolicy(exceptionsAllowedBeforeBreaking, durationOfBreakInMinutes);
+        }
+    }
+}

src/Web/WebMVC/Startup.cs

@@ -58,8 +58,14 @@ public void ConfigureServices(IServiceCollection services)
             services.AddTransient<IBasketService, BasketService>();
             services.AddTransient<IIdentityParser<ApplicationUser>, IdentityParser>();
 
-            if(Configuration.GetValue<string>("ActivateCircuitBreaker") == bool.TrueString)
+            if (Configuration.GetValue<string>("ActivateCircuitBreaker") == bool.TrueString)
             {
+                services.AddSingleton(
+                    new List<ResilientPolicy>
+                    {
+                        ResilientPolicyFactory.CreateRetryPolicy(6, 2, true),
+                        ResilientPolicyFactory.CreateCiscuitBreakerPolicy(5, 1)
+                    });
                 services.AddTransient<IHttpClient, ResilientHttpClient>();
             }
             else