Created Retry and CircuitBreaker policies for MVC App

src/Web/WebMVC/Controllers/OrderController.cs

@@ -7,6 +7,7 @@ using Microsoft.eShopOnContainers.WebMVC.Services;
 using Microsoft.eShopOnContainers.WebMVC.ViewModels;
 using Microsoft.AspNetCore.Authorization;
 using System.Net.Http;
+using Polly.CircuitBreaker;
 
 namespace Microsoft.eShopOnContainers.WebMVC.Controllers
 {
@@ -37,18 +38,24 @@ namespace Microsoft.eShopOnContainers.WebMVC.Controllers
         [HttpPost]
         public async Task<IActionResult> Create(Order model, string action)
         {
-            if (ModelState.IsValid)
+            try
             {
-                var user = _appUserParser.Parse(HttpContext.User);
+                if (ModelState.IsValid)
-                await _orderSvc.CreateOrder(model);
+                {
+                    var user = _appUserParser.Parse(HttpContext.User);
+                    await _orderSvc.CreateOrder(model);
 
-                //Empty basket for current user. 
+                    //Empty basket for current user. 
-                await _basketSvc.CleanBasket(user);
+                    await _basketSvc.CleanBasket(user);
 
-                //Redirect to historic list.
+                    //Redirect to historic list.
-                return RedirectToAction("Index");
+                    return RedirectToAction("Index");
+                }
+            }
+            catch(BrokenCircuitException ex)
+            {
+                ModelState.AddModelError("Error", "Not possible to create a new order, please try later on");
             }
-
             return View(model);
         }
 

src/Web/WebMVC/Services/BasketService.cs

@@ -1,21 +1,20 @@
-using System;
+using Microsoft.AspNetCore.Authentication;
-using System.Collections.Generic;
-using System.Linq;
-using System.Threading.Tasks;
-using Microsoft.eShopOnContainers.WebMVC.ViewModels;
 using Microsoft.AspNetCore.Http;
-using System.Net.Http;
+using Microsoft.eShopOnContainers.WebMVC.ViewModels;
 using Microsoft.Extensions.Options;
 using Newtonsoft.Json;
-using Microsoft.AspNetCore.Authentication;
+using System.Collections.Generic;
-using Microsoft.eShopOnContainers.WebMVC.Extensions;
+using System.Linq;
+using System.Net.Http;
+using System.Threading.Tasks;
+using WebMVC.Services.Utilities;
 
 namespace Microsoft.eShopOnContainers.WebMVC.Services
 {
     public class BasketService : IBasketService
     {
         private readonly IOptionsSnapshot<AppSettings> _settings;
-        private HttpClient _apiClient;
+        private HttpClientWrapper _apiClient;
         private readonly string _remoteServiceBaseUrl;
         private IHttpContextAccessor _httpContextAccesor;
 
@@ -31,8 +30,8 @@ namespace Microsoft.eShopOnContainers.WebMVC.Services
             var context = _httpContextAccesor.HttpContext;
             var token = await context.Authentication.GetTokenAsync("access_token");
 
-            _apiClient = new HttpClient();
+            var _apiClient = new HttpClientWrapper();
-            _apiClient.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", token);
+            _apiClient.Inst.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", token);
 
             var basketUrl = $"{_remoteServiceBaseUrl}/{user.Id.ToString()}";
             var dataString = await _apiClient.GetStringAsync(basketUrl);
@@ -53,12 +52,12 @@ namespace Microsoft.eShopOnContainers.WebMVC.Services
             var context = _httpContextAccesor.HttpContext;
             var token = await context.Authentication.GetTokenAsync("access_token");
 
-            _apiClient = new HttpClient();
+            _apiClient = new HttpClientWrapper();
-            _apiClient.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", token);
+            _apiClient.Inst.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", token);
 
             var basketUrl = _remoteServiceBaseUrl;
-            StringContent content = new StringContent(JsonConvert.SerializeObject(basket), System.Text.Encoding.UTF8, "application/json");
+            
-            var response = await _apiClient.PostAsync(basketUrl, content);
+            var response = await _apiClient.PostAsync(basketUrl, basket);
 
             return basket;
         }
@@ -120,8 +119,8 @@ namespace Microsoft.eShopOnContainers.WebMVC.Services
             var context = _httpContextAccesor.HttpContext;
             var token = await context.Authentication.GetTokenAsync("access_token");
 
-            _apiClient = new HttpClient();
+            _apiClient = new HttpClientWrapper();
-            _apiClient.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", token);
+            _apiClient.Inst.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", token);
             var basketUrl = $"{_remoteServiceBaseUrl}/{user.Id.ToString()}";
             var response = await _apiClient.DeleteAsync(basketUrl);
             

src/Web/WebMVC/Services/CatalogService.cs

@@ -1,22 +1,19 @@
-using System;
+using Microsoft.AspNetCore.Mvc.Rendering;
-using System.Collections.Generic;
-using System.Linq;
-using System.Threading.Tasks;
 using Microsoft.eShopOnContainers.WebMVC.ViewModels;
-using Microsoft.CodeAnalysis.Options;
+using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
-using System.Net.Http;
-using Microsoft.AspNetCore.Mvc.Rendering;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
-using Microsoft.Extensions.Logging;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using WebMVC.Services.Utilities;
 
 namespace Microsoft.eShopOnContainers.WebMVC.Services
 {
     public class CatalogService : ICatalogService
     {
         private readonly IOptionsSnapshot<AppSettings> _settings;
-        private HttpClient _apiClient;
+        private HttpClientWrapper _apiClient;
         private readonly string _remoteServiceBaseUrl;
   
         public CatalogService(IOptionsSnapshot<AppSettings> settings, ILoggerFactory loggerFactory) {
@@ -29,7 +26,7 @@ namespace Microsoft.eShopOnContainers.WebMVC.Services
          
         public async Task<Catalog> GetCatalogItems(int page,int take, int? brand, int? type)
         {
-            _apiClient = new HttpClient();
+            _apiClient = new HttpClientWrapper();
             var itemsQs = $"items?pageIndex={page}&pageSize={take}";
             var filterQs = "";
 
@@ -45,16 +42,10 @@ namespace Microsoft.eShopOnContainers.WebMVC.Services
             var dataString = "";
 
             //
-            // Using HttpClient with Retry and Exponential Backoff
+            // Using a HttpClient wrapper with Retry and Exponential Backoff
             //
-            var retry = new RetryWithExponentialBackoff();
+            dataString = await _apiClient.GetStringAsync(catalogUrl);
-            await retry.RunAsync(async () =>
-            {
-                // work with HttpClient call
-                dataString = await _apiClient.GetStringAsync(catalogUrl);
-            });
 
-            //var dataString = await _apiClient.GetStringAsync(catalogUrl);
             var response = JsonConvert.DeserializeObject<Catalog>(dataString);
 
             return response;
@@ -62,7 +53,7 @@ namespace Microsoft.eShopOnContainers.WebMVC.Services
 
         public async Task<IEnumerable<SelectListItem>> GetBrands()
         {
-            _apiClient = new HttpClient();
+            _apiClient = new HttpClientWrapper();
             var url = $"{_remoteServiceBaseUrl}catalogBrands";
             var dataString = await _apiClient.GetStringAsync(url);
 
@@ -81,7 +72,7 @@ namespace Microsoft.eShopOnContainers.WebMVC.Services
 
         public async Task<IEnumerable<SelectListItem>> GetTypes()
         {
-            _apiClient = new HttpClient();
+            _apiClient = new HttpClientWrapper();
             var url = $"{_remoteServiceBaseUrl}catalogTypes";
             var dataString = await _apiClient.GetStringAsync(url);
 

src/Web/WebMVC/Services/OrderingService.cs

@@ -8,12 +8,13 @@ using Microsoft.Extensions.Options;
 using System.Net.Http;
 using Newtonsoft.Json;
 using Microsoft.AspNetCore.Authentication;
+using WebMVC.Services.Utilities;
 
 namespace Microsoft.eShopOnContainers.WebMVC.Services
 {
     public class OrderingService : IOrderingService
     {
-        private HttpClient _apiClient;
+        private HttpClientWrapper _apiClient;
         private readonly string _remoteServiceBaseUrl;
         private readonly IOptionsSnapshot<AppSettings> _settings;
         private readonly IHttpContextAccessor _httpContextAccesor;
@@ -30,8 +31,8 @@ namespace Microsoft.eShopOnContainers.WebMVC.Services
             var context = _httpContextAccesor.HttpContext;
             var token = await context.Authentication.GetTokenAsync("access_token");
 
-            _apiClient = new HttpClient();
+            _apiClient = new HttpClientWrapper();
-            _apiClient.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", token);
+            _apiClient.Inst.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", token);
 
             var ordersUrl = $"{_remoteServiceBaseUrl}/{Id}";
             var dataString = await _apiClient.GetStringAsync(ordersUrl);
@@ -46,8 +47,8 @@ namespace Microsoft.eShopOnContainers.WebMVC.Services
             var context = _httpContextAccesor.HttpContext;
             var token = await context.Authentication.GetTokenAsync("access_token");
 
-            _apiClient = new HttpClient();
+            _apiClient = new HttpClientWrapper();
-            _apiClient.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", token);
+            _apiClient.Inst.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", token);
 
             var ordersUrl = _remoteServiceBaseUrl;
             var dataString = await _apiClient.GetStringAsync(ordersUrl);
@@ -77,17 +78,16 @@ namespace Microsoft.eShopOnContainers.WebMVC.Services
             var context = _httpContextAccesor.HttpContext;
             var token = await context.Authentication.GetTokenAsync("access_token");
 
-            _apiClient = new HttpClient();
+            _apiClient = new HttpClientWrapper();            
-            _apiClient.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", token);
+            _apiClient.Inst.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", token);
-            _apiClient.DefaultRequestHeaders.Add("x-requestid", order.RequestId.ToString());
+            _apiClient.Inst.DefaultRequestHeaders.Add("x-requestid", order.RequestId.ToString());
+
             var ordersUrl = $"{_remoteServiceBaseUrl}/new";
             order.CardTypeId = 1;
             order.CardExpirationApiFormat();
             SetFakeIdToProducts(order);
-            
+
-            StringContent content = new StringContent(JsonConvert.SerializeObject(order), System.Text.Encoding.UTF8, "application/json");
+            var response = await _apiClient.PostAsync(ordersUrl, order);
-           
-            var response = await _apiClient.PostAsync(ordersUrl, content);
 
             if (response.StatusCode == System.Net.HttpStatusCode.InternalServerError)
                 throw new Exception("Error creating order, try later");

src/Web/WebMVC/Services/Utilities/HttpClientWrapper.cs

@@ -0,0 +1,99 @@
+using Microsoft.Extensions.Logging;
+using Newtonsoft.Json;
+using Polly;
+using Polly.Wrap;
+using System;
+using System.Net.Http;
+using System.Threading.Tasks;
+
+namespace WebMVC.Services.Utilities
+{
+    public class HttpClientWrapper
+    {
+        private HttpClient _client;
+        private PolicyWrap _policyWrapper;
+        private ILogger _logger;
+        public HttpClient Inst => _client;
+        public HttpClientWrapper()
+        {
+            _client = new HttpClient();
+            _logger = new LoggerFactory().CreateLogger(nameof(HttpClientWrapper));
+
+            // Add Policies to be applied
+            _policyWrapper = Policy.WrapAsync(
+                CreateRetryPolicy(),
+                CreateCircuitBreakerPolicy()
+            );
+        }       
+
+        private Policy CreateCircuitBreakerPolicy()
+        {
+            return Policy
+                .Handle<HttpRequestException>()
+                .CircuitBreakerAsync(
+                    // number of exceptions before breaking circuit
+                    3, 
+                    // time circuit opened before retry
+                    TimeSpan.FromMinutes(1), 
+                    (exception, duration) => {
+                        // on circuit opened
+                        _logger.LogTrace("Circuit breaker opened");
+                    }, 
+                    () => {
+                        // on circuit closed
+                        _logger.LogTrace("Circuit breaker reset");
+                    }
+                );
+        }
+
+        private Policy CreateRetryPolicy()
+        {
+            return Policy
+                .Handle<HttpRequestException>()
+                .WaitAndRetryAsync(
+                    // number of retries
+                    3, 
+                    // exponential backofff
+                    retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)),
+                    // on retry
+                    (exception, timeSpan, retryCount, context) =>  
+                    {
+                        _logger.LogTrace($"Retry {retryCount} " +
+                            $"of {context.PolicyKey} " +
+                            $"at {context.ExecutionKey}, " +
+                            $"due to: {exception}.");
+                 });
+        }
+
+        public async Task<string> GetStringAsync(string uri)
+        {
+            return await HttpInvoker(async () => 
+                await _client.GetStringAsync(uri));
+        }
+
+        public async Task<HttpResponseMessage> PostAsync<T>(string uri, T item)
+        {
+            // a new StringContent must be created for each retry 
+            // as it is disposed after each call
+            return await HttpInvoker(async () =>
+                    await _client.PostAsync(uri, 
+                        new StringContent(JsonConvert.SerializeObject(item), 
+                        System.Text.Encoding.UTF8, "application/json")));
+        }
+
+        public async Task<HttpResponseMessage> DeleteAsync(string uri)
+        {
+            return await HttpInvoker(async () =>
+                await _client.DeleteAsync(uri));
+        }
+
+        private async Task<T> HttpInvoker<T>(Func<Task<T>> action)
+        {
+            // Executes the action applying all 
+            // the policies defined in the wrapper
+            return await _policyWrapper
+                .ExecuteAsync(async () => await action());
+        }
+    }
+
+}

src/Web/WebMVC/Services/Utilities/RetryWithExponentialBackoff.cs

@@ -1,90 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Diagnostics;
-using System.Linq;
-using System.Threading.Tasks;
-
-namespace Microsoft.eShopOnContainers.WebMVC.Services
-{
-    /// <summary>
-    /// When working with cloud services and Docker containers, it's very important to always catch
-    /// TimeoutException, and retry the operation.  
-    /// RetryWithExponentialBackoff makes it easy to implement such pattern. 
-    /// Usage:
-    ///     var retry = new RetryWithExponentialBackoff();
-    ///     await retry.RunAsync(async ()=>
-    ///     {
-    ///        // work with HttpClient
-    ///     });
-    /// </summary>
-    public sealed class RetryWithExponentialBackoff
-    {
-        private readonly int maxRetries, delayMilliseconds, maxDelayMilliseconds;
-
-        public RetryWithExponentialBackoff(int maxRetries = 50, int delayMilliseconds = 200, int maxDelayMilliseconds = 2000)
-        {
-            this.maxRetries = maxRetries;
-            this.delayMilliseconds = delayMilliseconds;
-            this.maxDelayMilliseconds = maxDelayMilliseconds;
-        }
-
-        public async Task RunAsync(Func<Task> func)
-        {
-            ExponentialBackoff backoff = new ExponentialBackoff(this.maxRetries, this.delayMilliseconds, this.maxDelayMilliseconds);
-        retry:
-            try
-            {
-                await func();
-            }
-            catch (Exception ex) when (ex is TimeoutException || ex is System.Net.Http.HttpRequestException)
-            {
-                Debug.WriteLine("Exception raised is: " + ex.GetType().ToString() + " -- Message: " + ex.Message + " -- Inner Message: " + ex.InnerException.Message);
-                await backoff.Delay();
-                goto retry;
-            }
-        }
-    }
-
-
-    /// <summary>
-    /// Usage:
-    /// ExponentialBackoff backoff = new ExponentialBackoff(3, 10, 100);
-    /// retry:
-    /// try {
-    ///        // ...
-    /// }
-    /// catch (Exception ex) {
-    ///    await backoff.Delay(cancellationToken);
-    ///    goto retry;
-    /// }
-    /// </summary>
-    public struct ExponentialBackoff
-    {
-        private readonly int m_maxRetries, m_delayMilliseconds, m_maxDelayMilliseconds;
-        private int m_retries, m_pow;
-
-        public ExponentialBackoff(int maxRetries, int delayMilliseconds, int maxDelayMilliseconds)
-        {
-            m_maxRetries = maxRetries;
-            m_delayMilliseconds = delayMilliseconds;
-            m_maxDelayMilliseconds = maxDelayMilliseconds;
-            m_retries = 0;
-            m_pow = 1;
-        }
-
-        public Task Delay()
-        {
-            if (m_retries == m_maxRetries)
-            {
-                throw new TimeoutException("Max retry attempts exceeded.");
-            }
-            ++m_retries;
-            if (m_retries < 31)
-            {
-                m_pow = m_pow << 1; // m_pow = Pow(2, m_retries - 1)
-            }
-            int delay = Math.Min(m_delayMilliseconds * (m_pow - 1) / 2, m_maxDelayMilliseconds);
-            return Task.Delay(delay);
-        }
-    }
-}

src/Web/WebMVC/Views/Order/Create.cshtml

@@ -11,6 +11,13 @@
 <div class="container">
     <form method="post" asp-controller="Order" asp-action="Create">
         <section class="esh-orders_new-section">
+            <div class="row">
+                @foreach (var error in ViewData.ModelState.Values.SelectMany(err => err.Errors)) {
+                    <div class="alert alert-warning" role="alert">                    
+                        &nbsp;@error.ErrorMessage
+                    </div>
+                }
+            </div>
             <h4 class="esh-orders_new-title">Shipping address</h4>
             <div class="row">
                 <div class="col-md-6">

src/Web/WebMVC/WebMVC.csproj

@@ -32,6 +32,7 @@
       <PrivateAssets>All</PrivateAssets>
     </PackageReference>
     <PackageReference Include="Newtonsoft.Json" Version="9.0.1" />
+    <PackageReference Include="Polly" Version="5.0.6" />
     <PackageReference Include="System.IdentityModel.Tokens.Jwt" Version="5.1.0" />
     <PackageReference Include="Microsoft.AspNetCore.Authentication.OpenIdConnect" Version="1.1.0" />
     <PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="1.1.0" />