From 49aac0ce77563c2832b1741d56095baafbb8b94c Mon Sep 17 00:00:00 2001
From: Sumit Ghosh <13281246+sughosneo@users.noreply.github.com>
Date: Mon, 24 Aug 2020 15:11:18 +0530
Subject: [PATCH] Introducted Retry logic in Marketing.API with polly policy.

---
 .../Controllers/CampaignsController.cs        |  2 +-
 .../Extensions/WebHostExtensions.cs           | 75 +++++++++++++++++++
 .../Marketing.API/Marketing.API.csproj        |  3 +
 .../Marketing/Marketing.API/Startup.cs        |  6 +-
 4 files changed, 82 insertions(+), 4 deletions(-)
 create mode 100644 src/Services/Marketing/Marketing.API/Extensions/WebHostExtensions.cs

diff --git a/src/Services/Marketing/Marketing.API/Controllers/CampaignsController.cs b/src/Services/Marketing/Marketing.API/Controllers/CampaignsController.cs
index 67ac1bca5..f8c395182 100644
--- a/src/Services/Marketing/Marketing.API/Controllers/CampaignsController.cs
+++ b/src/Services/Marketing/Marketing.API/Controllers/CampaignsController.cs
@@ -13,7 +13,7 @@ namespace Microsoft.eShopOnContainers.Services.Marketing.API.Controllers
     using EntityFrameworkCore;
     using Dto;
     using AspNetCore.Authorization;
-    using Extensions.Options;
+    using Microsoft.Extensions.Options;
     using Microsoft.eShopOnContainers.Services.Marketing.API.ViewModel;
     using Microsoft.AspNetCore.Http;
     using System.Net;
diff --git a/src/Services/Marketing/Marketing.API/Extensions/WebHostExtensions.cs b/src/Services/Marketing/Marketing.API/Extensions/WebHostExtensions.cs
new file mode 100644
index 000000000..7090b07d1
--- /dev/null
+++ b/src/Services/Marketing/Marketing.API/Extensions/WebHostExtensions.cs
@@ -0,0 +1,75 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Configuration;
+using System;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using Polly;
+using System.Data.SqlClient;
+using Microsoft.AspNetCore.Hosting;
+
+namespace Microsoft.eShopOnContainers.Services.Marketing.API.Extensions
+{
+    public static class WebHostExtensions
+    {
+        public static bool IsInKubernetes(this IWebHost host)
+        {
+            var cfg = host.Services.GetService<IConfiguration>();
+            var orchestratorType = cfg.GetValue<string>("OrchestratorType");
+            return orchestratorType?.ToUpper() == "K8S";
+        }
+
+        public static IWebHost MigrateDbContext<TContext>(this IWebHost host, Action<TContext, IServiceProvider> seeder) where TContext : DbContext
+        {
+            var underK8s = host.IsInKubernetes();
+
+            using (var scope = host.Services.CreateScope())
+            {
+                var services = scope.ServiceProvider;
+
+                var logger = services.GetRequiredService<ILogger<TContext>>();
+
+                var context = services.GetService<TContext>();
+
+                try
+                {
+                    logger.LogInformation("Migrating database associated with context {DbContextName}", typeof(TContext).Name);
+
+                    if (underK8s)
+                    {
+                        InvokeSeeder(seeder, context, services);
+                    }
+                    else
+                    {                       
+                        var retry = Policy.Handle<SqlException>()
+                             .WaitAndRetry(10, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)));
+
+                        //if the sql server container is not created on run docker compose this
+                        //migration can't fail for network related exception. The retry options for DbContext only 
+                        //apply to transient exceptions
+                        // Note that this is NOT applied when running some orchestrators (let the orchestrator to recreate the failing service)
+                        retry.Execute(() => InvokeSeeder(seeder, context, services));
+                    }
+
+                    logger.LogInformation("Migrated database associated with context {DbContextName}", typeof(TContext).Name);
+                }
+                catch (Exception ex)
+                {
+                    logger.LogError(ex, "An error occurred while migrating the database used on context {DbContextName}", typeof(TContext).Name);
+                    if (underK8s)
+                    {
+                        throw;          // Rethrow under k8s because we rely on k8s to re-run the pod
+                    }
+                }
+            }
+
+            return host;
+        }
+
+        private static void InvokeSeeder<TContext>(Action<TContext, IServiceProvider> seeder, TContext context, IServiceProvider services)
+            where TContext : DbContext
+        {
+            context.Database.Migrate();
+            seeder(context, services);
+        }
+    }
+}
diff --git a/src/Services/Marketing/Marketing.API/Marketing.API.csproj b/src/Services/Marketing/Marketing.API/Marketing.API.csproj
index bc3116fc3..0cf1566a4 100644
--- a/src/Services/Marketing/Marketing.API/Marketing.API.csproj
+++ b/src/Services/Marketing/Marketing.API/Marketing.API.csproj
@@ -38,11 +38,14 @@
     <PackageReference Include="Microsoft.AspNetCore.Diagnostics.HealthChecks" Version="2.2.0" />
     <PackageReference Include="Microsoft.AspNetCore.HealthChecks" Version="1.0.0" />
     <PackageReference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" Version="3.1.0" />
+    <PackageReference Include="Microsoft.Extensions.Configuration" Version="3.1.7" />
     <PackageReference Include="Microsoft.Extensions.Configuration.AzureKeyVault" Version="3.1.0" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="3.1.7" />
     <PackageReference Include="Microsoft.Extensions.Logging.AzureAppServices" Version="3.1.0" />
     <PackageReference Include="MongoDB.Bson" Version="2.10.0" />
     <PackageReference Include="MongoDB.Driver.Core" Version="2.10.0" />
     <PackageReference Include="MongoDB.Driver" Version="2.10.0" />
+    <PackageReference Include="Polly" Version="7.2.1" />
     <PackageReference Include="Serilog.AspNetCore" Version="3.2.0" />
     <PackageReference Include="Serilog.Enrichers.Environment" Version="2.1.3" />
     <PackageReference Include="Serilog.Settings.Configuration" Version="3.1.1-dev-00216" />
diff --git a/src/Services/Marketing/Marketing.API/Startup.cs b/src/Services/Marketing/Marketing.API/Startup.cs
index a7386a532..de22de6c5 100644
--- a/src/Services/Marketing/Marketing.API/Startup.cs
+++ b/src/Services/Marketing/Marketing.API/Startup.cs
@@ -11,9 +11,9 @@
     using BuildingBlocks.EventBusRabbitMQ;
     using BuildingBlocks.EventBusServiceBus;
     using EntityFrameworkCore;
-    using Extensions.Configuration;
-    using Extensions.DependencyInjection;
-    using Extensions.Logging;
+    using Microsoft.Extensions.Configuration;
+    using Microsoft.Extensions.DependencyInjection;
+    using Microsoft.Extensions.Logging;
     using HealthChecks.UI.Client;
     using Infrastructure;
     using Infrastructure.Filters;