Introduced polly retry policy for Ordering.API

src/Services/Ordering/Ordering.API/Extensions/WebHostExtensions.cs

@@ -0,0 +1,76 @@
+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 Ordering.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);
+        }
+    }
+}