eShopOnContainers/src/Services/Marketing/Marketing.API/Startup.cs

namespace Microsoft.eShopOnContainers.Services.Marketing.API
{
    using Autofac;
    using Autofac.Extensions.DependencyInjection;
    using IntegrationEvents.Events;
    using AspNetCore.Builder;
    using AspNetCore.Hosting;
    using AspNetCore.Http;
    using Azure.ServiceBus;
    using EntityFrameworkCore;
    using EntityFrameworkCore.Infrastructure;
    using BuildingBlocks.EventBus;
    using BuildingBlocks.EventBus.Abstractions;
    using BuildingBlocks.EventBusRabbitMQ;
    using BuildingBlocks.EventBusServiceBus;
    using Infrastructure;
    using Infrastructure.Filters;
    using Infrastructure.Repositories;
    using Infrastructure.Services;
    using Extensions.Configuration;
    using Extensions.DependencyInjection;
    using Extensions.Logging;
    using Polly;
    using RabbitMQ.Client;
    using System;
    using System.Data.SqlClient;
    using System.Reflection;
    using System.Threading.Tasks;
    using Extensions.HealthChecks;
    using Marketing.API.IntegrationEvents.Handlers;


    public class Startup
    {
        public Startup(IHostingEnvironment env)
        {
            var builder = new ConfigurationBuilder()
                .SetBasePath(env.ContentRootPath)
                .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
                .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
                .AddEnvironmentVariables();

            if (env.IsDevelopment())
            {
                builder.AddUserSecrets(typeof(Startup).GetTypeInfo().Assembly);
            }

            builder.AddEnvironmentVariables();

            Configuration = builder.Build();
        }

        public IConfigurationRoot Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public IServiceProvider ConfigureServices(IServiceCollection services)
        {
            // Add framework services.
            services.AddMvc(options =>
            {
                options.Filters.Add(typeof(HttpGlobalExceptionFilter));
            }).AddControllersAsServices();  //Injecting Controllers themselves thru DIFor further info see: http://docs.autofac.org/en/latest/integration/aspnetcore.html#controllers-as-services

            services.Configure<MarketingSettings>(Configuration);

            services.AddHealthChecks(checks => 
            {
                checks.AddValueTaskCheck("HTTP Endpoint", () => new ValueTask<IHealthCheckResult>(HealthCheckResult.Healthy("Ok")));

                var accountName = Configuration.GetValue<string>("AzureStorageAccountName");
                var accountKey = Configuration.GetValue<string>("AzureStorageAccountKey");
                if (!string.IsNullOrEmpty(accountName) && !string.IsNullOrEmpty(accountKey))
                {
                    checks.AddAzureBlobStorageCheck(accountName, accountKey);
                }
            });

            services.AddDbContext<MarketingContext>(options =>
            {
                options.UseSqlServer(Configuration["ConnectionString"],
                                     sqlServerOptionsAction: sqlOptions =>
                                     {
                                         sqlOptions.MigrationsAssembly(typeof(Startup).GetTypeInfo().Assembly.GetName().Name);
                                         //Configuring Connection Resiliency: https://docs.microsoft.com/en-us/ef/core/miscellaneous/connection-resiliency 
                                         sqlOptions.EnableRetryOnFailure(maxRetryCount: 5, maxRetryDelay: TimeSpan.FromSeconds(30), errorNumbersToAdd: null);
                                     });

                // Changing default behavior when client evaluation occurs to throw. 
                // Default in EF Core would be to log a warning when client evaluation is performed.
                options.ConfigureWarnings(warnings => warnings.Throw(RelationalEventId.QueryClientEvaluationWarning));
                //Check Client vs. Server evaluation: https://docs.microsoft.com/en-us/ef/core/querying/client-eval
            });

            if (Configuration.GetValue<bool>("AzureServiceBusEnabled"))
            {
                services.AddSingleton<IServiceBusPersisterConnection>(sp =>
                {
                    var logger = sp.GetRequiredService<ILogger<DefaultServiceBusPersisterConnection>>();

                    var serviceBusConnectionString = Configuration["EventBusConnection"];
                    var serviceBusConnection = new ServiceBusConnectionStringBuilder(serviceBusConnectionString);

                    return new DefaultServiceBusPersisterConnection(serviceBusConnection, logger);
                });
            }
            else
            {
                services.AddSingleton<IRabbitMQPersistentConnection>(sp =>
                {
                    var logger = sp.GetRequiredService<ILogger<DefaultRabbitMQPersistentConnection>>();

                    var factory = new ConnectionFactory()
                    {
                        HostName = Configuration["EventBusConnection"]
                    };

                    return new DefaultRabbitMQPersistentConnection(factory, logger);
                });
            }            

            // Add framework services.
            services.AddSwaggerGen(options =>
            {
                options.DescribeAllEnumsAsStrings();
                options.SwaggerDoc("v1", new Swashbuckle.AspNetCore.Swagger.Info
                {
                    Title = "Marketing HTTP API",
                    Version = "v1",
                    Description = "The Marketing Service HTTP API",
                    TermsOfService = "Terms Of Service"
                });
            });

            services.AddCors(options =>
            {
                options.AddPolicy("CorsPolicy",
                    builder => builder.AllowAnyOrigin()
                    .AllowAnyMethod()
                    .AllowAnyHeader()
                    .AllowCredentials());
            });

            RegisterEventBus(services);

            services.AddTransient<IMarketingDataRepository, MarketingDataRepository>();
            services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();
            services.AddTransient<IIdentityService, IdentityService>();

            services.AddOptions();

            //configure autofac
            var container = new ContainerBuilder();
            container.Populate(services);

            return new AutofacServiceProvider(container.Build());
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
        {
            loggerFactory.AddConsole(Configuration.GetSection("Logging"));
            loggerFactory.AddDebug();

            app.UseCors("CorsPolicy");

            ConfigureAuth(app);

            app.UseMvcWithDefaultRoute();

            app.UseSwagger()
               .UseSwaggerUI(c =>
               {
                   c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
               });            

            var context = (MarketingContext)app
                        .ApplicationServices.GetService(typeof(MarketingContext));

            WaitForSqlAvailabilityAsync(context, loggerFactory, app).Wait();

            ConfigureEventBus(app);
        }

        protected virtual void ConfigureAuth(IApplicationBuilder app)
        {
            var identityUrl = Configuration.GetValue<string>("IdentityUrl");
            app.UseIdentityServerAuthentication(new IdentityServerAuthenticationOptions
            {
                Authority = identityUrl.ToString(),
                ApiName = "marketing",
                RequireHttpsMetadata = false
            });
        }

        private void RegisterEventBus(IServiceCollection services)
        {
            if (Configuration.GetValue<bool>("AzureServiceBusEnabled"))
            {
                services.AddSingleton<IEventBus, EventBusServiceBus>(sp =>
                {
                    var serviceBusPersisterConnection = sp.GetRequiredService<IServiceBusPersisterConnection>();
                    var iLifetimeScope = sp.GetRequiredService<ILifetimeScope>();
                    var logger = sp.GetRequiredService<ILogger<EventBusServiceBus>>();
                    var eventBusSubcriptionsManager = sp.GetRequiredService<IEventBusSubscriptionsManager>();
                    var subscriptionClientName = Configuration["SubscriptionClientName"];

                    return new EventBusServiceBus(serviceBusPersisterConnection, logger,
                        eventBusSubcriptionsManager, subscriptionClientName, iLifetimeScope);
                });
            }
            else
            {
                services.AddSingleton<IEventBus, EventBusRabbitMQ>();
            }

            services.AddSingleton<IEventBusSubscriptionsManager, InMemoryEventBusSubscriptionsManager>();
            services.AddTransient<UserLocationUpdatedIntegrationEventHandler>();
        }

        private void ConfigureEventBus(IApplicationBuilder app)
        {
            var eventBus = app.ApplicationServices.GetRequiredService<IEventBus>();
            eventBus.Subscribe<UserLocationUpdatedIntegrationEvent, UserLocationUpdatedIntegrationEventHandler>();
        }

        private async Task WaitForSqlAvailabilityAsync(MarketingContext ctx, ILoggerFactory loggerFactory, IApplicationBuilder app, int retries = 0)
        {
            var logger = loggerFactory.CreateLogger(nameof(Startup));
            var policy = CreatePolicy(retries, logger, nameof(WaitForSqlAvailabilityAsync));
            await policy.ExecuteAsync(async () =>
            {
                await MarketingContextSeed.SeedAsync(app, loggerFactory);
            });
        }

        private Policy CreatePolicy(int retries, ILogger logger, string prefix)
        {
            return Policy.Handle<SqlException>().
                WaitAndRetryAsync(
                    retryCount: retries,
                    sleepDurationProvider: retry => TimeSpan.FromSeconds(5),
                    onRetry: (exception, timeSpan, retry, ctx) =>
                    {
                        logger.LogTrace($"[{prefix}] Exception {exception.GetType().Name} with message ${exception.Message} detected on attempt {retry} of {retries}");
                    }
                );
        }
    }
}