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

namespace Microsoft.eShopOnContainers.Services.Catalog.API
{
    using Autofac;
    using Autofac.Extensions.DependencyInjection;
    using global::Catalog.API.Infrastructure.Filters;
    using global::Catalog.API.IntegrationEvents;
    using Microsoft.AspNetCore.Builder;
    using Microsoft.AspNetCore.Hosting;
    using Microsoft.EntityFrameworkCore;
    using Microsoft.EntityFrameworkCore.Infrastructure;
    using Microsoft.eShopOnContainers.BuildingBlocks.EventBus;
    using Microsoft.eShopOnContainers.BuildingBlocks.EventBus.Abstractions;
    using Microsoft.eShopOnContainers.BuildingBlocks.EventBusRabbitMQ;
    using Microsoft.eShopOnContainers.BuildingBlocks.IntegrationEventLogEF;
    using Microsoft.eShopOnContainers.BuildingBlocks.IntegrationEventLogEF.Services;
    using Microsoft.eShopOnContainers.Services.Catalog.API.Infrastructure;
    using Microsoft.eShopOnContainers.Services.Catalog.API.IntegrationEvents.EventHandling;
    using Microsoft.eShopOnContainers.Services.Catalog.API.IntegrationEvents.Events;
    using Microsoft.Extensions.Configuration;
    using Microsoft.Extensions.DependencyInjection;
    using Microsoft.Extensions.HealthChecks;
    using Microsoft.Extensions.Logging;
    using Microsoft.Extensions.Options;
    using Polly;
    using RabbitMQ.Client;
    using System;
    using System.Data.Common;
    using System.Data.SqlClient;
    using System.Reflection;
    using System.Threading.Tasks;

    public class Startup
    {
        public IConfigurationRoot Configuration { get; }

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

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

            builder.AddEnvironmentVariables();

            Configuration = builder.Build();
        }

        public IServiceProvider ConfigureServices(IServiceCollection services)
        {
            // Add framework services.

            services.AddHealthChecks(checks =>
            {
                var minutes = 1;
                if (int.TryParse(Configuration["HealthCheck:Timeout"], out var minutesParsed))
                {
                    minutes = minutesParsed;
                }
                checks.AddSqlCheck("CatalogDb", Configuration["ConnectionString"], TimeSpan.FromMinutes(minutes));
            });

            services.AddMvc(options =>
            {
                options.Filters.Add(typeof(HttpGlobalExceptionFilter));
            }).AddControllersAsServices();

            services.AddDbContext<CatalogContext>(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
            });

            services.Configure<CatalogSettings>(Configuration);

            // Add framework services.
            services.AddSwaggerGen(options =>
            {
                options.DescribeAllEnumsAsStrings();
                options.SwaggerDoc("v1", new Swashbuckle.AspNetCore.Swagger.Info
                {
                    Title = "eShopOnContainers - Catalog HTTP API",
                    Version = "v1",
                    Description = "The Catalog Microservice HTTP API. This is a Data-Driven/CRUD microservice sample",
                    TermsOfService = "Terms Of Service"
                });
            });

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

            services.AddTransient<Func<DbConnection, IIntegrationEventLogService>>(
                sp => (DbConnection c) => new IntegrationEventLogService(c));

            services.AddTransient<ICatalogIntegrationEventService, CatalogIntegrationEventService>();

            services.AddSingleton<IRabbitMQPersistentConnection>(sp =>
            {
                var settings = sp.GetRequiredService<IOptions<CatalogSettings>>().Value;
                var logger = sp.GetRequiredService<ILogger<DefaultRabbitMQPersistentConnection>>();
                var factory = new ConnectionFactory()
                {
                    HostName = settings.EventBusConnection
                };

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

            RegisterServiceBus(services);

            var container = new ContainerBuilder();
            container.Populate(services);
            return new AutofacServiceProvider(container.Build());
        }

        public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
        {
            //Configure logs

            loggerFactory.AddConsole(Configuration.GetSection("Logging"));
            loggerFactory.AddDebug();

            app.UseCors("CorsPolicy");

            app.UseMvcWithDefaultRoute();

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

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

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

            ConfigureEventBus(app);

            var integrationEventLogContext = new IntegrationEventLogContext(
                new DbContextOptionsBuilder<IntegrationEventLogContext>()
                .UseSqlServer(Configuration["ConnectionString"], b => b.MigrationsAssembly("Catalog.API"))
                .Options);

            integrationEventLogContext.Database.Migrate();
        }

        private async Task WaitForSqlAvailabilityAsync(CatalogContext 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 CatalogContextSeed.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}");
                    }
                );
        }

        private void RegisterServiceBus(IServiceCollection services)
        {
            services.AddSingleton<IEventBusSubscriptionsManager, InMemoryEventBusSubscriptionsManager>();
            services.AddSingleton<IEventBus, EventBusRabbitMQ>();

            services.AddTransient<IIntegrationEventHandler<OrderStatusChangedToAwaitingValidationIntegrationEvent>,
                OrderStatusChangedToAwaitingValidationIntegrationEventHandler>();
            services.AddTransient<IIntegrationEventHandler<OrderStatusChangedToPaidIntegrationEvent>,
                OrderStatusChangedToPaidIntegrationEventHandler>();
        }

        private void ConfigureEventBus(IApplicationBuilder app)
        {
            var eventBus = app.ApplicationServices.GetRequiredService<IEventBus>();

            eventBus.Subscribe<OrderStatusChangedToAwaitingValidationIntegrationEvent, 
                IIntegrationEventHandler<OrderStatusChangedToAwaitingValidationIntegrationEvent>>();
            eventBus.Subscribe<OrderStatusChangedToPaidIntegrationEvent, 
                IIntegrationEventHandler<OrderStatusChangedToPaidIntegrationEvent>>();
        }
    }
}