Startup.cs

namespace Opc.Ua.Cloud.Publisher
{
    using Microsoft.AspNetCore.Builder;
    using Microsoft.AspNetCore.DataProtection;
    using Microsoft.AspNetCore.Hosting;
    using Microsoft.Extensions.Configuration;
    using Microsoft.Extensions.DependencyInjection;
    using Microsoft.Extensions.Hosting;
    using Microsoft.Extensions.Logging;
    using Opc.Ua.Cloud.Publisher.Configuration;
    using Opc.Ua.Cloud.Publisher.Interfaces;
    using Radzen;
    using System;
    using System.IO;
    using System.Threading.Tasks;

    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            // basic authentication for the UI is mandatory: fail fast if the credentials are not configured
            string basicAuthUsername = Environment.GetEnvironmentVariable(BasicAuthMiddleware.UsernameEnvVar);
            string basicAuthPassword = Environment.GetEnvironmentVariable(BasicAuthMiddleware.PasswordEnvVar);
            if (string.IsNullOrEmpty(basicAuthUsername) || string.IsNullOrEmpty(basicAuthPassword))
            {
                throw new InvalidOperationException(
                    $"Basic authentication credentials are not configured. Please set the '{BasicAuthMiddleware.UsernameEnvVar}' and '{BasicAuthMiddleware.PasswordEnvVar}' environment variables.");
            }

            // persist the Data Protection key ring to a stable location so session cookies remain
            // decryptable across app/container restarts
            string keyRingPath = Path.Combine(Directory.GetCurrentDirectory(), "settings", "dataprotection-keys");
            Directory.CreateDirectory(keyRingPath);
            services.AddDataProtection()
                .PersistKeysToFileSystem(new DirectoryInfo(keyRingPath))
                .SetApplicationName("UACloudPublisher");

            services.AddSession(options =>
            {
                options.IdleTimeout = TimeSpan.FromMinutes(5);

                // use a distinct cookie name so stale cookies issued before Data Protection key persistence
                // was configured are ignored (rather than failing to unprotect and logging warnings), and
                // set standard hardening flags
                options.Cookie.Name = ".UACloudPublisher.Session";
                options.Cookie.HttpOnly = true;
                options.Cookie.IsEssential = true;
            });

            services.AddControllersWithViews();

            services.AddRazorPages();

            services.AddServerSideBlazor();

            services.AddRadzenComponents();

            services.AddHttpClient();

            // add our singletons
            services.AddSingleton<IUAApplication, UAApplication>();
            services.AddSingleton<IUAClient, UAClient>();

            services.AddSingleton<KafkaClient>();
            services.AddSingleton<MQTTClient>();

            services.AddSingleton<Settings.BrokerResolver>(serviceProvider => key =>
            {
                switch (key)
                {
                    case "MQTT":
                        return serviceProvider.GetService<MQTTClient>();
                    case "Kafka":
                        return serviceProvider.GetService<KafkaClient>();
                    default:
                        return null;
                }
            });

            services.AddSingleton<IPublishedNodesFileHandler, PublishedNodesFileHandler>();
            services.AddSingleton<ICommandProcessor, CommandProcessor>();

            // add our message processing engine
            services.AddSingleton<IMessageProcessor, MessageProcessor>();
            services.AddSingleton<IMessageSource, MonitoredItemNotification>();
            services.AddSingleton<IMessageEncoder, PubSubTelemetryEncoder>();
            services.AddSingleton<IMessagePublisher, StoreForwardPublisher>();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app,
                              IWebHostEnvironment env,
                              ILogger<Startup> logger,
                              ILoggerFactory loggerFactory,
                              IUAApplication uaApp,
                              IMessageProcessor engine,
                              IMessagePublisher messagePublisher,
                              Settings.BrokerResolver brokerResolver,
                              IPublishedNodesFileHandler publishedNodesFileHandler)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Browser/Error");

                // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
                app.UseHsts();
            }

            app.UseHttpsRedirection();

            app.UseStaticFiles();

            // enforce mandatory HTTP Basic authentication for the whole application
            app.UseMiddleware<BasicAuthMiddleware>();

            app.UseSession();

            app.UseRouting();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllerRoute(
                    name: "default",
                    pattern: "{controller=Home}/{action=Index}/{id?}");
                endpoints.MapBlazorHub();
            });

            // do all further initialization on a background thread to load the webserver independently
            _ = Task.Run(async () =>
            {
                try
                {
                    // kick off the task to show periodic diagnostic info (fire-and-forget)
                    _ = Task.Run(async () => await Diagnostics.Singleton.RunAsync().ConfigureAwait(false));

                    // create our app
                    await uaApp.CreateAsync().ConfigureAwait(false);

                    IBrokerClient broker;
                    IBrokerClient altBroker;
                    if (Settings.Instance.UseKafka)
                    {
                        broker = brokerResolver("Kafka");
                    }
                    else
                    {
                        broker = brokerResolver("MQTT");
                    }

                    // connect to broker
                    await broker.ConnectAsync().ConfigureAwait(false);

                    // check if we need a second broker (for receiving UA over MQTT,
                    // or for sending metadata via a different broker kind than the primary)
                    bool altKindDiffersForMetadata = Settings.Instance.UseAltBrokerForMetadata && (Settings.Instance.UseKafkaForAlt != Settings.Instance.UseKafka);
                    if (altKindDiffersForMetadata)
                    {
                        altBroker = brokerResolver(Settings.Instance.UseKafkaForAlt ? "Kafka" : "MQTT");
                        await altBroker.ConnectAsync(true).ConfigureAwait(false);

                        if (altKindDiffersForMetadata)
                        {
                            messagePublisher.ApplyAltClient(altBroker);
                        }
                    }

                    // run the telemetry engine (fire-and-forget)
                    _ = Task.Run(async () => await engine.RunAsync().ConfigureAwait(false));

                    // load our persistency file
                    if (Settings.Instance.AutoLoadPersistedNodes)
                    {
                        try
                        {
                            string persistencyFilePath = Path.Combine(Directory.GetCurrentDirectory(), "settings", "persistency.json");
                            if (!File.Exists(persistencyFilePath))
                            {
                                // no file persisted yet
                                logger.LogInformation("No persistency file found at {Path}; skipping auto-load.", persistencyFilePath);
                            }
                            else
                            {
                                byte[] persistencyFile = await File.ReadAllBytesAsync(persistencyFilePath).ConfigureAwait(false);

                                // parse the file (fire-and-forget)
                                _ = Task.Run(async () => await publishedNodesFileHandler.ParseFileAsync(persistencyFile).ConfigureAwait(false));
                            }
                        }
                        catch (Exception ex)
                        {
                            logger.LogError(ex, "Failed to auto-load persisted nodes.");
                        }
                    }
                }
                catch (Exception ex)
                {
                    logger.LogError(ex, "Background initialization failed.");
                }
            });
        }
    }
}