refactor: replace periodic tasks loop with background service

Foxnouns.Backend/Extensions/WebApplicationExtensions.cs

@@ -5,6 +5,7 @@ using Foxnouns.Backend.Jobs;
 using Foxnouns.Backend.Middleware;
 using Foxnouns.Backend.Services;
 using Microsoft.EntityFrameworkCore;
+using Minio;
 using NodaTime;
 using Prometheus;
 using Serilog;
@@ -57,16 +58,6 @@ public static class WebApplicationExtensions
         return config;
     }
 
-    public static WebApplicationBuilder AddMetrics(this WebApplicationBuilder builder, Config config)
-    {
-        builder.Services.AddMetricServer(o => o.Port = config.Logging.MetricsPort)
-            .AddSingleton<MetricsCollectionService>();
-        if (!config.Logging.EnableMetrics)
-            builder.Services.AddHostedService<BackgroundMetricsCollectionService>();
-
-        return builder;
-    }
-
     public static IConfigurationBuilder AddConfiguration(this IConfigurationBuilder builder)
     {
         var file = Environment.GetEnvironmentVariable("FOXNOUNS_CONFIG_FILE") ?? "config.ini";
@@ -78,7 +69,21 @@ public static class WebApplicationExtensions
             .AddEnvironmentVariables();
     }
 
-    public static IServiceCollection AddCustomServices(this IServiceCollection services) => services
+    /// <summary>
+    /// Adds required services to the IServiceCollection.
+    /// This should only add services that are not ASP.NET-related (i.e. no middleware).
+    /// </summary>
+    public static IServiceCollection AddServices(this IServiceCollection services, Config config)
+    {
+        services
+            .AddQueue()
+            .AddDbContext<DatabaseContext>()
+            .AddMetricServer(o => o.Port = config.Logging.MetricsPort)
+            .AddMinio(c =>
+                c.WithEndpoint(config.Storage.Endpoint)
+                    .WithCredentials(config.Storage.AccessKey, config.Storage.SecretKey)
+                    .Build())
+            .AddSingleton<MetricsCollectionService>()
             .AddSingleton<IClock>(SystemClock.Instance)
             .AddSnowflakeGenerator()
             .AddScoped<UserRendererService>()
@@ -87,10 +92,18 @@ public static class WebApplicationExtensions
             .AddScoped<KeyCacheService>()
             .AddScoped<RemoteAuthService>()
             .AddScoped<ObjectStorageService>()
+            // Background services
+            .AddHostedService<PeriodicTasksService>()
             // Transient jobs
             .AddTransient<MemberAvatarUpdateInvocable>()
             .AddTransient<UserAvatarUpdateInvocable>();
         
+        if (!config.Logging.EnableMetrics)
+            services.AddHostedService<BackgroundMetricsCollectionService>();
+
+        return services;
+    }
+
     public static IServiceCollection AddCustomMiddleware(this IServiceCollection services) => services
         .AddScoped<ErrorHandlerMiddleware>()
         .AddScoped<AuthenticationMiddleware>()

Foxnouns.Backend/Program.cs

@@ -1,12 +1,9 @@
-using Coravel;
 using Foxnouns.Backend;
-using Foxnouns.Backend.Database;
 using Serilog;
 using Foxnouns.Backend.Extensions;
 using Foxnouns.Backend.Services;
 using Foxnouns.Backend.Utils;
 using Microsoft.AspNetCore.Mvc;
-using Minio;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Serialization;
 using Prometheus;
@@ -19,9 +16,7 @@ var builder = WebApplication.CreateBuilder(args);
 
 var config = builder.AddConfiguration();
 
-builder
+builder.AddSerilog();
-    .AddSerilog()
-    .AddMetrics(config);
 
 builder.WebHost
     .UseSentry(opts =>
@@ -64,16 +59,10 @@ JsonConvert.DefaultSettings = () => new JsonSerializerSettings
 };
 
 builder.Services
-    .AddQueue()
+    .AddServices(config)
-    .AddDbContext<DatabaseContext>()
-    .AddCustomServices()
     .AddCustomMiddleware()
     .AddEndpointsApiExplorer()
-    .AddSwaggerGen()
+    .AddSwaggerGen();
-    .AddMinio(c =>
-        c.WithEndpoint(config.Storage.Endpoint)
-            .WithCredentials(config.Storage.AccessKey, config.Storage.SecretKey)
-            .Build());
 
 var app = builder.Build();
 
@@ -97,23 +86,5 @@ app.Urls.Add(config.Address);
 Metrics.DefaultRegistry.AddBeforeCollectCallback(async ct =>
     await app.Services.GetRequiredService<MetricsCollectionService>().CollectMetricsAsync(ct));
 
-// Fire off the periodic tasks loop in the background
-_ = new Timer(_ =>
-{
-    var __ = RunPeriodicTasksAsync();
-}, null, TimeSpan.FromSeconds(30), TimeSpan.FromMinutes(1));
-
 app.Run();
 Log.CloseAndFlush();
-
-return;
-
-async Task RunPeriodicTasksAsync()
-{
-    await using var scope = app.Services.CreateAsyncScope();
-    var logger = scope.ServiceProvider.GetRequiredService<ILogger>();
-    logger.Debug("Running periodic tasks");
-
-    var keyCacheSvc = scope.ServiceProvider.GetRequiredService<KeyCacheService>();
-    await keyCacheSvc.DeleteExpiredKeysAsync();
-}

Foxnouns.Backend/Services/KeyCacheService.cs

@@ -37,9 +37,9 @@ public class KeyCacheService(DatabaseContext db, IClock clock, ILogger logger)
         return value.Value;
     }
 
-    public async Task DeleteExpiredKeysAsync()
+    public async Task DeleteExpiredKeysAsync(CancellationToken ct)
     {
-        var count = await db.TemporaryKeys.Where(k => k.Expires < clock.GetCurrentInstant()).ExecuteDeleteAsync();
+        var count = await db.TemporaryKeys.Where(k => k.Expires < clock.GetCurrentInstant()).ExecuteDeleteAsync(ct);
         if (count != 0) logger.Information("Removed {Count} expired keys from the database", count);
     }
 

Foxnouns.Backend/Services/PeriodicTasksService.cs

@@ -0,0 +1,26 @@
+namespace Foxnouns.Backend.Services;
+
+public class PeriodicTasksService(ILogger logger, IServiceProvider services) : BackgroundService
+{
+    private readonly ILogger _logger = logger.ForContext<PeriodicTasksService>();
+
+    protected override async Task ExecuteAsync(CancellationToken ct)
+    {
+        using var timer = new PeriodicTimer(TimeSpan.FromMinutes(1));
+        while (await timer.WaitForNextTickAsync(ct))
+        {
+            _logger.Debug("Collecting metrics");
+            await RunPeriodicTasksAsync(ct);
+        }
+    }
+
+    private async Task RunPeriodicTasksAsync(CancellationToken ct)
+    {
+        _logger.Debug("Running periodic tasks");
+        
+        await using var scope = services.CreateAsyncScope();
+
+        var keyCacheSvc = scope.ServiceProvider.GetRequiredService<KeyCacheService>();
+        await keyCacheSvc.DeleteExpiredKeysAsync(ct);
+    }
+}