Refactor RepeatingTaskHandler (#796)

* Refactor RepeatingTaskHandler into an ASP.NET service

* Add unit tests for RepeatingTaskService

* Make repeating task unit tests work independent of time

* Fix weird behavior when task is canceled

ProjectLighthouse.Servers.GameServer/Startup/GameServerStartup.cs

@@ -1,4 +1,5 @@
 using System.Net;
+using LBPUnion.ProjectLighthouse.Administration.Maintenance;
 using LBPUnion.ProjectLighthouse.Configuration;
 using LBPUnion.ProjectLighthouse.Database;
 using LBPUnion.ProjectLighthouse.Logging;
@@ -6,6 +7,7 @@ using LBPUnion.ProjectLighthouse.Mail;
 using LBPUnion.ProjectLighthouse.Middlewares;
 using LBPUnion.ProjectLighthouse.Serialization;
 using LBPUnion.ProjectLighthouse.Servers.GameServer.Middlewares;
+using LBPUnion.ProjectLighthouse.Services;
 using LBPUnion.ProjectLighthouse.Types.Logging;
 using LBPUnion.ProjectLighthouse.Types.Mail;
 using Microsoft.AspNetCore.Authorization;
@@ -63,6 +65,8 @@ public class GameServerStartup
             : new NullMailService();
         services.AddSingleton(mailService);
 
+        services.AddHostedService(provider => new RepeatingTaskService(provider, MaintenanceHelper.RepeatingTasks));
+
         services.Configure<ForwardedHeadersOptions>
         (
             options =>

ProjectLighthouse.Servers.Website/Startup/WebsiteStartup.cs

@@ -1,5 +1,6 @@
 using System.Globalization;
 using System.Net;
+using LBPUnion.ProjectLighthouse.Administration.Maintenance;
 using LBPUnion.ProjectLighthouse.Configuration;
 using LBPUnion.ProjectLighthouse.Configuration.ConfigurationCategories;
 using LBPUnion.ProjectLighthouse.Database;
@@ -8,6 +9,7 @@ using LBPUnion.ProjectLighthouse.Mail;
 using LBPUnion.ProjectLighthouse.Middlewares;
 using LBPUnion.ProjectLighthouse.Servers.Website.Captcha;
 using LBPUnion.ProjectLighthouse.Servers.Website.Middlewares;
+using LBPUnion.ProjectLighthouse.Services;
 using LBPUnion.ProjectLighthouse.Types.Mail;
 using Microsoft.AspNetCore.HttpOverrides;
 using Microsoft.AspNetCore.Localization;
@@ -59,6 +61,8 @@ public class WebsiteStartup
             : new NullMailService();
         services.AddSingleton(mailService);
 
+        services.AddHostedService(provider => new RepeatingTaskService(provider, MaintenanceHelper.RepeatingTasks));
+
         services.AddHttpClient<ICaptchaService, CaptchaService>("CaptchaAPI",
             client =>
             {

ProjectLighthouse.Tests/Unit/RepeatingTaskTests.cs

@@ -0,0 +1,120 @@
+using System;
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+using LBPUnion.ProjectLighthouse.Database;
+using LBPUnion.ProjectLighthouse.Services;
+using LBPUnion.ProjectLighthouse.Types.Maintenance;
+using Microsoft.Extensions.DependencyInjection;
+using Moq;
+using Xunit;
+
+namespace LBPUnion.ProjectLighthouse.Tests.Unit;
+
+[Trait("Category", "Unit")]
+public class RepeatingTaskTests
+{
+    private class TestTask : IRepeatingTask
+    {
+        public string Name { get; init; } = "";
+        public TimeSpan RepeatInterval => TimeSpan.FromSeconds(5);
+        public DateTime LastRan { get; set; }
+        public Task Run(DatabaseContext database) => Task.CompletedTask;
+    }
+
+    [Fact]
+    public void GetNextTask_ShouldReturnNull_WhenTaskListEmpty()
+    {
+        List<IRepeatingTask> tasks = new();
+        IServiceProvider provider = new DefaultServiceProviderFactory().CreateServiceProvider(new ServiceCollection());
+        RepeatingTaskService service = new(provider, tasks);
+
+        bool gotTask = service.TryGetNextTask(out IRepeatingTask? outTask);
+        Assert.False(gotTask);
+        Assert.Null(outTask);
+    }
+
+    [Fact]
+    public void GetNextTask_ShouldReturnTask_WhenTaskListContainsOne()
+    {
+        List<IRepeatingTask> tasks = new()
+        {
+            new TestTask(),
+        };
+        IServiceProvider provider = new DefaultServiceProviderFactory().CreateServiceProvider(new ServiceCollection());
+        RepeatingTaskService service = new(provider, tasks);
+
+        bool gotTask = service.TryGetNextTask(out IRepeatingTask? outTask);
+        Assert.True(gotTask);
+        Assert.NotNull(outTask);
+    }
+
+    [Fact]
+    public void GetNextTask_ShouldReturnShortestTask_WhenTaskListContainsMultiple()
+    {
+        List<IRepeatingTask> tasks = new()
+        {
+            new TestTask
+            {
+                Name = "Task 1",
+                LastRan = DateTime.UtcNow,
+            },
+            new TestTask
+            {
+                Name = "Task 2",
+                LastRan = DateTime.UtcNow.AddMinutes(1),
+            },
+            new TestTask
+            {
+                Name = "Task 3",
+                LastRan = DateTime.UtcNow.AddMinutes(-1),
+            },
+        };
+        IServiceProvider provider = new DefaultServiceProviderFactory().CreateServiceProvider(new ServiceCollection());
+        RepeatingTaskService service = new(provider, tasks);
+
+        bool gotTask = service.TryGetNextTask(out IRepeatingTask? outTask);
+        Assert.True(gotTask);
+        Assert.NotNull(outTask);
+        Assert.Equal("Task 3", outTask.Name);
+    }
+
+    [Fact]
+    public async Task BackgroundService_ShouldExecuteTask_AndUpdateTime()
+    {
+        Mock<IRepeatingTask> taskMock = new();
+        taskMock.Setup(t => t.Run(It.IsAny<DatabaseContext>())).Returns(Task.CompletedTask);
+        taskMock.SetupGet(t => t.RepeatInterval).Returns(TimeSpan.FromSeconds(10));
+        TaskCompletionSource taskCompletion = new();
+        DateTime lastRan = default;
+        taskMock.SetupSet(t => t.LastRan = It.IsAny<DateTime>())
+            .Callback<DateTime>(time =>
+            {
+                lastRan = time;
+                taskCompletion.TrySetResult();
+            });
+        taskMock.SetupGet(t => t.LastRan).Returns(() => lastRan);
+        List<IRepeatingTask> tasks = new()
+        {
+            taskMock.Object,
+        };
+        ServiceCollection serviceCollection = new();
+        serviceCollection.AddScoped(_ => new Mock<DatabaseContext>().Object);
+        IServiceProvider provider = new DefaultServiceProviderFactory().CreateServiceProvider(serviceCollection);
+
+        RepeatingTaskService service = new(provider, tasks);
+
+        CancellationTokenSource stoppingToken = new();
+
+        await service.StartAsync(stoppingToken.Token);
+
+        await taskCompletion.Task;
+        stoppingToken.Cancel();
+
+        Assert.NotNull(service.ExecuteTask);
+        await service.ExecuteTask;
+
+        taskMock.Verify(x => x.Run(It.IsAny<DatabaseContext>()), Times.Once);
+        taskMock.VerifySet(x => x.LastRan = It.IsAny<DateTime>(), Times.Once());
+    }
+}

ProjectLighthouse/Administration/RepeatingTaskHandler.cs

@@ -1,65 +0,0 @@
-#nullable enable
-using System;
-using System.Collections.Generic;
-using System.Diagnostics;
-using System.Diagnostics.CodeAnalysis;
-using System.Threading;
-using System.Threading.Tasks;
-using LBPUnion.ProjectLighthouse.Administration.Maintenance;
-using LBPUnion.ProjectLighthouse.Database;
-using LBPUnion.ProjectLighthouse.Logging;
-using LBPUnion.ProjectLighthouse.Types.Logging;
-using LBPUnion.ProjectLighthouse.Types.Maintenance;
-
-namespace LBPUnion.ProjectLighthouse.Administration;
-
-public static class RepeatingTaskHandler
-{
-    private static bool initialized = false;
-
-    public static void Initialize()
-    {
-        if (initialized) throw new InvalidOperationException("RepeatingTaskHandler was initialized twice");
-
-        initialized = true;
-        Task.Factory.StartNew(taskLoop);
-    }
-
-    [SuppressMessage("ReSharper", "FunctionNeverReturns")]
-    private static async Task taskLoop()
-    {
-        Queue<IRepeatingTask> taskQueue = new();
-        foreach (IRepeatingTask task in MaintenanceHelper.RepeatingTasks) taskQueue.Enqueue(task);
-
-        DatabaseContext database = DatabaseContext.CreateNewInstance();
-
-        while (true)
-        {
-            try
-            {
-                if (!taskQueue.TryDequeue(out IRepeatingTask? task))
-                {
-                    Thread.Sleep(100);
-                    continue;
-                }
-
-                Debug.Assert(task != null);
-
-                if ((task.LastRan + task.RepeatInterval) <= DateTime.Now)
-                {
-                    await task.Run(database);
-                    task.LastRan = DateTime.Now;
-
-                    Logger.Debug($"Ran task \"{task.Name}\"", LogArea.Maintenance);
-                }
-
-                taskQueue.Enqueue(task);
-                Thread.Sleep(500); // Doesn't need to be that precise.
-            }
-            catch(Exception e)
-            {
-                Logger.Warn($"Error occured while processing repeating tasks: \n{e}", LogArea.Maintenance);
-            }
-        }
-    }
-}

ProjectLighthouse/Database/DatabaseContext.cs

@@ -64,6 +64,10 @@ public partial class DatabaseContext : DbContext
 
     #endregion
 
+    // Used for mocking DbContext
+    protected internal DatabaseContext()
+    { }
+
     public DatabaseContext(DbContextOptions<DatabaseContext> options) : base(options)
     { }
 

ProjectLighthouse/Services/RepeatingTaskService.cs

@@ -0,0 +1,81 @@
+#nullable enable
+using System;
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+using LBPUnion.ProjectLighthouse.Database;
+using LBPUnion.ProjectLighthouse.Logging;
+using LBPUnion.ProjectLighthouse.Types.Logging;
+using LBPUnion.ProjectLighthouse.Types.Maintenance;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+
+namespace LBPUnion.ProjectLighthouse.Services;
+
+public class RepeatingTaskService : BackgroundService
+{
+    private readonly IServiceProvider provider;
+    private readonly List<IRepeatingTask> taskList;
+
+    public RepeatingTaskService(IServiceProvider provider, List<IRepeatingTask> tasks)
+    {
+        this.provider = provider;
+        this.taskList = tasks;
+
+        Logger.Info("Initializing repeating tasks service", LogArea.Startup);
+    }
+
+    public bool TryGetNextTask(out IRepeatingTask? outTask)
+    {
+        TimeSpan smallestSpan = TimeSpan.MaxValue;
+        IRepeatingTask? smallestTask = null;
+        foreach (IRepeatingTask task in this.taskList)
+        {
+            TimeSpan smallestTimeRemaining = task.RepeatInterval.Subtract(DateTime.UtcNow.Subtract(task.LastRan));
+            if (smallestTimeRemaining >= smallestSpan) continue;
+
+            smallestSpan = smallestTimeRemaining;
+            smallestTask = task;
+        }
+        outTask = smallestTask;
+
+        return outTask != null;
+    }
+
+    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+    {
+        await Task.Yield();
+        while (!stoppingToken.IsCancellationRequested)
+        {
+            if (!this.TryGetNextTask(out IRepeatingTask? task) || task == null)
+            {
+                // If we fail to fetch the next task then something has gone wrong and the service should halt
+                Logger.Debug("Failed to fetch next smallest task", LogArea.Maintenance);
+                return;
+            }
+
+            TimeSpan timeElapsedSinceRun = DateTime.UtcNow.Subtract(task.LastRan);
+
+            // If the task's repeat interval hasn't elapsed
+            if (timeElapsedSinceRun < task.RepeatInterval)
+            {
+                TimeSpan timeToWait = task.RepeatInterval.Subtract(timeElapsedSinceRun);
+                Logger.Debug($"Waiting {timeToWait} for {task.Name}", LogArea.Maintenance);
+                try
+                {
+                    await Task.Delay(timeToWait, stoppingToken);
+                }
+                catch (TaskCanceledException)
+                {
+                    break;
+                }
+            }
+
+            using IServiceScope scope = this.provider.CreateScope();
+            DatabaseContext database = scope.ServiceProvider.GetRequiredService<DatabaseContext>();
+            await task.Run(database);
+            Logger.Debug($"Successfully ran task \"{task.Name}\"", LogArea.Maintenance);
+            task.LastRan = DateTime.UtcNow;
+        }
+    }
+}

ProjectLighthouse/StartupTasks.cs

@@ -5,7 +5,6 @@ using System.Linq;
 using System.Reflection;
 using System.Threading;
 using System.Threading.Tasks;
-using LBPUnion.ProjectLighthouse.Administration;
 using LBPUnion.ProjectLighthouse.Administration.Maintenance;
 using LBPUnion.ProjectLighthouse.Configuration;
 using LBPUnion.ProjectLighthouse.Database;
@@ -93,9 +92,6 @@ public static class StartupTasks
         Logger.Info("Initializing Redis...", LogArea.Startup);
         RedisDatabase.Initialize().Wait();
 
-        Logger.Info("Initializing repeating tasks...", LogArea.Startup);
-        RepeatingTaskHandler.Initialize();
-
         // Create admin user if no users exist
         if (serverType == ServerType.Website && database.Users.CountAsync().Result == 0)
         {