Do not use a Thread to Periodically check for Due workers.

Each Periodic Worker has it's own Thread that waits for execution.

API/Controllers/WorkerController.cs

@@ -20,7 +20,7 @@ public class WorkerController() : Controller
     [ProducesResponseType<string[]>(Status200OK, "application/json")]
     public IActionResult GetAllWorkers()
     {
-        return Ok(Tranga.AllWorkers.Select(w => w.Key).ToArray());
+        return Ok(Tranga.GetRunningWorkers().Select(w => w.Key).ToArray());
     }
     
     /// <summary>
@@ -32,7 +32,7 @@ public class WorkerController() : Controller
     [ProducesResponseType<BaseWorker[]>(Status200OK, "application/json")]
     public IActionResult GetWorkers([FromBody]string[] WorkerIds)
     {
-        return Ok(Tranga.AllWorkers.Where(worker => WorkerIds.Contains(worker.Key)).ToArray());
+        return Ok(Tranga.GetRunningWorkers().Where(worker => WorkerIds.Contains(worker.Key)).ToArray());
     }
 
     /// <summary>
@@ -44,7 +44,7 @@ public class WorkerController() : Controller
     [ProducesResponseType<BaseWorker[]>(Status200OK, "application/json")]
     public IActionResult GetWorkersInState(WorkerExecutionState State)
     {
-        return Ok(Tranga.AllWorkers.Where(worker => worker.State == State).ToArray());
+        return Ok(Tranga.GetRunningWorkers().Where(worker => worker.State == State).ToArray());
     }
 
     /// <summary>
@@ -58,7 +58,7 @@ public class WorkerController() : Controller
     [ProducesResponseType(Status404NotFound)]
     public IActionResult GetWorker(string WorkerId)
     {
-        if(Tranga.AllWorkers.FirstOrDefault(w => w.Key == WorkerId) is not { } worker)
+        if(Tranga.GetRunningWorkers().FirstOrDefault(w => w.Key == WorkerId) is not { } worker)
             return NotFound(nameof(WorkerId));
         return Ok(worker);
     }
@@ -74,39 +74,12 @@ public class WorkerController() : Controller
     [ProducesResponseType(Status404NotFound)]
     public IActionResult DeleteWorker(string WorkerId)
     {
-        if(Tranga.AllWorkers.FirstOrDefault(w => w.Key == WorkerId) is not { } worker)
+        if(Tranga.GetRunningWorkers().FirstOrDefault(w => w.Key == WorkerId) is not { } worker)
             return NotFound(nameof(WorkerId));
-        Tranga.RemoveWorker(worker);
+        Tranga.StopWorker(worker);
         return Ok();
     }
 
-    /// <summary>
-    /// Modify <see cref="BaseWorker"/> with <paramref name="WorkerId"/>
-    /// </summary>
-    /// <param name="WorkerId"><see cref="BaseWorker"/>.Key</param>
-    /// <param name="modifyWorkerRecord">Fields to modify, set to null to keep previous value</param>
-    /// <response code="202"></response>
-    /// <response code="400"></response>
-    /// <response code="404"><see cref="BaseWorker"/> with <paramref name="WorkerId"/> could not be found</response>
-    /// <response code="409"><see cref="BaseWorker"/> is not <see cref="IPeriodic"/>, can not modify <paramref name="modifyWorkerRecord.IntervalMs"/></response>
-    [HttpPatch("{WorkerId}")]
-    [ProducesResponseType<BaseWorker>(Status202Accepted, "application/json")]
-    [ProducesResponseType(Status400BadRequest)]
-    [ProducesResponseType(Status404NotFound)]
-    [ProducesResponseType<string>(Status409Conflict, "text/plain")]
-    public IActionResult ModifyWorker(string WorkerId, [FromBody]ModifyWorkerRecord modifyWorkerRecord)
-    {
-        if(Tranga.AllWorkers.FirstOrDefault(w => w.Key == WorkerId) is not { } worker)
-            return NotFound(nameof(WorkerId));
-        
-        if(modifyWorkerRecord.IntervalMs is not null && worker is not IPeriodic)
-            return Conflict("Can not modify Interval of non-Periodic worker");
-        else if(modifyWorkerRecord.IntervalMs is not null && worker is IPeriodic periodic)
-            periodic.Interval = TimeSpan.FromMilliseconds((long)modifyWorkerRecord.IntervalMs);
-        
-        return Accepted(worker);
-    }
-
     /// <summary>
     /// Starts <see cref="BaseWorker"/> with <paramref name="WorkerId"/>
     /// </summary>
@@ -120,13 +93,13 @@ public class WorkerController() : Controller
     [ProducesResponseType<string>(Status412PreconditionFailed, "text/plain")]
     public IActionResult StartWorker(string WorkerId)
     {
-        if(Tranga.AllWorkers.FirstOrDefault(w => w.Key == WorkerId) is not { } worker)
+        if(Tranga.GetRunningWorkers().FirstOrDefault(w => w.Key == WorkerId) is not { } worker)
             return NotFound(nameof(WorkerId));
         
         if (worker.State >= WorkerExecutionState.Waiting)
             return StatusCode(Status412PreconditionFailed, "Already running");
 
-        Tranga.MarkWorkerForStart(worker);
+        Tranga.StartWorker(worker);
         return Ok();
     }
 
@@ -141,7 +114,7 @@ public class WorkerController() : Controller
     [ProducesResponseType(Status501NotImplemented)]
     public IActionResult StopWorker(string WorkerId)
     {
-        if(Tranga.AllWorkers.FirstOrDefault(w => w.Key == WorkerId) is not { } worker)
+        if(Tranga.GetRunningWorkers().FirstOrDefault(w => w.Key == WorkerId) is not { } worker)
             return NotFound(nameof(WorkerId));
         
         if(worker.State is < WorkerExecutionState.Running or >= WorkerExecutionState.Completed)

API/Program.cs

@@ -135,12 +135,10 @@ using (IServiceScope scope = app.Services.CreateScope())
     context.Sync();
 }
 
+Tranga.SetServiceProvider(app.Services);
 Tranga.StartLogger();
-
 Tranga.AddDefaultWorkers();
 
-Tranga.PeriodicWorkerStarterThread.Start(app.Services);
-
 app.UseCors("AllowAll");
 
 app.Run();

API/Tranga.cs

@@ -1,4 +1,5 @@
-using System.Diagnostics.CodeAnalysis;
+using System.Collections.Concurrent;
+using System.Diagnostics.CodeAnalysis;
 using API.MangaConnectors;
 using API.Schema.LibraryContext;
 using API.Schema.MangaContext;
@@ -23,7 +24,8 @@ public static class Tranga
         "  |___|  |__|  |___._||__|__||___  ||___._|\n" +
         "                             |_____|       \n\n";
     
-    public static Thread PeriodicWorkerStarterThread { get; } = new (WorkerStarter);
+    private static IServiceProvider? ServiceProvider;
+    
     private static readonly ILog Log = LogManager.GetLogger(typeof(Tranga));
     internal static readonly MetadataFetcher[] MetadataFetchers = [new MyAnimeList()];
     internal static readonly MangaConnector[] MangaConnectors = [new Global(), new MangaDex(), new ComickIo()];
@@ -57,6 +59,11 @@ public static class Tranga
         AddWorker(UpdateCoversWorker);
     }
 
+    internal static void SetServiceProvider(IServiceProvider serviceProvider)
+    {
+        ServiceProvider = serviceProvider;
+    }
+
     internal static bool TryGetMangaConnector(string name, [NotNullWhen(true)]out MangaConnector? mangaConnector)
     {
         mangaConnector =
@@ -64,115 +71,84 @@ public static class Tranga
         return mangaConnector != null;
     }
     
-    internal static HashSet<BaseWorker> AllWorkers { get; private set; } = new ();
+    internal static readonly Dictionary<IPeriodic, Task> PeriodicWorkers = new ();
 
     public static void AddWorker(BaseWorker worker)
     {
-        Log.Debug($"Adding {worker} to AllWorkers.");
-        AllWorkers.Add(worker);
+        Log.Debug($"Adding {worker}");
+        StartWorker(worker);
+        if(worker is IPeriodic periodic)
+            AddPeriodicWorker(worker, periodic);
     }
+
+    private static void AddPeriodicWorker(BaseWorker worker, IPeriodic periodic)
+    {
+        Log.Debug($"Adding Periodic {worker}");
+        PeriodicWorkers.Add((worker as IPeriodic)!, PeriodicTask(worker, periodic));
+        PeriodicWorkers[(worker as IPeriodic)!].Start();
+    }
+
+    private static Task PeriodicTask(BaseWorker worker, IPeriodic periodic) => new (() =>
+    {
+        Log.Debug($"Waiting {periodic.Interval} for {worker}");
+        Thread.Sleep(periodic.Interval);
+        StartWorker(worker, RefreshTask(worker, periodic));
+    });
+
+    private static Action RefreshTask(BaseWorker worker, IPeriodic periodic) => () =>
+    {
+        if (worker.State < WorkerExecutionState.Created) //Failed
+            return;
+        PeriodicWorkers[(worker as IPeriodic)!] = PeriodicTask(worker, periodic);
+        PeriodicWorkers[(worker as IPeriodic)!].Start();
+    };
+    
     public static void AddWorkers(IEnumerable<BaseWorker> workers)
     {
         foreach (BaseWorker baseWorker in workers)
-        {
             AddWorker(baseWorker);
-        }
-    }
-    
-    public static void RemoveWorker(BaseWorker removeWorker)
-    {
-        IEnumerable<BaseWorker> baseWorkers = AllWorkers.Where(w => w.DependenciesAndSelf.Any(worker => worker == removeWorker));
-        
-        foreach (BaseWorker worker in baseWorkers)
-        {
-             StopWorker(worker);
-             Log.Debug($"Removing {removeWorker} from AllWorkers.");
-             AllWorkers.Remove(worker);
-        }
     }
 
-    private static readonly Dictionary<BaseWorker, Task<BaseWorker[]>> RunningWorkers = new();
+    private static readonly ConcurrentDictionary<BaseWorker, Task<BaseWorker[]>> RunningWorkers = new();
     public static BaseWorker[] GetRunningWorkers() => RunningWorkers.Keys.ToArray();
-    private static readonly HashSet<BaseWorker> StartWorkers = new();
-    private static void WorkerStarter(object? serviceProviderObj)
+    
+    internal static void StartWorker(BaseWorker worker, Action? callback = null)
     {
-        Log.Info("WorkerStarter Thread running.");
-        if (serviceProviderObj is null)
+        Log.Debug($"Starting {worker}");
+        if (ServiceProvider is null)
         {
-            Log.Error("serviceProviderObj is null");
+            Log.Fatal("ServiceProvider is null");
             return;
         }
-        IServiceProvider serviceProvider = (IServiceProvider)serviceProviderObj;
-        
-        while (true)
+        Action callBack = AfterWork(worker, callback);
+        if (worker is BaseWorkerWithContext<MangaContext> mangaContextWorker)
         {
-            CheckRunningWorkers();
-
-            foreach (BaseWorker baseWorker in AllWorkers.DueWorkers().ToArray())
-                StartWorkers.Add(baseWorker);
-            
-            foreach (BaseWorker worker in StartWorkers.ToArray())
-            {
-                if(RunningWorkers.ContainsKey(worker))
-                    continue;
-                if (worker is BaseWorkerWithContext<MangaContext> mangaContextWorker)
-                {
-                    mangaContextWorker.SetScope(serviceProvider.CreateScope());
-                    RunningWorkers.Add(mangaContextWorker, mangaContextWorker.DoWork());
-                }else if (worker is BaseWorkerWithContext<NotificationsContext> notificationContextWorker)
-                {
-                    notificationContextWorker.SetScope(serviceProvider.CreateScope());
-                    RunningWorkers.Add(notificationContextWorker, notificationContextWorker.DoWork());
-                }else if (worker is BaseWorkerWithContext<LibraryContext> libraryContextWorker)
-                {
-                    libraryContextWorker.SetScope(serviceProvider.CreateScope());
-                    RunningWorkers.Add(libraryContextWorker, libraryContextWorker.DoWork());
-                }else
-                    RunningWorkers.Add(worker, worker.DoWork());
-
-                StartWorkers.Remove(worker);
-            }
-            Thread.Sleep(Settings.WorkCycleTimeoutMs);
-        }
+            mangaContextWorker.SetScope(ServiceProvider.CreateScope());
+            RunningWorkers.TryAdd(mangaContextWorker, mangaContextWorker.DoWork(callBack));
+        }else if (worker is BaseWorkerWithContext<NotificationsContext> notificationContextWorker)
+        {
+            notificationContextWorker.SetScope(ServiceProvider.CreateScope());
+            RunningWorkers.TryAdd(notificationContextWorker, notificationContextWorker.DoWork(callBack));
+        }else if (worker is BaseWorkerWithContext<LibraryContext> libraryContextWorker)
+        {
+            libraryContextWorker.SetScope(ServiceProvider.CreateScope());
+            RunningWorkers.TryAdd(libraryContextWorker, libraryContextWorker.DoWork(callBack));
+        }else
+            RunningWorkers.TryAdd(worker, worker.DoWork(callBack));
     }
 
-    private static void CheckRunningWorkers()
+    private static Action AfterWork(BaseWorker worker, Action? callback) => () =>
     {
-        KeyValuePair<BaseWorker, Task<BaseWorker[]>>[] done = RunningWorkers.Where(kv => kv.Value.IsCompleted).ToArray();
-        if (done.Length < 1)
-            return;
-        Log.Info($"Done: {done.Length}");
-        Log.Debug(string.Join("\n", done.Select(d => d.Key.ToString())));
-        foreach ((BaseWorker worker, Task<BaseWorker[]> task) in done)
-        {
-            RunningWorkers.Remove(worker);
-            foreach (BaseWorker newWorker in task.Result)
-                AllWorkers.Add(newWorker);
-            if (worker is not IPeriodic)
-                AllWorkers.Remove(worker);
-            task.Dispose();
-        }
-    }
-
-    private static IEnumerable<BaseWorker> DueWorkers(this IEnumerable<BaseWorker> workers)
-    {
-        return workers.Where(worker =>
-        {
-            if (worker.State is >= WorkerExecutionState.Running and < WorkerExecutionState.Completed)
-                return false;
-            if (worker is IPeriodic periodicWorker)
-                return periodicWorker.IsDue;
-            return true;
-        });
-    }
-
-    internal static void MarkWorkerForStart(BaseWorker worker) => StartWorkers.Add(worker);
+        RunningWorkers.Remove(worker, out _);
+        callback?.Invoke();
+    };
 
     internal static void StopWorker(BaseWorker worker)
     {
-        StartWorkers.Remove(worker);
+        if(worker is IPeriodic periodicWorker)
+            PeriodicWorkers.Remove(periodicWorker);
         worker.Cancel();
-        RunningWorkers.Remove(worker);
+        RunningWorkers.Remove(worker, out _);
     }
     
     internal static bool AddMangaToContext((Manga, MangaConnectorId<Manga>) addManga, MangaContext context, [NotNullWhen(true)]out Manga? manga) => AddMangaToContext(addManga.Item1, addManga.Item2, context, out manga);

API/Workers/BaseWorker.cs

@@ -68,7 +68,7 @@ public abstract class BaseWorker : Identifiable
     /// <item>If <see cref="BaseWorker"/> has run, additional <see cref="BaseWorker"/>.</item>
     /// </list>
     /// </returns>
-    public Task<BaseWorker[]> DoWork()
+    public Task<BaseWorker[]> DoWork(Action? callback = null)
     {
         Log.Debug($"Checking {this}");
         this.State = WorkerExecutionState.Waiting;
@@ -93,6 +93,7 @@ public abstract class BaseWorker : Identifiable
         });
         task.Start();
         this.State = WorkerExecutionState.Running;
+        callback?.Invoke();
         return task;
     }