fix: startup deadlock

src/Fluss.PostgreSQL/ServiceCollectionExtensions.cs

@@ -65,14 +65,17 @@ protected override Task ExecuteAsync(CancellationToken stoppingToken)
                 var migrationRunner = scope.ServiceProvider.GetRequiredService<IMigrationRunner>();
                 migrationRunner.MigrateUp();
 
-                _didFinish = true;
-                _didFinishChanged.Release();
             }
             catch (Exception e)
             {
                 logger.LogError(e, "Error while migrating");
                 Environment.Exit(-1);
             }
+            finally
+            {
+                _didFinish = true;
+                _didFinishChanged.Release();
+            }
         }, stoppingToken);
     }
 }

src/Fluss/SideEffects/SideEffectDispatcher.cs

@@ -32,11 +32,16 @@ public SideEffectDispatcher(IEnumerable<SideEffect> sideEffects, IServiceProvide
         CacheSideEffects(sideEffects);
     }
 
-    public async Task StartAsync(CancellationToken cancellationToken)
+    public Task StartAsync(CancellationToken cancellationToken)
+    {
+        Init();
+        return Task.CompletedTask;
+    }
+
+    private async void Init()
     {
         var upcaster = _serviceProvider.GetRequiredService<EventUpcasterService>();
         await upcaster.WaitForCompletionAsync();
-
         _transientEventRepository.NewEvents += HandleNewEvents;
         _transientEventRepository.NewTransientEvents += HandleNewTransientEvents;
     }

src/Fluss/Upcasting/EventUpcasterService.cs

@@ -17,7 +17,7 @@ public class EventUpcasterService(
 {
     private readonly List<IUpcaster> _sortedUpcasters = sorter.SortByDependencies(upcasters);
 
-    private readonly CancellationTokenSource _onCompletedSource = new();
+    private readonly TaskCompletionSource _onCompletedSource = new();
 
     public async ValueTask Run()
     {
@@ -47,13 +47,11 @@ public async ValueTask Run()
             events = upcastedEvents;
         }
 
-        _onCompletedSource.Cancel();
+        _onCompletedSource.SetResult();
     }
 
     public async Task WaitForCompletionAsync()
     {
-        var tcs = new TaskCompletionSource<bool>();
-        _onCompletedSource.Token.Register(s => ((TaskCompletionSource<bool>)s!).SetResult(true), tcs);
-        await tcs.Task;
+        await _onCompletedSource.Task;
     }
 }