fix(outbox): don't remove outbox prematurely

Prevent deleting an outbox when there may still be messages to process (batch was full, messages delayed, or redelivery scheduled). Also simplify channel retrieval by removing a redundant CreateUnbounded call.

Author: winromulus

src/ES.FX.TransactionalOutbox.EntityFrameworkCore/Delivery/OutboxDeliveryService.cs

@@ -190,6 +190,7 @@ await dbContext.Database.CreateExecutionStrategy().ExecuteAsync(async () =>
                                 .ConfigureAwait(false);
 
 
+                            var outboxHasRemainingMessages = false;
                             foreach (var message in messages)
                             {
                                 if (DateTimeOffset.UtcNow > message.DeliveryNotAfter)
@@ -212,6 +213,7 @@ await dbContext.Database.CreateExecutionStrategy().ExecuteAsync(async () =>
                                     outbox.DeliveryDelayedUntil = message.DeliveryNotBefore;
 
                                     //Proceed to the next available outbox, since this one is delayed
+                                    outboxHasRemainingMessages = true;
                                     break;
                                 }
 
@@ -270,6 +272,7 @@ await DeliverMessage(message, messageContext, messageHandler, deliveryTimeout.To
                                         outbox.DeliveryDelayedUntil =
                                             DateTimeOffset.UtcNow.Add(redeliverMessageAction.Delay);
 
+                                        outboxHasRemainingMessages = true;
                                         break;
                                     }
 
@@ -287,11 +290,14 @@ await DeliverMessage(message, messageContext, messageHandler, deliveryTimeout.To
                                 }
                             }
 
+                            // If the batch was full, there may be more messages beyond this batch
+                            if (messages.Count >= outboxDeliveryOptions.BatchSize)
+                                outboxHasRemainingMessages = true;
 
                             outbox.Lock = null;
                             dbContext.Update(outbox);
 
-                            if (messages.Count == 0)
+                            if (!outboxHasRemainingMessages)
                             {
                                 logger.LogTrace("Removing empty outbox {outboxId}", outbox.Id);
                                 dbContext.Remove(outbox);

src/ES.FX.TransactionalOutbox.EntityFrameworkCore/Internals/OutboxDeliverySignal.cs

@@ -10,11 +10,8 @@ internal static class OutboxDeliverySignal
 {
     private static readonly ConcurrentDictionary<Type, Channel<string>> Channels = new();
 
-    public static Channel<string> GetChannel(Type type)
-    {
-        Channel.CreateUnbounded<string>(new UnboundedChannelOptions());
-        return Channels.GetOrAdd(type, _ => Channel.CreateUnbounded<string>());
-    }
+    public static Channel<string> GetChannel(Type type) =>
+        Channels.GetOrAdd(type, _ => Channel.CreateUnbounded<string>());
 
     public static Channel<string> GetChannel<TType>() => GetChannel(typeof(TType));