Refactor RabbitMQ channel and connection handling for improved efficiency and reliability

framework/src/Volo.Abp.EventBus.RabbitMQ/Volo/Abp/EventBus/RabbitMq/RabbitMqDistributedEventBus.cs

@@ -225,7 +225,7 @@ public class RabbitMqDistributedEventBus : DistributedEventBusBase, IRabbitMqDis
         OutboxConfig outboxConfig)
     {
         using (var channel = await (await ConnectionPool.GetAsync(AbpRabbitMqEventBusOptions.ConnectionName))
-                   .CreateChannelAsync(new CreateChannelOptions(publisherConfirmationsEnabled: true, publisherConfirmationTrackingEnabled: true)))
+                   .CreateChannelAsync(new CreateChannelOptions(publisherConfirmationsEnabled: true, publisherConfirmationTrackingEnabled: true, new ThrottlingRateLimiter(256))))
         {
             var outgoingEventArray = outgoingEvents.ToArray();
 
@@ -298,8 +298,7 @@ public class RabbitMqDistributedEventBus : DistributedEventBusBase, IRabbitMqDis
         Guid? eventId = null,
         string? correlationId = null)
     {
-        using (var channel = await (await ConnectionPool.GetAsync(AbpRabbitMqEventBusOptions.ConnectionName))
-                   .CreateChannelAsync(new CreateChannelOptions(publisherConfirmationsEnabled: true, publisherConfirmationTrackingEnabled: true)))
+        using (var channel = await (await ConnectionPool.GetAsync(AbpRabbitMqEventBusOptions.ConnectionName)).CreateChannelAsync())
         {
             await PublishAsync(channel, eventName, body, headersArguments, eventId, correlationId);
         }
@@ -335,7 +334,7 @@ public class RabbitMqDistributedEventBus : DistributedEventBusBase, IRabbitMqDis
         await channel.BasicPublishAsync(
             exchange: AbpRabbitMqEventBusOptions.ExchangeName,
             routingKey: eventName,
-            mandatory: true,
+            mandatory: false,
             basicProperties: properties,
             body: body
         );
@@ -350,9 +349,7 @@ public class RabbitMqDistributedEventBus : DistributedEventBusBase, IRabbitMqDis
 
         try
         {
-            using (var temporaryChannel = await(await ConnectionPool.GetAsync(AbpRabbitMqEventBusOptions.ConnectionName))
-                       .CreateChannelAsync(new CreateChannelOptions(publisherConfirmationsEnabled: true,
-                           publisherConfirmationTrackingEnabled: true)))
+            using (var temporaryChannel = await (await ConnectionPool.GetAsync(AbpRabbitMqEventBusOptions.ConnectionName)).CreateChannelAsync())
             {
                 await temporaryChannel.ExchangeDeclarePassiveAsync(AbpRabbitMqEventBusOptions.ExchangeName);
             }

framework/src/Volo.Abp.RabbitMQ/Volo/Abp/RabbitMQ/ChannelPool.cs

@@ -49,14 +49,14 @@ public class ChannelPool : IChannelPool, ISingletonDependency
         {
             using (await Semaphore.LockAsync())
             {
-                if (!Channels.TryGetValue(channelName, out var channel))
+                if (Channels.TryGetValue(channelName, out var existingChannelPoolItem2))
                 {
-                    poolItem = new ChannelPoolItem(await CreateChannelAsync(channelName, connectionName));
-                    Channels.TryAdd(channelName, poolItem);
+                    poolItem = existingChannelPoolItem2;
                 }
                 else
                 {
-                    poolItem = channel;
+                    poolItem = new ChannelPoolItem(await CreateChannelAsync(channelName, connectionName));
+                    Channels.TryAdd(channelName, poolItem);
                 }
             }
         }
@@ -70,8 +70,15 @@ public class ChannelPool : IChannelPool, ISingletonDependency
 
             using (await Semaphore.LockAsync())
             {
-                poolItem = new ChannelPoolItem(await CreateChannelAsync(channelName, connectionName));
-                Channels.TryAdd(channelName, poolItem);
+                if (Channels.TryGetValue(channelName, out var existingChannelPoolItem3))
+                {
+                    poolItem = existingChannelPoolItem3;
+                }
+                else
+                {
+                    poolItem = new ChannelPoolItem(await CreateChannelAsync(channelName, connectionName));
+                    Channels.TryAdd(channelName, poolItem);
+                }
             }
 
             poolItem.Acquire();

framework/src/Volo.Abp.RabbitMQ/Volo/Abp/RabbitMQ/ConnectionPool.cs

@@ -39,18 +39,25 @@ public class ConnectionPool : IConnectionPool, ISingletonDependency
         {
             using (await Semaphore.LockAsync())
             {
-                var connectionFactory = Options.Connections.GetOrDefault(connectionName);
                 try
                 {
-                    connection = await GetConnectionAsync(connectionName, connectionFactory);
-                    Connections.TryAdd(connectionName, connection);
-
-                    if (!connection.IsOpen)
+                    var connectionFactory = Options.Connections.GetOrDefault(connectionName);
+                    if (Connections.TryGetValue(connectionName, out var existingConnection2))
+                    {
+                        connection = existingConnection2;
+                    }
+                    else
                     {
-                        connection.Dispose();
-                        Connections.TryRemove(connectionName, out _);
                         connection = await GetConnectionAsync(connectionName, connectionFactory);
                         Connections.TryAdd(connectionName, connection);
+
+                        if (!connection.IsOpen)
+                        {
+                            connection.Dispose();
+                            Connections.TryRemove(connectionName, out _);
+                            connection = await GetConnectionAsync(connectionName, connectionFactory);
+                            Connections.TryAdd(connectionName, connection);
+                        }
                     }
                 }
                 catch (Exception)