Implemented channel pooling.

framework/src/Volo.Abp.BackgroundJobs.RabbitMQ/Volo/Abp/BackgroundJobs/RabbitMQ/JobQueue.cs

@@ -111,7 +111,7 @@ namespace Volo.Abp.BackgroundJobs.RabbitMQ
                 return Task.CompletedTask;
             }
 
-            ChannelAccessor = ChannelPool.Acquire(QueueName);
+            ChannelAccessor = ChannelPool.Acquire(QueueName + ".JobQueue");
 
             var queueOptions = RabbitMqOptions.Queues.GetOrDefault(QueueName)
                                ?? new QueueOptions(QueueName);

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

@@ -16,7 +16,10 @@ namespace Volo.Abp.RabbitMQ
 
         public override void OnApplicationShutdown(ApplicationShutdownContext context)
         {
-            context.ServiceProvider.GetRequiredService<IConnectionPool>().Dispose();
+            context.ServiceProvider
+                .GetRequiredService<IConnectionPool>()
+                .Dispose();
+
             //TODO: Dispose channel pool when it's implemented! 
         }
     }

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

@@ -1,4 +1,7 @@
-using RabbitMQ.Client;
+using System;
+using System.Collections.Concurrent;
+using System.Threading;
+using RabbitMQ.Client;
 using Volo.Abp.DependencyInjection;
 
 namespace Volo.Abp.RabbitMQ
@@ -7,16 +10,43 @@ namespace Volo.Abp.RabbitMQ
     {
         protected IConnectionPool ConnectionPool { get; }
 
+        protected ConcurrentDictionary<string, ChannelPoolItem> Channels { get; }
+        
         public ChannelPool(IConnectionPool connectionPool)
         {
             ConnectionPool = connectionPool;
+            Channels = new ConcurrentDictionary<string, ChannelPoolItem>();
         }
 
         public virtual IChannelAccessor Acquire(string channelName = null)
         {
-            //TODO: Pool channels!
+            channelName = channelName ?? "";
+
+            var poolItem = Channels.GetOrAdd(channelName, _ => new ChannelPoolItem
+            {
+                Channel = CreateChannel(channelName)
+            });
+
+            lock (poolItem)
+            {
+                while (poolItem.IsInUse)
+                {
+                    Monitor.Wait(poolItem);
+                }
+                
+                poolItem.IsInUse = true;
+            }
+
             return new ChannelAccessor(
-                CreateChannel(channelName)
+                poolItem.Channel,
+                () =>
+                {
+                    lock (poolItem)
+                    {
+                        poolItem.IsInUse = false;
+                        Monitor.PulseAll(poolItem);
+                    }
+                }
             );
         }
 
@@ -29,15 +59,17 @@ namespace Volo.Abp.RabbitMQ
         protected class ChannelAccessor : IChannelAccessor
         {
             public IModel Channel { get; }
+            private readonly Action _disposeAction;
 
-            public ChannelAccessor(IModel channel)
+            public ChannelAccessor(IModel channel, Action disposeAction)
             {
+                _disposeAction = disposeAction;
                 Channel = channel;
             }
 
             public void Dispose()
             {
-                Channel.Dispose();
+                _disposeAction.Invoke();
             }
         }
     }

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

@@ -0,0 +1,16 @@
+using RabbitMQ.Client;
+
+namespace Volo.Abp.RabbitMQ
+{
+    public class ChannelPoolItem
+    {
+        public IModel Channel { get; set; }
+
+        public bool IsInUse
+        {
+            get => _isInUse;
+            set => _isInUse = value;
+        }
+        private volatile bool _isInUse;
+    }
+}

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

@@ -1,5 +1,4 @@
-using System;
-using System.Collections.Concurrent;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using Microsoft.Extensions.Options;
 using RabbitMQ.Client;
@@ -7,7 +6,7 @@ using Volo.Abp.DependencyInjection;
 
 namespace Volo.Abp.RabbitMQ
 {
-    public class ConnectionPool : IConnectionPool, IDisposable, ISingletonDependency
+    public class ConnectionPool : IConnectionPool, ISingletonDependency
     {
         protected AbpRabbitMqOptions Options { get; }
 

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

@@ -5,6 +5,11 @@ namespace Volo.Abp.RabbitMQ
 {
     public interface IChannelAccessor : IDisposable
     {
+        /// <summary>
+        /// Reference to the channel.
+        /// Never dispose the <see cref="Channel"/> object.
+        /// Instead, dispose the <see cref="IChannelAccessor"/> after usage.
+        /// </summary>
         IModel Channel { get; }
     }
 }

modules/background-jobs/app/Volo.Abp.BackgroundJobs.DemoApp.Shared/Jobs/WriteToConsoleGreenJob.cs

@@ -9,7 +9,7 @@ namespace Volo.Abp.BackgroundJobs.DemoApp.Shared.Jobs
         {
             if (RandomHelper.GetRandom(0, 100) < 70)
             {
-                throw new ApplicationException("A sample exception from the WriteToConsoleGreenJob!");
+                //throw new ApplicationException("A sample exception from the WriteToConsoleGreenJob!");
             }
 
             var oldColor = Console.ForegroundColor;