Added IRabbitMQPersisterConnection and more resilient work on rabbitmq event bus

Author: Unai Zorrilla Castro

src/BuildingBlocks/EventBus/EventBusRabbitMQ/DefaultRabbitMQPersisterConnection.cs

@@ -0,0 +1,130 @@
+using Microsoft.Extensions.Logging;
+using Polly;
+using Polly.Retry;
+using RabbitMQ.Client;
+using RabbitMQ.Client.Events;
+using RabbitMQ.Client.Exceptions;
+using System;
+using System.IO;
+using System.Net.Sockets;
+
+namespace Microsoft.eShopOnContainers.BuildingBlocks.EventBusRabbitMQ
+{
+    public class DefaultRabbitMQPersisterConnection
+       : IRabbitMQPersisterConnection
+    {
+        private readonly IConnectionFactory _connectionFactory;
+        private readonly ILogger<DefaultRabbitMQPersisterConnection> _logger;
+
+        IConnection _connection;
+        bool _disposed;
+
+        object sync_root = new object();
+
+        public DefaultRabbitMQPersisterConnection(IConnectionFactory connectionFactory,ILogger<DefaultRabbitMQPersisterConnection> logger)
+        {
+            _connectionFactory = connectionFactory ?? throw new ArgumentNullException(nameof(connectionFactory));
+            _logger = logger ?? throw new ArgumentNullException(nameof(logger));
+        }
+
+        public bool IsConnected
+        {
+            get
+            {
+                return _connection != null && _connection.IsOpen && !_disposed;
+            }
+        }
+
+        public IModel CreateModel()
+        {
+            if (!IsConnected)
+            {
+                throw new InvalidOperationException("No RabbitMQ connections are available to perform this action");
+            }
+
+            return _connection.CreateModel();
+        }
+
+        public void Dispose()
+        {
+            if (_disposed) return;
+
+            _disposed = true;
+
+            try
+            {
+                _connection.Dispose();
+            }
+            catch (IOException ex)
+            {
+                _logger.LogCritical(ex.ToString());
+            }
+        }
+
+        public bool TryConnect()
+        {
+            _logger.LogInformation("RabbitMQ Client is trying to connect");
+
+            lock (sync_root)
+            {
+                var policy = RetryPolicy.Handle<SocketException>()
+                    .Or<BrokerUnreachableException>()
+                    .WaitAndRetry(5, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)), (ex, time) =>
+                    {
+                        _logger.LogWarning(ex.ToString());
+                    }
+                );
+
+                policy.Execute(() =>
+                {
+                    _connection = _connectionFactory
+                          .CreateConnection();
+                });
+
+                if (IsConnected)
+                {
+                    _connection.ConnectionShutdown += OnConnectionShutdown;
+                    _connection.CallbackException += OnCallbackException;
+                    _connection.ConnectionBlocked += OnConnectionBlocked;
+
+                    _logger.LogInformation($"RabbitMQ persister connection acquire a connection {_connection.Endpoint.HostName} and is subscribed to failure events");
+                 
+                    return true;
+                }
+                else
+                {
+                    _logger.LogCritical("FATAL ERROR: RabbitMQ connections can't be created and opened");
+
+                    return false;
+                }
+            }
+        }
+
+        private void OnConnectionBlocked(object sender, ConnectionBlockedEventArgs e)
+        {
+            if (_disposed) return;
+
+            _logger.LogWarning("A RabbitMQ connection is shutdown. Trying to re-connect...");
+
+            TryConnect();
+        }
+
+        void OnCallbackException(object sender, CallbackExceptionEventArgs e)
+        {
+            if (_disposed) return;
+
+            _logger.LogWarning("A RabbitMQ connection throw exception. Trying to re-connect...");
+
+            TryConnect();
+        }
+
+        void OnConnectionShutdown(object sender, ShutdownEventArgs reason)
+        {
+            if (_disposed) return;
+
+            _logger.LogWarning("A RabbitMQ connection is on shutdown. Trying to re-connect...");
+
+            TryConnect();
+        }
+    }
+}