.Net 使用 RabbitMQ中的几个细节

1、使用 ConnectionFactory 创建 IConnection 时，如果有多线程的情况下，比如会有多个Consumer，需要加锁，同时确保 Connection 对象唯一，可以使用单例模式。

 public bool _isConnected => _connection is { IsOpen: true };

在 RabbitMQ 持久化时，可以用到 Polly 第三方库中的 Policy 做连接失败重试。

if (_isConnected) return;

lock(obj){

    var policy = Policy.Handle().Or                            ().WaitAndRetry(5,
                    times =>
                        TimeSpan.FromSeconds(Math.Pow(2, times)),
                    (exception, span) =>
                    {
                        Console.WriteLine(
                            $"rabbitmq client cannot connected. after {span.TotalSeconds:n1}. ex:{exception.Message}");
                    });

    policy.Execute(() =>
                {
                    var factory = new ConnectionFactory()
                    {
                        HostName = "xxxxx",
                        Port = 1000,
                        UserName = "xxxxx",
                        Password = "xxxxx"
                    };
                    _connection = factory.CreateConnection();
                    Console.WriteLine("connected to rabbitmq...");
                });

    if (_connection.IsOpen)
    {
                    _connection.ConnectionShutdown += OnConnectionShutdown;
                    _connection.CallbackException += OnCallBackException;
                    _connection.ConnectionBlocked += OnConnectionBlocked;
    }
    else
    {
                    Console.WriteLine(" fatal error : rabbitmq connection could not be created or opened ");
    }

}

 2、发布消息的时候 记得加 using 及时释放 channel

using var model = _connection.CreateModel();

3、消费者不能使用 using，否则在没有消息的时候会被释放掉。