本文转载于：https://www.itsvse.com/thread-4636-1-1.html；
参考文献：http://www.likecs.com/show-29874.html；https://stackoverflow.com/questions/41279186/guaranteed-publishing-of-messages-on-rabbitmq-on-network-loss;
Rabbitmq 官方给的NET consumer示例代码如下，但使用过程，会遇到connection断开的问题，一旦断开，这个代码就会报错，就会导致消费者或者生产者挂掉。
下图是生产者发送消息，我手动停止了rabbitmq，然后又重新启动了rabbitmq，大概等启动成功以后，为了防止服务没有完全启动，我又等待了10秒钟
服务完全启动成功以后，我尝试重新发送一些消息，报错，如下：
************** 异常文本 **************
RabbitMQ.Client.Exceptions.AlreadyClosedException: Already closed: The AMQP operation was interrupted: AMQP close-reason, initiated by Peer, code=320, text="CONNECTION_FORCED - broker forced connection closure with reason 'shutdown'", classId=0, methodId=0, cause=
在 RabbitMQ.Client.Impl.SessionBase.Transmit(Command cmd)
在 RabbitMQ.Client.Impl.ModelBase.ModelSend(MethodBase method, ContentHeaderBase header, Byte[] body)
在 RabbitMQ.Client.Impl.ModelBase.BasicPublish(String exchange, String routingKey, Boolean mandatory, IBasicProperties basicProperties, Byte[] body)
在 RabbitMQ.Client.Impl.ModelBase.BasicPublish(String exchange, String routingKey, IBasicProperties basicProperties, Byte[] body)
在 rabbitMQ_Publish.Form1.button1_Click(Object sender, EventArgs e) 位置 C:\project\my\RabbitMQ-demo\rabbitMQ-Publish\Form1.cs:行号 37
在 System.Windows.Forms.Control.OnClick(EventArgs e)
在 System.Windows.Forms.Button.OnClick(EventArgs e)
在 System.Windows.Forms.Button.PerformClick()
在 System.Windows.Forms.Form.ProcessDialogKey(Keys keyData)
在 System.Windows.Forms.TextBoxBase.ProcessDialogKey(Keys keyData)
在 System.Windows.Forms.Control.PreProcessMessage(Message& msg)
在 System.Windows.Forms.Control.PreProcessControlMessageInternal(Control target, Message& msg)
在 System.Windows.Forms.Application.ThreadContext.PreTranslateMessage(MSG& msg)
那么如何会异常恢复呢？或者说断线重连呢？
RabbitMQ NET Client的源码，研究发现一种自动的错误恢复机制 AutomaticRecoveryEnabled = true 使用方式如下
var factory = new ConnectionFactory() { HostName = "localhost", AutomaticRecoveryEnabled = true };
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具体的恢复机制如下
1.在AutoRecoveringConnection初始化时，在链接关闭事件委托上增加断开处理
public void init()
{
m_delegate = new Connection(m_factory, false, m_factory.CreateFrameHandler());
AutorecoveringConnection self = this;
EventHandler recoveryListener = (_, args) =>
{
lock (recoveryLockTarget)
{
if (ShouldTriggerConnectionRecovery(args))
{
try
{
self.BeginAutomaticRecovery();
}
catch (Exception e)
{
// TODO: logging
Console.WriteLine("BeginAutomaticRecovery() failed: {0}", e);
}
}
}
};
lock (m_eventLock)
{
ConnectionShutdown += recoveryListener;
if (!m_recordedShutdownEventHandlers.Contains(recoveryListener))
{
m_recordedShutdownEventHandlers.Add(recoveryListener);
}
}
}
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观察调用的方式BeginAutomaticRecovery，可以看到这个方法内部调用了PerformAutomaticRecovery方法。我们直接看这个方法的内容，其中第一个调用的是方法RecoverConnectionDelegate
protected void PerformAutomaticRecovery()
{
lock (recoveryLockTarget)
{
RecoverConnectionDelegate();
RecoverConnectionShutdownHandlers();
RecoverConnectionBlockedHandlers();
RecoverConnectionUnblockedHandlers();
RecoverModels();
if (m_factory.TopologyRecoveryEnabled)
{
RecoverEntities();
RecoverConsumers();
}
RunRecoveryEventHandlers();
}
}
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这个方法中调用的是
protected void RecoverConnectionDelegate()
{
bool recovering = true;
while (recovering)
{
try
{
m_delegate = new Connection(m_factory, false, m_factory.CreateFrameHandler());
recovering = false;
}
catch (Exception)
{
// TODO: exponential back-off
Thread.Sleep(m_factory.NetworkRecoveryInterval);
// TODO: provide a way to handle these exceptions
}
}
}
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可以看出，它是执行了死循环，直到连接重新打开，当然，如果遇到异常，它会调用Thread.Sleep来等待一下，然后再次执行连接恢复。