面试题：C#中RabbitMQ集群环境下消息队列与集成的高可用优化

队列的镜像设置

RabbitMQ集群配置：
- 在RabbitMQ集群节点上，通过命令行工具或管理界面设置镜像队列。例如，使用命令行设置镜像队列策略：
```
rabbitmqctl set_policy ha-all "^" '{"ha-mode":"all"}'
```
上述命令将所有队列（匹配^正则表达式，即所有队列）设置为镜像队列，ha - mode为all表示在所有节点上镜像。也可以设置更灵活的策略，比如只在部分节点镜像：
```
rabbitmqctl set_policy ha-two "^" '{"ha - mode":"nodes","ha - params":["rabbit@node1","rabbit@node2"]}'
```

C#代码层面：C#代码与镜像队列交互和普通队列基本一致，因为对客户端来说，镜像队列看起来和普通队列一样。例如，使用RabbitMQ.Client库发送消息：

using RabbitMQ.Client;
using System.Text;

class Program
{
    static void Main()
    {
        var factory = new ConnectionFactory() { HostName = "your - hostname" };
        using (var connection = factory.CreateConnection())
        using (var channel = connection.CreateModel())
        {
            channel.QueueDeclare(queue: "your - queue - name",
                 durable: true,
                 exclusive: false,
                 autoDelete: false,
                 arguments: null);

            string message = "Hello World!";
            var body = Encoding.UTF8.GetBytes(message);

            channel.BasicPublish(exchange: "",
                 routingKey: "your - queue - name",
                 basicProperties: null,
                 body: body);
            Console.WriteLine(" [x] Sent {0}", message);
        }
    }
}

负载均衡策略

RabbitMQ集群配置：RabbitMQ内置了负载均衡机制。当多个消费者连接到集群时，RabbitMQ会自动将消息分发给不同的消费者。可以通过x - queue - master - locator参数进一步优化负载均衡。例如，将队列的主节点定位在特定节点上：
```
rabbitmqctl set_policy ha - master - locator "^" '{"ha - mode":"exactly","ha - params":2,"x - queue - master - locator":"min - masters"}'
```
min - masters策略会将队列主节点定位在拥有最少主队列的节点上。

C#代码层面：消费者代码只需要正常连接到集群并消费消息。例如：

using RabbitMQ.Client;
using RabbitMQ.Client.Events;
using System.Text;

class Program
{
    static void Main()
    {
        var factory = new ConnectionFactory() { HostName = "your - hostname" };
        using (var connection = factory.CreateConnection())
        using (var channel = connection.CreateModel())
        {
            channel.QueueDeclare(queue: "your - queue - name",
                 durable: true,
                 exclusive: false,
                 autoDelete: false,
                 arguments: null);

            var consumer = new EventingBasicConsumer(channel);
            consumer.Received += (model, ea) =>
            {
                var body = ea.Body.ToArray();
                var message = Encoding.UTF8.GetString(body);
                Console.WriteLine(" [x] Received {0}", message);
            };
            channel.BasicConsume(queue: "your - queue - name",
                 autoAck: true,
                 consumer: consumer);

            Console.WriteLine(" Press [enter] to exit.");
            Console.ReadLine();
        }
    }
}

处理脑裂问题

RabbitMQ集群配置：
- 确保集群节点之间网络稳定。可以通过增加网络冗余（如多网卡、冗余网络链路）来减少网络故障导致脑裂的可能性。
- 合理设置cluster_partition_handling参数。可以将其设置为pause_minority，当发生脑裂时，少数派节点会暂停服务，避免数据不一致。在rabbitmq.config文件中设置：
```
[
    {rabbit, [
        {cluster_partition_handling, pause_minority}
    ]}
].
```

C#代码层面：在C#代码中，需要处理连接异常。例如，当连接因为脑裂等网络问题中断时，重新连接到集群：

using RabbitMQ.Client;
using RabbitMQ.Client.Exceptions;
using System;
using System.Text;
using System.Threading;

class Program
{
    static IConnection connection;
    static IModel channel;
    static void Main()
    {
        Connect();
        while (true)
        {
            try
            {
                // 正常的消息发送或接收操作
                channel.QueueDeclare(queue: "your - queue - name",
                     durable: true,
                     exclusive: false,
                     autoDelete: false,
                     arguments: null);

                string message = "Hello World!";
                var body = Encoding.UTF8.GetBytes(message);

                channel.BasicPublish(exchange: "",
                     routingKey: "your - queue - name",
                     basicProperties: null,
                     body: body);
                Console.WriteLine(" [x] Sent {0}", message);
            }
            catch (BrokerUnreachableException)
            {
                Console.WriteLine("Connection lost, trying to reconnect...");
                Connect();
            }
            Thread.Sleep(1000);
        }
    }

    static void Connect()
    {
        var factory = new ConnectionFactory() { HostName = "your - hostname" };
        while (true)
        {
            try
            {
                connection = factory.CreateConnection();
                channel = connection.CreateModel();
                break;
            }
            catch (BrokerUnreachableException)
            {
                Console.WriteLine("Could not connect, retrying in 5 seconds...");
                Thread.Sleep(5000);
            }
        }
    }
}

面试题：C#中RabbitMQ集群环境下消息队列与集成的高可用优化

知识考点

面试题答案

队列的镜像设置

负载均衡策略

处理脑裂问题