將 RabbitMQ 的連線參數移至 Config 中

之前文章使用 .Net client 連線至 RabbitMQ 收發訊息介紹了如何連線至 RabbitMQ 收發訊息，不過當時直接在程式碼指定了相關的連線資訊，身為一個優秀的工程師都曉得連線字串這東西絕對不能寫死在程式碼中，不然如果有一天需要修改時，會改到哭出來，所以我們應該將連線字串移至 config 中來共用，另外也會將 deueue 用法改使用新的 api (舊 api 已被標記為 Deprectated)，除此之外也將原本散落各處的名稱定義(e.g. queue,exchange,routingkey…)做個整理

今天修改的部份並不多，但連線字串的寫法有點特別，一定要紀錄下來避免忘記，加上日後需要才能快速找到東西 c.c.

原程式碼

Consumer

void Main()
{
    //初始化連線資訊
    var factory = new ConnectionFactory()
    {
        //設定 RabbitMQ 位置
        HostName = "localhost",
        //設定 RabbitMQ port
        Port = 5672,
        //設定連線 RabbitMQ username
        UserName = "yowko",
        //設定 RabbitMQ password
        Password = "pass.123"
    };
    //開啟連線
    using (var connection = factory.CreateConnection())
    //開啟 channel
    using (var channel = connection.CreateModel())
    {
        //宣告 queues
        channel.QueueDeclare("yowkoTest", false, false, false, null);
        //建立 consumer
        var consumer = new QueueingBasicConsumer(channel);
        channel.BasicConsume("yowkoTest", true, consumer);
        Console.WriteLine(" waiting for message.");
        //持續等著接收訊息
        while (true)
        {
            //從 RabbitMQ 取得訊息
            var ea = (BasicDeliverEventArgs)consumer.Queue.Dequeue();
                        var body = ea.Body;
            var message = Encoding.UTF8.GetString(body);
            Console.WriteLine("Received {0}", message);
            Thread.Sleep(5000);
        }
    }
}

Publisher

void Main()
{
    //初始化連線資訊
    var factory = new ConnectionFactory();
    //設定 RabbitMQ 位置
    factory.HostName = "localhost";
    //設定 RabbitMQ port
    factory.Port = 5672;
    //設定連線 RabbitMQ username
    factory.UserName = "yowko";
    //設定 RabbitMQ password
    factory.Password = "pass.123";
                    
    //開啟連線
    using (var connection = factory.CreateConnection())
    //開啟 channel
    using (var channel = connection.CreateModel())
    {
        //宣告 exchanges，RabbitMQ提供了四種Exchange模式：fanout,direct,topic,header
        channel.ExchangeDeclare("yowko", ExchangeType.Fanout);
        //宣告 queues
        channel.QueueDeclare("yowkoTest", false, false, false, null);
        //將 exchnage、queue 依 route rule 綁定
        channel.QueueBind("yowkoTest", "yowko", "hello", null);
        //  channel.QueueDeclare("hello", false, false, false, null);
        string message = $"Hello World-{Guid.NewGuid()}";
        var body = Encoding.UTF8.GetBytes(message);
        channel.BasicPublish("yowko", "hello", null, body);
        Console.WriteLine(" set {0}", message);
    }
}

將連線字串移至 config

Pattern
amqp://{帳號}:{帳碼}@{rabbitMQ_url}:{rabbitMQ_port}
實際寫法
amqp://yowko:pass.123@localhost:5672

使用 EventHandler 來調整 Consumer

var consumer = new EventingBasicConsumer(channel);
consumer.Received += (model, ea) =>
{
    var body = ea.Body;
    var message = Encoding.UTF8.GetString(body);
    Console.WriteLine($"Received： {message}");
    channel.BasicAck(deliveryTag: ea.DeliveryTag, multiple: false);
    Console.WriteLine("OK");
};

修改後程式碼

Consumer

void Main()
{
    //初始化連線資訊
    var factory = new ConnectionFactory();
    factory.Uri = "amqp://yowko:pass.123@localhost:5672";
    var queueName = "yowkoTest";
        
    using (var connection = factory.CreateConnection())
    using (var channel = connection.CreateModel())
    {
        channel.QueueDeclare(queue: queueName,
            durable: true,
            exclusive: false,
            autoDelete: false,
            arguments: null);
        channel.BasicQos(prefetchSize: 0, prefetchCount: 1, global: false);
        Console.WriteLine(" [*] Waiting for messages.");
        var consumer = new EventingBasicConsumer(channel);
        consumer.Received += (model, ea) =>
        {
            var body = ea.Body;
            var message = Encoding.UTF8.GetString(body);
            Console.WriteLine($"Received： {message}");
            channel.BasicAck(deliveryTag: ea.DeliveryTag, multiple: false);
            Console.WriteLine("OK");
        };
        channel.BasicConsume(queue: queueName,
            noAck: false,
            consumer: consumer);
        Console.WriteLine(" Press [enter] to exit.");
        Console.ReadLine();
    }
}

Publisher

void Main()
{
    //初始化連線資訊
    var factory = new ConnectionFactory();
    factory.Uri = "amqp://yowko:pass.123@localhost:5672";
    //開啟連線
    using (var connection = factory.CreateConnection())
    //開啟 channel
    using (var channel = connection.CreateModel())
    {
        string exchange = "yowko";
        string queue = "yowkoTest";
        string routingKey = "hello";
        //宣告 exchanges，RabbitMQ提供了四種Exchange模式：fanout,direct,topic,header
        channel.ExchangeDeclare(exchange, ExchangeType.Fanout);
        //宣告 queues
        channel.QueueDeclare(queue, true, false, false, null);
        //將 exchnage、queue 依 route rule 綁定
        channel.QueueBind(queue, exchange, routingKey, null);
        channel.BasicQos(0, 1, true);
        string message = $"Hello World-{Guid.NewGuid()}";
        var body = Encoding.UTF8.GetBytes(message);
        channel.BasicPublish(exchange, routingKey, new RabbitMQ.Client.Framing.BasicProperties { Persistent = true }, body);
        Console.WriteLine($"Send Message：{message}");
    }
}

心得

原本只是用來進行 POC 的程式碼，因為要實際應用在 production 環境上，所以需要考量到良好的可閱讀性及較佳的可維護性，在 code review 後發展出較佳的寫法，這讓我想到或許不一定每次都能有其他團隊成員協助 code review ，但仍然可以自行 code review 以確認是否滿足團隊的規範，持續自我要求，漸漸地就會養成寫出較佳程式碼的習慣

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