RabbitMQ Routing功能

交換器(Exchange)的路由(Routing)功能

現在我們已經更正確的使用交換器功能，而非將訊息直接寫入佇列，為什麼需要這樣做呢？因為RabbitMQ交換器擁有路由功能，當訊息進入交換器時，可以透過種類來分配到不同的佇列裡，以官網的例子就是LOG處理機制。

LOG的重要程度可大致分為 Debug, Info, Warning, Error, Fatal.
Warning以上要分配到 Queue1
Debug與Info 等級則要放到 Queue2

這樣在宣告佇列時就可以綁定到該分配器，但指定不同QueneName, RouteKey. EX:

channel.QueueBind(queue: queueName, exchange: "direct_logs", routingKey: "INFO");
channel.QueueBind(queue: queueName, exchange: "direct_logs", routingKey: "WARNING");

以下會用publisher分別發送兩個訊息到交換器，並指定不同的RouteKEY

Publisher

宣告兩個訊息並指定RouteKey分別為”ERROR”與”INFO”

channel.ExchangeDeclare(exchange: "direct_logs", type: "direct");
var msg_error = $"This is Error msg.";
var msg_info = $"This is Info msg";

channel.BasicPublish(exchange: "direct_logs",
    routingKey: "ERROR",
    basicProperties: null,
    body: Encoding.UTF8.GetBytes(msg_error));
channel.BasicPublish(exchange: "direct_logs",
    routingKey: "INFO",
    basicProperties: null,
    body: Encoding.UTF8.GetBytes(msg_info));

Subscriber

這邊雖然只用了一個佇列但綁定了四個不同RouteKey，收到訊息後印出是指定哪個RouteKey與內容。

channel.QueueBind(queue: queueName, exchange: "direct_logs", routingKey: "INFO");
channel.QueueBind(queue: queueName, exchange: "direct_logs", routingKey: "WARNING");
channel.QueueBind(queue: queueName, exchange: "direct_logs", routingKey: "ERROR");
channel.QueueBind(queue: queueName, exchange: "direct_logs", routingKey: "FATAL");

var consumer = new EventingBasicConsumer(channel);
consumer.Received += (model, ea) =>
{
    var body = ea.Body;
    var msg = Encoding.UTF8.GetString(body);
    var routingKey = ea.RoutingKey;
    Console.WriteLine($"Receiving RoutingKey:{routingKey}, Msg:{msg}.");
};

最後分別執行兩支程式，結果如下圖：

程式範例檔

完整的範例檔放在這 範例，有興趣的可以自行下載，此版本與之前文章不同，是用 .Net Core開發的。