前言

在上一篇文章中，我們知道了RabbitMQ的消息流程如下：

但在具體的使用中，我們還需知道exchange的類型，因為不同的類型對應不同的隊列和路由規則。

在rabbitmq中，exchange有4個類型：direct，topic，fanout，header。

direct exchange

此類型的exchange路由規則很簡單：

exchange在和queue進行binding時會設定routingkey

channel.QueueBind(queue: "create_pdf_queue",
                    exchange: "pdf_events",
                    routingKey: "pdf_create",
                    arguments: null);

然後我們在将消息發送到exchange時會設定對應的routingkey：

channel.BasicPublish(exchange: "pdf_events",
                        routingKey: "pdf_create",
                        basicProperties: properties,
                        body: body);

在direct類型的exchange中，隻有這兩個routingkey完全相同，exchange才會選擇對應的binging進行消息路由。

具體的流程如下：

通過代碼可以會了解好一點：

var factory = new ConnectionFactory() { HostName = "localhost" };
using (var connection = factory.CreateConnection())
using (var channel = connection.CreateModel())
{
    // Direct類型的exchange, 名稱 pdf_events
    channel.ExchangeDeclare(exchange: "pdf_events",
                            type: ExchangeType.Direct,
                            durable: true,
                            autoDelete: false,
                            arguments: null);

    // 建立create_pdf_queue隊列
    channel.QueueDeclare(queue: "create_pdf_queue",
                            durable: true,
                            exclusive: false,
                            autoDelete: false,
                            arguments: null);

    //建立 pdf_log_queue隊列
    channel.QueueDeclare(queue: "pdf_log_queue",
                            durable: true,
                            exclusive: false,
                            autoDelete: false,
                            arguments: null);

    //綁定 pdf_events --> create_pdf_queue 使用routingkey:pdf_create
    channel.QueueBind(queue: "create_pdf_queue",
                        exchange: "pdf_events",
                        routingKey: "pdf_create",
                        arguments: null);

    //綁定 pdf_events --> pdf_log_queue 使用routingkey:pdf_log
    channel.QueueBind(queue: "pdf_log_queue",
                        exchange: "pdf_events",
                        routingKey: "pdf_log",
                        arguments: null);


    var message = "Demo some pdf creating...";
    var body = Encoding.UTF8.GetBytes(message);
    var properties = channel.CreateBasicProperties();
    properties.Persistent = true;

    //發送消息到exchange :pdf_events ,使用routingkey: pdf_create
    //通過binding routinekey的比較，次消息會路由到隊列 create_pdf_queue
    channel.BasicPublish(exchange: "pdf_events",
                routingKey: "pdf_create",
                basicProperties: properties,
                body: body);

    message = "pdf loging ...";
    body = Encoding.UTF8.GetBytes(message);
    properties = channel.CreateBasicProperties();
    properties.Persistent = true;

    //發送消息到exchange :pdf_events ,使用routingkey: pdf_log
    //通過binding routinekey的比較，次消息會路由到隊列 pdf_log_queue
    channel.BasicPublish(exchange: "pdf_events",
            routingKey: "pdf_log",
            basicProperties: properties,
            body: body);

    
}

topic exchange

此類型exchange和上面的direct類型差不多，但direct類型要求routingkey完全相等，這裡的routingkey可以有通配符：'*','#'.

其中'*'表示比對一個單詞， '#'則表示比對沒有或者多個單詞

如上圖第一個binding：

exchange: agreements
queue A: berlin_agreements
binding routingkey: agreements.eu.berlin.#

第二個binding:

queue B: all_agreements
binding routingkey: agreements.#

第三個binding：

queue c: headstore_agreements
binding routingkey: agreements.eu.*.headstore

是以如果我們消息的routingkey為agreements.eu.berlin那麼符合第一和第二個binding，但最後一個不符合，具體的代碼如下：

var factory = new ConnectionFactory() { HostName = "localhost" };
using (var connection = factory.CreateConnection())
using (var channel = connection.CreateModel())
{
    // Topic類型的exchange, 名稱 agreements
    channel.ExchangeDeclare(exchange: "agreements",
                            type: ExchangeType.Topic,
                            durable: true,
                            autoDelete: false,
                            arguments: null);

    // 建立berlin_agreements隊列
    channel.QueueDeclare(queue: "berlin_agreements",
                            durable: true,
                            exclusive: false,
                            autoDelete: false,
                            arguments: null);

    //建立 all_agreements 隊列
    channel.QueueDeclare(queue: "all_agreements",
                            durable: true,
                            exclusive: false,
                            autoDelete: false,
                            arguments: null);

    //建立 headstore_agreements 隊列
    channel.QueueDeclare(queue: "headstore_agreements",
                            durable: true,
                            exclusive: false,
                            autoDelete: false,
                            arguments: null);

    //綁定 agreements --> berlin_agreements 使用routingkey:agreements.eu.berlin.#
    channel.QueueBind(queue: "berlin_agreements",
                        exchange: "agreements",
                        routingKey: "agreements.eu.berlin.#",
                        arguments: null);

    //綁定 agreements --> all_agreements 使用routingkey:agreements.#
    channel.QueueBind(queue: "all_agreements",
                        exchange: "agreements",
                        routingKey: "agreements.#",
                        arguments: null);

    //綁定 agreements --> headstore_agreements 使用routingkey:agreements.eu.*.headstore
    channel.QueueBind(queue: "headstore_agreements",
                        exchange: "agreements",
                        routingKey: "agreements.eu.*.headstore",
                        arguments: null);


    var message = "hello world";
    var body = Encoding.UTF8.GetBytes(message);
    var properties = channel.CreateBasicProperties();
    properties.Persistent = true;

    //發送消息到exchange :agreements ,使用routingkey: agreements.eu.berlin
    //agreements.eu.berlin 比對  agreements.eu.berlin.# 和agreements.#
    //agreements.eu.berlin 不比對  agreements.eu.*.headstore
    //最終次消息會路由到隊裡：berlin_agreements（agreements.eu.berlin.#） 和 all_agreements（agreements.#）
    channel.BasicPublish(exchange: "agreements",
                            routingKey: "agreements.eu.berlin",
                            basicProperties: properties,
                            body: body);

               
}

fanout exchange

此exchange的路由規則很簡單直接将消息路由到所有綁定的隊列中，無須對消息的routingkey進行比對操作。

header exchange

此類型的exchange和以上三個都不一樣，其路由的規則是根據header來判斷，其中的header就是以下方法的arguments參數：

Dictionary<string, object> aHeader = new Dictionary<string, object>();
aHeader.Add("format", "pdf");
aHeader.Add("type", "report");
aHeader.Add("x-match", "all");
channel.QueueBind(queue: "queue.A",
                    exchange: "agreements",
                    routingKey: string.Empty,
                    arguments: aHeader);

其中的x-match為特殊的header，可以為all則表示要比對所有的header，如果為any則表示隻要比對其中的一個header即可。

在釋出消息的時候就需要傳入header值：

var properties = channel.CreateBasicProperties();
properties.Persistent = true;
Dictionary<string, object> mHeader1 = new Dictionary<string, object>();
mHeader1.Add("format", "pdf");
mHeader1.Add("type", "report");
properties.Headers = mHeader1;

具體的規則可以看以下代碼：

var factory = new ConnectionFactory() { HostName = "localhost" };
using (var connection = factory.CreateConnection())
using (var channel = connection.CreateModel())
{
    // Headers類型的exchange, 名稱 agreements
    channel.ExchangeDeclare(exchange: "agreements",
                            type: ExchangeType.Headers,
                            durable: true,
                            autoDelete: false,
                            arguments: null);

    // 建立queue.A隊列
    channel.QueueDeclare(queue: "queue.A", durable: true, exclusive: false, autoDelete: false, arguments: null);

    //建立 queue.B 隊列
    channel.QueueDeclare(queue: "queue.B", durable: true, exclusive: false, autoDelete: false, arguments: null);

    //建立 queue.C 隊列
    channel.QueueDeclare(queue: "queue.C", durable: true, exclusive: false, autoDelete: false, arguments: null);

    //綁定 agreements --> queue.A 使用arguments (format=pdf, type=report, x-match=all)
    Dictionary<string, object> aHeader = new Dictionary<string, object>();
    aHeader.Add("format", "pdf");
    aHeader.Add("type", "report");
    aHeader.Add("x-match", "all");
    channel.QueueBind(queue: "queue.A",
                        exchange: "agreements",
                        routingKey: string.Empty,
                        arguments: aHeader);

    //綁定 agreements --> queue.B 使用arguments (format=pdf, type=log, x-match=any)
    Dictionary<string, object> bHeader = new Dictionary<string, object>();
    bHeader.Add("format", "pdf");
    bHeader.Add("type", "log");
    bHeader.Add("x-match", "any");
    channel.QueueBind(queue: "queue.B",
                        exchange: "agreements",
                        routingKey: string.Empty,
                        arguments: bHeader);

    //綁定 agreements --> queue.C 使用arguments (format=zip, type=report, x-match=all)
    Dictionary<string, object> cHeader = new Dictionary<string, object>();
    cHeader.Add("format", "zip");
    cHeader.Add("type", "report");
    cHeader.Add("x-match", "all");
    channel.QueueBind(queue: "queue.C",
                        exchange: "agreements",
                        routingKey: string.Empty,
                        arguments: cHeader);


    string message1 = "hello world";
    var body = Encoding.UTF8.GetBytes(message1);
    var properties = channel.CreateBasicProperties();
    properties.Persistent = true;
    Dictionary<string, object> mHeader1 = new Dictionary<string, object>();
    mHeader1.Add("format", "pdf");
    mHeader1.Add("type", "report");
    properties.Headers = mHeader1;
    //此消息路由到 queue.A 和 queue.B
    //queue.A 的binding (format=pdf, type=report, x-match=all)
    //queue.B 的binding (format = pdf, type = log, x - match = any)
    channel.BasicPublish(exchange: "agreements",
                            routingKey: string.Empty,
                            basicProperties: properties,
                            body: body);


    string message2 = "hello world";
    body = Encoding.UTF8.GetBytes(message2);
    properties = channel.CreateBasicProperties();
    properties.Persistent = true;
    Dictionary<string, object> mHeader2 = new Dictionary<string, object>();
    mHeader2.Add("type", "log");
    properties.Headers = mHeader2;
    //x-match 配置queue.B 
    //queue.B 的binding (format = pdf, type = log, x-match = any)
    channel.BasicPublish(exchange: "agreements",
                    routingKey: string.Empty,
                    basicProperties: properties,
                    body: body);

    string message3= "hello world";
    body = Encoding.UTF8.GetBytes(message3);
    properties = channel.CreateBasicProperties();
    properties.Persistent = true;
    Dictionary<string, object> mHeader3 = new Dictionary<string, object>();
    mHeader3.Add("format", "zip");
    properties.Headers = mHeader3;
    //配置失敗，不會被路由
    channel.BasicPublish(exchange: "agreements",
                    routingKey: string.Empty,
                    basicProperties: properties,
                    body: body);


}

總計

以上就是exchange 類型的總結，一般來說direct和topic用來具體的路由消息，如果要用廣播的消息一般用fanout的exchange。

header類型用的比較少，但還是知道一點好。

RabbitMQ Exchange類型詳解

前言

direct exchange

topic exchange

fanout exchange

header exchange

總計

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