In rabbitmq, Fanout Exchange will route messages to all of the queues that are bound to it.
The fanout exchange is useful when we want to publish a common message to all the queues that are bound with a particular exchange and in the fanout exchange, the routing key is ignored.
For example, if the company has updated some guidelines and you want to push those guidelines to all the branches that time you can use fanout exchange.
Generally, in rabbitmq when the producer creates a message that will not directly send to the queue, instead first the message will be sent to exchanges, then after that, a routing agent reads and sends it to the appropriate queue with help of header attributes, bindings and routing keys.
In rabbitmq, we have different types of exchanges available are
To know more about exchanges in rabbitmq, check this RabbitMQ Exchanges.
Following is the pictorial representation of message flow in the rabbit fanout exchange.
Now, we will learn how to use Fanout Exchange to push and read messages from rabbitmq in c# or .net application with examples.
Let’s create a simple console application with the Name “RequestRabbitMQ” as shown below to publish messages to the rabbitmq queue using fanout exchange in c#.
After creating an application, now we will add the “RabbitMQ.Client” NuGet package in our c# application to communicate with rabbitmq server to publish or consume messages from queues in rabbitmq.
In c#, we can publish or consume messages from rabbitmq by using RabbitMQ.Client NuGet package for that, right-click on your application and select Manage NuGet Packages as shown below.
Now search for RabbitMQ.Client package and install it in your application as shown below.
Following is another way to install RabbitMQ.Client package by using Package Manager Console as shown below by entering the following command.
Command to install - Install-Package RabbitMQ.Client -Version 5.1.0
Before we start writing a code in c# to publish messages to rabbitmq, we will create a fanout exchange, queue and will bind a queue to exchange using the web admin console.
To create an exchange in rabbitmq web management portal, open http://localhost:15672/#/exchanges url and then go to Add a new exchange panel and enter details as shown below by selecting Type as “fanout” and click on Add exchange button to create an exchange (fanout.exchange).
After creating an exchange (fanout.exchange), next, we will create 4 queues (Mumbai, Hyderabad, Bangalore, and Chennai) and bind them to the same exchange (fanout.exchange) in the web management portal.
To create a queue in rabbitmq web management portal, open http://localhost:15672/#/queues url and then go to Add a new queue panel and enter details as shown below, and click on Add queue button to create a queue (Mumbai).
Similar way, add the remaining three queues (Bangalore, Chennai, Hyderabad) in rabbitmq as shown below.
To bind a queue with an exchange, click on the queue (Bangalore) name, then the Bindings panel will expand and enter details like exchange name as “fanout.exchange” and click on the Bind button as shown below.
After binding a queue (Bangalore) to exchange (fanout.exchange), the binding will be as shown below.
Same way, bind the remaining queues (Chennai, Hyderabad, Mumbai) also to an exchange (fanout.exchange) in rabbitmq web admin console.
After the completion of binding queues (Bangalore, Chennai, Hyderabad, Mumbai) to an exchange (fanout.exchange), now we will publish messages from the c# application to rabbitmq queues using RabbitMQ.Client service.
To publish messages to the rabbitmq queue, add a class with the name “Fanoutmessages.cs” in your application as shown below.
Now, open the Fanoutmessages.cs class file and write the code as shown below.
If you observe the above code, to establish a connection with rabbitmq server we are passing the required credentials along with the HostName to ConnectionFactory() method. After that, we are publishing a message (Message is of fanout Exchange type) to the queue by passing required parameters like an exchange, routing key, properties, and message to the BasicPublish method.
Now open Program.cs class file and write a code in the Main method to call Fanoutmessages.cs class to get messages from rabbitmq.
Following is the code which we need to write in Program.cs class file Main method to publish messages to rabbitmq server.
When we execute the above c# program, we will get the result as shown below.
After executing the above program, if we check the queues (Bangalore, Chennai, Hyderabad, Mumbai) status details in rabbitmq web management portal, the Ready column is having 1 like as shown below which means the message was published successfully to all the queues of fanout exchange.
After creating an application, now add “RabbitMQ.Client” NuGet package reference to your application like as we did in publishing application to communicate with rabbitmq server.
After installing RabbitMQ.Client, next add a class with the name “MessageReceiver.cs” in your application as shown below to read or get messages from queues in rabbitmq.
Now, open MessageReceiver.cs class file and write the code as shown below.
If you observe the above code, we created a MessageReceiver class and it’s inheriting from DefaultBasicConsumer class of RabbitMQ.Client service and we implemented a HandleBasicDeliver method by overriding it to receive a message body.
Now open Program.cs class file and write a code in the Main method to call MessageReceiver.cs class to get messages from rabbitmq.
Following is the code which we need to write in Program.cs class file Main method to receive data from rabbitmq server.
If you observe the above example, to establish a connection with rabbitmq server we are passing the required credentials along with the HostName to ConnectionFactory() method. After that, we created a connection and channel by calling the “CreateConnection” and “CreateModel” methods and we set a prefetchCount to 1, so that it tells RabbitMQ not to give more than one message at a time to the worker.
Next, we created an instance of MessageReceiver class and passed IModel (channel) to it, in the final step we called the “BasicConsume” method and passed the queue name to it “Mumbai” along with we have set autoAck to false and passed the messageReceiver instance to it.
Here, prefetchCount is used to tell RabbitMQ not to give more than one message at a time to the worker. Or, in other words, don't dispatch a new message to a worker until it has been processed and acknowledged the previous one. Instead, it will dispatch to the next worker that is not still busy.
When we execute our application, we will get messages from the queue (Mumbai) as shown below.
After reading the messages from the Mumbai queue, the following is the status of a queue in the web management portal.
Same way, we can read messages from Bangalore or Chennai, or Hyderabad queues based on our requirements.
This is how we can use fanout exchange in rabbitmq to publish messages to all the queues which are bound with an exchange.