Losing messages when using RabbitMQ with .NET Core WebAPI

Question

I am trying to receive and send simple messages from two web APIs using RabbitMQ. It is a pretty simple code for now, and I am trying to see if both the APIs are properly able to communicate with each other. The issue is that I am not receiving all the messages and unable to establish a pattern between those that I am losing and those I am receiving. Below is the sample code.

For sending messages

public class QueueController : Controller
    {
        [HttpGet]
        [Route("send")]
        public async Task Send()
        {
            QueueManager.Send();
            return Ok();
        }
   }

public class QueueManager
    {
        public static string queueName = "test-queue";
        public static int count = 0;
        public static void Send()
        {
            var factory = new ConnectionFactory() { HostName = "localhost" };
            using (var connection = factory.CreateConnection())
            Using (var channel = connection.CreateModel())
            {
            var queue = channel.QueueDeclare(queueName,
                                     durable: false,
                                     exclusive: false,
                                     autoDelete: false,
                                     arguments: null);
            count++;
            var message = new { Message = "Sent Message", count = count };
            var body = JsonSerializer.Serialize(message);
            var queueMessage = Encoding.UTF8.GetBytes(body);
            channel.BasicPublish("", queueName, null, queueMessage);
            }
        }
    }

For receiving messages

public class QueueController : Controller
    {
        [HttpGet]
        [Route("receive")]
        public async Task Receive()
        {
            QueueManager.Receive();
            return Ok();
        }
    }

public class QueueManager
    {
        public static string queueName = "test-queue";
        public static void Receive()
        {
            var factory = new ConnectionFactory() { HostName = "localhost" };
            using (var connection = factory.CreateConnection())
            using (var channel = connection.CreateModel())
            {
                channel.QueueDeclare(queueName,
                                         durable: false,
                                         exclusive: false,
                                         autoDelete: false,
                                         arguments: null);
                var consumer = new EventingBasicConsumer(channel);
                consumer.Received += (model, ea) =>
                {
                    var msg = ea.Body.ToArray();
                    var message = Encoding.UTF8.GetString(msg);
                    Console.WriteLine(message);
                };
                channel.BasicConsume(queueName, true, consumer);
            }
        }
    }

When I check the console of my receiver API, the message count is random. E.g., when I sent 7 messages, the ones that I received were of the number 2,3, and 7. So I lost 4 of the 7 messages. Not sure what is wrong here. Also, when I check the management console, I can see that the queue is emptied only when I call the endpoint in the receiver API, however the message still does not appear in the console. Any help will be appreciated.

user_5432783 · Answer

I create two solutions and used your code inside it, but it does not work. I changed it like this.

your producer class :

public class QueueManager2
{
    public static string queueName = "test-queue";
    public static int count = 0;
    public static void Send()
    {
        var factory = new ConnectionFactory() { HostName = "localhost" };
        using (var connection = factory.CreateConnection())
        using (var channel = connection.CreateModel())
        {
            channel.QueueDeclare(queue: queueName,
                                 durable: false,
                                 exclusive: false,
                                 autoDelete: false,
                                 arguments: null);

            count++;
            var message = new { Message = "Sent Message", count = count };

            var body = JsonSerializer.Serialize(message);
            var queueMessage = Encoding.UTF8.GetBytes(body);
             
            channel.BasicPublish(exchange: "",
                                 routingKey: queueName,
                                 basicProperties: null,
                                 body: queueMessage);
        }
    }
}

and your consumer class:

public class QueueManager2
{
    public static string queueName = "test-queue";
    public static void Receive()
    {
        var factory = new ConnectionFactory() { HostName = "localhost" };
         var rabbitMqConnection = factory.CreateConnection();
        var rabbitMqChannel = rabbitMqConnection.CreateModel();

        rabbitMqChannel.QueueDeclare(queue: queueName,
                             durable: false,
                             exclusive: false,
                             autoDelete: false,
                             arguments: null);

        rabbitMqChannel.BasicQos(prefetchSize: 0, prefetchCount: 1, global: false);

        int messageCount = Convert.ToInt16(rabbitMqChannel.MessageCount(queueName));            

        var consumer = new EventingBasicConsumer(rabbitMqChannel);
        consumer.Received += (model, ea) =>
        {
            var body = ea.Body;
            var message = Encoding.UTF8.GetString(body.ToArray());                
            rabbitMqChannel.BasicAck(deliveryTag: ea.DeliveryTag, multiple: false);
            
        };
        rabbitMqChannel.BasicConsume(queue: queueName,
                             autoAck: false,
                             consumer: consumer); 
    }
}

Now, If you run your project, you can produce a message and consume it. actually, for consumer, it's better to have a hosted service which is always in running mode. having an endpoint for getting messages is not a good idea

Losing messages when using RabbitMQ with .NET Core WebAPI

1 Answers