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RabbitMQ: Fast processing of time consuming events

I'm experimenting with RabbitMQ and I hope someone can give me some hints.
I try to do the following: Processing events, which are time consuming to process, as quickly as possible with one consumer.
The test: 5 events and each one takes 2 seconds to process.
First attempt: 'Hello world' example from RabbitMQ (https://www.rabbitmq.com/tutorials/tutorial-one-dotnet.html).
static void Main(string[] args)
{
// Sender
var factory = new ConnectionFactory { HostName = "localhost"};
using var connection = factory.CreateConnection();
using var channel = connection.CreateModel();
channel.QueueDeclare(queue: "hello", durable: false, exclusive: false, autoDelete: false, arguments: null);
const string message = "Hello World!";
for (int i = 1; i <= 5; i++)
{
var body = Encoding.UTF8.GetBytes($"{message} {i}");
channel.BasicPublish(exchange: string.Empty,
routingKey: "hello",
basicProperties: null,
body: body);
Console.WriteLine($"Sent {message} {i}");
}
// Consumer
var consumer = new EventingBasicConsumer(channel);
consumer.Received += (model, ea) =>
{
var body = ea.Body.ToArray();
var message = Encoding.UTF8.GetString(body);
Thread.Sleep(2000);
Console.WriteLine($"Received {message}");
};
channel.BasicConsume(queue: "hello",
autoAck: true,
consumer: consumer);
Console.WriteLine("Press [enter] to exit.");
Console.ReadLine();
}
Conclusion: Too slow because events are processed synchronously.
Second attempt: Asynchronous processing using AsyncEventingBasicConsumer.
Code changes:
DispatchConsumersAsync-property is set in the ConnectionFactory
AsyncEventingBasicConsumer is used
consumer.Received is async
static void Main(string[] args)
{
// Sender
var factory = new ConnectionFactory { HostName = "localhost", DispatchConsumersAsync = true };
using var connection = factory.CreateConnection();
using var channel = connection.CreateModel();
channel.QueueDeclare(queue: "hello", durable: false, exclusive: false, autoDelete: false, arguments: null);
const string message = "Hello World!";
for (int i = 1; i <= 5; i++)
{
var body = Encoding.UTF8.GetBytes($"{message} {i}");
channel.BasicPublish(exchange: string.Empty,
routingKey: "hello",
basicProperties: null,
body: body);
Console.WriteLine($"Sent {message} {i}");
}
// Consumer
var consumer = new AsyncEventingBasicConsumer(channel);
consumer.Received += async (model, ea) =>
{
var body = ea.Body.ToArray();
var message = Encoding.UTF8.GetString(body);
await Task.Delay(2000);
Console.WriteLine($"Received {message}");
};
channel.BasicConsume(queue: "hello",
autoAck: true,
consumer: consumer);
Console.WriteLine("Press [enter] to exit.");
Console.ReadLine();
}
Conclusion: Too slow because events are still processed synchronously.
Third attempt: Async event handler for the consumer.
Code changes:
DispatchConsumersAsync-property is removed in the ConnectionFactory.
EventingBasicConsumer is used again
static void Main(string[] args)
{
// Sender
var factory = new ConnectionFactory { HostName = "localhost" };
using var connection = factory.CreateConnection();
using var channel = connection.CreateModel();
channel.QueueDeclare(queue: "hello", durable: false, exclusive: false, autoDelete: false, arguments: null);
const string message = "Hello World!";
for (int i = 1; i <= 101; i++)
{
var body = Encoding.UTF8.GetBytes($"{message} {i}");
channel.BasicPublish(exchange: string.Empty,
routingKey: "hello",
basicProperties: null,
body: body);
Console.WriteLine($"Sent {message} {i}");
}
// Consumer
var consumer = new EventingBasicConsumer(channel);
consumer.Received += async (model, ea) =>
{
var body = ea.Body.ToArray();
var message = Encoding.UTF8.GetString(body);
await Task.Delay(2000);
Console.WriteLine($"Received {message}");
};
channel.BasicConsume(queue: "hello",
autoAck: true,
consumer: consumer);
Console.WriteLine("Press [enter] to exit.");
Console.ReadLine();
}
Conclusion: This is the result I want. The messages are processed very fast even when 1000 events are published.
But is this a proper solution for usage in a production environment?
I hope someone can help to clarify this or share their experience for processing events fast in a production environment.

Console.WriteLine is not working on consumer.received - RabbitMQ C#

I wrote these code lines, but I couldn't figure out how I can print some values on console in consumer.receive. This code is working because I checked some values on RabbitMQ CloudAMQP, but I cannot see any changes on console.
Problem is here:
Console.WriteLine(Encoding.UTF8.GetString(e.Body.ToArray()) + " received");
Full code:
// publisher
ConnectionFactory factory = new ConnectionFactory();
factory.Uri = new Uri("amqps://guest:guest#localhost");
using (IConnection connection = factory.CreateConnection())
using (IModel channel = connection.CreateModel())
{
channel.ExchangeDeclare("kuyruk", type: ExchangeType.Fanout);
for (int i = 1; i <= 100; i++)
{
byte [] bytemessage = Encoding.UTF8.GetBytes($"is - {i}");
IBasicProperties properties = channel.CreateBasicProperties();
properties.Persistent = true;
channel.BasicPublish(exchange: "kuyruk", routingKey: "", basicProperties: properties, body: bytemessage);
}
}
// Consumer
ConnectionFactory factory = new ConnectionFactory();
factory.Uri = new Uri("amqps://guest:guest#localhost");
using (IConnection connection = factory.CreateConnection())
using (IModel channel = connection.CreateModel())
{
channel.ExchangeDeclare("kuyruk", type: ExchangeType.Fanout);
// Here consumer İçin Oluşturulacak Kuyruklara Random İsim Oluşturma
string queueName = channel.QueueDeclare().QueueName;
channel.QueueBind(queue: queueName, exchange: "kuyruk", routingKey: "");
channel.BasicQos(prefetchSize: 0, prefetchCount: 1, global: false);
EventingBasicConsumer consumer = new EventingBasicConsumer(channel);
channel.BasicConsume(queueName, false, consumer);
consumer.Received += (sender, e) =>
{
Thread.Sleep(500);
Console.WriteLine(Encoding.UTF8.GetString(e.Body.ToArray()) + " received");
channel.BasicAck(e.DeliveryTag, false);
};
Console.Read();
}

First you have to create the queue. When you publish a message after this point, it will be queued. If you publish the message first, the message will disappear because there is no queue to send the message to.
Another bug in your code is this: you are creating a consumer channel. You define the action to be taken when the message arrives. Then, when your code run into to the publishing process below, you exit the using block which is wrap your consumer channel. For this reason, consumer is closed and cannot consume message.
//consumer
using System.Text;
using RabbitMQ.Client;
using RabbitMQ.Client.Events;
var factory = new ConnectionFactory
{
Uri = new Uri("amqp://guest:guest#localhost")
};
using (IConnection connection = factory.CreateConnection())
using (IModel consumeChannel = connection.CreateModel())
{
consumeChannel.ExchangeDeclare("kuyruk", type: ExchangeType.Fanout);
//#region Her Consumer İçin Oluşturulacak Kuyruklara Random İsim Oluşturma
string queueName = consumeChannel.QueueDeclare().QueueName;
consumeChannel.QueueBind(queue: queueName, exchange: "kuyruk", routingKey: "");
//#endregion
consumeChannel.BasicQos(prefetchSize: 0, prefetchCount: 1, global: false);
var consumer = new EventingBasicConsumer(consumeChannel);
consumeChannel.BasicConsume(queueName, false, consumer);
consumer.Received += (sender, e) =>
{
Thread.Sleep(500);
Console.WriteLine(Encoding.UTF8.GetString(e.Body.ToArray()) + " recieved");
consumeChannel.BasicAck(e.DeliveryTag, false);
};
//publisher
using (IModel publishChannel = connection.CreateModel())
{
publishChannel.ExchangeDeclare("kuyruk", type: ExchangeType.Fanout);
for (int i = 1; i <= 100; i++)
{
var str = $"is - {i}";
byte[] byteMessage = Encoding.UTF8.GetBytes(str);
IBasicProperties properties = publishChannel.CreateBasicProperties();
properties.Persistent = true;
publishChannel.BasicPublish(exchange: "kuyruk", routingKey: "", basicProperties: properties, body: byteMessage);
}
}
Console.Read();
}

How do I get RabbitMQ to read from the queue one by one?

I am just playing with RabbitMQ and trying to get a test sender and receiver set up in two C# projects.
TestSender.cs
using System;
using RabbitMQ.Client;
using System.Text;
public class TestSender
{
public TestSender()
{
}
public static void Main()
{
var factory = new ConnectionFactory() { HostName = "localhost" };
using (var connection = factory.CreateConnection())
{
using (var channel = connection.CreateModel())
{
channel.QueueDeclare(queue: "Test Queue",
durable: true,
exclusive: false,
autoDelete: false,
arguments: null);
Console.WriteLine(" Press [S] to send a message, [Enter] to exit.");
ConsoleKey key;
int messageId = 0;
while (true)
{
key = Console.ReadKey(true).Key;
if (key == ConsoleKey.Enter)
break;
if (key == ConsoleKey.S)
{
string message = "Message " + (++messageId).ToString();
var body = Encoding.UTF8.GetBytes(message);
channel.BasicPublish(exchange: "",
routingKey: "hello",
basicProperties: null,
body: body);
Console.WriteLine("Sent {0}", message);
}
}
}
}
}
}
TestReceiver.cs
using RabbitMQ.Client;
using RabbitMQ.Client.Events;
using System;
using System.Text;
public class TestReceiver
{
public TestReceiver()
{
}
public static void Main()
{
var factory = new ConnectionFactory() { HostName = "localhost" };
using (var connection = factory.CreateConnection())
{
using (var channel = connection.CreateModel())
{
// Declare the queue here because we might start the consumer before the publisher
// so the queue should exist before we try to consume messages from it.
channel.QueueDeclare(queue: "Test Queue",
durable: true,
exclusive: false,
autoDelete: false,
arguments: null);
var consumer = new EventingBasicConsumer(channel);
Console.WriteLine(" Press [R] to receive a message, [Enter] to exit.");
// Register a consumer to listen to a specific queue.
channel.BasicConsume(queue: "Test Queue",
autoAck: true,
consumer: consumer);
ConsoleKey key;
while (true)
{
key = Console.ReadKey(true).Key;
if (key == ConsoleKey.Enter)
break;
if (key == ConsoleKey.R)
{
consumer.Received += (model, ea) =>
{
var body = ea.Body;
var message = Encoding.UTF8.GetString(body);
Console.WriteLine("Received {0}", message);
};
}
}
}
}
}
}
I set it up in such a way that if you press the S key, it sends a message to the queue and if you press the R key, it reads from the queue. The sending works but the receiving does absolutely nothing. I removed the while loop and keypress code and the receiving works. However, I would like to figure out how to get messages consumed one by one and not all at once. In addition, does anyone know if RabbitMQ can persist messages in the queue or do they have to be dequeued when consumed?

RabbitMQ sends a new message to consumer/subscriber when you Acknowledge the current message. RabbitMQ will persist message in the queue(durable mode only) until not acknowledged.
Remove autoAck: true options from channel.BasicConsume function. use channel.BasicAck function to ack a message when R key pressed.

RabbitMQ Can't Send and Receive from same process

I'm working through my first steps with RabbitMQ and have a question on why this didn't work.
The basic tutorial (https://www.rabbitmq.com/tutorials/tutorial-one-dotnet.html) has one executable to send to the broker and another to receive it.
I ran this code through a single console app in Visual Studio and couldn't receive any messages.
If I take the "Receive" code and put it into a separate console app and open that, I get the message (no other code changes).
Can someone explain why I'm not able to have both in the same process? I had figured that the connection factory would handle independent connections accordingly regardless of whether it was the same process or not.
For the sake of completeness (though I doubt it's required), here's the code that didn't work until I pulled out the "Receiver" code and put it into it's own console app:
class Program
{
static void Main(string[] args) {
Receiver.Receive();
Console.WriteLine("receiver set up");
System.Threading.Thread.Sleep(5000);
Console.WriteLine("sending...");
Test.Send();
// can also reverse order of send/receive methods, same result
Console.ReadKey();
}
}
public class Receiver
{
public static void Receive() {
var factory = new ConnectionFactory() { HostName = "localhost" };
using (var connection = factory.CreateConnection()) {
using (var channel = connection.CreateModel()) {
channel.QueueDeclare("hello", false, false, false, null);
var consumer = new EventingBasicConsumer(channel);
consumer.Received += (model, ea) => {
var body = ea.Body;
var message = Encoding.UTF8.GetString(body);
System.Diagnostics.Debug.WriteLine("=====================");
System.Diagnostics.Debug.WriteLine(message);
System.Diagnostics.Debug.WriteLine("=====================");
};
channel.BasicConsume("hello", true, consumer);
}
}
}
}
public class Test
{
public static void Send() {
var factory = new ConnectionFactory() { HostName = "localhost" };
using (var connection = factory.CreateConnection()) {
using (var channel = connection.CreateModel()) {
channel.QueueDeclare("hello", false, false, false, null);
string message = "Check it!";
var body = Encoding.UTF8.GetBytes(message);
channel.BasicPublish("", "hello", null, body);
}
}
}
}

I think code has a problem. When you send message then Receive connection and channel already dead (Dispose called).
Standard code from RabbitMQ site:
using(var connection = factory.CreateConnection())
using(var channel = connection.CreateModel())
{
channel.QueueDeclare(queue: "hello",
durable: false,
exclusive: false,
autoDelete: false,
arguments: null);
var consumer = new EventingBasicConsumer(channel);
consumer.Received += (model, ea) =>
{
var body = ea.Body;
var message = Encoding.UTF8.GetString(body);
Console.WriteLine(" [x] Received {0}", message);
};
channel.BasicConsume(queue: "hello",
noAck: true,
consumer: consumer);
Console.WriteLine(" Press [enter] to exit.");
Console.ReadLine();
}
connection and channel are yet alive when client received message.

Why declare Exchange in RabbitMQ?

I am working on a project with RabbitMQ. My code is below.
Producer:
public static void Main()
{
var factory = new ConnectionFactory() { HostName = "localhost" };
using (var connection = factory.CreateConnection())
{
using (var channel = connection.CreateModel())
{
channel.QueueDeclare("hello", false, false, false, null);
string message = "Hello World!";
var body = Encoding.UTF8.GetBytes(message);
channel.BasicPublish("", "hello", null, body);
Console.WriteLine(" [x] Sent {0}", message);
}
}
}
Consumer with Exchange declared:
public static void Main()
{
var factory = new ConnectionFactory() { HostName = "localhost" };
using (var connection = factory.CreateConnection())
{
using (var channel = connection.CreateModel())
{
channel.ExchangeDeclare("hello", "direct",false, false, false, null);
channel.QueueDeclare("hello", false, false, false, null);
var consumer = new QueueingBasicConsumer(channel);
channel.BasicConsume("hello", true, consumer);
Console.WriteLine(" [*] Waiting for messages." +
"To exit press CTRL+C");
while (true)
{
var ea = (BasicDeliverEventArgs)consumer.Queue.Dequeue();
var body = ea.Body;
var message = Encoding.UTF8.GetString(body);
Console.WriteLine(" [x] Received {0}", message);
}
}
}
Consumer without Exchange declared:
public static void Main()
{
var factory = new ConnectionFactory() { HostName = "localhost" };
using (var connection = factory.CreateConnection())
{
using (var channel = connection.CreateModel())
{
channel.QueueDeclare("hello", false, false, false, null);
var consumer = new QueueingBasicConsumer(channel);
channel.BasicConsume("hello", true, consumer);
Console.WriteLine(" [*] Waiting for messages." +
"To exit press CTRL+C");
while (true)
{
var ea = (BasicDeliverEventArgs)consumer.Queue.Dequeue();
var body = ea.Body;
var message = Encoding.UTF8.GetString(body);
Console.WriteLine(" [x] Received {0}", message);
}
}
}
Both consumer code works well, so what's the main use of declaring exchange? I am confused. Can anyone clarify?

Publishing to queues lets you only implement basic publish-subscribe scenarios, where the producer and consumer use the exact queue. In case of multiple consumers a single queue of messages is distributed between multiple consumers.
Publishing to exchanges lets you create complicated scenarios, because of routing between exchanges and queues.
For example, a fanout exchange routes messages to all bound queues. This way, you can have one producer and multiple consumers and each message is copied to all bound queues independently and received independently.
Another example of exchange, a topic exchange routes messages to bound queues based on routing key in a message and a pattern on a queue. This introduces an interesting possibility of tagging messages and delivering them conditionally.
For a complete reference of exchange types and their profiles refer to the documentation:
https://www.rabbitmq.com/tutorials/amqp-concepts.html
https://www.rabbitmq.com/getstarted.html