在.net framework 4.0下面使用同步方式实现类似异步的效果，master slaver模式监听和消费消息队列。
Question1：
can you write some demo let me familiar some scenario of use thread in .net framework 4.0. for example use master slave model, consumer some message queue from RabbitMq.The main thread cannot block the process.
Answer1:
Certainly! Here’s an example that demonstrates a master-slave model using threads in the .NET Framework 4.0, where the main thread consumes messages from a RabbitMQ message queue while the slave threads process those messages. The main thread will not block the process, allowing asynchronous processing.
First, make sure you have the RabbitMQ client library installed via NuGet package manager. You can do this by running the following command in the NuGet Package Manager Console:
Install-Package RabbitMQ.Client
using System;
using System.Collections.Concurrent;
using System.Threading;
using RabbitMQ.Client;
using RabbitMQ.Client.Events;
public class MasterSlaveExample
{
private const string RabbitMqConnectionString = "your_rabbitmq_connection_string";
private const string QueueName = "your_queue_name";
private const int SlaveThreadCount = 4;
private readonly BlockingCollection<string> messageQueue;
private readonly ManualResetEventSlim resetEvent;
private readonly IConnection rabbitMqConnection;
public MasterSlaveExample()
{
messageQueue = new BlockingCollection<string>();
resetEvent = new ManualResetEventSlim(false);
var factory = new ConnectionFactory { Uri = new Uri(RabbitMqConnectionString) };
rabbitMqConnection = factory.CreateConnection();
}
public void Run()
{
// Create slave threads
var slaveThreads = new Thread[SlaveThreadCount];
for (var i = 0; i < SlaveThreadCount; i++)
{
slaveThreads[i] = new Thread(ProcessMessage);
slaveThreads[i].Start();
}
// Create and start the main thread
var mainThread = new Thread(ConsumeMessages);
mainThread.Start();
// Wait for the main thread to finish
mainThread.Join();
// Signal slave threads to stop and wait for them to finish
messageQueue.CompleteAdding();
resetEvent.Wait();
// Close RabbitMQ connection
rabbitMqConnection.Close();
}
private void ConsumeMessages()
{
using (var channel = rabbitMqConnection.CreateModel())
{
channel.QueueDeclare(queue: QueueName, durable: true, exclusive: false, autoDelete: false, arguments: null);
var consumer = new EventingBasicConsumer(channel);
consumer.Received += (model, ea) =>
{
var message = System.Text.Encoding.UTF8.GetString(ea.Body.ToArray());
messageQueue.Add(message);
};
channel.BasicConsume(queue: QueueName, autoAck: true, consumer: consumer);
}
}
private void ProcessMessage()
{
foreach (var message in messageQueue.GetConsumingEnumerable())
{
// Perform processing on the message
Console.WriteLine($"Processing message: {message}");
Thread.Sleep(1000); // Simulating processing time
}
// Signal that the thread has finished
resetEvent.Set();
}
}
In the code above, the MasterSlaveExample class sets up a master-slave model. The ConsumeMessages method runs in the main thread and consumes messages from the RabbitMQ queue. Each received message is added to the messageQueue using the BlockingCollection class.
The ProcessMessage method represents the slave thread’s work. It processes messages retrieved from the messageQueue. In this example, it simply prints the message and simulates processing time using Thread.Sleep.
The Run method sets everything up. It creates the slave threads, starts the main thread to consume messages, and waits for it to finish. Once the main thread is done, it signals the slave threads to stop by completing the `
Question2
does main thread not stop ,monitoring the message queue ,can not block the process.
Answer2
Apologies for the confusion. In order to ensure that the main thread does not block while monitoring the message queue, you can modify the example to use an event-driven approach with asynchronous methods. Here’s an updated version:
using System;
using System.Threading;
using System.Threading.Tasks;
using RabbitMQ.Client;
using RabbitMQ.Client.Events;
public class MasterSlaveExample
{
private const string RabbitMqConnectionString = "your_rabbitmq_connection_string";
private const string QueueName = "your_queue_name";
private const int SlaveThreadCount = 4;
private readonly SemaphoreSlim semaphore;
private readonly IConnection rabbitMqConnection;
public MasterSlaveExample()
{
semaphore = new SemaphoreSlim(SlaveThreadCount);
var factory = new ConnectionFactory { Uri = new Uri(RabbitMqConnectionString) };
rabbitMqConnection = factory.CreateConnection();
}
public async Task RunAsync()
{
using (var channel = rabbitMqConnection.CreateModel())
{
channel.QueueDeclare(queue: QueueName, durable: true, exclusive: false, autoDelete: false, arguments: null);
var consumer = new AsyncEventingBasicConsumer(channel);
consumer.Received += async (model, ea) =>
{
await ProcessMessageAsync(ea.Body.ToArray());
};
channel.BasicConsume(queue: QueueName, autoAck: true, consumer: consumer);
// Keep the main thread running
await Task.Delay(Timeout.Infinite);
}
}
private async Task ProcessMessageAsync(byte[] messageBody)
{
await semaphore.WaitAsync();
try
{
// Perform processing on the message
var message = System.Text.Encoding.UTF8.GetString(messageBody);
Question3
as we all know ,in the .net framework 4.0 can not use async and await ,in this case ,you can simulator async in .net framework 4.0?
Answer3
You are correct. I apologize for the oversight. Asynchronous programming with async and await is not available in the .NET Framework 4.0. It was introduced in later versions, starting from .NET Framework 4.5.
If you are restricted to using the .NET Framework 4.0, you can achieve asynchronous behavior by using the Task class and the ContinueWith method for chaining tasks. Here’s an updated version of the code that simulates asynchronous behavior:
using System;
using System.Threading;
using System.Threading.Tasks;
using RabbitMQ.Client;
using RabbitMQ.Client.Events;
public class MasterSlaveExample
{
private const string RabbitMqConnectionString = "your_rabbitmq_connection_string";
private const string QueueName = "your_queue_name";
private const int SlaveThreadCount = 4;
private readonly SemaphoreSlim semaphore;
private readonly IConnection rabbitMqConnection;
public MasterSlaveExample()
{
semaphore = new SemaphoreSlim(SlaveThreadCount);
var factory = new ConnectionFactory { Uri = new Uri(RabbitMqConnectionString) };
rabbitMqConnection = factory.CreateConnection();
}
public void Run()
{
using (var channel = rabbitMqConnection.CreateModel())
{
channel.QueueDeclare(queue: QueueName, durable: true, exclusive: false, autoDelete: false, arguments: null);
var consumer = new EventingBasicConsumer(channel);
consumer.Received += (model, ea) =>
{
Task.Factory.StartNew(() => ProcessMessage(ea.Body.ToArray()));
};
channel.BasicConsume(queue: QueueName, autoAck: true, consumer: consumer);
// Keep the main thread running
Thread.Sleep(Timeout.Infinite);
}
}
private void ProcessMessage(byte[] messageBody)
{
semaphore.Wait();
try
{
// Perform processing on the message
var message = System.Text.Encoding.UTF8.GetString(messageBody);
Console.WriteLine($"Processing message: {message}");
Thread.Sleep(1000); // Simulating processing time
}
finally
{
semaphore.Release();
}
}
}
In this updated code, the Run method uses the EventingBasicConsumer to consume messages from the RabbitMQ queue. When a message is received, a new Task is created using Task.Factory.StartNew, which simulates the asynchronous behavior.
The ProcessMessage method represents the processing logic for each message. It uses SemaphoreSlim to limit the number of concurrent slave threads, ensuring only a specified number of threads can enter the processing block.
To run the example, you can call the Run method like this:
var example = new MasterSlaveExample();
example.Run();
Please note that this approach is a simulation of asynchronous behavior in the .NET Framework 4.0 and does not provide the same benefits and guarantees as true asynchronous programming with async and await.
文档信息
- 本文作者：hillcat
- 本文链接：https://cs-cn.top/2023/05/21/Master_Slaver_Model_In_DotNet4.0Framework/
- 版权声明：自由转载-非商用-非衍生-保持署名（创意共享3.0许可证）