Print Queue State Every 10 seconds C# SignalR

Question

I am learning SignalR and need your help. In the following code, you can see one of the hubs of my first project. In this hub, I create a Queue and fill it using the JoinQueue method. Now I am looking for a technique to print the number of members in the Queue on the console every 5 seconds. I need a way to manage queue outside this hub I guess.

using BackEnd.Model;
using Microsoft.AspNetCore.SignalR;
using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

namespace BackEnd.Hubs
{
    public class QueueHub : Hub
    {
        private Queue<QueueItem> userQueue = new Queue<QueueItem>();

        public async Task JoinQueue(string userToken)
        {
            QueueItem user = new QueueItem
            {
                UserToken = userToken,
                ConnectionString = Context.ConnectionId
            };

            userQueue.Enqueue(user);

            Console.WriteLine(userQueue.Count);
        }

        public override Task OnConnectedAsync()
        {
            string connectionId = Context.ConnectionId;
            Console.WriteLine($"{connectionId} is Connected to the server");
            return base.OnConnectedAsync();
        }
    }

Answer 1

Using Background Service, it can help you implement this requirement.

Here is the test result in my side.

The structure of my test project.

QueueMonitorService.cs

using WebApplication2.IServices;

namespace WebApplication2.BackgroundServices
{
    public class QueueMonitorService : BackgroundService
    {
        private readonly IQueueManager _queueManager;

        public QueueMonitorService(IQueueManager queueManager)
        {
            _queueManager = queueManager;
        }

        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            while (!stoppingToken.IsCancellationRequested)
            {
                Console.WriteLine(DateTime.UtcNow.ToString("yyyy-MM-dd HH:mm:ss")+$"   The number of members in the queue: {_queueManager?.UserQueue?.Count}");
                await Task.Delay(5000, stoppingToken);
            }
        }
    }
}

QueueHub.cs

using Microsoft.AspNetCore.SignalR;
using WebApplication2.IServices;

namespace WebApplication2.Hubs
{
    public class QueueHub : Hub
    {
        private readonly IQueueManager _queueManager;

        public QueueHub(IQueueManager queueManager)
        {
            _queueManager = queueManager;
        }

        public Task AddToQueue(string userToken)
        {
            _queueManager.JoinQueue(userToken, Context.ConnectionId);
            return Task.CompletedTask;
        }
        public override Task OnConnectedAsync()
        {
            string connectionId = Context.ConnectionId;
            Console.WriteLine($"{connectionId} is Connected to the server");
            return base.OnConnectedAsync();
        }
    }
}

IQueueManager.cs

using WebApplication2.Models;

namespace WebApplication2.IServices
{
    public interface IQueueManager
    {
        Queue<QueueItem>? UserQueue { get; }
        void JoinQueue(string userToken, string connectionId);
    }
}

QueueItem.cs

namespace WebApplication2.Models
{
    public class QueueItem
    {
        public string? UserToken { get; set; }
        public string? ConnectionString { get; set; }
    }
}

QueueManager.cs

using WebApplication2.IServices;
using WebApplication2.Models;

namespace WebApplication2.Services
{
    public class QueueManager : IQueueManager
    {
        public Queue<QueueItem> UserQueue { get; } = new Queue<QueueItem>();

        public void JoinQueue(string userToken, string connectionId)
        {
            QueueItem user = new QueueItem
            {
                UserToken = userToken,
                ConnectionString = connectionId
            };

            UserQueue.Enqueue(user);
            Console.WriteLine(UserQueue.Count);
        }
    }
}

The last step, we need to register it in the Program.cs file.

builder.Services.AddSingleton<IQueueManager, QueueManager>(); 
builder.Services.AddHostedService<QueueMonitorService>(); 
builder.Services.AddSignalR();