Implementing SIgnalR to check for data in database for every few seconds

Question

I have Implemented SingalR with existing web Api Application, where SignalR hub class will check the database for every few seconds and update the clients which are connected based on connection Id.

here is my hub class :

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Microsoft.AspNet.SignalR;
using System.Threading.Tasks;
using VHC.Core.Business.Managers.Old;
using VHC.Core.Common.Requests;
using VHC.Core.Business.Interfaces;
using VHC.Core.ServiceProxy.ServiceProxies;

namespace VHC.Core.WebAPI
{
    public class NotifyHub : Hub
    {

        public static string ConnectionId { get; set; }
        public string NotificationResult { get; set; }

        //public NotifyHub()
        //{
    //}


        public void PushNotificationData(Int32 userId, Int16 userTypeId)
        {

            lock (this)
            {
                var request = new PushNotificationRequest
                {
                    FilterProperty = new Common.Filters.FilterProperty { Offset = 0, RecordLimit = 0, OrderBy = "datechecked desc" },
                    Filters = new List<Common.Filters.FilterObject> { new Common.Filters.FilterObject { LogicOperator = 0, ConditionOperator = 0, Function = 0, FieldName = "", FieldValue = "", FieldType = 0 } }
                };
                INotificationManager inotifity = new NotificationManager();
                var taskTimer = Task.Run(async () =>
                {
                    while (true)
                    {
                        //var serviceProxy = new NotificationServiceProxy();
                        // var NotificationResult = inotifity.PublishResultsAsync(request, userId, userTypeId);--check database

                        if (userId == 3134)
                        {
                            NotificationResult = "validated";
                           //Sending the server time to all the connected clients on the client method SendServerTime()
                            Clients.Client(ConnectionId).NotificationToClient(NotificationResult);
                        }
                        else
                        {
                           NotificationResult = "not validated";

                           //Sending the server time to all the connected clients on the client method SendServerTime()
                           Clients.Client(ConnectionId).NotificationToClient(NotificationResult);
                        }

                        //Delaying by 6 seconds.
                        await Task.Delay(6000);
                    }
                } );
            }
        }

        public override Task OnConnected()
        {
            ConnectionId = Context.ConnectionId;

            return base.OnConnected();
        }
    }
}

Problem I'm facing is, As we know Client Application will create hub instance and connection will be established. When I'm running a client application at once, I didn't get any issue. When I'm running the client application at two or more parallely, I'm getting an issue which means data are completely messed up.

eg: for PushNotificationData method, Client application will pass the userID dynamically. In above code , I have written a logic when userID ==3143 ,the response should be 'validated', else 'not validated'.

if i'm running an application in one browser, I'm getting the response every 6 seconds as 'validated'

but if i'm running an application at two or more parallely,I'm getting the response every 6 seconds as sometime 'validated' some time 'not validated'.

I guess something messed up. kindly assist me. I hope its clear.

Answer 1

Hubs lifecycle is "per request".

So you should not save any state in hub and call async cycling function of course. Try to rewrite you code as follows:

• Create separated cycle during your app startup (near app.MapSinglaR() or something like this).
• Create static concurrent dictionary or list or whatever you need and use it to store active users.
• Get Hub instance inside your async cycle using GlobalHost.ConnectionManager.GetHubContext<NotifyHub>().