server/src/Notifications/HeartbeatHostedService.cs

using Bit.Core.Settings;
using Microsoft.AspNetCore.SignalR;

namespace Bit.Notifications
{
    public class HeartbeatHostedService : IHostedService, IDisposable
    {
        private readonly ILogger _logger;
        private readonly IHubContext<NotificationsHub> _hubContext;
        private readonly GlobalSettings _globalSettings;

        private Task _executingTask;
        private CancellationTokenSource _cts;

        public HeartbeatHostedService(
            ILogger<AzureQueueHostedService> logger,
            IHubContext<NotificationsHub> hubContext,
            GlobalSettings globalSettings)
        {
            _logger = logger;
            _hubContext = hubContext;
            _globalSettings = globalSettings;
        }

        public Task StartAsync(CancellationToken cancellationToken)
        {
            _cts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
            _executingTask = ExecuteAsync(_cts.Token);
            return _executingTask.IsCompleted ? _executingTask : Task.CompletedTask;
        }

        public async Task StopAsync(CancellationToken cancellationToken)
        {
            if (_executingTask == null)
            {
                return;
            }
            _logger.LogWarning("Stopping service.");
            _cts.Cancel();
            await Task.WhenAny(_executingTask, Task.Delay(-1, cancellationToken));
            cancellationToken.ThrowIfCancellationRequested();
        }

        public void Dispose()
        { }

        private async Task ExecuteAsync(CancellationToken cancellationToken)
        {
            while (!cancellationToken.IsCancellationRequested)
            {
                await _hubContext.Clients.All.SendAsync("Heartbeat");
                await Task.Delay(120000);
            }
            _logger.LogWarning("Done with heartbeat.");
        }
    }
}