server/src/Notifications/AzureQueueHostedService.cs

using Azure.Storage.Queues;
using Bit.Core.Settings;
using Bit.Core.Utilities;
using Microsoft.AspNetCore.SignalR;

namespace Bit.Notifications;

public class AzureQueueHostedService : IHostedService, IDisposable
{
    private readonly ILogger _logger;
    private readonly IHubContext<NotificationsHub> _hubContext;
    private readonly GlobalSettings _globalSettings;

    private Task _executingTask;
    private CancellationTokenSource _cts;
    private QueueClient _queueClient;

    public AzureQueueHostedService(
        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)
    {
        _queueClient = new QueueClient(_globalSettings.Notifications.ConnectionString, "notifications");
        while (!cancellationToken.IsCancellationRequested)
        {
            try
            {
                var messages = await _queueClient.ReceiveMessagesAsync(32);
                if (messages.Value?.Any() ?? false)
                {
                    foreach (var message in messages.Value)
                    {
                        try
                        {
                            await HubHelpers.SendNotificationToHubAsync(
                                message.DecodeMessageText(), _hubContext, cancellationToken);
                            await _queueClient.DeleteMessageAsync(message.MessageId, message.PopReceipt);
                        }
                        catch (Exception e)
                        {
                            _logger.LogError("Error processing dequeued message: " +
                                $"{message.MessageId} x{message.DequeueCount}. {e.Message}", e);
                            if (message.DequeueCount > 2)
                            {
                                await _queueClient.DeleteMessageAsync(message.MessageId, message.PopReceipt);
                            }
                        }
                    }
                }
                else
                {
                    await Task.Delay(TimeSpan.FromSeconds(5), cancellationToken);
                }
            }
            catch (Exception e)
            {
                _logger.LogError("Error processing messages.", e);
            }
        }

        _logger.LogWarning("Done processing.");
    }
}