.net - 如何在 .net Core 3.0 中将 SignalR 添加到 Worker 服务

Question

我正在开发一个使用 Kafka 消息的工作人员服务。我想在检索到消息时进行 signalR 事件，但目前无法使其工作。

public static async Task Main(string[] args)
{
    using (var host = Host.CreateDefaultBuilder(args)
      .ConfigureServices((hostContext, services) =>
      {
          services.AddHostedService<Worker>();
          services.AddTransient<IKafkaClient, KafkaClient>();
          services.AddSignalR();
      })
      .Build())
        {
            // Start the host
            await host.StartAsync();

            // Wait for the host to shutdown
            await host.WaitForShutdownAsync();
        }
}

在我的工人服务中

public class Worker : BackgroundService
{
    private readonly ILogger<Worker> _logger;
    private readonly IKafkaClient _kafkaClient;
    private readonly IHubContext<NotificationHub> _notificationHub;

    public Worker(ILogger<Worker> logger,
                  IKafkaClient kafkaClient,
                  IHubContext<NotificationHub> notificationHub)
    {
        _logger = logger;
        _kafkaClient = kafkaClient;
        _notificationHub = notificationHub;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
      // code here
    }
}

标签： .net.net-coreapache-kafkasignalr

Answer 1

在您的启动AddAdditionalServices方法中添加：

services.AddSingleton<NotificationHub>()

然后将其注入您的工人阶级，如：

private readonly IServiceProvider serviceProvider;

private NotificationHub NotificationHub
{
    get
    {
        return this.serviceProvider.GetRequiredService<NotificationsHub>();
    }
}

您需要创建要从类中调用的集线器方法，例如：

public async Task BroadcastMessage(string message){
  // your code here
}

所以你可以在工人中调用它。

protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
  // code here

 string message = // serialize kafka message

 await NotificationHub.BroadcastMessage(message)
}