这是WebSocket接收消息事件处理程序。但是，这些订阅正在等待，并且它们当前没有并行运行，因此存在处理时间提示消息。其想法是使这些数据处理程序并行运行，这意味着应该使用Task.WhenAll。数据处理程序的类型为Func<T, ValueTask>，因此并行执行是有意义的。这样，如果其中一个数据处理程序包含await Task.Delay(5000)，它就不会阻塞其他数据处理程序。

private async ValueTask OnDataReceived(DataReceivedEventArgs e)
{
    var timestamp = DateTimeOffset.Now;

    var messageEvent = new MessageEvent(e.Message, timestamp);

    foreach (var subscription in _subscriptions
                    .GetAll()
                    .Where(subscription => MessageMatchesHandler(messageEvent.Data, subscription.Request)))
    {
        var userProcessTime = await MeasureUserProcessTime(async () => await subscription.DataHandler(messageEvent));

        if (userProcessTime.TotalMilliseconds > 500)
        {
            _logger.LogTrace("Detected slow data handler ({UserProcessTimeMs} ms user code), consider offloading data handling to another thread. Data from this socket may arrive late or not at all if message processing is continuously slow.",
                userProcessTime.TotalMilliseconds);
        }
    }
}

下面的版本呢？

private async ValueTask OnDataReceived(DataReceivedEventArgs e)
{
    var timestamp = DateTimeOffset.Now;

    var messageEvent = new MessageEvent(e.Message, timestamp);

    var handlers = _subscriptions
        .GetAll()
        .Where(subscription => MessageMatchesHandler(messageEvent.Data, subscription.Request))
        .Select(subscription => subscription.DataHandler(messageEvent).AsTask());

    _ = Task.WhenAll(handlers);
}

或

private async ValueTask OnDataReceived(DataReceivedEventArgs e)
{
    var timestamp = DateTimeOffset.Now;

    var messageEvent = new MessageEvent(e.Message, timestamp);

    var handlers = _subscriptions
        .GetAll()
        .Where(subscription => MessageMatchesHandler(messageEvent.Data, subscription.Request))
        .Select(subscription => Task.Run(() => subscription.DataHandler(messageEvent)));

    await Task.WhenAll(handlers);
}