使方法异步运行

Question

有人能看看这段代码，告诉我我做错了什么吗。在我看来，这三个方法应该在相同的环境中运行，但它们一个接一个地运行。请看控制台上写的时间。在我看来，所有控制台。WriteLine应显示约60ms。以下代码示例：

private async void GetOneCombination(string firstMarket, string secondMarket, string thirdMarket, decimal amountOfFirstCurrency)
{
Stopwatch sw = new Stopwatch();
sw.Start();
Task<GetMarketResponse> result = _accessMethods.GetOrderbook(firstMarket);
Console.WriteLine(sw.ElapsedMilliseconds); // ~60ms
Task<GetMarketResponse> result1 = _accessMethods.GetOrderbook(secondMarket);
Console.WriteLine(sw.ElapsedMilliseconds); // ~130 ms
Task<GetMarketResponse> result2 = _accessMethods.GetOrderbook(thirdMarket);
Console.WriteLine(sw.ElapsedMilliseconds); // ~200 ms
var getMarketResponses = await Task.WhenAll(result, result1, result2);
}

编辑：老实说，我认为这种方法里面有什么并不重要，我认为无论里面做什么，都会同时做3次

public async Task<GetMarketResponse> GetOrderbook(string market = "USD")
{
var address = AddressBook._orderbook + market;
var response = MethodExecutionTimeMeasurer.Invoke(() => 
_client.ExecuteGetAsyncPublic<GetMarketResponse>(address), out timespan);
_logger.LogInformation(string.Format("OrderBook requested for [{0}], response message: {1}. Time[ms]:{2}", 
address, 
response.Status,
timespan));
return response; 
}

和ExecuteGetAsyncPublic:

public async Task<T> ExecuteGetAsyncPublic<T>(string method)
where T : IBasicResponse
{
var response = await _httpClient.GetAsync(method).ConfigureAwait(false);
response.EnsureSuccessStatusCode();
var json = await response.Content.ReadAsStringAsync();
var responseData = JsonConvert.DeserializeObject<T>(json);
return responseData;
}

方法执行计时器

public static class MethodExecutionTimeMeasurer
{
public static T Invoke<T>(Func<Task<T>> action, out TimeSpan timeSpan)
{
var timer = Stopwatch.StartNew();
var res = action.Invoke();
res.Wait();
timer.Stop();
timeSpan = timer.Elapsed;
return res.Result;
}
public static void Invoke(Action action, out TimeSpan timeSpan)
{
var timer = Stopwatch.StartNew();
action.Invoke();
timer.Stop();
timeSpan = timer.Elapsed;
}
}

Answer 1

这里有两个问题：

1. GetOrderbook方法具有异步签名，但其实现是同步的。您可能会收到缺少await运算符的async方法的警告。

2. MethodExecutionTimeMeasurer.Invoke具有参数Func<Task<T>> action(异步委托(，但创建的Task与Wait方法同步等待。因此，在任务执行期间，当前线程被阻塞。

三个_accessMethods.GetOrderbook调用中的每一个都返回一个已完成的任务，然后组合的任务Task.WhenAll(result, result1, result2)也在创建时完成，简而言之，从当前线程的角度来看，没有任何东西在同步运行a。这个案例与昨天提出的一个问题非常相似，请查看。

Answer 2

调用异步Task方法不会立即在新线程上启动。它将在被调用的线程上运行，直到遇到等待。

so for example
var task = DoSomething();
public async Task DoSomething()
{
// MAIN THREAD
await Task.Delay(1);
// WORKER THREAD
}

如果你这样做，它可能会工作

public async Task<GetMarketResponse> GetOrderbook(string market = "USD")
{
await Task.Delay(1);
var address = AddressBook._orderbook + market;
var response = MethodExecutionTimeMeasurer.Invoke(() => 
_client.ExecuteGetAsyncPublic<GetMarketResponse>(address), out timespan);
_logger.LogInformation(string.Format("OrderBook requested for [{0}], response message: {1}. Time[ms]:{2}", 
address, 
response.Status,
timespan));
return response; 
}

你可以采取的另一种方法是

Parallel.Invoke(
() => _accessMethods.GetOrderbook(firstMarket).Wait(),
() => _accessMethods.GetOrderbook(secondMarket).Wait(),
() => _accessMethods.GetOrderbook(thirdMarket).Wait(),
);