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HttpContext异步在中是否安全asp.net核心?

asp.net-core asynchronous c#

1

Steve · 技术社区 · 6 年前

根据我读到的 asp.net core 已删除同步上下文。这意味着执行代码的线程 await 等待

是的 HttpContext async 方法?或者有没有可能在打电话?

例如在控制器动作中

public async Task<IActionResult> Index()
{
    var context1 = HttpContext;
    await Task.Delay(1000);
    var context2 = HttpContext;
    ....
}

IHttpContextAccessor

是 IHttpContextAccessor.HttpContext 安全的 异步 模式?

public async void Foo(IHttpContextAccessor accessor)
{
    var context1 = accessor.HttpContext;
    await Task.Delay(1000);
    var context2 = accessor.HttpContext;
}

0 回复 | 直到 6 年前

1

5

Stephen Cleary 6 年前

那么HttpContext在异步方法中使用仍然安全吗?或者有没有可能在等待呼叫后得到不同的上下文?

整个问题 async 和 HttpContext 以及ASP.NETpre-Core是因为代码通常从 HttpContext.Current . ASP.NET是一个多线程服务器 await AspNetSynchronizationContext 有管理的环境在异步代码恢复之前。

没有同步上下文。但没关系,因为也 HttpContext.Current 请求上下文 实例通过本地属性(例如。, 请求上下文 IHttpContextAccessor ).

(学究注:上面的解释有点简化了-ASP.NET核心前同步上下文处理了除此之外的其他事情 HttpContext.Current

所以,上下文不可能不同。它们是相同的属性-相同的对象实例。问题在于ASP.NET前核心是值属性 HttpContext.Current ,已在中删除ASP.NET核心。

2

1

0lukasz0 5 年前

根据文件: https://docs.microsoft.com/en-en/aspnet/core/performance/performance-best-practices?view=aspnetcore-3.1#do-not-capture-the-httpcontext-in-background-threads

并行线程会导致未定义的行为,例如挂起, 崩溃和数据损坏。

并在传出HTTP之前和之后记录传入请求路径

public class AsyncBadSearchController : Controller
{       
    [HttpGet("/search")]
    public async Task<SearchResults> Get(string query)
    {
       var query1 = SearchAsync(SearchEngine.Google, query);
       var query2 = SearchAsync(SearchEngine.Bing, query);
       var query3 = SearchAsync(SearchEngine.DuckDuckGo, query);

       await Task.WhenAll(query1, query2, query3);

       var results1 = await query1;
       var results2 = await query2;
       var results3 = await query3;

       return SearchResults.Combine(results1, results2, results3);
    }       

    private async Task<SearchResults> SearchAsync(SearchEngine engine, string query)
    {
        var searchResults = _searchService.Empty();
        try
        {
            _logger.LogInformation("Starting search query from {path}.", 
                                    HttpContext.Request.Path);
            searchResults = _searchService.Search(engine, query);
            _logger.LogInformation("Finishing search query from {path}.", 
                                    HttpContext.Request.Path);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed query from {path}", 
                             HttpContext.Request.Path);
        }

        return await searchResults;
    }
}

执行以下操作:下面的示例复制传入的所有数据在发出三个并行请求之前请求。

public class AsyncGoodSearchController : Controller
{       
    [HttpGet("/search")]
    public async Task<SearchResults> Get(string query)
    {
        string path = HttpContext.Request.Path;
        var query1 = SearchAsync(SearchEngine.Google, query,
                             path);
        var query2 = SearchAsync(SearchEngine.Bing, query, path);
        var query3 = SearchAsync(SearchEngine.DuckDuckGo, query, path);

        await Task.WhenAll(query1, query2, query3);

        var results1 = await query1;
        var results2 = await query2;
        var results3 = await query3;

        return SearchResults.Combine(results1, results2, results3);
    }

       private async Task<SearchResults> SearchAsync(SearchEngine engine, string query,
                                                  string path)
       {
        var searchResults = _searchService.Empty();
        try
        {
            _logger.LogInformation("Starting search query from {path}.",
                                   path);
            searchResults = await _searchService.SearchAsync(engine, query);
            _logger.LogInformation("Finishing search query from {path}.", path);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed query from {path}", path);
        }

        return await searchResults;
    }
}