c# – 通过HTTP调用Azure功能150次导致异常

我在Azure上运行asp.net mvc Web App.在一个方法中,我对Azure Function Web API进行了几次HTTP调用.在此Azure函数中,我使用DbContext将新记录插入数据库.

// Method in web application making http requests to azure function web api
public async Task CreateRecords() {
    int amountOfCalls = 150;
    var allTasks = new List<Task<HttpResponseMessage>>();

    for (int i = 0; i < amountOfCalls; i++) {
        var task = HttpClientInstance.Instance.PostAsync(<uri>, new StringContent(i.ToString()));
        allTasks.Add(task);
    }

    await Task.WhenAll(allTasks); // Gives an exception
}

当amountOfCalls设置为25,50或100时,一切都很好.但是,当我将amountOfCalls设置为150时,最初它会将一些记录插入到数据库中,但最终会导致错误：

Unable to connect to the remote server.

所以首先我认为它必须是Azure sql数据库的最大并发登录.所以我将那个升级到定价层S9(1600 DTU,最多3200个并发登录,标注为here).

但这并没有解决问题.然后我开始远程调试Azure功能.并且它不会在Azure功能本身中提供异常.
因此,下一步是研究Application Insights.我看到DbContext的构造函数给出了一个异常(不幸的是没有堆栈跟踪)：

type: System.InvalidOperationException

method: WebApp.DataAccess.PocDbContext..ctor

requestName: InsertRecordFunction

requestDuration: 55,643.2201

Azure Function看起来像这样：

[DependencyInjectionConfig(typeof(DependencyConfig))] // Autofac
public static class InsertRecordFunction
{
    [FunctionName("InsertRecordFunction")]
    public static async Task<HttpResponseMessage> Run(
        [HttpTrigger(AuthorizationLevel.Function, "post", Route = "InsertRecordFunction")]HttpRequestMessage req,
        TraceWriter log,
        [Inject]IRecordDataService recordDataService)
    {
        log.Info("InsertRecordFunction was triggered by Http.");
        try {
            await recordDataService.AddRandomRecordAsync();
        }
        catch (Exception ex) {
            return req.CreateErrorResponse(HttpStatusCode.InternalServerError, ex);
        }

        return req.CreateResponse(HttpStatusCode.OK);
    }

而PocDbContext的代码如下：

public PocDbContext() : base("DefaultConnection") {
    Database.SetInitializer<PocDbContext>(null);
}

我仍然觉得它与连接池到Azure sql数据库有关.在此问题出现之前,我遇到另一个告诉我将执行策略设置为SqlAzureExecutionStrategy(我做了this way).

使用(静态)HttpClient从Azure Web App进行的Web api调用是否存在某种最大值？我还能做些什么来找出确切的例外情况？谢谢.

更新

在Application Insights中,我找到了有关异常的其他信息：

Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached.

升级Azure sql数据库的定价层后,不是我所期望的.

解决方法:

来自ADO.NET的文档,它是实体框架(SQL Server Connection Pooling (ADO.NET))的基础：

By default, connection pooling is enabled in ADO.NET. Unless you explicitly disable it, the pooler optimizes the connections as they are opened and closed in your application.

在Adding Connections部分稍微向下：

Connections are added to the pool as needed, up to the maximum pool size specified (100 is the default).

因此明确地将连接字符串的最大池大小设置为> = 150应该可以解决问题.

标签：c,asp-net-mvc,azure-web-sites,dotnet-httpclient,azure-functions
来源： https://codeday.me/bug/20190627/1305436.html