HttpClientFactory open many connections

[gsGabriel]

I'm using .net core 2.2 and microsoft/dotnet:2.2-aspnetcore-runtime-alpine docker image and used AddHttpClient to create a typed HttpClient

The problem is several open socket connections, even using the factory
I replicated the problem in an application for testing in the following repository: https://github.com/gsGabriel/httpclient-factory/

the connections listed

Could someone tell me what is wrong with my implementation? I can't currently upgrade to .net core 3.0

Originally posted by @gsGabriel in #28842 (comment)

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[ClementeGao]

watching

[ShreyasJejurkar]

I have opened PR for this, please let me know the outcome!

[gsGabriel]

I have opened PR for this, please let me know the outcome!

@MCCshreyas Thank You

The reason I used the code snippet below

            for (int i = 0; i < 100; i++)
            {
                using (var scope = service.CreateScope())
                {
                    var gitHubService = scope.ServiceProvider.GetService<IGitHubService>();
                    tasks.Add(gitHubService.GetAspNetDocsIssues());
                }
            }

it is to simulate the life-cycle of a request, at each request we take an instance of the injection container, so the use of the service provider as it is an endpoint to simulate the problem.

Maybe it's not the best way to test, but I simulate the error only when many requests are made at the endpoint, if the controller has a typed http client, it generates many open socket connections

so I think your PR didn't solve the problem...

[ShreyasJejurkar]

The thing is like all Tasks are getting executed asynchronously at the same time, so everyone started creating socket at very first time, because it's not available at very first time, because of which you get this many sockets open at same time.

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[gsGabriel]

The thing is like all Tasks are getting executed asynchronously at the same time, so everyone started creating socket at very first time, because it's not available at very first time, because of which you get this many sockets open at same time.

Okay, you're right ...

but in an application that has a high number of requests per second, wouldn't that be a problem? I believe that the factory should do the control even in a simultaneous scenario

[ShreyasJejurkar]

The thing is like all Tasks are getting executed asynchronously at the same time, so everyone started creating socket at very first time, because it's not available at very first time, because of which you get this many sockets open at same time.

Okay, you're right ...

but in an application that has a high number of requests per second, wouldn't that be a problem? I believe that the factory should do the control even in a simultaneous scenario

How come factory even know that there is an instance if everything started at once asynchronously! And also the code that you have written its not a good practice as well, you should directly use your injected service because you have already add it to DI in startup rather than service provider which is OK, but not needed in this example, as the required service is already present in DI.

[CarnaViire]

@gsGabriel thanks for reporting this! I confirm that I am able to reproduce the issue.

However, it seems that the problem is not on the HttpClientFactory's side. You may observe the same behavior even if you use a single instance of a plain HttpClient.

using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Threading.Tasks;

namespace httpclienthandler_many_connections
{
    class Program
    {
        static async Task Main(string[] args)
        {
            var client = new HttpClient();
            client.BaseAddress = new Uri("https://api.github.com/");
            client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json");
            client.DefaultRequestHeaders.Add("User-Agent", "httpclienthandler_many_connections");

            var tasks = new List<Task>();
            for (int i = 0; i < 10; i++)
            {
                tasks.Add(GetZenAsync(client));
            }
            await Task.WhenAll(tasks.ToArray());

            Console.ReadKey();
        }

        private static async Task<string> GetZenAsync(HttpClient httpClient)
        {
            var response = await httpClient.GetAsync("/zen");
            var result = await response.Content.ReadAsStringAsync();
            Console.WriteLine(result);
            return result;
        }
    }
}

I wasn't able to find an open issue for that. We will investigate this further.
cc @karelz @dotnet/ncl