SqlClientBug.md

This is regarding dotnet/SqlClient#2378

using Microsoft.Data.SqlClient;

namespace SqlTest
{
	internal class Program
	{
		private static string _connectionString = "user id=MyUser;data source=172.24.144.1,1433;initial catalog=MYDATABASE;password=PASSWORD;Encrypt=false";

		static async Task Main(string[] args)
		{
			Console.WriteLine("Let's go");

			var taskList = new List<Task>();

			for (int i = 0; i < 50; i++)
			{
				taskList.Add(Task.Run(OpenConn));
			}
			await Task.WhenAll(taskList);

			Console.WriteLine("done, press enter to close");
			Console.ReadLine();
		}

		private static async Task OpenConn()
		{
			using (var cn = new SqlConnection(_connectionString))
			{
				cn.Open();
				await Task.Delay(100);
			}
		}
	}
}

The above code when used with Microsoft.Data.SqlClient 5.2.1 fails ON LINUX but runs fine ON WINDOWS under .NET 8 default empty Console project.

The bug is reproducable under WSL2 on Windows (the IP address is the Windows host-machine IP visible from WSL2, can be obtained from /etc/resolv.conf), make sure to select "WSL" in Visual Studio and press F5. In that case the exception thrown is System.InvalidOperationException: Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. Increasing the pool size to 250 in the connection string does not help, it still fails on 50 iterations.

On windows everything works fine & fast.

The above code works fine on both Windows and Linux when using Microsoft.Data.SqlClient 5.1.5

P.S. I'm intentionally using Task.Run here since I need the code to "emulate" ASP.NET bahavior, where requests run on thread pool