EffectiveAsyncLoadWithSemaphoreslim.cs

using System.Net;
using System.Net.NetworkInformation;
using System.Runtime.CompilerServices;
namespace DummyConsole;

class EffectiveLoad
{
	static async Task Main()
	{
		#region string[] list
		string[] list = {
						"www.youtube.com",
						"www.facebook.com		",
						"www.baidu.com			",
						"www.yahoo.com			",
						"www.amazon.com			",
						"www.wikipedia.org		",
						"www.qq.com				",
						"www.google.co.in		",
						"www.twitter.com		 ",
						"www.live.com			",
						"www.taobao.com			",
						"www.bing.com			",
						"www.instagram.com		",
						"www.weibo.com			",
						"www.sina.com.cn		 ",
						"www.linkedin.com		",
						"www.yahoo.co.jp		 ",
						"www.msn.com			 ",
						"www.vk.com				",
						"www.google.de			",
						"www.yandex.ru			",
						"www.hao123.com			",
						"www.google.co.uk		",
						"www.reddit.com			",
						"www.ebay.com			",
						"www.google.fr			",
						"www.t.co				",
						"www.tmall.com			",
						"www.google.com.br		",
						"www.360.cn				",
						"www.sohu.com			",
						"www.amazon.co.jp		",
						"www.pinterest.com		",
						"www.netflix.com		 ",
						"www.google.it			",
						"www.google.ru			",
						"www.microsoft.com		",
						"www.google.es			",
						"www.wordpress.com		",
						"www.gmw.cn				",
						"www.tumblr.com			",
						"www.paypal.com			",
						"www.blogspot.com		",
						"www.imgur.com			",
						"www.stackoverflow.com	",
						"www.aliexpress.com		",
						"www.naver.com			",
						"www.ok.ru				",
						"www.apple.com			",
						"www.github.com			",
						"www.chinadaily.com.cn	",
						"www.imdb.com			",
						"www.google.co.kr		",
						"www.fc2.com			 ",
						"www.jd.com				",
						"www.blogger.com		 ",
						"www.163.com			 ",
						"www.google.ca			",
						"www.whatsapp.com		",
						"www.amazon.in			",
						"www.office.com			",
						"www.tianya.cn			",
						"www.google.co.id		",
						"www.youku.com			",
						"www.rakuten.co.jp		",
						"www.craigslist.org		",
						"www.amazon.de			",
						"www.nicovideo.jp		",
						"www.google.pl			",
						"www.soso.com			",
						"www.bilibili.com		",
						"www.dropbox.com		 ",
						"www.xinhuanet.com		",
						"www.outbrain.com		",
						"www.pixnet.net			",
						"www.alibaba.com		 ",
						"www.alipay.com			",
						"www.microsoftonline.com	 ",
						"www.booking.com			 ",
						"www.googleusercontent.com",
						"www.google.com.au		 ",
						"www.popads.net			 ",
						"www.cntv.cn				 ",
						"www.zhihu.com			 ",
						"www.amazon.co.uk		 ",
						"www.diply.com			 ",
						"www.coccoc.com			 ",
						"www.cnn.com				 ",
						"www.bbc.co.uk			 ",
						"www.twitch.tv			 ",
						"www.wikia.com			 ",
						"www.google.co.th		 ",
						"www.go.com				 ",
						"www.google.com.ph		 ",
						"www.doubleclick.net		 ",
						"www.onet.pl				 ",
						"www.googleadservices.com ",
						"www.accuweather.com		 ",
						"www.googleweblight.com	 ",
						"www.answers.yahoo.com    "
															};

		list = list.Select(l => l.Trim()).ToArray();
		list = list.Concat(list).ToArray();
		#endregion

		// pass a timeout accordingly
		await PrintPingList(list);
	}

	public readonly struct NetworkInfo
	{
		public string Website { get; init; }
		public IPAddress Address { get; init; }
		public IPStatus Status { get; init; }
		public long RoundTripTime { get; init; }
	}

	public static async Task PrintPingList(string[] sites, int timeout = -1)
	{
		using CancellationTokenSource source = new(timeout);

		try
		{
			// PingAsync(sites,source.Token) is to cancel running tasks
			// pingResultList.WithCancellation(source.Token) is to cancel IAsyncEnumerable's enumerator ==> IAsyncEnumerable <out T>.GetAsyncEnumerator(CancellationToken)

			var pingResultList = PingAsync(sites, source.Token);
			await Print(pingResultList, source.Token);
		}
		catch (OperationCanceledException)
		{
			Console.WriteLine("Operation has been cancelled!");
			// log it!
		}
	}

	public static async Task Print(IAsyncEnumerable<NetworkInfo> pingResultList,
	CancellationToken token = default)
	{
		await foreach (var pingResult in pingResultList
			.WithCancellation(token).ConfigureAwait(false))
		{
			Console.WriteLine($"Website:{pingResult.Website}\n"
		+ $"Address:{pingResult.Address}\nStatus:{pingResult.Status}\n"
		+ $"RoundTripTime: {pingResult.RoundTripTime}");

			Console.WriteLine();

			// catch the cancellation quicker
			if (token.IsCancellationRequested)
				throw new OperationCanceledException();
		}
	}
	public static async IAsyncEnumerable<NetworkInfo> PingAsync(string[] websites, [EnumeratorCancellation] CancellationToken cancellationToken = default)
	{
		var length = websites.Length;
		var taskNetworkInfo = new Queue<Task<NetworkInfo>>();

		// allow 20 worker thread in at a time, this will prevent the thread exhaustion.
		using (var semaphore_20 = new SemaphoreSlim(20))
		{
			for (int i = 0; i < length; i++)
			{
				var k = i;
				NetworkInfo info = new();
				await semaphore_20.WaitAsync(cancellationToken);

				taskNetworkInfo.Enqueue(Task.Run(async () =>
				{

					Ping ping = new();

					try
					{
						var pingResult = await ping.SendPingAsync(websites[k], 500);

						info = new NetworkInfo
						{
							Address = pingResult.Address,
							Website = websites[k],
							RoundTripTime = pingResult.RoundtripTime,
							Status = pingResult.Status
						};
					}
					catch { /* log the errors */}
					finally
					{
						ping.Dispose();
					}

					return info;

				}, cancellationToken));

				// flush 10 items to IAsyncEnumerable at a time
				// other 10 items in queue will be completed in the meantime
				// this will create a nice throughput.
				int qFlush = (i + 1) % 10;
				if (qFlush == 0 || i >= length - 10)
				{
                    			while (taskNetworkInfo.TryDequeue(out var networkInfo))
                    			{
                    			    if (!cancellationToken.IsCancellationRequested)
                    			        semaphore_20.Release();
			
                    			    yield return await networkInfo; 
                    			}
				}
			}
		}
	}
}