Implement a /health endpoint (lighttube-org#170)

* Implement health managing

* Consider cache hits

LightTube/ApiModels/HealthResponse.cs

@@ -0,0 +1,10 @@
+using InnerTube.Models;
+
+namespace LightTube.ApiModels;
+
+public class HealthResponse
+{
+	public int VideoHealth { get; set; }
+	public double AveragePlayerResponseTime { get; set; }
+	public CacheStats CacheStats { get; set; }
+}

LightTube/Controllers/ApiController.cs

@@ -1,4 +1,5 @@
-using System.Net;
+using System.Diagnostics;
+using System.Net;
 using System.Text.RegularExpressions;
 using InnerTube;
 using InnerTube.Models;
@@ -9,6 +10,7 @@
 using LightTube.Attributes;
 using LightTube.Database;
 using LightTube.Database.Models;
+using LightTube.Health;
 using LightTube.Localization;
 using Microsoft.AspNetCore.Mvc;
 using Endpoint = InnerTube.Protobuf.Endpoint;
@@ -37,6 +39,15 @@ public LightTubeInstanceInfo GetInstanceInfo() =>
 			}
 		};
 
+	[Route("health")]
+	public HealthResponse GetHealth() =>
+		new()
+		{
+			VideoHealth = (int)HealthManager.GetHealthPercentage(),
+			AveragePlayerResponseTime = HealthManager.GetAveragePlayerResponseTime(),
+			CacheStats = innerTube.GetPlayerCacheStats()
+		};
+
 	private ApiResponse<T> Error<T>(string message, int code, HttpStatusCode statusCode)
 	{
 		Response.StatusCode = (int)statusCode;
@@ -55,11 +66,15 @@ public async Task<ApiResponse<InnerTubePlayer>> GetPlayerInfo(string? id, bool c
 		if (!videoIdRegex.IsMatch(id) || id.Length != 11)
 			return Error<InnerTubePlayer>($"Invalid video ID: {id}", 400, HttpStatusCode.BadRequest);
 
+		Stopwatch sp = Stopwatch.StartNew();
 		try
 		{
 			InnerTubePlayer player = await innerTube.GetVideoPlayerAsync(id, contentCheckOk,
 				HttpContext.GetInnerTubeLanguage(),
 				HttpContext.GetInnerTubeRegion());
+			sp.Stop();
+			// we dont check if the video id is correct here, might be an issue for the future
+			HealthManager.PushVideoResponse(id, true, sp.ElapsedMilliseconds);
 
 			DatabaseUser? user = await DatabaseManager.Oauth2.GetUserFromHttpRequest(Request);
 			ApiUserData? userData = ApiUserData.GetFromDatabaseUser(user);
@@ -69,6 +84,8 @@ public async Task<ApiResponse<InnerTubePlayer>> GetPlayerInfo(string? id, bool c
 		}
 		catch (Exception e)
 		{
+			sp.Stop();
+			HealthManager.PushVideoResponse(id, false, sp.ElapsedMilliseconds);
 			return Error<InnerTubePlayer>(e.Message, 500, HttpStatusCode.InternalServerError);
 		}
 	}

LightTube/Controllers/YoutubeController.cs

@@ -1,14 +1,15 @@
-using System.Text.Json;
+using System.Diagnostics;
+using System.Text.Json;
 using InnerTube;
 using InnerTube.Models;
 using InnerTube.Protobuf.Params;
 using InnerTube.Protobuf.Responses;
 using LightTube.Contexts;
 using LightTube.Database;
 using LightTube.Database.Models;
+using LightTube.Health;
 using LightTube.Localization;
 using Microsoft.AspNetCore.Mvc;
-using Serilog;
 using Endpoint = InnerTube.Protobuf.Endpoint;
 
 namespace LightTube.Controllers;
@@ -19,6 +20,7 @@ public class YoutubeController(SimpleInnerTubeClient innerTube, HttpClient clien
 	public async Task<IActionResult> Embed(string v, bool contentCheckOk, bool compatibility = false,
 		bool audioOnly = false)
 	{
+		Stopwatch sp = Stopwatch.StartNew();
 		InnerTubePlayer? player;
 		Exception? e;
 		try
@@ -32,6 +34,7 @@ public async Task<IActionResult> Embed(string v, bool contentCheckOk, bool compa
 			player = null;
 			e = ex;
 		}
+		sp.Stop();
 
 		SponsorBlockSegment[] sponsors;
 		try
@@ -48,6 +51,7 @@ public async Task<IActionResult> Embed(string v, bool contentCheckOk, bool compa
 
 		InnerTubeVideo video = await innerTube.GetVideoDetailsAsync(v, contentCheckOk, null, null, null,
 			language: HttpContext.GetInnerTubeLanguage(), region: HttpContext.GetInnerTubeRegion());
+		HealthManager.PushVideoResponse(v, player != null, sp.ElapsedMilliseconds);
 		if (player is null || e is not null)
 			return View(new EmbedContext(HttpContext, e ?? new Exception("player is null"), video));
 		return View(new EmbedContext(HttpContext, player, video, compatibility, sponsors, audioOnly));
@@ -57,6 +61,7 @@ public async Task<IActionResult> Embed(string v, bool contentCheckOk, bool compa
 	public async Task<IActionResult> Watch(string v, string? list, bool contentCheckOk, bool compatibility = false,
 		bool audioOnly = false)
 	{
+		Stopwatch sp = Stopwatch.StartNew();
 		InnerTubePlayer? player;
 		Exception? e;
 		bool localPlaylist = list?.StartsWith("LT-PL") ?? false;
@@ -77,9 +82,11 @@ public async Task<IActionResult> Watch(string v, string? list, bool contentCheck
 			player = null;
 			e = ex;
 		}
+		sp.Stop();
 
 		InnerTubeVideo video = await innerTube.GetVideoDetailsAsync(v, contentCheckOk, localPlaylist ? null : list,
 			null, null, language: HttpContext.GetInnerTubeLanguage(), region: HttpContext.GetInnerTubeRegion());
+		HealthManager.PushVideoResponse(v, player != null, sp.ElapsedMilliseconds);
 		ContinuationResponse? comments = null;
 
 		if (HttpContext.GetDefaultCompatibility())

LightTube/Health/HealthManager.cs

@@ -0,0 +1,32 @@
+namespace LightTube.Health;
+
+public static class HealthManager
+{
+	private static List<KeyValuePair<string, bool>> videoStatuses = [];
+	private static List<long> playerResponseTimes = [];
+
+	public static void PushVideoResponse(string videoId, bool isSuccess, long playerResponseTime)
+	{
+		// don't include cache hits 
+		if (playerResponseTime < 50) return;
+
+		// if entry with the same videoId exists, remove it
+		videoStatuses.RemoveAll(x => x.Key == videoId);
+
+		// only keep last 100 requests
+		if (videoStatuses.Count >= 100) videoStatuses.RemoveAt(0);
+		if (playerResponseTimes.Count >= 100) playerResponseTimes.RemoveAt(0);
+
+		playerResponseTimes.Add(playerResponseTime);
+		videoStatuses.Add(new KeyValuePair<string, bool>(videoId, isSuccess));
+	}
+
+	public static float GetHealthPercentage() =>
+		Math.Clamp(MathF.Round((float)videoStatuses.Count(x => x.Value) / Math.Max(videoStatuses.Count, 1) * 100), 0, 100);
+
+	public static double GetAveragePlayerResponseTime()
+	{
+		if (playerResponseTimes.Count == 0) return 0;
+		 return playerResponseTimes.Average();
+	}
+}