Fix Mongo crashes, perf, fire&forget db population

server/Services/Implementations/DataManager.cs

@@ -24,7 +24,7 @@ namespace Server.Services.Implementations {
 
 				var station = await InfoferScraper.Scrapers.StationScraper.Scrape(stationName, zonedDate.ToDateTimeOffset());
 				if (station != null) {
-					await Database.OnStationData(station);
+					_ = Task.Run(async () => await Database.OnStationData(station));
 				}
 				return station;
 			}, TimeSpan.FromMinutes(1));
@@ -34,7 +34,7 @@ namespace Server.Services.Implementations {
 
 				var train = await InfoferScraper.Scrapers.TrainScraper.Scrape(trainNumber, zonedDate.ToDateTimeOffset());
 				if (train != null) {
-					await Database.OnTrainData(train);
+					_ = Task.Run(async () => await Database.OnTrainData(train));
 				}
 				return train;
 			}, TimeSpan.FromSeconds(30));

server/Services/Implementations/Database.cs

@@ -5,6 +5,7 @@ using System.Linq;
 using System.Text.Json;
 using System.Text.Json.Nodes;
 using System.Text.Json.Serialization;
+using System.Threading;
 using System.Threading.Tasks;
 using InfoferScraper.Models.Station;
 using Microsoft.Extensions.Logging;
@@ -13,6 +14,7 @@ using MongoDB.Bson;
 using MongoDB.Bson.Serialization.Attributes;
 using MongoDB.Driver;
 using Server.Models.Database;
+using Server.Utils;
 
 namespace Server.Services.Implementations;
 
@@ -43,13 +45,15 @@ public class Database : Server.Services.Interfaces.IDatabase {
 	private readonly IMongoCollection<DbRecord> dbRecordCollection;
 	private readonly IMongoCollection<TrainListing> trainListingsCollection;
 	private readonly IMongoCollection<StationListing> stationListingsCollection;
+	private readonly AsyncThrottle throttle;
 
 	public Database(ILogger<Database> logger, IOptions<MongoSettings> mongoSettings) {
 		Logger = logger;
 
 		var settings = MongoClientSettings.FromConnectionString(mongoSettings.Value.ConnectionString);
-		settings.MaxConnectionPoolSize = 100000;
+		settings.MaxConnectionPoolSize = 10000;
 		MongoClient mongoClient = new(settings);
+		throttle = new(mongoClient.Settings.MaxConnectionPoolSize / 2);
 		db = mongoClient.GetDatabase(mongoSettings.Value.DatabaseName) ?? throw new NullReferenceException("Unable to get Mongo database");
 		dbRecordCollection = db.GetCollection<DbRecord>("db");
 		trainListingsCollection = db.GetCollection<TrainListing>("trainListings");
@@ -162,42 +166,104 @@ public class Database : Server.Services.Interfaces.IDatabase {
 		}
 	}
 
+	private readonly SemaphoreSlim insertTrainLock = new (1, 1);
 	public async Task<string> FoundTrain(string rank, string number, string company) {
 		number = string.Join("", number.TakeWhile(c => c is >= '0' and <= '9'));
-		if (!await (await trainListingsCollection.FindAsync(Builders<TrainListing>.Filter.Eq("number", number))).AnyAsync()) {
+		await insertTrainLock.WaitAsync();
+		try {
+			if (!await (await throttle.MakeRequest(() =>
+					    trainListingsCollection.FindAsync(Builders<TrainListing>.Filter.Eq("number", number))))
+				    .AnyAsync()) {
 				Logger.LogDebug("Found train {Rank} {Number} from {Company}", rank, number, company);
-			await trainListingsCollection.InsertOneAsync(new(number: number, rank: rank, company: company));
+				await throttle.MakeRequest(() =>
+					trainListingsCollection.InsertOneAsync(new(number: number, rank: rank, company: company)));
+			}
+		}
+		finally {
+			insertTrainLock.Release();
 		}
+
 		return number;
 	}
 
+	private readonly SemaphoreSlim insertStationLock = new (1, 1);
+
 	public async Task FoundStation(string name) {
-		if (!await (stationListingsCollection.Find(Builders<StationListing>.Filter.Eq("name", name))).AnyAsync()) {
+		// if (!await throttle.MakeRequest(() => stationListingsCollection.Find(Builders<StationListing>.Filter.Eq("name", name)).AnyAsync())) {
+		// 	Logger.LogDebug("Found station {StationName}", name);
+		// 	await throttle.MakeRequest(() => stationListingsCollection.InsertOneAsync(new(name, new())));
+		// }
+		await insertStationLock.WaitAsync();
+		UpdateResult update;
+		try {
+			update = await stationListingsCollection.UpdateOneAsync(
+				Builders<StationListing>.Filter.Eq("name", name),
+				Builders<StationListing>.Update.Combine(
+					Builders<StationListing>.Update.SetOnInsert("name", name),
+					Builders<StationListing>.Update.SetOnInsert("stoppedAtBy", new List<string>())
+				),
+				new UpdateOptions {
+					IsUpsert = true,
+				}
+			);
+		}
+		finally {
+			insertStationLock.Release();
+		}
+
+		if (update.IsAcknowledged && update.MatchedCount == 0) {
 			Logger.LogDebug("Found station {StationName}", name);
-			await stationListingsCollection.InsertOneAsync(new(name, new()));
 		}
 	}
 
+	public async Task FoundStations(IEnumerable<string> names) {
+		var enumerable = names as string[] ?? names.ToArray();
+		var existingStations = await (await stationListingsCollection.FindAsync(
+			Builders<StationListing>.Filter.StringIn("name", enumerable.Select((n) => new StringOrRegularExpression(n)))
+		)).ToListAsync();
+		var notExistingStations = enumerable.Where((n) => !existingStations.Select((s) => s.Name).Contains(n)).ToList();
+		if (notExistingStations.Count == 0) return;
+		await stationListingsCollection.InsertManyAsync(
+			notExistingStations.Select(
+				(s) => new StationListing(s, new())
+			)
+		);
+		Logger.LogDebug("Found stations {StationNames}", notExistingStations);
+	}
+
 	public async Task FoundTrainAtStation(string stationName, string trainNumber) {
 		trainNumber = string.Join("", trainNumber.TakeWhile(c => c is >= '0' and <= '9'));
 		await FoundStation(stationName);
-		var updateResult = await stationListingsCollection.UpdateOneAsync(
+		var updateResult = await throttle.MakeRequest(() => stationListingsCollection.UpdateOneAsync(
 			Builders<StationListing>.Filter.Eq("name", stationName),
 			Builders<StationListing>.Update.AddToSet("stoppedAtBy", trainNumber)
-		);
+		));
 		if (updateResult.IsAcknowledged && updateResult.ModifiedCount > 0) {
 			Logger.LogDebug("Found train {TrainNumber} at station {StationName}", trainNumber, stationName);
 		}
 	}
 
+	public async Task FoundTrainAtStations(IEnumerable<string> stationNames, string trainNumber) {
+		trainNumber = string.Join("", trainNumber.TakeWhile(c => c is >= '0' and <= '9'));
+		var enumerable = stationNames as string[] ?? stationNames.ToArray();
+		await FoundStations(enumerable);
+		var updateResult = await throttle.MakeRequest(() => stationListingsCollection.UpdateManyAsync(
+			Builders<StationListing>.Filter.StringIn("name", enumerable.Select(sn => new StringOrRegularExpression(sn))),
+			Builders<StationListing>.Update.AddToSet("stoppedAtBy", trainNumber)
+		));
+		if (updateResult.IsAcknowledged && updateResult.ModifiedCount > 0) {
+			Logger.LogDebug("Found train {TrainNumber} at stations {StationNames}", trainNumber, stationNames);
+		}
+	}
+
 	public async Task OnTrainData(InfoferScraper.Models.Train.ITrainScrapeResult trainData) {
 		var trainNumber = await FoundTrain(trainData.Rank, trainData.Number, trainData.Operator);
-		await Task.WhenAll(
+		await FoundTrainAtStations(
 			trainData.Groups
 			.SelectMany(g => g.Stations)
 			.Select(trainStop => trainStop.Name)
-				.Distinct()
+			.Distinct(), 
-				.Select(station => FoundTrainAtStation(station, trainNumber))
+			trainNumber
 		);
 	}
 
@@ -207,10 +273,7 @@ public class Database : Server.Services.Interfaces.IDatabase {
 		async Task ProcessTrain(InfoferScraper.Models.Station.IStationArrDep train) {
 			var trainNumber = train.Train.Number;
 			trainNumber = await FoundTrain(train.Train.Rank, trainNumber, train.Train.Operator);
-			await FoundTrainAtStation(stationName, trainNumber);
+			await FoundTrainAtStations(Enumerable.Repeat(stationName, 1).Concat(train.Train.Route).Distinct(), trainNumber);
-			if (train.Train.Route.Count != 0) {
-				await Task.WhenAll(train.Train.Route.Select(station => FoundTrainAtStation(station, trainNumber)));
-			}
 		}
 
 		List<IStationArrDep> arrdep = new();
@@ -221,7 +284,9 @@ public class Database : Server.Services.Interfaces.IDatabase {
 			arrdep.AddRange(stationData.Departures);
 		}
 
-		await Task.WhenAll(arrdep.Select(ProcessTrain));
+		foreach (var train in arrdep.DistinctBy((t) => t.Train.Number)) {
+			await ProcessTrain(train);
+		}
 	}
 }
 

server/Utils/AsyncThrottle.cs

@@ -0,0 +1,38 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Server.Utils; 
+
+// Inspired from: https://stackoverflow.com/a/57517920
+public class AsyncThrottle {
+    private readonly SemaphoreSlim openConnectionSemaphore;
+
+    public AsyncThrottle(int limit) {
+        openConnectionSemaphore = new(limit, limit);
+    }
+
+    public async Task<T> MakeRequest<T>(Task<T> task) => await MakeRequest(() => task);
+    public async Task<T> MakeRequest<T>(Func<Task<T>> taskCreator) {
+        await openConnectionSemaphore.WaitAsync();
+        try {
+            var result = await taskCreator();
+            return result;
+        }
+        finally {
+            openConnectionSemaphore.Release();
+        }
+    }
+    
+    
+    public async Task MakeRequest(Task task) => await MakeRequest(() => task);
+    public async Task MakeRequest(Func<Task> taskCreator) {
+        await openConnectionSemaphore.WaitAsync();
+        try {
+            await taskCreator();
+        }
+        finally {
+            openConnectionSemaphore.Release();
+        }
+    }
+}

server/server.csproj

@@ -20,8 +20,4 @@
         <ProjectReference Include="..\scraper\scraper.csproj" />
     </ItemGroup>
 
-    <ItemGroup>
-      <Folder Include="Utils" />
-    </ItemGroup>
-
 </Project>