add hub invocation concurrency filter

MareSynchronosServer/MareSynchronosServer/Hubs/ConcurrencyFilter.cs

@@ -0,0 +1,77 @@
+using MareSynchronosShared.Metrics;
+using MareSynchronosShared.Services;
+using MareSynchronosShared.Utils.Configuration;
+using Microsoft.AspNetCore.SignalR;
+
+namespace MareSynchronosServer.Hubs;
+
+public sealed class ConcurrencyFilter : IHubFilter, IDisposable
+{
+    private SemaphoreSlim _limiter;
+    private int _setLimit = 0;
+    private readonly IConfigurationService<ServerConfiguration> _config;
+    private readonly CancellationTokenSource _cancellationToken;
+
+    private bool _disposed;
+
+    public ConcurrencyFilter(IConfigurationService<ServerConfiguration> config, MareMetrics mareMetrics)
+    {
+        _config = config;
+        _config.ConfigChangedEvent += OnConfigChange;
+
+        RecreateSemaphore();
+
+        _ = Task.Run(async () =>
+        {
+            var token = _cancellationToken.Token;
+            while (!token.IsCancellationRequested)
+            {
+                mareMetrics.SetGaugeTo(MetricsAPI.GaugeHubConcurrency, _limiter.CurrentCount);
+                await Task.Delay(TimeSpan.FromSeconds(1)).ConfigureAwait(false);
+            }
+        });
+    }
+
+    private void OnConfigChange(object sender, EventArgs e)
+    {
+        RecreateSemaphore();
+    }
+
+    private void RecreateSemaphore()
+    {
+        var newLimit = _config.GetValueOrDefault(nameof(ServerConfiguration.HubExecutionConcurrencyFilter), 50);
+        if (newLimit != _setLimit)
+        {
+            _setLimit = newLimit;
+            _limiter?.Dispose();
+            _limiter = new(initialCount: _setLimit, maxCount: _setLimit);
+        }
+    }
+
+    public async ValueTask<object> InvokeMethodAsync(
+    HubInvocationContext invocationContext, Func<HubInvocationContext, ValueTask<object>> next)
+    {
+        await _limiter.WaitAsync(invocationContext.Context.ConnectionAborted).ConfigureAwait(false);
+
+        try
+        {
+            return await next(invocationContext).ConfigureAwait(false);
+        }
+        finally
+        {
+            _limiter.Release();
+        }
+    }
+
+    public void Dispose()
+    {
+        if (_disposed)
+        {
+            return;
+        }
+
+        _disposed = true;
+        _cancellationToken.Cancel();
+        _config.ConfigChangedEvent -= OnConfigChange;
+    }
+}

MareSynchronosServer/MareSynchronosServer/Startup.cs

@@ -113,6 +113,7 @@ public class Startup
     private static void ConfigureSignalR(IServiceCollection services, IConfigurationSection mareConfig)
     {
         services.AddSingleton<IUserIdProvider, IdBasedUserIdProvider>();
+        services.AddSingleton<ConcurrencyFilter>();
 
         var signalRServiceBuilder = services.AddSignalR(hubOptions =>
         {
@@ -122,6 +123,7 @@ public class Startup
             hubOptions.StreamBufferCapacity = 200;
 
             hubOptions.AddFilter<SignalRLimitFilter>();
+            hubOptions.AddFilter<ConcurrencyFilter>();
         }).AddMessagePackProtocol(opt =>
         {
             var resolver = CompositeResolver.Create(StandardResolverAllowPrivate.Instance,

MareSynchronosServer/MareSynchronosShared/Metrics/MetricsAPI.cs

@@ -48,4 +48,5 @@ public class MetricsAPI
     public const string CounterUserPairCacheUpdatedEntries = "mare_pairscache_updated_entries";
     public const string GaugeGposeLobbies = "mare_gpose_lobbies";
     public const string GaugeGposeLobbyUsers = "mare_gpose_lobby_users";
+    public const string GaugeHubConcurrency = "mare_free_concurrent_hub_calls";
 }

MareSynchronosServer/MareSynchronosShared/Utils/Configuration/ServerConfiguration.cs

@@ -31,6 +31,7 @@ public class ServerConfiguration : MareConfigurationBase
     [RemoteConfiguration]
     public int MaxCharaDataByUserVanity { get; set; } = 50;
     public bool RunPermissionCleanupOnStartup { get; set; } = true;
+    public int HubExecutionConcurrencyFilter { get; set; } = 50;
 
     public override string ToString()
     {
@@ -45,6 +46,7 @@ public class ServerConfiguration : MareConfigurationBase
         sb.AppendLine($"{nameof(PurgeUnusedAccounts)} => {PurgeUnusedAccounts}");
         sb.AppendLine($"{nameof(PurgeUnusedAccountsPeriodInDays)} => {PurgeUnusedAccountsPeriodInDays}");
         sb.AppendLine($"{nameof(RunPermissionCleanupOnStartup)} => {RunPermissionCleanupOnStartup}");
+        sb.AppendLine($"{nameof(HubExecutionConcurrencyFilter)} => {HubExecutionConcurrencyFilter}");
         return sb.ToString();
     }
 }