feat: add actual metrics using prometheus-net

Foxnouns.Backend/Config.cs

@@ -10,7 +10,7 @@ public class Config
     public string MediaBaseUrl { get; set; } = null!;
 
     public string Address => $"http://{Host}:{Port}";
-    public string? MetricsAddress => Logging.MetricsPort != null ? $"http://{Host}:{Logging.MetricsPort}" : null;
+    public string MetricsAddress => $"http://{Host}:{Logging.MetricsPort}";
 
     public LoggingConfig Logging { get; init; } = new();
     public DatabaseConfig Database { get; init; } = new();
@@ -27,7 +27,8 @@ public class Config
         public bool SentryTracing { get; init; } = false;
         public double SentryTracesSampleRate { get; init; } = 0.0;
         public bool LogQueries { get; init; } = false;
-        public int? MetricsPort { get; init; }
+        public bool EnableMetrics { get; init; } = false;
+        public ushort MetricsPort { get; init; } = 5001;
     }
 
     public class DatabaseConfig

Foxnouns.Backend/Controllers/MetaController.cs

@@ -1,30 +1,23 @@
-using Foxnouns.Backend.Database;
-using Microsoft.EntityFrameworkCore;
 using Microsoft.AspNetCore.Mvc;
-using NodaTime;
 
 namespace Foxnouns.Backend.Controllers;
 
 [Route("/api/v2/meta")]
-public class MetaController(DatabaseContext db, IClock clock) : ApiControllerBase
+public class MetaController : ApiControllerBase
 {
     private const string Repository = "https://codeberg.org/pronounscc/pronouns.cc";
 
     [HttpGet]
     [ProducesResponseType<MetaResponse>(StatusCodes.Status200OK)]
-    public async Task<IActionResult> GetMeta()
+    public IActionResult GetMeta()
     {
-        var now = clock.GetCurrentInstant();
-        var users = await db.Users.Select(u => u.LastActive).ToListAsync();
-        var memberCount = await db.Members.CountAsync();
-
         return Ok(new MetaResponse(
-            Repository, BuildInfo.Version, BuildInfo.Hash, memberCount,
+            Repository, BuildInfo.Version, BuildInfo.Hash, (int)FoxnounsMetrics.MemberCount.Value,
             new UserInfo(
-                users.Count,
+                (int)FoxnounsMetrics.UsersCount.Value,
-                users.Count(i => i > now - Duration.FromDays(30)),
+                (int)FoxnounsMetrics.UsersActiveMonthCount.Value,
-                users.Count(i => i > now - Duration.FromDays(7)),
+                (int)FoxnounsMetrics.UsersActiveWeekCount.Value,
-                users.Count(i => i > now - Duration.FromDays(1))
+                (int)FoxnounsMetrics.UsersActiveDayCount.Value
             ))
         );
     }

Foxnouns.Backend/Extensions/WebApplicationExtensions.cs

@@ -1,6 +1,3 @@
-using App.Metrics;
-using App.Metrics.AspNetCore;
-using App.Metrics.Formatters.Prometheus;
 using Coravel;
 using Coravel.Queuing.Interfaces;
 using Foxnouns.Backend.Database;
@@ -9,6 +6,7 @@ using Foxnouns.Backend.Middleware;
 using Foxnouns.Backend.Services;
 using Microsoft.EntityFrameworkCore;
 using NodaTime;
+using Prometheus;
 using Serilog;
 using Serilog.Events;
 using IClock = NodaTime.IClock;
@@ -59,32 +57,12 @@ public static class WebApplicationExtensions
         return config;
     }
 
-    public static WebApplicationBuilder AddMetrics(this WebApplicationBuilder builder)
+    public static WebApplicationBuilder AddMetrics(this WebApplicationBuilder builder, Config config)
     {
-        var config = builder.Configuration.Get<Config>() ?? new();
+        builder.Services.AddMetricServer(o => o.Port = config.Logging.MetricsPort)
-        var metrics = AppMetrics.CreateDefaultBuilder()
+            .AddSingleton<MetricsCollectionService>();
-            .OutputMetrics.AsPrometheusPlainText()
+        if (!config.Logging.EnableMetrics)
-            .Build();
+            builder.Services.AddHostedService<BackgroundMetricsCollectionService>();
-
-        builder.Services.AddSingleton(metrics);
-        builder.Services.AddSingleton<IMetrics>(metrics);
-
-        builder.WebHost
-            .ConfigureMetrics(metrics)
-            .UseMetrics(opts =>
-            {
-                opts.EndpointOptions = options =>
-                {
-                    // Metrics must listen on a separate port for security reasons. If no metrics port is set, disable the endpoint entirely.
-                    options.MetricsEndpointEnabled = config.Logging.MetricsPort != null;
-                    options.EnvironmentInfoEndpointEnabled = config.Logging.MetricsPort != null;
-                    options.MetricsTextEndpointEnabled = false;
-                    options.MetricsEndpointOutputFormatter = metrics.OutputMetricsFormatters
-                        .OfType<MetricsPrometheusTextOutputFormatter>().First();
-                };
-            })
-            .UseMetricsWebTracking()
-            .ConfigureAppMetricsHostingConfiguration(opts => { opts.AllEndpointsPort = config.Logging.MetricsPort; });
 
         return builder;
     }

Foxnouns.Backend/Foxnouns.Backend.csproj

@@ -6,9 +6,6 @@
     </PropertyGroup>
 
     <ItemGroup>
-        <PackageReference Include="App.Metrics" Version="4.3.0" />
-        <PackageReference Include="App.Metrics.AspNetCore.All" Version="4.3.0" />
-        <PackageReference Include="App.Metrics.Prometheus" Version="4.3.0" />
         <PackageReference Include="Coravel" Version="5.0.4" />
         <PackageReference Include="EFCore.NamingConventions" Version="8.0.3"/>
         <PackageReference Include="EntityFrameworkCore.Exceptions.PostgreSQL" Version="8.1.2" />
@@ -25,6 +22,8 @@
         <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="8.0.4"/>
         <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL.NodaTime" Version="8.0.4"/>
         <PackageReference Include="Npgsql.Json.NET" Version="8.0.3" />
+        <PackageReference Include="prometheus-net" Version="8.2.1" />
+        <PackageReference Include="prometheus-net.AspNetCore" Version="8.2.1" />
         <PackageReference Include="Sentry.AspNetCore" Version="4.9.0" />
         <PackageReference Include="Serilog" Version="4.0.1" />
         <PackageReference Include="Serilog.AspNetCore" Version="8.0.1"/>

Foxnouns.Backend/FoxnounsMetrics.cs

@@ -0,0 +1,37 @@
+using Prometheus;
+
+namespace Foxnouns.Backend;
+
+public static class FoxnounsMetrics
+{
+    public static readonly Gauge UsersCount =
+        Metrics.CreateGauge("foxnouns_user_count", "Number of total users");
+
+    public static readonly Gauge UsersActiveMonthCount =
+        Metrics.CreateGauge("foxnouns_user_count_active_month", "Number of users active in the last month");
+
+    public static readonly Gauge UsersActiveWeekCount =
+        Metrics.CreateGauge("foxnouns_user_count_active_week", "Number of users active in the last week");
+
+    public static readonly Gauge UsersActiveDayCount =
+        Metrics.CreateGauge("foxnouns_user_count_active_day", "Number of users active in the last day");
+    
+    public static readonly Gauge MemberCount =
+        Metrics.CreateGauge("foxnouns_member_count", "Number of total members");
+
+    public static readonly Summary MetricsCollectionTime =
+        Metrics.CreateSummary("foxnouns_time_metrics", "Time it took to collect metrics");
+
+    public static Gauge ProcessPhysicalMemory =>
+        Metrics.CreateGauge("foxnouns_process_physical_memory", "Process physical memory");
+
+    public static Gauge ProcessVirtualMemory =>
+        Metrics.CreateGauge("foxnouns_process_virtual_memory", "Process virtual memory");
+
+    public static Gauge ProcessPrivateMemory =>
+        Metrics.CreateGauge("foxnouns_process_private_memory", "Process private memory");
+
+    public static Gauge ProcessThreads => Metrics.CreateGauge("foxnouns_process_threads", "Process thread count");
+
+    public static Gauge ProcessHandles => Metrics.CreateGauge("foxnouns_process_handles", "Process handle count");
+}

Foxnouns.Backend/Metrics.cs

@@ -1,6 +0,0 @@
-namespace Foxnouns.Backend;
-
-public static class Metrics
-{
-    
-}

Foxnouns.Backend/Program.cs

@@ -9,6 +9,7 @@ using Microsoft.AspNetCore.Mvc;
 using Minio;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Serialization;
+using Prometheus;
 using Sentry.Extensibility;
 
 // Read version information from .version in the repository root
@@ -18,7 +19,9 @@ var builder = WebApplication.CreateBuilder(args);
 
 var config = builder.AddConfiguration();
 
-builder.AddSerilog().AddMetrics();
+builder
+    .AddSerilog()
+    .AddMetrics(config);
 
 builder.WebHost
     .UseSentry(opts =>
@@ -89,7 +92,10 @@ app.MapControllers();
 
 app.Urls.Clear();
 app.Urls.Add(config.Address);
-if (config.MetricsAddress != null) app.Urls.Add(config.MetricsAddress);
+
+// Make sure metrics are updated whenever Prometheus scrapes them
+Metrics.DefaultRegistry.AddBeforeCollectCallback(async ct =>
+    await app.Services.GetRequiredService<MetricsCollectionService>().CollectMetricsAsync(ct));
 
 // Fire off the periodic tasks loop in the background
 _ = new Timer(_ =>

Foxnouns.Backend/Services/MetricsCollectionService.cs

@@ -0,0 +1,66 @@
+using System.Diagnostics;
+using Foxnouns.Backend.Database;
+using Microsoft.EntityFrameworkCore;
+using NodaTime;
+using Prometheus;
+
+namespace Foxnouns.Backend.Services;
+
+public class MetricsCollectionService(
+    ILogger logger,
+    IServiceProvider services,
+    IClock clock)
+{
+    private readonly ILogger _logger = logger.ForContext<MetricsCollectionService>();
+
+    private static readonly Duration Month = Duration.FromDays(30);
+    private static readonly Duration Week = Duration.FromDays(7);
+    private static readonly Duration Day = Duration.FromDays(1);
+
+    public async Task CollectMetricsAsync(CancellationToken ct = default)
+    {
+        var timer = FoxnounsMetrics.MetricsCollectionTime.NewTimer();
+        var now = clock.GetCurrentInstant();
+
+        await using var scope = services.CreateAsyncScope();
+        await using var db = scope.ServiceProvider.GetRequiredService<DatabaseContext>();
+
+        var users = await db.Users.Where(u => !u.Deleted).Select(u => u.LastActive).ToListAsync(ct);
+        FoxnounsMetrics.UsersCount.Set(users.Count);
+        FoxnounsMetrics.UsersActiveMonthCount.Set(users.Count(i => i > now - Month));
+        FoxnounsMetrics.UsersActiveWeekCount.Set(users.Count(i => i > now - Week));
+        FoxnounsMetrics.UsersActiveDayCount.Set(users.Count(i => i > now - Day));
+
+        var memberCount = await db.Members.Include(m => m.User)
+            .Where(m => !m.Unlisted && !m.User.ListHidden && !m.User.Deleted).CountAsync(ct);
+        FoxnounsMetrics.MemberCount.Set(memberCount);
+
+        var process = Process.GetCurrentProcess();
+        FoxnounsMetrics.ProcessPhysicalMemory.Set(process.WorkingSet64);
+        FoxnounsMetrics.ProcessVirtualMemory.Set(process.VirtualMemorySize64);
+        FoxnounsMetrics.ProcessPrivateMemory.Set(process.PrivateMemorySize64);
+        FoxnounsMetrics.ProcessThreads.Set(process.Threads.Count);
+        FoxnounsMetrics.ProcessHandles.Set(process.HandleCount);
+
+        _logger.Information("Collected metrics in {DurationMilliseconds} ms",
+            timer.ObserveDuration().TotalMilliseconds);
+    }
+}
+
+public class BackgroundMetricsCollectionService(ILogger logger, MetricsCollectionService innerService)
+    : BackgroundService
+{
+    private readonly ILogger _logger = logger.ForContext<BackgroundMetricsCollectionService>();
+
+    protected override async Task ExecuteAsync(CancellationToken ct)
+    {
+        _logger.Information("Metrics are disabled, periodically collecting metrics manually");
+
+        using var timer = new PeriodicTimer(TimeSpan.FromMinutes(1));
+        while (await timer.WaitForNextTickAsync(ct))
+        {
+            _logger.Debug("Collecting metrics");
+            await innerService.CollectMetricsAsync(ct);
+        }
+    }
+}

Foxnouns.Backend/config.example.ini

@@ -20,7 +20,11 @@ SentryTracing = true
 SentryTracesSampleRate = 1.0
 ; Whether to log SQL queries. Note that this is very verbose. Defaults to false.
 LogQueries = false
-; The port the /metrics endpoint will listen on. If not set, metrics will be disabled.
+; Whether metrics are enabled. If this is set to true, Foxnouns.NET will rely on Prometheus scraping metrics to update stats.
+; If set to false, a background service will be used instead. Does not actually disable the /metrics endpoint.
+; Defaults to false.
+EnableMetrics = true
+; The port the /metrics endpoint will listen on. Defaults to 5001.
 MetricsPort = 5001
 
 [Database]