Started implementing metrics system

Moonlight.ApiServer/Implementations/Metrics/ApplicationMetric.cs

@@ -0,0 +1,35 @@
+using System.Diagnostics.Metrics;
+using Moonlight.ApiServer.Interfaces;
+using Moonlight.ApiServer.Services;
+
+namespace Moonlight.ApiServer.Implementations.Metrics;
+
+public class ApplicationMetric : IMetric
+{
+    private Gauge<long> MemoryUsage;
+    private Gauge<int> CpuUsage;
+    private Gauge<double> Uptime;
+    
+    public Task Initialize(Meter meter)
+    {
+        MemoryUsage = meter.CreateGauge<long>("moonlight_memory_usage");
+        CpuUsage = meter.CreateGauge<int>("moonlight_cpu_usage");
+        Uptime = meter.CreateGauge<double>("moonlight_uptime");
+        
+        return Task.CompletedTask;
+    }
+
+    public async Task Run(IServiceProvider provider, CancellationToken cancellationToken)
+    {
+        var applicationService = provider.GetRequiredService<ApplicationService>();
+
+        var memory = await applicationService.GetMemoryUsage();
+        MemoryUsage.Record(memory);
+
+        var uptime = await applicationService.GetUptime();
+        Uptime.Record(uptime.TotalSeconds);
+
+        var cpu = await applicationService.GetCpuUsage();
+        CpuUsage.Record(cpu);
+    }
+}

Moonlight.ApiServer/Implementations/Metrics/UsersMetric.cs

@@ -0,0 +1,27 @@
+using System.Diagnostics.Metrics;
+using Microsoft.EntityFrameworkCore;
+using MoonCore.Extended.Abstractions;
+using Moonlight.ApiServer.Database.Entities;
+using Moonlight.ApiServer.Interfaces;
+
+namespace Moonlight.ApiServer.Implementations.Metrics;
+
+public class UsersMetric : IMetric
+{
+    private Gauge<int> Users;
+    
+    public Task Initialize(Meter meter)
+    {
+        Users = meter.CreateGauge<int>("moonlight_users");
+        
+        return Task.CompletedTask;
+    }
+
+    public async Task Run(IServiceProvider provider, CancellationToken cancellationToken)
+    {
+        var usersRepo = provider.GetRequiredService<DatabaseRepository<User>>();
+        var count = await usersRepo.Get().CountAsync(cancellationToken: cancellationToken);
+        
+        Users.Record(count);
+    }
+}

Moonlight.ApiServer/Implementations/Startup/CoreStartup.cs

@@ -2,8 +2,12 @@ using Microsoft.OpenApi.Models;
 using Moonlight.ApiServer.Configuration;
 using Moonlight.ApiServer.Database;
 using Moonlight.ApiServer.Implementations.Diagnose;
+using Moonlight.ApiServer.Implementations.Metrics;
 using Moonlight.ApiServer.Interfaces;
 using Moonlight.ApiServer.Plugins;
+using Moonlight.ApiServer.Services;
+using OpenTelemetry.Metrics;
+using OpenTelemetry.Trace;
 
 namespace Moonlight.ApiServer.Implementations.Startup;
 
@@ -13,13 +17,13 @@ public class CoreStartup : IPluginStartup
     public Task BuildApplication(IServiceProvider serviceProvider, IHostApplicationBuilder builder)
     {
         var configuration = serviceProvider.GetRequiredService<AppConfiguration>();
-        
+
         #region Api Docs
 
         if (configuration.Development.EnableApiDocs)
         {
             builder.Services.AddEndpointsApiExplorer();
-        
+
             // Configure swagger api specification generator and set the document title for the api docs to use
             builder.Services.AddSwaggerGen(options =>
             {
@@ -27,9 +31,9 @@ public class CoreStartup : IPluginStartup
                 {
                     Title = "Moonlight API"
                 });
-                
+
                 options.CustomSchemaIds(x => x.FullName);
-                
+
                 options.AddSecurityDefinition("Bearer", new OpenApiSecurityScheme
                 {
                     Name = "Authorization",
@@ -54,22 +58,53 @@ public class CoreStartup : IPluginStartup
         builder.Services.AddSingleton<IDiagnoseProvider, LogsDiagnoseProvider>();
 
         #endregion
-        
+
+        #region Prometheus
+
+        if (configuration.Metrics.Enable)
+        {
+            builder.Services.AddSingleton<MetricsBackgroundService>();
+            builder.Services.AddHostedService(sp => sp.GetRequiredService<MetricsBackgroundService>());
+
+            builder.Services.AddSingleton<IMetric, ApplicationMetric>();
+            builder.Services.AddSingleton<IMetric, UsersMetric>();
+
+            builder.Services.AddOpenTelemetry()
+                .WithMetrics(providerBuilder =>
+                {
+                    providerBuilder.AddPrometheusExporter();
+                    providerBuilder.AddAspNetCoreInstrumentation();
+
+                    providerBuilder.AddMeter("moonlight");
+                });
+        }
+
+        #endregion
+
         return Task.CompletedTask;
     }
 
     public Task ConfigureApplication(IServiceProvider serviceProvider, IApplicationBuilder app)
     {
+        var configuration = serviceProvider.GetRequiredService<AppConfiguration>();
+        
+        #region Prometheus
+
+        if(configuration.Metrics.Enable)
+            app.UseOpenTelemetryPrometheusScrapingEndpoint();
+
+        #endregion
+        
         return Task.CompletedTask;
     }
 
     public Task ConfigureEndpoints(IServiceProvider serviceProvider, IEndpointRouteBuilder routeBuilder)
     {
         var configuration = serviceProvider.GetRequiredService<AppConfiguration>();
-        
-        if(configuration.Development.EnableApiDocs)
+
+        if (configuration.Development.EnableApiDocs)
             routeBuilder.MapSwagger("/api/swagger/{documentName}");
-        
+
         return Task.CompletedTask;
     }
 }