add metrics (without reporting, for now)

Catalogger.Backend/Services/MetricsCollectionService.cs

@@ -0,0 +1,61 @@
+using System.Diagnostics;
+using App.Metrics;
+using Catalogger.Backend.Cache;
+using Catalogger.Backend.Database;
+using Humanizer;
+using Microsoft.EntityFrameworkCore;
+using NodaTime.Extensions;
+
+namespace Catalogger.Backend.Services;
+
+public class MetricsCollectionService(
+    ILogger logger,
+    GuildCacheService guildCache,
+    ChannelCacheService channelCache,
+    UserCacheService userCache,
+    IMetrics metrics,
+    IServiceProvider services) : BackgroundService
+{
+    private readonly ILogger _logger = logger.ForContext<MetricsCollectionService>();
+
+    private async Task CollectMetricsAsync()
+    {
+        var stopwatch = new Stopwatch();
+        stopwatch.Start();
+
+        await using var scope = services.CreateAsyncScope();
+        await using var db = scope.ServiceProvider.GetRequiredService<DatabaseContext>();
+
+        var messageCount = await db.Messages.CountAsync();
+
+        metrics.Measure.Gauge.SetValue(CataloggerMetrics.GuildsCached, guildCache.Size);
+        metrics.Measure.Gauge.SetValue(CataloggerMetrics.ChannelsCached, channelCache.Size);
+        metrics.Measure.Gauge.SetValue(CataloggerMetrics.UsersCached, userCache.Size);
+        metrics.Measure.Gauge.SetValue(CataloggerMetrics.MessagesStored, messageCount);
+
+        var process = Process.GetCurrentProcess();
+        metrics.Measure.Gauge.SetValue(CataloggerMetrics.ProcessPhysicalMemory, process.WorkingSet64);
+        metrics.Measure.Gauge.SetValue(CataloggerMetrics.ProcessVirtualMemory, process.VirtualMemorySize64);
+        metrics.Measure.Gauge.SetValue(CataloggerMetrics.ProcessPrivateMemory, process.PrivateMemorySize64);
+        metrics.Measure.Gauge.SetValue(CataloggerMetrics.ProcessThreads, process.Threads.Count);
+        metrics.Measure.Gauge.SetValue(CataloggerMetrics.ProcessHandles, process.HandleCount);
+
+        stopwatch.Stop();
+
+        metrics.Measure.Timer.Time(CataloggerMetrics.MetricsCollectionTime, stopwatch.ElapsedMilliseconds);
+        _logger.Information("Collected metrics in {Duration}", stopwatch.ElapsedDuration());
+
+        await Task.WhenAll(((IMetricsRoot)metrics).ReportRunner.RunAllAsync());
+    }
+
+    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+    {
+        using var timer = new PeriodicTimer(1.Minutes());
+        while (await timer.WaitForNextTickAsync(stoppingToken))
+        {
+            _logger.Debug("Collecting periodic metrics");
+            await CollectMetricsAsync();
+            _logger.Debug("Reported metrics to backend");
+        }
+    }
+}