added queue length metrics #16 #17

Author: zetroot

src/NTorSpectator.Observer/Services/SpectatorJob.cs

@@ -1,12 +1,14 @@
 using NTorSpectator.Observer.TorIntegration;
 using NTorSpectator.Services;
 using NTorSpectator.Services.Models;
+using Prometheus;
 using Quartz;
 
 namespace NTorSpectator.Observer.Services;
 
 public class SpectatorJob : IJob
 {
+    private static readonly Gauge QueueLength = Metrics.CreateGauge("sites_queue_length", "Length of the queue left to observe");
     private readonly ILogger<SpectatorJob> _logger;
     private readonly ISitesCatalogue _sitesCatalogue;
     private readonly TorControlManager _torControl;
@@ -29,6 +31,7 @@ public async Task Execute(IJobExecutionContext context)
         var siteQueue = new Queue<QueuedSite>(sites.Select(x => new QueuedSite(x, 0)));
         while(siteQueue.TryDequeue(out var queuedSite))
         {
+            QueueLength.Set(siteQueue.Count);
             using var _ = _logger.BeginScope(new Dictionary<string, object> { { "HiddenService", queuedSite.Site.SiteUri } });
             _logger.LogDebug("Starting observations on the next site");
             try