Add custom metrics.

src/Imagine.Students.Api/Services/TrackedStudentsStore.cs

@@ -0,0 +1,41 @@
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using Imagine.Students.Api.Models;
+using Prometheus;
+
+namespace Imagine.Students.Api.Services
+{
+	public class TrackedStudentsStore : IStudentsStore
+	{
+		private const string MetricName = "student_api_operation_duration_seconds";
+
+		private const string MetricDescrption = "student_api_operation_duration_seconds";
+
+		private static readonly HistogramConfiguration Config = new HistogramConfiguration
+		{
+			StaticLabels = new()
+			{
+				{ "class", nameof(TrackedStudentsStore) },
+				{ "method", nameof(GetStudents) }
+			}
+		};
+
+		private static readonly Histogram Histogram = Metrics.CreateHistogram(MetricName, MetricDescrption, Config);
+
+		private readonly IStudentsStore _store;
+
+		public TrackedStudentsStore(IStudentsStore store)
+		{
+			_store = store;
+		}
+
+		public async Task<IEnumerable<Student>> GetStudents(Guid classroomId)
+		{
+			using (Histogram.NewTimer())
+			{
+				return await _store.GetStudents(classroomId);
+			}
+		}
+	}
+}

src/Imagine.Students.Api/Startup.cs

@@ -29,6 +29,7 @@ public void ConfigureServices(IServiceCollection services)
 
 			services.AddTransient<IStudentsStore, StudentsStore>();
 			services.Decorate<IStudentsStore, BrokenStudentsStore>();
+			services.Decorate<IStudentsStore, TrackedStudentsStore>();
 		}
 
 		// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.