[examples] Add manual activities and custom metrics to ASP.NET Core example

examples/AspNetCore/Controllers/WeatherForecastController.cs

@@ -16,6 +16,7 @@
 
 namespace Examples.AspNetCore.Controllers;
 
+using Examples.AspNetCore;
 using Microsoft.AspNetCore.Mvc;
 
 [ApiController]
@@ -24,16 +25,18 @@ public class WeatherForecastController : ControllerBase
 {
     private static readonly string[] Summaries = new[]
     {
-            "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching",
+        "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching",
     };
 
     private static readonly HttpClient HttpClient = new();
 
     private readonly ILogger<WeatherForecastController> logger;
+    private readonly ITelemetryService telemetryService;
 
-    public WeatherForecastController(ILogger<WeatherForecastController> logger)
+    public WeatherForecastController(ILogger<WeatherForecastController> logger, ITelemetryService telemetryService)
     {
         this.logger = logger ?? throw new ArgumentNullException(nameof(logger));
+        this.telemetryService = telemetryService ?? throw new ArgumentNullException(nameof(telemetryService));
     }
 
     [HttpGet]
@@ -45,6 +48,11 @@ public IEnumerable<WeatherForecast> Get()
         // how dependency calls will be captured and treated
         // automatically as child of incoming request.
         var res = HttpClient.GetStringAsync("http://google.com").Result;
+
+        // Manually create an activity. This will become a child of
+        // the incoming request.
+        using var activity = this.telemetryService.ActivitySource.StartActivity("calculate forecast");
+
         var rng = new Random();
         var forecast = Enumerable.Range(1, 5).Select(index => new WeatherForecast
         {
@@ -54,6 +62,9 @@ public IEnumerable<WeatherForecast> Get()
         })
         .ToArray();
 
+        // Count the freezing days
+        this.telemetryService.FreezingDaysCounter.Add(forecast.Count(f => f.TemperatureC < 0));
+
         this.logger.LogInformation(
             "WeatherForecasts generated {count}: {forecasts}",
             forecast.Length,

examples/AspNetCore/ITelemetryService.cs

@@ -0,0 +1,29 @@
+// <copyright file="ITelemetryService.cs" company="OpenTelemetry Authors">
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// </copyright>
+
+namespace Examples.AspNetCore;
+
+using System.Diagnostics;
+using System.Diagnostics.Metrics;
+
+public interface ITelemetryService
+{
+    ActivitySource ActivitySource { get; }
+
+    Meter Meter { get; }
+
+    Counter<int> FreezingDaysCounter { get; }
+}

examples/AspNetCore/Program.cs

@@ -15,6 +15,7 @@
 // </copyright>
 
 using System.Reflection;
+using Examples.AspNetCore;
 using OpenTelemetry;
 using OpenTelemetry.Exporter;
 using OpenTelemetry.Instrumentation.AspNetCore;
@@ -34,12 +35,19 @@
 // Note: Switch between Console/OTLP by setting UseLogExporter in appsettings.json.
 var logExporter = appBuilder.Configuration.GetValue<string>("UseLogExporter").ToLowerInvariant();
 
+var version = Assembly.GetExecutingAssembly().GetName().Version?.ToString() ?? "unknown";
+
 // Build a resource configuration action to set service information.
 Action<ResourceBuilder> configureResource = r => r.AddService(
     serviceName: appBuilder.Configuration.GetValue<string>("ServiceName"),
-    serviceVersion: Assembly.GetExecutingAssembly().GetName().Version?.ToString() ?? "unknown",
+    serviceVersion: version,
     serviceInstanceId: Environment.MachineName);
 
+// Create a container to hold ActivitySource, Meter, and all
+// instruments so that DI can be used to inject these dependencies
+var telemetryService = new TelemetryService(version);
+appBuilder.Services.AddSingleton<ITelemetryService>(telemetryService);
+
 // Configure OpenTelemetry tracing & metrics with auto-start using the
 // StartWithHost extension from OpenTelemetry.Extensions.Hosting.
 appBuilder.Services.AddOpenTelemetry()
@@ -48,7 +56,9 @@
     {
         // Tracing
 
+        // Ensure the TracerProvider subscribes to any custom ActivitySources.
         builder
+            .AddSource(telemetryService.ActivitySource.Name)
             .SetSampler(new AlwaysOnSampler())
             .AddHttpClientInstrumentation()
             .AddAspNetCoreInstrumentation();
@@ -98,7 +108,9 @@
     {
         // Metrics
 
+        // Ensure the MeterProvider subscribes to any custom Meters.
         builder
+            .AddMeter(telemetryService.Meter.Name)
             .AddRuntimeInstrumentation()
             .AddHttpClientInstrumentation()
             .AddAspNetCoreInstrumentation();

examples/AspNetCore/TelemetryService.cs

@@ -0,0 +1,38 @@
+// <copyright file="TelemetryService.cs" company="OpenTelemetry Authors">
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// </copyright>
+
+namespace Examples.AspNetCore;
+
+using System.Diagnostics;
+using System.Diagnostics.Metrics;
+
+public class TelemetryService : ITelemetryService
+{
+    private const string InstrumentationScopeName = "Examples.AspNetCore";
+
+    public TelemetryService(string version)
+    {
+        this.ActivitySource = new ActivitySource(InstrumentationScopeName, version);
+        this.Meter = new Meter(InstrumentationScopeName, version);
+        this.FreezingDaysCounter = this.Meter.CreateCounter<int>("weather.days.freezing", "The number of days where the temperature is below freezing");
+    }
+
+    public ActivitySource ActivitySource { get; }
+
+    public Meter Meter { get; }
+
+    public Counter<int> FreezingDaysCounter { get; }
+}