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

…xample

examples/AspNetCore/Controllers/WeatherForecastController.cs

@@ -16,6 +16,8 @@
 
 namespace Examples.AspNetCore.Controllers;
 
+using System.Diagnostics;
+using System.Diagnostics.Metrics;
 using Microsoft.AspNetCore.Mvc;
 
 [ApiController]
@@ -24,16 +26,23 @@ 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 ActivitySource activitySource;
+    private readonly Counter<int> counter;
 
-    public WeatherForecastController(ILogger<WeatherForecastController> logger)
+    public WeatherForecastController(ILogger<WeatherForecastController> logger, ActivitySource activitySource, Meter meter)
     {
         this.logger = logger ?? throw new ArgumentNullException(nameof(logger));
+        this.activitySource = activitySource ?? throw new ArgumentNullException(nameof(activitySource));
+        ArgumentNullException.ThrowIfNull(meter);
+
+        // Create a custom metric
+        this.counter = meter.CreateCounter<int>("weather.days.freezing", "The number of days where the temperature is below freezing");
     }
 
     [HttpGet]
@@ -45,6 +54,11 @@ 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.activitySource.StartActivity("calculate forecast");
+
         var rng = new Random();
         var forecast = Enumerable.Range(1, 5).Select(index => new WeatherForecast
         {
@@ -54,6 +68,9 @@ public IEnumerable<WeatherForecast> Get()
         })
         .ToArray();
 
+        // Count the freezing days
+        this.counter.Add(forecast.Count(f => f.TemperatureC < 0));
+
         this.logger.LogInformation(
             "WeatherForecasts generated {count}: {forecasts}",
             forecast.Length,

examples/AspNetCore/Program.cs

@@ -14,6 +14,8 @@
 // limitations under the License.
 // </copyright>
 
+using System.Diagnostics;
+using System.Diagnostics.Metrics;
 using System.Reflection;
 using OpenTelemetry;
 using OpenTelemetry.Exporter;
@@ -34,10 +36,13 @@
 // Note: Switch between Console/OTLP by setting UseLogExporter in appsettings.json.
 var logExporter = appBuilder.Configuration.GetValue<string>("UseLogExporter").ToLowerInvariant();
 
+var instrumentationScopeName = appBuilder.Configuration.GetValue<string>("InstrumentationScopeName");
+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);
 
 // Configure OpenTelemetry tracing & metrics with auto-start using the
@@ -48,7 +53,11 @@
     {
         // Tracing
 
+        // Create an ActivitySource for custom instrumentation
+        // and ensure the TracerPprovider subscribes to it.
+        appBuilder.Services.AddSingleton(new ActivitySource(instrumentationScopeName, version));
         builder
+            .AddSource(instrumentationScopeName)
             .SetSampler(new AlwaysOnSampler())
             .AddHttpClientInstrumentation()
             .AddAspNetCoreInstrumentation();
@@ -98,7 +107,11 @@
     {
         // Metrics
 
+        // Create a Meter for custom instrumentation
+        // and ensure the MeterProvider subscribes to it.
+        appBuilder.Services.AddSingleton(new Meter(instrumentationScopeName, version));
         builder
+            .AddMeter(instrumentationScopeName)
             .AddRuntimeInstrumentation()
             .AddHttpClientInstrumentation()
             .AddAspNetCoreInstrumentation();

examples/AspNetCore/appsettings.json

@@ -9,6 +9,7 @@
       "ParseStateValues": true
     }
   },
+  "InstrumentationScopeName": "Examples.AspNetCore",
   "ServiceName": "otel-test",
   "AllowedHosts": "*",
   "UseTracingExporter": "console",