Generated Output

Generated Output

This page shows real generated output from the sample application, produced by 5.0.0. The interface:

[ActivitySource]
[Logger]
[Meter]
interface IEntityStoreTelemetry
{
    [Activity]
    [Info]
    [AutoCounter]
    Activity? GettingEntityFromStore(int entityId, [Baggage] string serviceUrl);

    [Event]
    [Trace]
    void GetDuration(Activity? activity, int durationInMS);

    [Context]
    void RetrievedEntity(Activity? activity, float totalValue, int lastUpdatedByUserId);

    [Warning]
    void EntityNotFound(int entityId);

    [Histogram]
    void RecordEntitySize(int sizeInBytes);
}

generates one partial EntityStoreTelemetryCore class split across Activity, Logging, and Metric files, plus a DI extension class and an assembly-level [GeneratedTelemetryNames] attribute recording the generated names.

Note

To inspect the generated output in your own project, enable EmitCompilerGeneratedFiles and look under obj/<Configuration>/<tfm>/generated/Purview.Telemetry.SourceGenerator/Purview.Telemetry.SourceGenerator.TelemetrySourceGenerator/.

Activities (EntityStoreTelemetryCore.Activity.g.cs)

// <auto-generated />
#nullable enable

[global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
internal sealed partial class EntityStoreTelemetryCore : IEntityStoreTelemetry
{
  private static readonly global::System.Diagnostics.ActivitySource _activitySource = new global::System.Diagnostics.ActivitySource("sample-weather-app-api");

  public static void RecordExceptionInternal(
    global::System.Diagnostics.Activity? activity,
    global::System.Exception? exception,
    bool escape
  )
  {
    if (activity == null || exception == null)
    {
      return;
    }

    global::System.Diagnostics.ActivityTagsCollection tagsCollection = new global::System.Diagnostics.ActivityTagsCollection();
    tagsCollection.Add("exception.escaped", escape);
    tagsCollection.Add("exception.message", exception.Message);
    tagsCollection.Add("exception.type", exception.GetType().FullName);
    tagsCollection.Add("exception.stacktrace", exception.StackTrace);

    global::System.Diagnostics.ActivityEvent recordExceptionEvent = new global::System.Diagnostics.ActivityEvent(name: "exception", timestamp: default, tags: tagsCollection);

    activity.AddEvent(recordExceptionEvent);
  }

  private global::System.Diagnostics.Activity? GettingEntityFromStore_Activity(
    int entityId,
    string serviceUrl
  )
  {
    if (!_activitySource.HasListeners())
    {
      return null;
    }

    global::System.Diagnostics.Activity? activityGettingEntityFromStore = _activitySource.StartActivity("GettingEntityFromStore", global::System.Diagnostics.ActivityKind.Internal, parentId: default, tags: default, links: default, startTime: default);

    if (activityGettingEntityFromStore != null)
    {
      activityGettingEntityFromStore.SetTag("entity_id", entityId);
      activityGettingEntityFromStore.SetBaggage("service_url", serviceUrl);
    }
    return activityGettingEntityFromStore;
  }

  public global::System.Diagnostics.Activity? GettingEntityFromStore(
    int entityId,
    string serviceUrl
  )
  {
    var activityResult = GettingEntityFromStore_Activity(entityId, serviceUrl);
    GettingEntityFromStore_Logging(entityId, serviceUrl);
    GettingEntityFromStore_Metrics(entityId, serviceUrl);

    return activityResult;
  }

  public void RetrievedEntity(
    global::System.Diagnostics.Activity? activity,
    float totalValue,
    int lastUpdatedByUserId
  )
  {
    if (!_activitySource.HasListeners())
    {
      return;
    }

    if (activity != null)
    {
      activity.SetTag("total_value", totalValue);
      activity.SetTag("last_updated_by_user_id", lastUpdatedByUserId);
    }
  }
}

Key points:

• A HasListeners() fast-path avoids work when no listener is subscribed.
• Tag/baggage keys use snake_case (entity_id, service_url) — the OpenTelemetry naming convention.
• Multi-target methods orchestrate the per-target private methods.

Logging (EntityStoreTelemetryCore.Logging.g.cs)

internal sealed partial class EntityStoreTelemetryCore : IEntityStoreTelemetry
{
  private readonly global::Microsoft.Extensions.Logging.ILogger<IEntityStoreTelemetry> _logger;

  private static readonly global::System.Action<global::Microsoft.Extensions.Logging.ILogger, int, string, global::System.Exception?> _gettingEntityFromStoreAction = global::Microsoft.Extensions.Logging.LoggerMessage.Define<int, string>(global::Microsoft.Extensions.Logging.LogLevel.Information, new global::Microsoft.Extensions.Logging.EventId(0, "GettingEntityFromStore"), "GettingEntityFromStore: EntityId = {EntityId}, ServiceUrl = {ServiceUrl}");
  private static readonly global::System.Action<global::Microsoft.Extensions.Logging.ILogger, int, global::System.Exception?> _entityNotFoundAction = global::Microsoft.Extensions.Logging.LoggerMessage.Define<int>(global::Microsoft.Extensions.Logging.LogLevel.Warning, new global::Microsoft.Extensions.Logging.EventId(0, "EntityNotFound"), "EntityNotFound: EntityId = {EntityId}");

  public EntityStoreTelemetryCore(
    global::Microsoft.Extensions.Logging.ILogger<IEntityStoreTelemetry> logger,
    global::System.Diagnostics.Metrics.IMeterFactory meterFactory
  )
  {
    _logger = logger;
    InitializeMeters(meterFactory);
  }

  private void GettingEntityFromStore_Logging(int entityId, string serviceUrl)
  {
    if (!_logger.IsEnabled(global::Microsoft.Extensions.Logging.LogLevel.Information))
    {
      return;
    }

    _gettingEntityFromStoreAction(_logger, entityId, serviceUrl, null);
  }

  public void EntityNotFound(int entityId)
  {
    if (!_logger.IsEnabled(global::Microsoft.Extensions.Logging.LogLevel.Warning))
    {
      return;
    }

    _entityNotFoundAction(_logger, entityId, null);
  }
}

These methods fit the v1 limits (≤ 6 non-exception parameters, no [ExpandEnumerable]/[LogProperties]), so LoggerGenerationMode.Auto selected v1 LoggerMessage.Define generation with an IsEnabled fast-path. See Logging.

Metrics (EntityStoreTelemetryCore.Metric.g.cs)

internal sealed partial class EntityStoreTelemetryCore : IEntityStoreTelemetry
{
  private global::System.Diagnostics.Metrics.Meter _meter = default!;

  private global::System.Diagnostics.Metrics.Counter<int> _gettingEntityFromStoreInstrument = default!;
  private global::System.Diagnostics.Metrics.Histogram<int> _recordEntitySizeInstrument = default!;

  public void InitializeMeters(global::System.Diagnostics.Metrics.IMeterFactory meterFactory)
  {
    if (_meter != null)
    {
      throw new global::System.Exception("The meters have already been initialized.");
    }

    global::System.Collections.Generic.Dictionary<string, object?> meterTags = new global::System.Collections.Generic.Dictionary<string, object?>();

    PopulateMeterTags(meterTags);

    _meter = meterFactory.Create(new global::System.Diagnostics.Metrics.MeterOptions("SampleApp.APIService") {
      Version = null,
      Tags = meterTags
    });

    _gettingEntityFromStoreInstrument = _meter.CreateCounter<int>(name: "entity_store.getting_entity_from_store", unit: null, description: null, tags: gettingEntityFromStoreTags);
    _recordEntitySizeInstrument = _meter.CreateHistogram<int>(name: "entity_store.record_entity_size", unit: null, description: null, tags: recordEntitySizeTags);
  }

  partial void PopulateMeterTags(global::System.Collections.Generic.Dictionary<string, object?> meterTags);
  partial void PopulateGettingEntityFromStoreTags(global::System.Collections.Generic.Dictionary<string, object?> instrumentTags);
  partial void PopulateRecordEntitySizeTags(global::System.Collections.Generic.Dictionary<string, object?> instrumentTags);

  private void GettingEntityFromStore_Metrics(int entityId, string serviceUrl)
  {
    _gettingEntityFromStoreInstrument.Add(1, new global::System.Collections.Generic.KeyValuePair<string, object?>("entity_id", entityId), new global::System.Collections.Generic.KeyValuePair<string, object?>("service_url", serviceUrl));
  }

  public void RecordEntitySize(int sizeInBytes)
  {
    _recordEntitySizeInstrument.Record(sizeInBytes);
  }
}

Key points:

• The meter name defaults to the assembly name (SampleApp.APIService).
• [AutoCounter] emits Add(1, ...).
• PopulateMeterTags/Populate{Method}Tags partial methods let you add tags at initialisation.

DI registration (EntityStoreTelemetryCoreDIExtension.DependencyInjection.g.cs)

namespace Microsoft.Extensions.DependencyInjection
{
  [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
  internal static partial class EntityStoreTelemetryCoreDIExtension
  {
    public static global::Microsoft.Extensions.DependencyInjection.IServiceCollection AddEntityStoreTelemetry(
      this global::Microsoft.Extensions.DependencyInjection.IServiceCollection services
    )
    {
      return services.AddSingleton<IEntityStoreTelemetry, global::EntityStoreTelemetryCore>();
    }
  }
}

Recorded names (SampleApp.APIService.GeneratedTelemetryNames.g.cs)

[assembly: global::Purview.Telemetry.GeneratedTelemetryNamesAttribute(new string[] { "SampleApp.APIService" }, new string[] { "SampleApp.APIService" })]

Emitted for every assembly that generates an ActivitySource or a Meter, so downstream assemblies can read the names back out of metadata. Both names default to the assembly name here; an assembly-level [ActivitySourceGeneration] or [MeterGeneration], or a name on the interface attribute, overrides them.

Telemetry names (SampleApp.APIService.TelemetryNames.g.cs)

Opt in with [assembly: TelemetryGeneration(GenerateTelemetryNamesClass = true)]:

namespace SampleApp.APIService
{
  public static partial class TelemetryNames
  {
    public static readonly string[] MeterNames = new string[] { "SampleApp.APIService", "SampleApp.Shared" };

    public static readonly string[] ActivitySourceNames = new string[] { "SampleApp.APIService", "SampleApp.Shared" };
  }
}

SampleApp.Shared comes from the referenced project of the same name, whose IWeatherForecastTelemetry declares an ActivitySource and a Meter: the class aggregates this assembly’s names with the names recorded by everything it references. See Generation.

See also

• Sample Application — the full source
• Generation — controlling class names, DI, and names
• Diagnostics — analyzer rules