[tracing] Add new RecordAnnotation method to CallTracer API (#33696)

Adding a new method for custom Annotation types (per design suggested in
#33649) to unblock metadata annotation.

src/core/lib/channel/call_tracer.h

@@ -49,11 +49,31 @@ namespace grpc_core {
 // The base class for all tracer implementations.
 class CallTracerAnnotationInterface {
  public:
+  // Enum associated with types of Annotations.
+  enum class AnnotationType {
+    kDoNotUse_MustBeLast,
+  };
+
+  // Base class to define a new type of annotation.
+  class Annotation {
+   public:
+    explicit Annotation(AnnotationType type) : type_(type) {}
+    AnnotationType type() const { return type_; }
+    virtual std::string ToString() const = 0;
+
+   protected:
+    ~Annotation() {}
+
+   private:
+    const AnnotationType type_;
+  };
+
   virtual ~CallTracerAnnotationInterface() {}
   // Records an annotation on the call attempt.
   // TODO(yashykt): If needed, extend this to attach attributes with
   // annotations.
   virtual void RecordAnnotation(absl::string_view annotation) = 0;
+  virtual void RecordAnnotation(const Annotation& annotation) = 0;
   virtual std::string TraceId() = 0;
   virtual std::string SpanId() = 0;
   virtual bool IsSampled() = 0;

src/cpp/ext/filters/census/client_filter.cc

@@ -284,10 +284,24 @@ void OpenCensusCallTracer::OpenCensusCallAttemptTracer::RecordEnd(
 
 void OpenCensusCallTracer::OpenCensusCallAttemptTracer::RecordAnnotation(
     absl::string_view annotation) {
-  // If tracing is disabled, the following will be a no-op.
+  if (!context_.Span().IsRecording()) {
+    return;
+  }
   context_.AddSpanAnnotation(annotation, {});
 }
 
+void OpenCensusCallTracer::OpenCensusCallAttemptTracer::RecordAnnotation(
+    const Annotation& annotation) {
+  if (!context_.Span().IsRecording()) {
+    return;
+  }
+
+  switch (annotation.type()) {
+    default:
+      context_.AddSpanAnnotation(annotation.ToString(), {});
+  }
+}
+
 //
 // OpenCensusCallTracer
 //
@@ -355,10 +369,23 @@ OpenCensusCallTracer::StartNewAttempt(bool is_transparent_retry) {
 }
 
 void OpenCensusCallTracer::RecordAnnotation(absl::string_view annotation) {
-  // If tracing is disabled, the following will be a no-op.
+  if (!context_.Span().IsRecording()) {
+    return;
+  }
   context_.AddSpanAnnotation(annotation, {});
 }
 
+void OpenCensusCallTracer::RecordAnnotation(const Annotation& annotation) {
+  if (!context_.Span().IsRecording()) {
+    return;
+  }
+
+  switch (annotation.type()) {
+    default:
+      context_.AddSpanAnnotation(annotation.ToString(), {});
+  }
+}
+
 void OpenCensusCallTracer::RecordApiLatency(absl::Duration api_latency,
                                             absl::StatusCode status_code) {
   if (OpenCensusStatsEnabled()) {

src/cpp/ext/filters/census/open_census_call_tracer.h

@@ -99,6 +99,7 @@ class OpenCensusCallTracer : public grpc_core::ClientCallTracer {
     void RecordCancel(grpc_error_handle cancel_error) override;
     void RecordEnd(const gpr_timespec& /*latency*/) override;
     void RecordAnnotation(absl::string_view annotation) override;
+    void RecordAnnotation(const Annotation& annotation) override;
 
     experimental::CensusContext* context() { return &context_; }
 
@@ -136,6 +137,7 @@ class OpenCensusCallTracer : public grpc_core::ClientCallTracer {
   OpenCensusCallAttemptTracer* StartNewAttempt(
       bool is_transparent_retry) override;
   void RecordAnnotation(absl::string_view annotation) override;
+  void RecordAnnotation(const Annotation& annotation) override;
 
   // APIs to record API call latency
   void RecordApiLatency(absl::Duration api_latency,

src/cpp/ext/filters/census/server_call_tracer.cc

@@ -157,9 +157,23 @@ class OpenCensusServerCallTracer : public grpc_core::ServerCallTracer {
   void RecordEnd(const grpc_call_final_info* final_info) override;
 
   void RecordAnnotation(absl::string_view annotation) override {
+    if (!context_.Span().IsRecording()) {
+      return;
+    }
     context_.AddSpanAnnotation(annotation, {});
   }
 
+  void RecordAnnotation(const Annotation& annotation) override {
+    if (!context_.Span().IsRecording()) {
+      return;
+    }
+
+    switch (annotation.type()) {
+      default:
+        context_.AddSpanAnnotation(annotation.ToString(), {});
+    }
+  }
+
  private:
   experimental::CensusContext context_;
   // server method

src/cpp/ext/otel/otel_call_tracer.h

@@ -85,6 +85,7 @@ class OpenTelemetryCallTracer : public grpc_core::ClientCallTracer {
     void RecordCancel(grpc_error_handle cancel_error) override;
     void RecordEnd(const gpr_timespec& /*latency*/) override;
     void RecordAnnotation(absl::string_view /*annotation*/) override;
+    void RecordAnnotation(const Annotation& /*annotation*/) override;
 
    private:
     const OpenTelemetryCallTracer* parent_;
@@ -115,6 +116,7 @@ class OpenTelemetryCallTracer : public grpc_core::ClientCallTracer {
   OpenTelemetryCallAttemptTracer* StartNewAttempt(
       bool is_transparent_retry) override;
   void RecordAnnotation(absl::string_view /*annotation*/) override;
+  void RecordAnnotation(const Annotation& /*annotation*/) override;
 
  private:
   // Client method.

src/cpp/ext/otel/otel_client_filter.cc

@@ -167,6 +167,11 @@ void OpenTelemetryCallTracer::OpenTelemetryCallAttemptTracer::RecordAnnotation(
   // Not implemented
 }
 
+void OpenTelemetryCallTracer::OpenTelemetryCallAttemptTracer::RecordAnnotation(
+    const Annotation& /*annotation*/) {
+  // Not implemented
+}
+
 //
 // OpenTelemetryCallTracer
 //
@@ -208,5 +213,10 @@ void OpenTelemetryCallTracer::RecordAnnotation(
   // Not implemented
 }
 
+void OpenTelemetryCallTracer::RecordAnnotation(
+    const Annotation& /*annotation*/) {
+  // Not implemented
+}
+
 }  // namespace internal
 }  // namespace grpc

src/cpp/ext/otel/otel_server_call_tracer.cc

@@ -114,6 +114,10 @@ class OpenTelemetryServerCallTracer : public grpc_core::ServerCallTracer {
     // Not implemented
   }
 
+  void RecordAnnotation(const Annotation& /*annotation*/) override {
+    // Not implemented
+  }
+
  private:
   grpc_core::Slice path_;
   absl::string_view method_;