Do not construct NPCMetricsKeyValueIterable when calling OTel API when

the instrument has empty label and optional label

src/cpp/ext/otel/otel_plugin.cc

@@ -637,6 +637,11 @@ void OpenTelemetryPluginImpl::AddCounter(
       grpc_core::GlobalInstrumentsRegistry::GetInstrumentDescriptor(handle);
   CHECK(descriptor.label_keys.size() == label_values.size());
   CHECK(descriptor.optional_label_keys.size() == optional_values.size());
+  if (label_values.empty() && optional_values.empty()) {
+    absl::get<std::unique_ptr<opentelemetry::metrics::Counter<uint64_t>>>(
+        instrument_data.instrument)
+        ->Add(value);
+  } else {
     absl::get<std::unique_ptr<opentelemetry::metrics::Counter<uint64_t>>>(
         instrument_data.instrument)
         ->Add(value, NPCMetricsKeyValueIterable(
@@ -644,6 +649,7 @@ void OpenTelemetryPluginImpl::AddCounter(
                          descriptor.optional_label_keys, optional_values,
                          instrument_data.optional_labels_bits));
   }
+}
 
 void OpenTelemetryPluginImpl::AddCounter(
     grpc_core::GlobalInstrumentsRegistry::GlobalInstrumentHandle handle,
@@ -661,6 +667,11 @@ void OpenTelemetryPluginImpl::AddCounter(
       grpc_core::GlobalInstrumentsRegistry::GetInstrumentDescriptor(handle);
   CHECK(descriptor.label_keys.size() == label_values.size());
   CHECK(descriptor.optional_label_keys.size() == optional_values.size());
+  if (label_values.empty() && optional_values.empty()) {
+    absl::get<std::unique_ptr<opentelemetry::metrics::Counter<double>>>(
+        instrument_data.instrument)
+        ->Add(value);
+  } else {
     absl::get<std::unique_ptr<opentelemetry::metrics::Counter<double>>>(
         instrument_data.instrument)
         ->Add(value, NPCMetricsKeyValueIterable(
@@ -668,6 +679,7 @@ void OpenTelemetryPluginImpl::AddCounter(
                          descriptor.optional_label_keys, optional_values,
                          instrument_data.optional_labels_bits));
   }
+}
 
 void OpenTelemetryPluginImpl::RecordHistogram(
     grpc_core::GlobalInstrumentsRegistry::GlobalInstrumentHandle handle,
@@ -685,15 +697,21 @@ void OpenTelemetryPluginImpl::RecordHistogram(
       grpc_core::GlobalInstrumentsRegistry::GetInstrumentDescriptor(handle);
   CHECK(descriptor.label_keys.size() == label_values.size());
   CHECK(descriptor.optional_label_keys.size() == optional_values.size());
+  if (label_values.empty() && optional_values.empty()) {
+    absl::get<std::unique_ptr<opentelemetry::metrics::Histogram<uint64_t>>>(
+        instrument_data.instrument)
+        ->Record(value, opentelemetry::context::Context{});
+  } else {
     absl::get<std::unique_ptr<opentelemetry::metrics::Histogram<uint64_t>>>(
         instrument_data.instrument)
         ->Record(value,
-               NPCMetricsKeyValueIterable(descriptor.label_keys, label_values,
-                                          descriptor.optional_label_keys,
-                                          optional_values,
+                 NPCMetricsKeyValueIterable(
+                     descriptor.label_keys, label_values,
+                     descriptor.optional_label_keys, optional_values,
                      instrument_data.optional_labels_bits),
                  opentelemetry::context::Context{});
   }
+}
 
 void OpenTelemetryPluginImpl::RecordHistogram(
     grpc_core::GlobalInstrumentsRegistry::GlobalInstrumentHandle handle,
@@ -711,15 +729,21 @@ void OpenTelemetryPluginImpl::RecordHistogram(
       grpc_core::GlobalInstrumentsRegistry::GetInstrumentDescriptor(handle);
   CHECK(descriptor.label_keys.size() == label_values.size());
   CHECK(descriptor.optional_label_keys.size() == optional_values.size());
+  if (label_values.empty() && optional_values.empty()) {
+    absl::get<std::unique_ptr<opentelemetry::metrics::Histogram<double>>>(
+        instrument_data.instrument)
+        ->Record(value, opentelemetry::context::Context{});
+  } else {
     absl::get<std::unique_ptr<opentelemetry::metrics::Histogram<double>>>(
         instrument_data.instrument)
         ->Record(value,
-               NPCMetricsKeyValueIterable(descriptor.label_keys, label_values,
-                                          descriptor.optional_label_keys,
-                                          optional_values,
+                 NPCMetricsKeyValueIterable(
+                     descriptor.label_keys, label_values,
+                     descriptor.optional_label_keys, optional_values,
                      instrument_data.optional_labels_bits),
                  opentelemetry::context::Context{});
   }
+}
 
 void OpenTelemetryPluginImpl::AddCallback(
     grpc_core::RegisteredMetricCallback* callback) {
@@ -881,6 +905,12 @@ void OpenTelemetryPluginImpl::CallbackGaugeState<ValueType>::Observe(
   for (const auto& pair : cache) {
     CHECK(pair.first.size() <= (descriptor.label_keys.size() +
                                 descriptor.optional_label_keys.size()));
+    if (descriptor.label_keys.empty() &&
+        descriptor.optional_label_keys.empty()) {
+      opentelemetry::nostd::get<opentelemetry::nostd::shared_ptr<
+          opentelemetry::metrics::ObserverResultT<ValueType>>>(result)
+          ->Observe(pair.second);
+    } else {
       auto& instrument_data = ot_plugin->instruments_data_.at(id);
       opentelemetry::nostd::get<opentelemetry::nostd::shared_ptr<
           opentelemetry::metrics::ObserverResultT<ValueType>>>(result)
@@ -897,6 +927,7 @@ void OpenTelemetryPluginImpl::CallbackGaugeState<ValueType>::Observe(
                         instrument_data.optional_labels_bits));
     }
   }
+}
 
 // OpenTelemetry calls our callback with its observable_registry's lock
 // held.