Connect async storage with async instruments

api/include/opentelemetry/metrics/meter.h

@@ -56,17 +56,15 @@ class Meter
    * @param callback the function to be observed by the instrument.
    * @return a shared pointer to the created Observable Counter.
    */
-  virtual nostd::shared_ptr<ObservableCounter<long>> CreateLongObservableCounter(
-      nostd::string_view name,
-      void (*callback)(ObserverResult<long> &),
-      nostd::string_view description = "",
-      nostd::string_view unit        = "") noexcept = 0;
+  virtual void CreateLongObservableCounter(nostd::string_view name,
+                                           void (*callback)(ObserverResult<long> &),
+                                           nostd::string_view description = "",
+                                           nostd::string_view unit        = "") noexcept = 0;
 
-  virtual nostd::shared_ptr<ObservableCounter<double>> CreateDoubleObservableCounter(
-      nostd::string_view name,
-      void (*callback)(ObserverResult<double> &),
-      nostd::string_view description = "",
-      nostd::string_view unit        = "") noexcept = 0;
+  virtual void CreateDoubleObservableCounter(nostd::string_view name,
+                                             void (*callback)(ObserverResult<double> &),
+                                             nostd::string_view description = "",
+                                             nostd::string_view unit        = "") noexcept = 0;
 
   /**
    * Creates a Histogram with the passed characteristics and returns a shared_ptr to that Histogram.
@@ -96,17 +94,15 @@ class Meter
    * @param callback the function to be observed by the instrument.
    * @return a shared pointer to the created Observable Gauge.
    */
-  virtual nostd::shared_ptr<ObservableGauge<long>> CreateLongObservableGauge(
-      nostd::string_view name,
-      void (*callback)(ObserverResult<long> &),
-      nostd::string_view description = "",
-      nostd::string_view unit        = "") noexcept = 0;
+  virtual void CreateLongObservableGauge(nostd::string_view name,
+                                         void (*callback)(ObserverResult<long> &),
+                                         nostd::string_view description = "",
+                                         nostd::string_view unit        = "") noexcept = 0;
 
-  virtual nostd::shared_ptr<ObservableGauge<double>> CreateDoubleObservableGauge(
-      nostd::string_view name,
-      void (*callback)(ObserverResult<double> &),
-      nostd::string_view description = "",
-      nostd::string_view unit        = "") noexcept = 0;
+  virtual void CreateDoubleObservableGauge(nostd::string_view name,
+                                           void (*callback)(ObserverResult<double> &),
+                                           nostd::string_view description = "",
+                                           nostd::string_view unit        = "") noexcept = 0;
 
   /**
    * Creates an UpDownCounter with the passed characteristics and returns a shared_ptr to that
@@ -137,17 +133,15 @@ class Meter
    * @param callback the function to be observed by the instrument.
    * @return a shared pointer to the created Observable UpDownCounter.
    */
-  virtual nostd::shared_ptr<ObservableUpDownCounter<long>> CreateLongObservableUpDownCounter(
-      nostd::string_view name,
-      void (*callback)(ObserverResult<long> &),
-      nostd::string_view description = "",
-      nostd::string_view unit        = "") noexcept = 0;
-
-  virtual nostd::shared_ptr<ObservableUpDownCounter<double>> CreateDoubleObservableUpDownCounter(
-      nostd::string_view name,
-      void (*callback)(ObserverResult<double> &),
-      nostd::string_view description = "",
-      nostd::string_view unit        = "") noexcept = 0;
+  virtual void CreateLongObservableUpDownCounter(nostd::string_view name,
+                                                 void (*callback)(ObserverResult<long> &),
+                                                 nostd::string_view description = "",
+                                                 nostd::string_view unit        = "") noexcept = 0;
+
+  virtual void CreateDoubleObservableUpDownCounter(nostd::string_view name,
+                                                   void (*callback)(ObserverResult<double> &),
+                                                   nostd::string_view description = "",
+                                                   nostd::string_view unit = "") noexcept = 0;
 };
 }  // namespace metrics
 OPENTELEMETRY_END_NAMESPACE

api/include/opentelemetry/metrics/noop.h

@@ -137,25 +137,17 @@ class NoopMeter final : public Meter
     return nostd::shared_ptr<Counter<double>>{new NoopCounter<double>(name, description, unit)};
   }
 
-  nostd::shared_ptr<ObservableCounter<long>> CreateLongObservableCounter(
-      nostd::string_view name,
-      void (*callback)(ObserverResult<long> &),
-      nostd::string_view description = "",
-      nostd::string_view unit        = "") noexcept override
-  {
-    return nostd::shared_ptr<ObservableCounter<long>>{
-        new NoopObservableCounter<long>(name, callback, description, unit)};
-  }
+  void CreateLongObservableCounter(nostd::string_view name,
+                                   void (*callback)(ObserverResult<long> &),
+                                   nostd::string_view description = "",
+                                   nostd::string_view unit        = "") noexcept override
+  {}
 
-  nostd::shared_ptr<ObservableCounter<double>> CreateDoubleObservableCounter(
-      nostd::string_view name,
-      void (*callback)(ObserverResult<double> &),
-      nostd::string_view description = "",
-      nostd::string_view unit        = "") noexcept override
-  {
-    return nostd::shared_ptr<ObservableCounter<double>>{
-        new NoopObservableCounter<double>(name, callback, description, unit)};
-  }
+  void CreateDoubleObservableCounter(nostd::string_view name,
+                                     void (*callback)(ObserverResult<double> &),
+                                     nostd::string_view description = "",
+                                     nostd::string_view unit        = "") noexcept override
+  {}
 
   nostd::shared_ptr<Histogram<long>> CreateLongHistogram(
       nostd::string_view name,
@@ -173,25 +165,17 @@ class NoopMeter final : public Meter
     return nostd::shared_ptr<Histogram<double>>{new NoopHistogram<double>(name, description, unit)};
   }
 
-  nostd::shared_ptr<ObservableGauge<long>> CreateLongObservableGauge(
-      nostd::string_view name,
-      void (*callback)(ObserverResult<long> &),
-      nostd::string_view description = "",
-      nostd::string_view unit        = "") noexcept override
-  {
-    return nostd::shared_ptr<ObservableGauge<long>>{
-        new NoopObservableGauge<long>(name, callback, description, unit)};
-  }
+  void CreateLongObservableGauge(nostd::string_view name,
+                                 void (*callback)(ObserverResult<long> &),
+                                 nostd::string_view description = "",
+                                 nostd::string_view unit        = "") noexcept override
+  {}
 
-  nostd::shared_ptr<ObservableGauge<double>> CreateDoubleObservableGauge(
-      nostd::string_view name,
-      void (*callback)(ObserverResult<double> &),
-      nostd::string_view description = "",
-      nostd::string_view unit        = "") noexcept override
-  {
-    return nostd::shared_ptr<ObservableGauge<double>>{
-        new NoopObservableGauge<double>(name, callback, description, unit)};
-  }
+  void CreateDoubleObservableGauge(nostd::string_view name,
+                                   void (*callback)(ObserverResult<double> &),
+                                   nostd::string_view description = "",
+                                   nostd::string_view unit        = "") noexcept override
+  {}
 
   nostd::shared_ptr<UpDownCounter<long>> CreateLongUpDownCounter(
       nostd::string_view name,
@@ -211,25 +195,17 @@ class NoopMeter final : public Meter
         new NoopUpDownCounter<double>(name, description, unit)};
   }
 
-  nostd::shared_ptr<ObservableUpDownCounter<long>> CreateLongObservableUpDownCounter(
-      nostd::string_view name,
-      void (*callback)(ObserverResult<long> &),
-      nostd::string_view description = "",
-      nostd::string_view unit        = "") noexcept override
-  {
-    return nostd::shared_ptr<ObservableUpDownCounter<long>>{
-        new NoopObservableUpDownCounter<long>(name, callback, description, unit)};
-  }
+  void CreateLongObservableUpDownCounter(nostd::string_view name,
+                                         void (*callback)(ObserverResult<long> &),
+                                         nostd::string_view description = "",
+                                         nostd::string_view unit        = "") noexcept override
+  {}
 
-  nostd::shared_ptr<ObservableUpDownCounter<double>> CreateDoubleObservableUpDownCounter(
-      nostd::string_view name,
-      void (*callback)(ObserverResult<double> &),
-      nostd::string_view description = "",
-      nostd::string_view unit        = "") noexcept override
-  {
-    return nostd::shared_ptr<ObservableUpDownCounter<double>>{
-        new NoopObservableUpDownCounter<double>(name, callback, description, unit)};
-  }
+  void CreateDoubleObservableUpDownCounter(nostd::string_view name,
+                                           void (*callback)(ObserverResult<double> &),
+                                           nostd::string_view description = "",
+                                           nostd::string_view unit        = "") noexcept override
+  {}
 };
 
 /**

examples/common/metrics_foo_library/foo_library.cc

@@ -6,13 +6,16 @@
 #  include <chrono>
 #  include <map>
 #  include <thread>
+#  include <vector>
+#  include "opentelemetry/context/context.h"
 #  include "opentelemetry/metrics/provider.h"
 
 namespace nostd       = opentelemetry::nostd;
 namespace metrics_api = opentelemetry::metrics;
 
 namespace
 {
+
 std::map<std::string, std::string> get_random_attr()
 {
   static const std::vector<std::pair<std::string, std::string>> labels = {{"key1", "value1"},
@@ -23,6 +26,18 @@ std::map<std::string, std::string> get_random_attr()
   return std::map<std::string, std::string>{labels[rand() % (labels.size() - 1)],
                                             labels[rand() % (labels.size() - 1)]};
 }
+
+class MeasurementFetcher
+{
+public:
+  static void Fetcher(opentelemetry::metrics::ObserverResult<double> &observer_result)
+  {
+    double val                                = (rand() % 700) + 1.1;
+    std::map<std::string, std::string> labels = get_random_attr();
+    auto labelkv = opentelemetry::common::KeyValueIterableView<decltype(labels)>{labels};
+    observer_result.Observe(val /*, labelkv*/);
+  }
+};
 }  // namespace
 
 void foo_library::counter_example(const std::string &name)
@@ -40,6 +55,18 @@ void foo_library::counter_example(const std::string &name)
   }
 }
 
+void foo_library::observable_counter_example(const std::string &name)
+{
+  std::string counter_name                    = name + "_observable_counter";
+  auto provider                               = metrics_api::Provider::GetMeterProvider();
+  nostd::shared_ptr<metrics_api::Meter> meter = provider->GetMeter(name, "1.2.0");
+  meter->CreateDoubleObservableCounter(counter_name, MeasurementFetcher::Fetcher);
+  while (true)
+  {
+    std::this_thread::sleep_for(std::chrono::milliseconds(500));
+  }
+}
+
 void foo_library::histogram_example(const std::string &name)
 {
   std::string histogram_name                  = name + "_histogram";

examples/common/metrics_foo_library/foo_library.h

@@ -10,5 +10,6 @@ class foo_library
 public:
   static void counter_example(const std::string &name);
   static void histogram_example(const std::string &name);
+  static void observable_counter_example(const std::string &name);
 };
 #endif

examples/metrics_simple/metrics_ostream.cc

@@ -54,6 +54,18 @@ void initMetrics(const std::string &name)
       new metric_sdk::View{name, "description", metric_sdk::AggregationType::kSum}};
   p->AddView(std::move(instrument_selector), std::move(meter_selector), std::move(sum_view));
 
+  // observable counter view
+  std::string observable_counter_name = name + "_observable_counter";
+  std::unique_ptr<metric_sdk::InstrumentSelector> observable_instrument_selector{
+      new metric_sdk::InstrumentSelector(metric_sdk::InstrumentType::kObservableCounter,
+                                         observable_counter_name)};
+  std::unique_ptr<metric_sdk::MeterSelector> observable_meter_selector{
+      new metric_sdk::MeterSelector(name, version, schema)};
+  std::unique_ptr<metric_sdk::View> observable_sum_view{
+      new metric_sdk::View{name, "description", metric_sdk::AggregationType::kSum}};
+  p->AddView(std::move(observable_instrument_selector), std::move(observable_meter_selector),
+             std::move(observable_sum_view));
+
   // histogram view
   std::string histogram_name = name + "_histogram";
   std::unique_ptr<metric_sdk::InstrumentSelector> histogram_instrument_selector{
@@ -83,15 +95,22 @@ int main(int argc, char **argv)
   {
     foo_library::counter_example(name);
   }
+  else if (example_type == "observable_counter")
+  {
+    foo_library::observable_counter_example(name);
+  }
   else if (example_type == "histogram")
   {
     foo_library::histogram_example(name);
   }
   else
   {
     std::thread counter_example{&foo_library::counter_example, name};
+    std::thread observable_counter_example{&foo_library::observable_counter_example, name};
     std::thread histogram_example{&foo_library::histogram_example, name};
+
     counter_example.join();
+    observable_counter_example.join();
     histogram_example.join();
   }
 }

sdk/include/opentelemetry/sdk/metrics/meter.h

@@ -8,6 +8,8 @@
 #  include "opentelemetry/sdk/instrumentationlibrary/instrumentation_library.h"
 #  include "opentelemetry/sdk/metrics/instruments.h"
 #  include "opentelemetry/sdk/metrics/meter_context.h"
+#  include "opentelemetry/sdk/metrics/state/async_metric_storage.h"
+
 #  include "opentelemetry/sdk/resource/resource.h"
 #  include "opentelemetry/version.h"
 
@@ -40,18 +42,17 @@ class Meter final : public opentelemetry::metrics::Meter
       nostd::string_view description = "",
       nostd::string_view unit        = "") noexcept override;
 
-  nostd::shared_ptr<opentelemetry::metrics::ObservableCounter<long>> CreateLongObservableCounter(
+  void CreateLongObservableCounter(nostd::string_view name,
+                                   void (*callback)(opentelemetry::metrics::ObserverResult<long> &),
+                                   nostd::string_view description = "",
+                                   nostd::string_view unit        = "") noexcept override;
+
+  void CreateDoubleObservableCounter(
       nostd::string_view name,
-      void (*callback)(opentelemetry::metrics::ObserverResult<long> &),
+      void (*callback)(opentelemetry::metrics::ObserverResult<double> &),
       nostd::string_view description = "",
       nostd::string_view unit        = "") noexcept override;
 
-  nostd::shared_ptr<opentelemetry::metrics::ObservableCounter<double>>
-  CreateDoubleObservableCounter(nostd::string_view name,
-                                void (*callback)(opentelemetry::metrics::ObserverResult<double> &),
-                                nostd::string_view description = "",
-                                nostd::string_view unit        = "1") noexcept override;
-
   nostd::shared_ptr<opentelemetry::metrics::Histogram<long>> CreateLongHistogram(
       nostd::string_view name,
       nostd::string_view description = "",
@@ -62,13 +63,12 @@ class Meter final : public opentelemetry::metrics::Meter
       nostd::string_view description = "",
       nostd::string_view unit        = "") noexcept override;
 
-  nostd::shared_ptr<opentelemetry::metrics::ObservableGauge<long>> CreateLongObservableGauge(
-      nostd::string_view name,
-      void (*callback)(opentelemetry::metrics::ObserverResult<long> &),
-      nostd::string_view description = "",
-      nostd::string_view unit        = "") noexcept override;
+  void CreateLongObservableGauge(nostd::string_view name,
+                                 void (*callback)(opentelemetry::metrics::ObserverResult<long> &),
+                                 nostd::string_view description = "",
+                                 nostd::string_view unit        = "") noexcept override;
 
-  nostd::shared_ptr<opentelemetry::metrics::ObservableGauge<double>> CreateDoubleObservableGauge(
+  void CreateDoubleObservableGauge(
       nostd::string_view name,
       void (*callback)(opentelemetry::metrics::ObserverResult<double> &),
       nostd::string_view description = "",
@@ -84,15 +84,13 @@ class Meter final : public opentelemetry::metrics::Meter
       nostd::string_view description = "",
       nostd::string_view unit        = "") noexcept override;
 
-  nostd::shared_ptr<opentelemetry::metrics::ObservableUpDownCounter<long>>
-  CreateLongObservableUpDownCounter(
+  void CreateLongObservableUpDownCounter(
       nostd::string_view name,
       void (*callback)(opentelemetry::metrics::ObserverResult<long> &),
       nostd::string_view description = "",
       nostd::string_view unit        = "") noexcept override;
 
-  nostd::shared_ptr<opentelemetry::metrics::ObservableUpDownCounter<double>>
-  CreateDoubleObservableUpDownCounter(
+  void CreateDoubleObservableUpDownCounter(
       nostd::string_view name,
       void (*callback)(opentelemetry::metrics::ObserverResult<double> &),
       nostd::string_view description = "",
@@ -116,6 +114,25 @@ class Meter final : public opentelemetry::metrics::Meter
 
   std::unique_ptr<WritableMetricStorage> RegisterMetricStorage(
       InstrumentDescriptor &instrument_descriptor);
+
+  template <class T>
+  void RegisterAsyncMetricStorage(InstrumentDescriptor &instrument_descriptor,
+                                  void (*callback)(opentelemetry::metrics::ObserverResult<T> &))
+  {
+    auto view_registry = meter_context_->GetViewRegistry();
+    auto success       = view_registry->FindViews(
+        instrument_descriptor, *instrumentation_library_,
+        [this, &instrument_descriptor, callback](const View &view) {
+          auto view_instr_desc         = instrument_descriptor;
+          view_instr_desc.name_        = view.GetName();
+          view_instr_desc.description_ = view.GetDescription();
+          auto storage                 = std::shared_ptr<AsyncMetricStorage<T>>(
+              new AsyncMetricStorage<T>(view_instr_desc, view.GetAggregationType(), callback,
+                                        &view.GetAttributesProcessor()));
+          storage_registry_[instrument_descriptor.name_] = storage;
+          return true;
+        });
+  }
 };
 }  // namespace metrics
 }  // namespace sdk