Adding a tracer provider

api/include/opentelemetry/trace/noop.h

@@ -8,6 +8,7 @@
 #include "opentelemetry/nostd/unique_ptr.h"
 #include "opentelemetry/trace/span.h"
 #include "opentelemetry/trace/tracer.h"
+#include "opentelemetry/trace/tracer_provider.h"
 #include "opentelemetry/version.h"
 
 #include <memory>
@@ -54,5 +55,27 @@ class NoopTracer final : public Tracer, public std::enable_shared_from_this<Noop
     return nostd::unique_ptr<Span>{new (std::nothrow) NoopSpan{this->shared_from_this()}};
   }
 };
+
+/**
+ * No-op implementation of a TracerProvider.
+ */
+class NoopTracerProvider final : public opentelemetry::trace::TracerProvider
+{
+public:
+  NoopTracerProvider()
+      : tracer_{nostd::shared_ptr<opentelemetry::trace::NoopTracer>(
+            new opentelemetry::trace::NoopTracer)}
+  {}
+
+  nostd::shared_ptr<opentelemetry::trace::Tracer> GetTracer(
+      nostd::string_view library_name,
+      nostd::string_view library_version) override
+  {
+    return tracer_;
+  }
+
+private:
+  nostd::shared_ptr<opentelemetry::trace::Tracer> tracer_;
+};
 }  // namespace trace
 OPENTELEMETRY_END_NAMESPACE

api/include/opentelemetry/trace/provider.h

@@ -0,0 +1,60 @@
+#pragma once
+
+#include <atomic>
+
+#include "opentelemetry/nostd/shared_ptr.h"
+#include "opentelemetry/trace/noop.h"
+#include "opentelemetry/trace/tracer_provider.h"
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace trace
+{
+/**
+ * Stores the singleton global TracerProvider.
+ */
+class Provider
+{
+public:
+  /**
+   * Returns the singleton TracerProvider.
+   *
+   * By default, a no-op TracerProvider is returned. This will never return a
+   * nullptr TracerProvider.
+   */
+  static nostd::shared_ptr<TracerProvider> GetTracerProvider() noexcept
+  {
+    while (GetLock().test_and_set(std::memory_order_acquire))
+      ;
+    auto provider = nostd::shared_ptr<TracerProvider>(GetProvider());
+    GetLock().clear(std::memory_order_release);
+
+    return provider;
+  }
+
+  /**
+   * Changes the singleton TracerProvider.
+   */
+  static void SetTracerProvider(nostd::shared_ptr<TracerProvider> tp) noexcept
+  {
+    while (GetLock().test_and_set(std::memory_order_acquire))
+      ;
+    GetProvider() = tp;
+    GetLock().clear(std::memory_order_release);
+  }
+
+private:
+  static nostd::shared_ptr<TracerProvider> &GetProvider() noexcept
+  {
+    static nostd::shared_ptr<TracerProvider> provider(new NoopTracerProvider);
+    return provider;
+  }
+
+  static std::atomic_flag &GetLock() noexcept
+  {
+    static std::atomic_flag lock = ATOMIC_FLAG_INIT;
+    return lock;
+  }
+};
+
+}  // namespace trace
+OPENTELEMETRY_END_NAMESPACE

api/include/opentelemetry/trace/tracer.h

@@ -18,7 +18,6 @@ class Tracer
 {
 public:
   virtual ~Tracer() = default;
-
   /**
    * Starts a span.
    */

api/include/opentelemetry/trace/tracer_provider.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include "opentelemetry/nostd/shared_ptr.h"
+#include "opentelemetry/nostd/string_view.h"
+#include "opentelemetry/trace/tracer.h"
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace trace
+{
+/**
+ * Creates new Tracer instances.
+ */
+class TracerProvider
+{
+public:
+  virtual ~TracerProvider() = default;
+  /**
+   * Gets or creates a named tracer instance.
+   *
+   * Optionally a version can be passed to create a named and versioned tracer
+   * instance.
+   */
+  virtual nostd::shared_ptr<Tracer> GetTracer(nostd::string_view library_name,
+                                              nostd::string_view library_version = "") = 0;
+};
+}  // namespace trace
+OPENTELEMETRY_END_NAMESPACE

api/test/trace/BUILD

@@ -17,6 +17,17 @@ otel_cc_benchmark(
     deps = ["//api"],
 )
 
+cc_test(
+    name = "provider_test",
+    srcs = [
+        "provider_test.cc",
+    ],
+    deps = [
+        "//api",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
 cc_test(
     name = "span_id_test",
     srcs = [

api/test/trace/CMakeLists.txt

@@ -1,4 +1,5 @@
-foreach(testname noop_test span_id_test trace_id_test trace_flags_test)
+foreach(testname noop_test provider_test span_id_test trace_id_test
+                 trace_flags_test)
   add_executable(${testname} "${testname}.cc")
   target_link_libraries(${testname} ${GTEST_BOTH_LIBRARIES}
                         ${CMAKE_THREAD_LIBS_INIT} opentelemetry_api)

api/test/trace/provider_test.cc

@@ -0,0 +1,31 @@
+#include "opentelemetry/trace/provider.h"
+#include "opentelemetry/nostd/shared_ptr.h"
+
+#include <gtest/gtest.h>
+
+using opentelemetry::trace::Provider;
+using opentelemetry::trace::Tracer;
+using opentelemetry::trace::TracerProvider;
+
+class TestProvider : public TracerProvider
+{
+  opentelemetry::nostd::shared_ptr<Tracer> GetTracer(
+      opentelemetry::nostd::string_view library_name,
+      opentelemetry::nostd::string_view library_version) override
+  {
+    return opentelemetry::nostd::shared_ptr<Tracer>(nullptr);
+  }
+};
+
+TEST(Provider, GetTracerProviderDefault)
+{
+  auto tf = Provider::GetTracerProvider();
+  EXPECT_NE(nullptr, tf);
+}
+
+TEST(Provider, SetTracerProvider)
+{
+  auto tf = opentelemetry::nostd::shared_ptr<TracerProvider>(new TestProvider());
+  Provider::SetTracerProvider(tf);
+  ASSERT_EQ(tf, Provider::GetTracerProvider());
+}

sdk/BUILD

@@ -0,0 +1,7 @@
+package(default_visibility = ["//visibility:public"])
+
+cc_library(
+    name = "headers",
+    hdrs = glob(["include/**/*.h"]),
+    strip_include_prefix = "include",
+)

sdk/CMakeLists.txt

@@ -1 +1,5 @@
 add_subdirectory(src)
+
+if(BUILD_TESTING)
+  add_subdirectory(test)
+endif()

sdk/include/opentelemetry/sdk/trace/default_tracer_provider.h

@@ -0,0 +1,30 @@
+#pragma once
+
+#include <map>
+#include <memory>
+#include <string>
+
+#include "opentelemetry/nostd/shared_ptr.h"
+#include "opentelemetry/trace/tracer.h"
+#include "opentelemetry/trace/tracer_provider.h"
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace sdk
+{
+namespace trace
+{
+class DefaultTracerProvider final : public opentelemetry::trace::TracerProvider
+{
+public:
+  DefaultTracerProvider() noexcept;
+
+  opentelemetry::nostd::shared_ptr<opentelemetry::trace::Tracer> GetTracer(
+      nostd::string_view library_name,
+      nostd::string_view library_version = "") noexcept override;
+
+private:
+  opentelemetry::nostd::shared_ptr<opentelemetry::trace::Tracer> tracer_;
+};
+}  // namespace trace
+}  // namespace sdk
+OPENTELEMETRY_END_NAMESPACE

sdk/src/trace/BUILD

@@ -21,5 +21,6 @@ cc_library(
     include_prefix = "src/trace",
     deps = [
         "//api",
+        "//sdk:headers",
     ],
 )

sdk/src/trace/CMakeLists.txt

@@ -1 +1 @@
-add_library(opentelemetry_trace tracer.cc span.cc)
+add_library(opentelemetry_trace default_tracer_provider.cc tracer.cc span.cc)

sdk/src/trace/default_tracer_provider.cc

@@ -0,0 +1,21 @@
+#include "opentelemetry/sdk/trace/default_tracer_provider.h"
+#include "src/trace/tracer.h"
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace sdk
+{
+namespace trace
+{
+DefaultTracerProvider::DefaultTracerProvider() noexcept
+    : tracer_(new Tracer(std::unique_ptr<Recorder>(nullptr)))
+{}
+
+opentelemetry::nostd::shared_ptr<opentelemetry::trace::Tracer> DefaultTracerProvider::GetTracer(
+    nostd::string_view library_name,
+    nostd::string_view library_version) noexcept
+{
+  return tracer_;
+}
+}  // namespace trace
+}  // namespace sdk
+OPENTELEMETRY_END_NAMESPACE

sdk/test/CMakeLists.txt

@@ -0,0 +1 @@
+add_subdirectory(trace)

sdk/test/trace/BUILD

@@ -0,0 +1,10 @@
+cc_test(
+    name = "default_tracer_provider",
+    srcs = [
+        "default_tracer_provider_test.cc",
+    ],
+    deps = [
+        "//sdk/src/trace",
+        "@com_google_googletest//:gtest_main",
+    ],
+)

sdk/test/trace/CMakeLists.txt

@@ -0,0 +1,6 @@
+foreach(testname default_tracer_provider_test)
+  add_executable(${testname} "${testname}.cc")
+  target_link_libraries(${testname} ${GTEST_BOTH_LIBRARIES}
+                        ${CMAKE_THREAD_LIBS_INIT} opentelemetry_trace)
+  gtest_add_tests(TARGET ${testname} TEST_PREFIX trace. TEST_LIST ${testname})
+endforeach()

sdk/test/trace/default_tracer_provider_test.cc

@@ -0,0 +1,20 @@
+#include "opentelemetry/sdk/trace/default_tracer_provider.h"
+
+#include <gtest/gtest.h>
+
+using opentelemetry::sdk::trace::DefaultTracerProvider;
+
+TEST(TracerProvider, GetTracer)
+{
+  auto tf = DefaultTracerProvider();
+  auto t1 = tf.GetTracer("test");
+  auto t2 = tf.GetTracer("test");
+  auto t3 = tf.GetTracer("different", "1.0.0");
+  ASSERT_NE(nullptr, t1);
+  ASSERT_NE(nullptr, t2);
+  ASSERT_NE(nullptr, t3);
+
+  // Should return the same instance each time.
+  ASSERT_EQ(t1, t2);
+  ASSERT_EQ(t1, t3);
+}