add example file

Signed-off-by: dentiny <dentinyhao@gmail.com>

Author: dentiny

BUILD.bazel

@@ -860,6 +860,15 @@ ray_cc_library(
     ],
 )
 
+ray_cc_library(
+    name = "stats_opentelemetry",
+    srcs = ["src/ray/stats/opentelemetry_metrics.cc"],
+    deps = [
+        "@io_opentelemetry_cpp//sdk/src/logs:logs",
+        "@io_opentelemetry_cpp//sdk/src/trace:trace",
+    ],
+)
+
 ray_cc_library(
     name = "stats_metric",
     srcs = [

src/ray/stats/opentelemetry_metrics.cc

@@ -0,0 +1,34 @@
+// TODO(hjiang): This is an example file which demonstrates opentelemetry dependency is
+// correct, should be replaced with real metrics exporter implementation.
+
+#include "opentelemetry/nostd/shared_ptr.h"
+#include "opentelemetry/sdk/version/version.h"
+#include "opentelemetry/trace/provider.h"
+#include "opentelemetry/trace/scope.h"
+#include "opentelemetry/trace/tracer.h"
+#include "opentelemetry/trace/tracer_provider.h"
+
+namespace trace = opentelemetry::trace;
+namespace nostd = opentelemetry::nostd;
+
+namespace {
+nostd::shared_ptr<trace::Tracer> get_tracer() {
+  auto provider = trace::Provider::GetTracerProvider();
+  return provider->GetTracer("foo_library", OPENTELEMETRY_SDK_VERSION);
+}
+
+void f1() { auto scoped_span = trace::Scope(get_tracer()->StartSpan("f1")); }
+
+void f2() {
+  auto scoped_span = trace::Scope(get_tracer()->StartSpan("f2"));
+
+  f1();
+  f1();
+}
+}  // namespace
+
+void foo_library() {
+  auto scoped_span = trace::Scope(get_tracer()->StartSpan("library"));
+
+  f2();
+}