Always Off Sampler (open-telemetry#125)

.bazelversion

@@ -1 +1 @@
-3.2.0
+3.3.0

sdk/include/opentelemetry/sdk/trace/samplers/always_off.h

@@ -0,0 +1,41 @@
+#pragma once
+
+#include "opentelemetry/sdk/trace/sampler.h"
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace sdk
+{
+namespace trace
+{
+namespace trace_api = opentelemetry::trace;
+/**
+ * The always off sampler always returns NOT_RECORD, effectively disabling
+ * tracing functionality.
+ */
+class AlwaysOffSampler : public Sampler
+{
+public:
+  /**
+   * @return Returns NOT_RECORD always
+   */
+  SamplingResult ShouldSample(
+    const SpanContext * /*parent_context*/,
+    trace_api::TraceId /*trace_id*/,
+    nostd::string_view /*name*/,
+    trace_api::SpanKind /*span_kind*/,
+    const trace_api::KeyValueIterable & /*attributes*/) noexcept override
+  {
+    return { Decision::NOT_RECORD, nullptr };
+  }
+
+  /**
+   * @return Description MUST be AlwaysOffSampler
+   */
+  std::string GetDescription() const noexcept override
+  {
+    return "AlwaysOffSampler";
+  }
+};
+}  // namespace trace
+}  // namespace sdk
+OPENTELEMETRY_END_NAMESPACE

sdk/test/trace/BUILD

@@ -41,3 +41,14 @@ cc_test(
         "@com_google_googletest//:gtest_main",
     ],
 )
+
+cc_test(
+    name = "always_off_sampler_test",
+    srcs = [
+        "always_off_sampler_test.cc"
+    ],
+    deps = [
+        "//sdk/src/trace",
+        "@com_google_googletest//:gtest_main",
+    ]
+)

sdk/test/trace/CMakeLists.txt

@@ -1,5 +1,5 @@
 foreach(testname tracer_provider_test span_data_test simple_processor_test
-                 tracer_test)
+                 tracer_test always_off_sampler_test)
   add_executable(${testname} "${testname}.cc")
   target_link_libraries(${testname} ${GTEST_BOTH_LIBRARIES}
                         ${CMAKE_THREAD_LIBS_INIT} opentelemetry_trace)

sdk/test/trace/always_off_sampler_test.cc

@@ -0,0 +1,30 @@
+#include "opentelemetry/sdk/trace/samplers/always_off.h"
+
+#include <gtest/gtest.h>
+
+using opentelemetry::sdk::trace::AlwaysOffSampler;
+using opentelemetry::sdk::trace::Decision;
+
+TEST(AlwaysOffSampler, ShouldSample)
+{
+	AlwaysOffSampler sampler;
+
+	opentelemetry::trace::TraceId trace_id;
+	opentelemetry::trace::SpanKind span_kind = opentelemetry::trace::SpanKind::kInternal;
+
+	using M = std::map<std::string, int>;
+	M m1 = {{}};
+	opentelemetry::trace::KeyValueIterableView<M> view{m1};
+
+	auto sampling_result = sampler.ShouldSample(nullptr, trace_id, "", span_kind, view);
+
+	ASSERT_EQ(Decision::NOT_RECORD, sampling_result.decision);
+	ASSERT_EQ(nullptr, sampling_result.attributes);
+}
+
+TEST(AlwaysOffSampler, GetDescription)
+{
+	AlwaysOffSampler sampler;
+
+	ASSERT_EQ("AlwaysOffSampler", sampler.GetDescription());
+}