[OTel] Remove global fallback for meter provider (#34190)

Based on updates at https://github.com/grpc/proposal/pull/380

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src/cpp/ext/otel/otel_plugin.cc

@@ -26,7 +26,6 @@
 
 #include "opentelemetry/metrics/meter.h"
 #include "opentelemetry/metrics/meter_provider.h"
-#include "opentelemetry/metrics/provider.h"
 #include "opentelemetry/nostd/shared_ptr.h"
 #include "opentelemetry/nostd/unique_ptr.h"
 
@@ -118,13 +117,12 @@ OpenTelemetryPluginBuilder& OpenTelemetryPluginBuilder::DisableMetrics(
 void OpenTelemetryPluginBuilder::BuildAndRegisterGlobal() {
   opentelemetry::nostd::shared_ptr<opentelemetry::metrics::MeterProvider>
       meter_provider = meter_provider_;
-  if (meter_provider == nullptr) {
-    meter_provider = opentelemetry::metrics::Provider::GetMeterProvider();
-  }
-  auto meter = meter_provider->GetMeter("grpc");
   delete g_otel_plugin_state_;
   g_otel_plugin_state_ = new struct OTelPluginState;
-  g_otel_plugin_state_->meter_provider = std::move(meter_provider);
+  if (meter_provider == nullptr) {
+    return;
+  }
+  auto meter = meter_provider->GetMeter("grpc");
   if (metrics_.contains(OTelClientAttemptStartedInstrumentName())) {
     g_otel_plugin_state_->client.attempt.started = meter->CreateUInt64Counter(
         std::string(OTelClientAttemptStartedInstrumentName()));
@@ -166,6 +164,7 @@ void OpenTelemetryPluginBuilder::BuildAndRegisterGlobal() {
         meter->CreateUInt64Histogram(std::string(
             OTelServerCallRcvdTotalCompressedMessageSizeInstrumentName()));
   }
+  g_otel_plugin_state_->meter_provider = std::move(meter_provider);
   grpc_core::ServerCallTracerFactory::RegisterGlobal(
       new grpc::internal::OpenTelemetryServerCallTracerFactory);
   grpc_core::CoreConfiguration::RegisterBuilder(

test/cpp/ext/otel/otel_plugin_test.cc

@@ -64,23 +64,18 @@ class OTelPluginEnd2EndTest : public ::testing::Test {
  protected:
   using ::testing::Test::SetUp;
   void SetUp(const absl::flat_hash_set<absl::string_view>& metric_names,
-             bool global_meter_provider = false) {
+             bool test_no_meter_provider = false) {
     // We are resetting the MeterProvider and OpenTelemetry plugin at the start
     // of each test to avoid test results from one test carrying over to another
     // test. (Some measurements can get arbitrarily delayed.)
+    grpc_core::CoreConfiguration::Reset();
+    grpc::internal::OpenTelemetryPluginBuilder ot_builder;
+    ot_builder.EnableMetrics(metric_names);
+    if (!test_no_meter_provider) {
       auto meter_provider =
           std::make_shared<opentelemetry::sdk::metrics::MeterProvider>();
       reader_.reset(new grpc::testing::MockMetricReader);
       meter_provider->AddMetricReader(reader_);
-    grpc_core::CoreConfiguration::Reset();
-    grpc::internal::OpenTelemetryPluginBuilder ot_builder;
-    ot_builder.EnableMetrics(metric_names);
-    if (global_meter_provider) {
-      opentelemetry::metrics::Provider::SetMeterProvider(
-          opentelemetry::nostd::shared_ptr<
-              opentelemetry::metrics::MeterProvider>(
-              std::move(meter_provider)));
-    } else {
       ot_builder.SetMeterProvider(std::move(meter_provider));
     }
     ot_builder.BuildAndRegisterGlobal();
@@ -395,23 +390,11 @@ TEST_F(OTelPluginEnd2EndTest, ServerCallRcvdTotalCompressedMessageSize) {
   EXPECT_EQ(*status_value, "OK");
 }
 
-// Make sure that things work with the global meter provider as well
+// Make sure that no meter provider results in normal operations.
-TEST_F(OTelPluginEnd2EndTest, UseGlobalMeterProvider) {
+TEST_F(OTelPluginEnd2EndTest, NoMeterProviderRegistered) {
-  SetUp({grpc::internal::OTelClientAttemptStartedInstrumentName()});
+  SetUp({grpc::internal::OTelClientAttemptStartedInstrumentName()},
+        /*test_no_meter_provider=*/true);
   SendRPC();
-  const char* kMetricName = "grpc.client.attempt.started";
-  auto data = ReadCurrentMetricsData(
-      [&](const absl::flat_hash_map<
-          std::string,
-          std::vector<opentelemetry::sdk::metrics::PointDataAttributes>>&
-              data) { return !data.contains(kMetricName); });
-  ASSERT_EQ(data[kMetricName].size(), 1);
-  auto point_data = absl::get_if<opentelemetry::sdk::metrics::SumPointData>(
-      &data[kMetricName][0].point_data);
-  ASSERT_NE(point_data, nullptr);
-  auto client_started_value = absl::get_if<int64_t>(&point_data->value_);
-  ASSERT_NE(client_started_value, nullptr);
-  ASSERT_EQ(*client_started_value, 1);
 }
 
 }  // namespace