[CSM] Create an experimental target (#34381)

BUILD

@@ -2391,6 +2391,19 @@ grpc_cc_library(
     ],
 )
 
+# This is an EXPERIMENTAL target subject to change.
+grpc_cc_library(
+    name = "grpcpp_csm_observability",
+    hdrs = [
+        "include/grpcpp/ext/csm_observability.h",
+    ],
+    language = "c++",
+    tags = ["nofixdeps"],
+    deps = [
+        "//src/cpp/ext/csm:csm_observability",
+    ],
+)
+
 grpc_cc_library(
     name = "work_serializer",
     srcs = [

include/grpcpp/ext/csm_observability.h

@@ -0,0 +1,82 @@
+//
+//
+// Copyright 2023 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+//
+
+#ifndef GRPCPP_EXT_CSM_OBSERVABILITY_H
+#define GRPCPP_EXT_CSM_OBSERVABILITY_H
+
+#include <grpc/support/port_platform.h>
+
+#include <memory>
+
+#include "absl/functional/any_invocable.h"
+#include "absl/status/statusor.h"
+#include "absl/strings/string_view.h"
+#include "opentelemetry/sdk/metrics/meter_provider.h"
+
+#include "src/cpp/ext/otel/otel_plugin.h"
+
+namespace grpc {
+namespace experimental {
+
+// This is a no-op at present, but in the future, this object would be useful
+// for performing cleanup.
+class CsmObservability {};
+
+class CsmObservabilityBuilder {
+ public:
+  CsmObservabilityBuilder& SetMeterProvider(
+      std::shared_ptr<opentelemetry::sdk::metrics::MeterProvider>
+          meter_provider);
+  // Methods to manipulate which instruments are enabled in the OTel Stats
+  // Plugin. The default set of instruments are -
+  // grpc.client.attempt.started
+  // grpc.client.attempt.duration
+  // grpc.client.attempt.sent_total_compressed_message_size
+  // grpc.client.attempt.rcvd_total_compressed_message_size
+  // grpc.server.call.started
+  // grpc.server.call.duration
+  // grpc.server.call.sent_total_compressed_message_size
+  // grpc.server.call.rcvd_total_compressed_message_size
+  CsmObservabilityBuilder& EnableMetric(absl::string_view metric_name);
+  CsmObservabilityBuilder& DisableMetric(absl::string_view metric_name);
+  CsmObservabilityBuilder& DisableAllMetrics();
+  // If set, \a target_selector is called per channel to decide whether to
+  // collect metrics on that target or not.
+  CsmObservabilityBuilder& SetTargetSelector(
+      absl::AnyInvocable<bool(absl::string_view /*target*/) const>
+          target_selector);
+  // If set, \a target_attribute_filter is called per channel to decide whether
+  // to record the target attribute on client or to replace it with "other".
+  // This helps reduce the cardinality on metrics in cases where many channels
+  // are created with different targets in the same binary (which might happen
+  // for example, if the channel target string uses IP addresses directly).
+  CsmObservabilityBuilder& SetTargetAttributeFilter(
+      absl::AnyInvocable<bool(absl::string_view /*target*/) const>
+          target_attribute_filter);
+  // Builds the CsmObservability plugin. The return status shows whether
+  // CsmObservability was successfully enabled or not.
+  absl::StatusOr<CsmObservability> BuildAndRegister();
+
+ private:
+  internal::OpenTelemetryPluginBuilder builder_;
+};
+
+}  // namespace experimental
+}  // namespace grpc
+
+#endif  // GRPCPP_EXT_CSM_OBSERVABILITY_H

src/cpp/ext/csm/BUILD

@@ -37,6 +37,7 @@ grpc_cc_library(
     hdrs = [
         "csm_observability.h",
         "metadata_exchange.h",
+        "//:include/grpcpp/ext/csm_observability.h",
     ],
     external_deps = [
         "absl/functional:any_invocable",

src/cpp/ext/csm/csm_observability.cc

@@ -20,12 +20,17 @@
 
 #include "src/cpp/ext/csm/csm_observability.h"
 
+#include <memory>
 #include <string>
 #include <utility>
 
+#include "absl/functional/any_invocable.h"
+#include "absl/status/statusor.h"
 #include "absl/types/optional.h"
+#include "opentelemetry/sdk/metrics/meter_provider.h"
 
 #include <grpc/support/log.h>
+#include <grpcpp/ext/csm_observability.h>
 
 #include "src/core/ext/xds/xds_enabled_server.h"
 #include "src/core/lib/channel/channel_args.h"
@@ -33,7 +38,7 @@
 #include "src/cpp/ext/otel/otel_plugin.h"
 
 namespace grpc {
-namespace internal {
+namespace experimental {
 
 //
 // CsmObservabilityBuilder
@@ -81,11 +86,15 @@ absl::StatusOr<CsmObservability> CsmObservabilityBuilder::BuildAndRegister() {
   builder_.SetServerSelector([](const grpc_core::ChannelArgs& args) {
     return args.GetBool(GRPC_ARG_XDS_ENABLED_SERVER).value_or(false);
   });
+  builder_.SetTargetSelector(internal::CsmChannelTargetSelector);
   builder_.BuildAndRegisterGlobal();
-  builder_.SetTargetSelector(CsmChannelTargetSelector);
   return CsmObservability();
 }
 
+}  // namespace experimental
+
+namespace internal {
+
 bool CsmChannelTargetSelector(absl::string_view target) {
   auto uri = grpc_core::URI::Parse(target);
   if (!uri.ok()) {

src/cpp/ext/csm/csm_observability.h

@@ -21,61 +21,11 @@
 
 #include <grpc/support/port_platform.h>
 
-#include <memory>
-
-#include "absl/functional/any_invocable.h"
-#include "absl/status/statusor.h"
 #include "absl/strings/string_view.h"
-#include "opentelemetry/sdk/metrics/meter_provider.h"
-
-#include "src/cpp/ext/otel/otel_plugin.h"
 
 namespace grpc {
 namespace internal {
 
-// This is a no-op at present, but in the future, this object would be useful
-// for performing cleanup.
-class CsmObservability {};
-
-class CsmObservabilityBuilder {
- public:
-  CsmObservabilityBuilder& SetMeterProvider(
-      std::shared_ptr<opentelemetry::sdk::metrics::MeterProvider>
-          meter_provider);
-  // Methods to manipulate which instruments are enabled in the OTel Stats
-  // Plugin. The default set of instruments are -
-  // grpc.client.attempt.started
-  // grpc.client.attempt.duration
-  // grpc.client.attempt.sent_total_compressed_message_size
-  // grpc.client.attempt.rcvd_total_compressed_message_size
-  // grpc.server.call.started
-  // grpc.server.call.duration
-  // grpc.server.call.sent_total_compressed_message_size
-  // grpc.server.call.rcvd_total_compressed_message_size
-  CsmObservabilityBuilder& EnableMetric(absl::string_view metric_name);
-  CsmObservabilityBuilder& DisableMetric(absl::string_view metric_name);
-  CsmObservabilityBuilder& DisableAllMetrics();
-  // If set, \a target_selector is called per channel to decide whether to
-  // collect metrics on that target or not.
-  CsmObservabilityBuilder& SetTargetSelector(
-      absl::AnyInvocable<bool(absl::string_view /*target*/) const>
-          target_selector);
-  // If set, \a target_attribute_filter is called per channel to decide whether
-  // to record the target attribute on client or to replace it with "other".
-  // This helps reduce the cardinality on metrics in cases where many channels
-  // are created with different targets in the same binary (which might happen
-  // for example, if the channel target string uses IP addresses directly).
-  CsmObservabilityBuilder& SetTargetAttributeFilter(
-      absl::AnyInvocable<bool(absl::string_view /*target*/) const>
-          target_attribute_filter);
-  // Builds the CsmObservability plugin. The return status shows whether
-  // CsmObservability was successfully enabled or not.
-  absl::StatusOr<CsmObservability> BuildAndRegister();
-
- private:
-  OpenTelemetryPluginBuilder builder_;
-};
-
 // EXPOSED FOR TESTING PURPOSES ONLY
 // Returns true if the channel is a CSM channel.
 bool CsmChannelTargetSelector(absl::string_view target);

test/cpp/ext/csm/csm_observability_test.cc

@@ -21,6 +21,8 @@
 #include "google/cloud/opentelemetry/resource_detector.h"
 #include "gtest/gtest.h"
 
+#include <grpcpp/ext/csm_observability.h>
+
 #include "src/core/lib/gprpp/env.h"
 #include "test/core/util/test_config.h"
 
@@ -30,7 +32,7 @@ namespace {
 
 TEST(CsmObservabilityBuilderTest, Basic) {
   EXPECT_TRUE(
-      internal::CsmObservabilityBuilder().BuildAndRegister().status().ok());
+      experimental::CsmObservabilityBuilder().BuildAndRegister().status().ok());
 }
 
 TEST(GsmDependencyTest, GoogleCloudOpenTelemetryDependency) {