[OTel] Add latency view to example (#36601) (#36720)

Backport #36601 to v1.64.x

Needed to backport #36686

examples/cpp/otel/BUILD

@@ -14,11 +14,22 @@
 
 licenses(["notice"])
 
+cc_library(
+    name = "util",
+    srcs = ["util.cc"],
+    hdrs = ["util.h"],
+    deps = [
+        "//:grpc++",
+        "@io_opentelemetry_cpp//sdk/src/metrics",
+    ],
+)
+
 cc_binary(
     name = "greeter_callback_client",
     srcs = ["greeter_callback_client.cc"],
     defines = ["BAZEL_BUILD"],
     deps = [
+        "util",
         "//:grpc++",
         "//:grpcpp_otel_plugin",
         "//examples/protos:helloworld_cc_grpc",
@@ -34,6 +45,7 @@ cc_binary(
     srcs = ["greeter_callback_server.cc"],
     defines = ["BAZEL_BUILD"],
     deps = [
+        "util",
         "//:grpc++",
         "//:grpc++_reflection",
         "//:grpcpp_otel_plugin",

examples/cpp/otel/greeter_callback_client.cc

@@ -33,9 +33,11 @@
 #include <grpcpp/grpcpp.h>
 
 #ifdef BAZEL_BUILD
+#include "examples/cpp/otel/util.h"
 #include "examples/protos/helloworld.grpc.pb.h"
 #else
 #include "helloworld.grpc.pb.h"
+#include "util.h"
 #endif
 
 ABSL_FLAG(std::string, target, "localhost:50051", "Server address");
@@ -110,6 +112,10 @@ int main(int argc, char** argv) {
       opentelemetry::exporter::metrics::PrometheusExporterFactory::Create(opts);
   auto meter_provider =
       std::make_shared<opentelemetry::sdk::metrics::MeterProvider>();
+  // The default histogram boundaries are not granular enough for RPCs. Override
+  // the "grpc.client.attempt.duration" view as recommended by
+  // https://github.com/grpc/proposal/blob/master/A66-otel-stats.md.
+  AddLatencyView(meter_provider.get(), "grpc.client.attempt.duration", "s");
   meter_provider->AddMetricReader(std::move(prometheus_exporter));
   auto status = grpc::OpenTelemetryPluginBuilder()
                     .SetMeterProvider(std::move(meter_provider))

examples/cpp/otel/greeter_callback_server.cc

@@ -33,9 +33,11 @@
 #include <grpcpp/health_check_service_interface.h>
 
 #ifdef BAZEL_BUILD
+#include "examples/cpp/otel/util.h"
 #include "examples/protos/helloworld.grpc.pb.h"
 #else
 #include "helloworld.grpc.pb.h"
+#include "util.h"
 #endif
 
 ABSL_FLAG(uint16_t, port, 50051, "Server port for the service");
@@ -96,6 +98,10 @@ int main(int argc, char** argv) {
       opentelemetry::exporter::metrics::PrometheusExporterFactory::Create(opts);
   auto meter_provider =
       std::make_shared<opentelemetry::sdk::metrics::MeterProvider>();
+  // The default histogram boundaries are not granular enough for RPCs. Override
+  // the "grpc.server.call.duration" view as recommended by
+  // https://github.com/grpc/proposal/blob/master/A66-otel-stats.md.
+  AddLatencyView(meter_provider.get(), "grpc.server.call.duration", "s");
   meter_provider->AddMetricReader(std::move(prometheus_exporter));
   auto status = grpc::OpenTelemetryPluginBuilder()
                     .SetMeterProvider(std::move(meter_provider))

examples/cpp/otel/util.cc

@@ -0,0 +1,50 @@
+//
+//
+// Copyright 2024 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.
+//
+//
+
+#ifdef BAZEL_BUILD
+#include "examples/cpp/otel/util.h"
+#else
+#include "util.h"
+#endif
+
+#include "opentelemetry/sdk/metrics/view/instrument_selector_factory.h"
+#include "opentelemetry/sdk/metrics/view/meter_selector_factory.h"
+#include "opentelemetry/sdk/metrics/view/view_factory.h"
+
+#include <grpcpp/grpcpp.h>
+
+void AddLatencyView(opentelemetry::sdk::metrics::MeterProvider* provider,
+                    const std::string& name, const std::string& unit) {
+  auto histogram_config = std::make_shared<
+      opentelemetry::sdk::metrics::HistogramAggregationConfig>();
+  histogram_config->boundaries_ = {
+      0,     0.00001, 0.00005, 0.0001, 0.0003, 0.0006, 0.0008, 0.001, 0.002,
+      0.003, 0.004,   0.005,   0.006,  0.008,  0.01,   0.013,  0.016, 0.02,
+      0.025, 0.03,    0.04,    0.05,   0.065,  0.08,   0.1,    0.13,  0.16,
+      0.2,   0.25,    0.3,     0.4,    0.5,    0.65,   0.8,    1,     2,
+      5,     10,      20,      50,     100};
+  provider->AddView(
+      opentelemetry::sdk::metrics::InstrumentSelectorFactory::Create(
+          opentelemetry::sdk::metrics::InstrumentType::kHistogram, name, unit),
+      opentelemetry::sdk::metrics::MeterSelectorFactory::Create(
+          "grpc-c++", grpc::Version(), ""),
+      opentelemetry::sdk::metrics::ViewFactory::Create(
+          name, "", unit,
+          opentelemetry::sdk::metrics::AggregationType::kHistogram,
+          std::move(histogram_config)));
+}

examples/cpp/otel/util.h

@@ -0,0 +1,31 @@
+//
+//
+// Copyright 2024 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_EXAMPLES_CPP_OTEL_UTIL_H
+#define GRPCPP_EXAMPLES_CPP_OTEL_UTIL_H
+
+#include <string>
+
+#include "opentelemetry/sdk/metrics/meter_provider.h"
+
+// Helper function that adds view for gRPC latency instrument \a name with unit
+// \a unit with bucket boundaries that are more useful for RPCs.
+void AddLatencyView(opentelemetry::sdk::metrics::MeterProvider* provider,
+                    const std::string& name, const std::string& unit);
+
+#endif  // GRPCPP_EXAMPLES_CPP_OTEL_UTIL_H