feat(pubsub-open-telemetry): add quickstart example

pubsub-open-telemetry/.bazelrc

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+# Copyright 2023 Google LLC
+#
+# 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
+#
+#     https://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.
+
+# To workaround a bug in Bazel [1], gRPC requires this flag on macOS builds,
+# and there is (AFAIK) no way to "inherit" their definitions.
+#   [1]: https://github.com/bazelbuild/bazel/issues/4341
+build --copt=-DGRPC_BAZEL_BUILD
+
+# Use host-OS-specific config lines from bazelrc files.
+build --enable_platform_specific_config=true
+
+# The project requires C++ >= 14. By default Bazel adds `-std=c++0x` which
+# disables C++14 features, even if the compilers defaults to C++ >= 14
+build:linux --cxxopt=-std=c++14
+build:macos --cxxopt=-std=c++14
+
+# Do not create the convenience links. They are inconvenient when the build
+# runs inside a docker image.
+build --experimental_convenience_symlinks=ignore
+
+# Enable OpenTelemetry tracing instrumentation for google-cloud-cpp.
+build --@io_opentelemetry_cpp//api:with_abseil
+build --@google_cloud_cpp//:enable_opentelemetry

pubsub-open-telemetry/BUILD.bazel

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+# Copyright 2023 Google LLC
+#
+# 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
+#
+#     https://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.
+
+package(default_visibility = ["//visibility:private"])
+
+licenses(["notice"])  # Apache 2.0
+
+cc_binary(
+    name = "quickstart",
+    srcs = ["quickstart.cc"],
+      deps = [
+        "@google_cloud_cpp//:opentelemetry",
+        "@google_cloud_cpp//:pubsub",
+    ],
+)

pubsub-open-telemetry/CMakeLists.txt

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+# ~~~
+# Copyright 2023 Google LLC
+#
+# 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.
+# ~~~
+
+cmake_minimum_required(VERSION 3.20)
+
+# Define the project name and where to report bugs.
+set(PACKAGE_BUGREPORT
+    "https://github.com/GoogleCloudPlatform/cpp-samples/issues")
+project(pubsub-open-telemetry CXX)
+
+find_package(google_cloud_cpp_pubsub CONFIG REQUIRED)
+find_package(google_cloud_cpp_opentelemetry CONFIG REQUIRED)
+find_package(google_cloud_cpp_trace CONFIG REQUIRED)
+
+add_executable(quickstart quickstart.cc)
+target_compile_features(quickstart PRIVATE cxx_std_20)
+target_link_libraries(
+    quickstart PRIVATE google-cloud-cpp::pubsub google-cloud-cpp::opentelemetry
+                       google-cloud-cpp::trace)
+
+include(GNUInstallDirs)
+install(TARGETS quickstart RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})

pubsub-open-telemetry/README.md

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+# Enabling Open Telemetry for the Pub/Sub library with Cloud Trace
+
+## Overview
+
+In v2.16, we GA'd [OpenTelemetry tracing](https://github.com/googleapis/google-cloud-cpp/blob/v2.16.0/CHANGELOG.md#v2160---2023-10). This provides basic instrumentation for all the google-cloud-cpp libraries. 
+
+In v2.19 release[^1], we added instrumentation for the Google Cloud Pub/Sub C++ library on the Publish side. This example provides a basic tracing application that exports spans to Cloud Trace.
+
+[^1]: The [telemetry data](https://github.com/googleapis/google-cloud-cpp/blob/main/doc/public-api.md#telemetry-data) emitted by the google-cloud-cpp library does not follow any versioning guarentees and is subject to change without notice in later versions.
+
+## Prerequisites
+
+### 1. Create a project in the Google Cloud Platform Console 
+
+If you haven't already created a project, create one now.
+
+Projects enable you to manage all Google Cloud Platform resources for your app, including deployment, access control, billing, and services.
+
+1. Open the [Cloud Platform Console](https://console.cloud.google.com/).
+2. In the drop-down menu at the top, select Create a project.
+3. Give your project a name.
+4. Make a note of the project ID, which might be different from the project name. The project ID is used in commands and in configurations.
+
+### 2. Enable billing for your project
+If you haven't already enabled billing for your
+project, [enable billing now](https://console.cloud.google.com/project/_/settings). Enabling billing allows the
+application to consume billable resources such as Pub/Sub API calls.
+
+See [Cloud Platform Console Help](https://support.google.com/cloud/answer/6288653) for more information about billing
+settings.
+
+### 3. Enable APIs for your project
+[Click here](https://console.cloud.google.com/flows/enableapi?apiid=speech&showconfirmation=true) to visit Cloud
+Platform Console and enable the Pub/Sub and Trace API via the UI.
+
+Or use the CLI:
+
+```
+gcloud services enable trace.googleapis.com 
+gcloud services enable pubsub.googleapis.com 
+```
+
+### 4. If needed, override the Billing Project
+
+If you are using a [user account] for authentication, you need to set the `GOOGLE_CLOUD_CPP_USER_PROJECT`
+environment variable to the project you created in the previous step. Be aware that you must have
+`serviceusage.services.use` permission on the project.  Alternatively, use a service account as described next.
+
+[user account]: https://cloud.google.com/docs/authentication#principals 
+
+#### Download service account credentials
+
+These samples can use service accounts for authentication.
+
+ 1. Visit the [Cloud Console](http://cloud.google.com/console), and navigate to:
+    `API Manager > Credentials > Create credentials > Service account key`
+ 2. Under **Service account**, select `New service account`.
+ 3. Under **Service account name**, enter a service account name of your choosing. For example, `transcriber`.
+ 4. Under **Role**, select `Project > Owner`.
+ 5. Under **Key type**, leave `JSON` selected.
+ 6. Click **Create** to create a new service account, and download the json credentials file.
+ 7. Set the `GOOGLE_APPLICATION_CREDENTIALS` environment variable to point to your downloaded service account
+    credentials:
+    ```
+    export GOOGLE_APPLICATION_CREDENTIALS=/path/to/your/credentials-key.json
+    ```
+See the [Cloud Platform Auth Guide](https://cloud.google.com/docs/authentication#developer_workflow) for more
+information.
+
+### 5. Create the Cloud Pub/Sub topic
+
+```sh
+export=GOOGLE_CLOUD_PROJECT=<project-id>
+export=GOOGLE_CLOUD_TOPIC=<topic-id>
+gcloud pubsub topics create "--project=${GOOGLE_CLOUD_PROJECT}" ${GOOGLE_CLOUD_TOPIC}
+```
+
+## Build and run using CMake and Vcpkg
+### 1. Install vcpkg
+This project uses [`vcpkg`](https://github.com/microsoft/vcpkg) for dependency management. Clone the vcpkg repository
+to your preferred location. In these instructions we use`$HOME`:
+```shell
+git clone -C $HOME https://github.com/microsoft/vcpkg.git
+cd $HOME/vcpkg
+./vcpkg install google-cloud-cpp
+```
+
+### 2. Download or clone this repo
+
+```shell
+git clone https://github.com/GoogleCloudPlatform/cpp-samples
+```
+
+### 3. Compile these examples
+
+Use the `vcpkg` toolchain file to download and compile dependencies. This file would be in the directory you
+cloned `vcpkg` into, `$HOME/vcpkg` if you are following the instructions to the letter. Note that building all the
+dependencies can take up to an hour, depending on the performance of your workstation. These dependencies are cached,
+so a second build should be substantially faster.
+```sh
+cd cpp-samples/pubsub-open-telemetry
+cmake -S . -B .build -DCMAKE_TOOLCHAIN_FILE=$HOME/vcpkg/scripts/buildsystems/vcpkg.cmake -G Ninja
+cmake --build .build
+```
+
+### 4. Run the examples
+
+```shell
+.build/quickstart [project-name] [topic-id]
+```
+
+## Build and run using Bazel
+
+### 1. Download or clone this repo
+
+```shell
+git clone https://github.com/GoogleCloudPlatform/cpp-samples
+```
+
+### 2. Compile these examples
+
+```shell
+cd cpp-samples/pubsub-open-telemetry
+bazel build //:quickstart
+```
+
+### 3. Run these examples
+
+```shell
+ bazel run //:quickstart [project-name] [topic-id]
+```
+
+#### Run with a local version of google-cloud-cpp
+
+```shell
+bazel run //:quickstart --override_repository=google_cloud_cpp=$HOME/your-path-to-the-repo/google-cloud-cpp -- [project-name] [topic-id] 
+```
+
+## Platform Specific Notes
+
+### macOS
+
+gRPC [requires][grpc-roots-pem-bug] an environment variable to configure the
+trust store for SSL certificates, you can download and configure this using:
+
+```bash
+curl -Lo roots.pem https://pki.google.com/roots.pem
+export GRPC_DEFAULT_SSL_ROOTS_FILE_PATH="$PWD/roots.pem"
+```
+
+### Windows
+
+gRPC [requires][grpc-roots-pem-bug] an environment variable to configure the
+trust store for SSL certificates, you can download and configure this using:
+
+```console
+@powershell -NoProfile -ExecutionPolicy unrestricted -Command ^
+    (new-object System.Net.WebClient).Downloadfile( ^
+        'https://pki.google.com/roots.pem', 'roots.pem')
+set GRPC_DEFAULT_SSL_ROOTS_FILE_PATH=%cd%\roots.pem
+```
+
+[grpc-roots-pem-bug]: https://github.com/grpc/grpc/issues/16571
+[choco-cmake-link]: https://chocolatey.org/packages/cmake
+[homebrew-cmake-link]: https://formulae.brew.sh/formula/cmake
+[cmake-download-link]: https://cmake.org/download/

pubsub-open-telemetry/WORKSPACE.bazel

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+# Copyright 2023 Google LLC
+#
+# 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
+#
+#     https://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.
+
+workspace(name = "pubsub-open-telemetery")
+
+# Google Cloud Cpp
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+http_archive(
+    name = "google_cloud_cpp",
+    sha256 = "7ca7f583b60d2aa1274411fed3b9fb3887119b2e84244bb3fc69ea1db819e4e5",
+    strip_prefix = "google-cloud-cpp-2.16.0",
+    url = "https://github.com/googleapis/google-cloud-cpp/archive/v2.16.0.tar.gz",
+)
+
+load("@google_cloud_cpp//bazel:google_cloud_cpp_deps.bzl", "google_cloud_cpp_deps")
+google_cloud_cpp_deps()
+load("@com_google_googleapis//:repository_rules.bzl", "switched_rules_by_language")
+switched_rules_by_language(
+    name = "com_google_googleapis_imports",
+    cc = True,
+    grpc = True,
+)
+load("@com_github_grpc_grpc//bazel:grpc_deps.bzl", "grpc_deps")
+grpc_deps()
+load("@com_github_grpc_grpc//bazel:grpc_extra_deps.bzl", "grpc_extra_deps")
+grpc_extra_deps()

pubsub-open-telemetry/quickstart.cc

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+// Copyright 2023 Google LLC
+//
+// 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
+//
+// https://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.
+
+#include "google/cloud/opentelemetry/configure_basic_tracing.h"
+#include "google/cloud/opentelemetry_options.h"
+#include "google/cloud/pubsub/publisher.h"
+#include <iostream>
+#include <string_view>
+
+// Create a few namespace aliases to make the code easier to read.
+namespace gc = ::google::cloud;
+namespace pubsub = gc::pubsub;
+namespace otel = gc::otel;
+
+int main(int argc, char* argv[]) try {
+  if (argc != 3) {
+    std::cerr << "Usage: " << argv[0] << " <project-id> <topic-id>\n";
+    return 1;
+  }
+  std::string const project_id = argv[1];
+  std::string const topic_id = argv[2];
+  auto project = gc::Project(project_id);
+
+  //! [START pubsub_publish_otel_tracing]
+  auto configuration = otel::ConfigureBasicTracing(project);
+  auto publisher = pubsub::Publisher(pubsub::MakePublisherConnection(
+      pubsub::Topic(project_id, topic_id),
+      gc::Options{}.set<gc::OpenTelemetryTracingOption>(true)));
+
+  std::vector<gc::future<void>> ids;
+  for (int i = 0; i < 5; i++) {
+    auto id = publisher.Publish(pubsub::MessageBuilder().SetData("Hi!").Build())
+                  .then([](gc::future<gc::StatusOr<std::string>> f) {
+                    auto status = f.get();
+                    if (!status) {
+                      std::cout << "Error in publish: " << status.status()
+                                << "\n";
+                      return;
+                    }
+                    std::cout << "Sent message with id: (" << *status << ")\n";
+                  });
+    ids.push_back(std::move(id));
+  }
+  // Block until they are actually sent.
+  for (auto& id : ids) id.get();
+  //! [END pubsub_publish_otel_tracing]
+
+  return 0;
+} catch (google::cloud::Status const& status) {
+  std::cerr << "google::cloud::Status thrown: " << status << "\n";
+  return 1;
+}

pubsub-open-telemetry/vcpkg.json

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+{
+  "name": "gcp-cpp-samples-pubsub-open-telemetry-publisher",
+  "version-string": "unversioned",
+  "homepage": "https://github.com/GoogleCloudPlatform/cpp-samples/",
+  "description": "An example using Open Telemetry and the Pub/Sub library",
+  "dependencies": [
+    {
+      "name": "google-cloud-cpp",
+      "features": [
+        "pubsub",
+        "trace",
+        "opentelemetry"
+      ]
+    }
+  ]
+}