impl(pubsub-otel): add unary pull example (#301)

* impl(pubsub-otel): add unary pull example

* Update pubsub-open-telemetry/unary_pull_subscriber.cc

Co-authored-by: Carlos O'Ryan <coryan@google.com>

* Update pubsub-open-telemetry/unary_pull_subscriber.cc

Co-authored-by: Carlos O'Ryan <coryan@google.com>

---------

Co-authored-by: Carlos O'Ryan <coryan@google.com>

pubsub-open-telemetry/BUILD.bazel

@@ -67,3 +67,12 @@ cc_binary(
         "@google_cloud_cpp//:pubsub",
     ],
 )
+
+cc_binary(
+    name = "unary_pull_subscriber",
+    srcs = ["unary_pull_subscriber.cc"],
+    deps = [
+        "@google_cloud_cpp//:opentelemetry",
+        "@google_cloud_cpp//:pubsub",
+    ],
+)

pubsub-open-telemetry/CMakeLists.txt

@@ -63,3 +63,9 @@ add_executable(quickstart quickstart.cc)
 target_compile_features(quickstart PRIVATE cxx_std_14)
 target_link_libraries(quickstart PRIVATE google-cloud-cpp::pubsub
                                          google-cloud-cpp::opentelemetry)
+
+add_executable(unary_pull_subscriber unary_pull_subscriber.cc)
+target_compile_features(unary_pull_subscriber PRIVATE cxx_std_14)
+target_link_libraries(
+    unary_pull_subscriber PRIVATE google-cloud-cpp::pubsub
+                                  google-cloud-cpp::opentelemetry)

pubsub-open-telemetry/subscriber.md

@@ -0,0 +1,109 @@
+# Subscriber
+
+To try receiving a message using unary pull, run the `unary_pull_subscriber`
+application. It publishes a message to a topic and then pulls the same message
+from a subscription, and then exports the spans to cloud trace.
+
+**Note**: OTel ABI 2.0 adds the ability to add links after span creation. If an
+application is compiled with OTel ABI 2.0, it will produce different telemetery
+data. We currently do not support OTel ABI 2.0 with CMake.
+
+For setup instructions, refer to the [README.md](README.md).
+
+## Example traces
+
+To find the traces, navigate to the Cloud Trace UI.
+
+<!--- TODO(#299): Add screenshots
+#### With OTel ABI 1.0
+
+#### Receive trace
+
+![Screenshot of the receive span in the Cloud Trace UI.](assets/receive_span.png)
+
+#### Settle trace
+
+![Screenshot of the settle span in the Cloud Trace UI.](assets/settle_span.png)
+
+#### Extend trace
+
+![Screenshot of the extend span in the Cloud Trace UI.](assets/extend_span.png)
+
+#### With OTel ABI 2.0
+
+#### Receive trace
+
+![Screenshot of the receive span in the Cloud Trace UI.](assets/otel2/receive_span.png)
+
+#### Settle trace
+
+![Screenshot of the settle span in the Cloud Trace UI.](assets/otel2/settle_span.png)
+
+#### Extend trace
+
+![Screenshot of the extend span in the Cloud Trace UI.](assets/otel2/extend_span.png)
+-->
+
+### Setup
+
+### Create the Cloud Pub/Sub subscription attached to a topic
+
+If you don't already have them, create a topic and a subscription with pull
+delivery.
+
+Export the following environment variables:
+
+```sh
+export=GOOGLE_CLOUD_PROJECT=[PROJECT-ID]
+export=GOOGLE_CLOUD_SUBSCRIPTION=[SUBSCRIPTION-ID]
+export=GOOGLE_CLOUD_TOPIC=[TOPIC-ID]
+```
+
+Use the CLI to create the resources:
+
+```sh
+gcloud pubsub topics create "--project=${GOOGLE_CLOUD_PROJECT}" ${GOOGLE_CLOUD_TOPIC}
+gcloud pubsub subscriptions create "--project=${GOOGLE_CLOUD_PROJECT}" "--topic=${GOOGLE_CLOUD_TOPIC}" ${GOOGLE_CLOUD_SUBSCRIPTION}
+```
+
+### Publish a message
+
+Make sure you publish a message with tracing enabled. If not, the traces will
+not be linked.
+
+## Build and run
+
+### Using CMake and Vcpkg
+
+```sh
+cd cpp-samples/pubsub-open-telemetry
+cmake -S . -B .build -DCMAKE_TOOLCHAIN_FILE=$HOME/vcpkg/scripts/buildsystems/vcpkg.cmake -G Ninja
+cmake --build .build --target unary_pull_subscriber
+```
+
+#### Run the subscriber with the unary pull
+
+```shell
+.build/unary_pull_subscriber ${GOOGLE_CLOUD_PROJECT} ${GOOGLE_CLOUD_TOPIC} ${GOOGLE_CLOUD_SUBSCRIPTION}
+```
+
+## Build and run using Bazel
+
+### 1. Download or clone this repo
+
+```shell
+git clone https://github.com/GoogleCloudPlatform/cpp-samples
+```
+
+### 2. Compile and run these examples
+
+```shell
+cd cpp-samples/pubsub-open-telemetry
+bazel run //:unary_pull_subscriber -- ${GOOGLE_CLOUD_PROJECT} ${GOOGLE_CLOUD_TOPIC} ${GOOGLE_CLOUD_SUBSCRIPTION}
+```
+
+#### Run the example with otel ABI 2.0
+
+```shell
+bazel run --config=otel2 //:unary_pull_subscriber -- ${GOOGLE_CLOUD_PROJECT} ${GOOGLE_CLOUD_TOPIC} ${GOOGLE_CLOUD_SUBSCRIPTION}
+```

pubsub-open-telemetry/unary_pull_subscriber.cc

@@ -0,0 +1,65 @@
+// Copyright 2024 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/message.h"
+#include "google/cloud/pubsub/publisher.h"
+#include "google/cloud/pubsub/subscriber.h"
+#include "google/cloud/pubsub/subscription.h"
+#include <iostream>
+
+int main(int argc, char* argv[]) try {
+  if (argc != 4) {
+    std::cerr << "Usage: " << argv[0]
+              << " <project-id> <topic-id> <subscription-id>\n";
+    return 1;
+  }
+
+  std::string const project_id = argv[1];
+  std::string const topic_id = argv[2];
+  std::string const subscription_id = argv[3];
+
+  // Create a few namespace aliases to make the code easier to read.
+  namespace gc = ::google::cloud;
+  namespace otel = gc::otel;
+  namespace pubsub = gc::pubsub;
+
+  auto project = gc::Project(project_id);
+  auto configuration = otel::ConfigureBasicTracing(project);
+
+  // Publish a message with tracing enabled.
+  auto publisher = pubsub::Publisher(pubsub::MakePublisherConnection(
+      pubsub::Topic(project_id, topic_id),
+      gc::Options{}.set<gc::OpenTelemetryTracingOption>(true)));
+  // Block until the message is actually sent and throw on error.
+  auto id = publisher.Publish(pubsub::MessageBuilder().SetData("Hi!").Build())
+                .get()
+                .value();
+  std::cout << "Sent message with id: (" << id << ")\n";
+
+  // Receive a message using unary pull with tracing enabled.
+  auto subscriber = pubsub::Subscriber(pubsub::MakeSubscriberConnection(
+      pubsub::Subscription(project_id, subscription_id),
+      gc::Options{}.set<gc::OpenTelemetryTracingOption>(true)));
+
+  auto response = subscriber.Pull().value();
+  std::cout << "Received message " << response->message << "\n";
+  std::move(response->handler).ack();
+
+  return 0;
+} catch (google::cloud::Status const& status) {
+  std::cerr << "google::cloud::Status thrown: " << status << "\n";
+  return 1;
+}