doc: Subsribe sample (#1260)

Author: mukund-ananthu

packages/google-cloud-pubsub/samples/snippets/subscriber.py

@@ -68,6 +68,94 @@ def list_subscriptions_in_project(project_id: str) -> None:
     # [END pubsub_list_subscriptions]
 
 
+def pubsub_subscribe_otel_tracing(
+    subscription_project_id: str,
+    cloud_trace_project_id: str,
+    subscription_id: str,
+    timeout: Optional[float] = None,
+) -> None:
+    """
+    Subscribe to `subscription_id` in `subscription_project_id` with OpenTelemetry enabled.
+    Export the OpenTelemetry traces to Google Cloud Trace in project
+    `trace_project_id`
+    Args:
+        subscription_project_id: project ID of the subscription.
+        cloud_trace_project_id: project ID to export Cloud Trace to.
+        subscription_id: subscription ID to subscribe from.
+        timeout: time until which to subscribe to.
+    Returns:
+        None
+    """
+    # [START pubsub_subscribe_otel_tracing]
+    from opentelemetry import trace
+    from opentelemetry.sdk.trace import TracerProvider
+    from opentelemetry.sdk.trace.export import (
+        BatchSpanProcessor,
+    )
+    from opentelemetry.exporter.cloud_trace import CloudTraceSpanExporter
+    from opentelemetry.sdk.trace.sampling import TraceIdRatioBased, ParentBased
+
+    from google.cloud import pubsub_v1
+    from google.cloud.pubsub_v1 import SubscriberClient
+    from google.cloud.pubsub_v1.types import SubscriberOptions
+
+    # TODO(developer)
+    # subscription_project_id = "your-subscription-project-id"
+    # subscription_id = "your-subscription-id"
+    # cloud_trace_project_id = "your-cloud-trace-project-id"
+    # timeout = 300.0
+
+    # In this sample, we use a Google Cloud Trace to export the OpenTelemetry
+    # traces: https://cloud.google.com/trace/docs/setup/python-ot
+    # Choose and configure the exporter for your set up accordingly.
+
+    sampler = ParentBased(root=TraceIdRatioBased(1))
+    trace.set_tracer_provider(TracerProvider(sampler=sampler))
+
+    # Export to Google Trace
+    cloud_trace_exporter = CloudTraceSpanExporter(
+        project_id=cloud_trace_project_id,
+    )
+    trace.get_tracer_provider().add_span_processor(
+        BatchSpanProcessor(cloud_trace_exporter)
+    )
+    # Set the `enable_open_telemetry_tracing` option to True when creating
+    # the subscriber client. This in itself is necessary and sufficient for
+    # the library to export OpenTelemetry traces. However, where the traces
+    # must be exported to needs to be configured based on your OpenTelemetry
+    # set up. Refer: https://opentelemetry.io/docs/languages/python/exporters/
+    subscriber = SubscriberClient(
+        subscriber_options=SubscriberOptions(enable_open_telemetry_tracing=True)
+    )
+
+    # The `subscription_path` method creates a fully qualified identifier
+    # in the form `projects/{project_id}/subscriptions/{subscription_id}`
+    subscription_path = subscriber.subscription_path(
+        subscription_project_id, subscription_id
+    )
+
+    # Define callback to be called when a message is received.
+    def callback(message: pubsub_v1.subscriber.message.Message) -> None:
+        # Ack message after processing it.
+        print(message.data)
+        message.ack()
+
+    # Wrap subscriber in a 'with' block to automatically call close() when done.
+    with subscriber:
+        try:
+            # Optimistically subscribe to messages on the subscription.
+            streaming_pull_future = subscriber.subscribe(
+                subscription_path, callback=callback
+            )
+            streaming_pull_future.result(timeout=timeout)
+        except TimeoutError:
+            print("Successfully subscribed until the timeout passed.")
+            streaming_pull_future.cancel()  # Trigger the shutdown.
+            streaming_pull_future.result()  # Block until the shutdown is complete.
+
+    # [END pubsub_subscribe_otel_tracing]
+
+
 def create_subscription(project_id: str, topic_id: str, subscription_id: str) -> None:
     """Create a new pull subscription on the given topic."""
     # [START pubsub_create_pull_subscription]