docs(pubsub): add exactly-once samples

src/pubsub/examples/src/lib.rs

@@ -57,6 +57,12 @@ pub async fn run_subscription_samples(
 
     subscription::delete_subscription::sample(&client, &project_id, &id).await?;
 
+    let id = random_subscription_id();
+    subscription_names.push(format!("projects/{project_id}/subscriptions/{id}"));
+    subscription::create_subscription_exactly_once::sample(&client, &project_id, topic_id, &id)
+        .await?;
+    subscriber::exactly_once::sample(&project_id, &id).await?;
+
     Ok(())
 }
 

src/pubsub/examples/src/subscriber.rs

@@ -12,5 +12,6 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+pub mod exactly_once;
 pub mod quickstart_subscriber;
 pub mod subscriber_stream;

src/pubsub/examples/src/subscriber/exactly_once.rs

@@ -0,0 +1,60 @@
+// Copyright 2026 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.
+
+// [START pubsub_subscriber_exactly_once]
+use google_cloud_pubsub::client::Subscriber;
+use google_cloud_pubsub::subscriber::handler::Handler;
+use std::time::Duration;
+
+pub async fn sample(project_id: &str, subscription_id: &str) -> anyhow::Result<()> {
+    let subscription_name = format!("projects/{project_id}/subscriptions/{subscription_id}");
+    let client = Subscriber::builder().build().await?;
+    let mut stream = client.subscribe(subscription_name).build();
+
+    // Terminate the example after 10 seconds.
+    let shutdown_token = stream.shutdown_token();
+    let shutdown = tokio::spawn(async move {
+        tokio::time::sleep(Duration::from_secs(10)).await;
+        shutdown_token.shutdown().await;
+    });
+
+    let mut tasks = Vec::new();
+    println!("Listening for messages...");
+    while let Some((m, Handler::ExactlyOnce(h))) = stream.next().await.transpose()? {
+        println!("Received message: {m:?}");
+        tasks.push(tokio::spawn(async move {
+            // We spawn a background task so that receiving the next message
+            // is not blocked on the server confirming the ack for this
+            // message.
+            //
+            // You might choose to use a work queue in your application.
+            match h.confirmed_ack().await {
+                Ok(()) => println!(
+                    "Confirmed ack for message={m:?}. The message will not be redelivered."
+                ),
+                Err(e) => println!("Failed to confirm ack for message={m:?} with error={e:?}"),
+            }
+        }));
+    }
+    shutdown.await?;
+    println!("Done listening for messages");
+
+    for t in tasks {
+        t.await?;
+    }
+    println!("Done acking messages");
+
+    Ok(())
+}
+// [END pubsub_subscriber_exactly_once]

src/pubsub/examples/src/subscription.rs

@@ -13,5 +13,6 @@
 // limitations under the License.
 
 pub mod create_pull_subscription;
+pub mod create_subscription_exactly_once;
 pub mod delete_subscription;
 pub mod list_subscriptions;

src/pubsub/examples/src/subscription/create_subscription_exactly_once.rs

@@ -0,0 +1,38 @@
+// Copyright 2026 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.
+
+// [START pubsub_create_subscription_with_exactly_once_delivery]
+use google_cloud_pubsub::client::SubscriptionAdmin;
+
+pub async fn sample(
+    client: &SubscriptionAdmin,
+    project_id: &str,
+    topic_id: &str,
+    subscription_id: &str,
+) -> anyhow::Result<()> {
+    let subscription_name = format!("projects/{project_id}/subscriptions/{subscription_id}");
+    let topic_name = format!("projects/{project_id}/topics/{topic_id}");
+
+    let subscription = client
+        .create_subscription()
+        .set_name(subscription_name)
+        .set_topic(topic_name)
+        .set_enable_exactly_once_delivery(true)
+        .send()
+        .await?;
+
+    println!("successfully created subscription {subscription:?}");
+    Ok(())
+}
+// [END pubsub_create_subscription_with_exactly_once_delivery]