Struct Subscriber 

pub struct Subscriber { /* private fields */ }

A Subscriber client for the Cloud Pub/Sub API.

Use this client to receive messages from a pull subscription on a topic.

Example

let client = Subscriber::builder().build().await?;
let mut stream = client
    .subscribe("projects/my-project/subscriptions/my-subscription")
    .build();
while let Some((m, h)) = stream.next().await.transpose()? {
    println!("Received message m={m:?}");
    h.ack();
}

Ordered Delivery

The subscriber returns messages in order if ordered delivery is enabled on the subscription. The client provides the same guarantees as the service.

For more details on how the service works, see:

• Considerations when using ordered delivery
• Google Cloud Pub/Sub Ordered Delivery

Exactly-once Delivery

The subscriber supports exactly-once delivery.

If you enable exactly-once delivery for a subscription, your application can be opinionated about the delivery type, by destructuring the handler into its Handler::ExactlyOnce branch.

use google_cloud_pubsub::subscriber::MessageStream;
use google_cloud_pubsub::subscriber::handler::Handler;
async fn exactly_once_stream(mut stream: MessageStream) -> anyhow::Result<()> {
  while let Some((m, Handler::ExactlyOnce(h))) = stream.next().await.transpose()? {
      println!("Received message m={m:?}");

      // Await the result of the ack. Typically you would not block the loop
      // with an `await` point like this.
      h.confirmed_ack().await?;
  }
  unreachable!("Oops, my subscription must have at-least-once semantics")
}

You should not change the delivery type of a subscription midstream. If you do, the subscriber will honor the delivery setting at the time each message was received.

Configuration

To configure a Subscriber use the with_* methods in the type returned by builder(). The default configuration should work for most applications. Common configuration changes include:

• with_endpoint(): by default this client uses the global default endpoint (https://pubsub.googleapis.com). Applications using regional endpoints or running in restricted networks (e.g. a network configured with Private Google Access with VPC Service Controls) may want to override this default.
• with_credentials(): by default this client uses Application Default Credentials. Applications using custom authentication may need to override this default.

Pooling and Cloning

Subscriber holds a connection pool internally, it is advised to create one and then reuse it. You do not need to wrap Subscriber in an Rc or Arc to reuse it, because it already uses an Arc internally.

Implementations

impl Subscriber

pub fn builder() -> ClientBuilder

Returns a builder for Subscriber.

Example

let client = Subscriber::builder().build().await?;

pub fn subscribe<T>(&self, subscription: T) -> Subscribe

where T: Into<String>,

Receive messages from a subscription.

The subscription is the full name, in the format of projects/*/subscriptions/*.

Example

let mut stream = client
    .subscribe("projects/my-project/subscriptions/my-subscription")
    .build();
while let Some((m, h)) = stream.next().await.transpose()? {
    println!("Received message m={m:?}");
    h.ack();
}

Trait Implementations

impl Clone for Subscriber

fn clone(&self) -> Subscriber

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Subscriber

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.