pull messages from Google PubSub using rust

main.rs

use google_pubsub1::{api::AcknowledgeRequest, Pubsub};
use std::fs::File;
use std::io::BufReader;
use yup_oauth2::ServiceAccountKey;

static SUBSCRIPTION_PATH: &'static str =
    "projects/PROJECT_ID/subscriptions/SUBSCRIPTION";
static ACCOUNT_KEY = &'static str = "YOUR_ACCOUNT_KEY.json";

#[tokio::main]
async fn main() {
    let file = std::fs::File::open(ACCOUNT_KEY).unwrap();
    let buffer = std::io::BufReader::new(file);

    let account_key =
        serde_json::from_reader::<BufReader<File>, ServiceAccountKey>(buffer).unwrap();

    let auth = yup_oauth2::ServiceAccountAuthenticator::builder(account_key)
        .build()
        .await
        .unwrap();

    let hub = Pubsub::new(
        hyper::Client::builder().build(hyper_rustls::HttpsConnector::with_native_roots()),
        auth,
    );

    let mut pull_req = google_pubsub1::api::PullRequest::default();
    pull_req.max_messages = Some(1);

    let (_, messages) = hub
        .projects()
        .subscriptions_pull(pull_req, SUBSCRIPTION_PATH)
        .doit()
        .await
        .unwrap();

    if let Some(messages) = messages.received_messages {
        println!("pulled {} messages", messages.len());

        let ack_ids = messages
            .into_iter()
            .flat_map(|m| m.ack_id)
            .collect::<Vec<String>>();

        if ack_ids.len() > 0 {
            let mut ack_req = AcknowledgeRequest::default();
            ack_req.ack_ids = Some(ack_ids);

            let _ack_res = hub
                .projects()
                .subscriptions_acknowledge(ack_req, SUBSCRIPTION_PATH)
                .doit()
                .await
                .unwrap();

            println!("ACKd messages");
        }
    } else {
        println!("no messages available to pull");
    }

    println!("exiting");
}