examples/runtime_async_std.rs

use std::future::Future;
use std::pin::Pin;
use std::process;
use std::time::Duration;

use clap::{Arg, Command};
use futures::stream::StreamExt;

use rdkafka::config::ClientConfig;
use rdkafka::consumer::{Consumer, StreamConsumer};
use rdkafka::message::Message;
use rdkafka::producer::{FutureProducer, FutureRecord};
use rdkafka::util::AsyncRuntime;

use crate::example_utils::setup_logger;

mod example_utils;

pub struct AsyncStdRuntime;

impl AsyncRuntime for AsyncStdRuntime {
    type Delay = Pin<Box<dyn Future<Output = ()> + Send>>;

    fn spawn<T>(task: T)
    where
        T: Future<Output = ()> + Send + 'static,
    {
        async_std::task::spawn(task);
    }

    fn delay_for(duration: Duration) -> Self::Delay {
        Box::pin(async_std::task::sleep(duration))
    }
}

#[async_std::main]
async fn main() {
    let matches = Command::new("smol runtime example")
        .version(option_env!("CARGO_PKG_VERSION").unwrap_or(""))
        .about("Demonstrates using rust-rdkafka with a custom async runtime")
        .arg(
            Arg::new("brokers")
                .short('b')
                .long("brokers")
                .help("Broker list in kafka format")
                .default_value("localhost:9092"),
        )
        .arg(Arg::new("topic").long("topic").help("topic").required(true))
        .arg(
            Arg::new("log-conf")
                .long("log-conf")
                .help("Configure the logging format (example: 'rdkafka=trace')"),
        )
        .get_matches();

    setup_logger(true, matches.get_one("log-conf"));

    let brokers = matches.get_one::<String>("brokers").unwrap();
    let topic = matches.get_one::<String>("topic").unwrap().to_owned();

    let producer: FutureProducer<_, AsyncStdRuntime> = ClientConfig::new()
        .set("bootstrap.servers", brokers)
        .set("message.timeout.ms", "5000")
        .create()
        .expect("Producer creation error");

    let delivery_status = producer
        .send::<Vec<u8>, _, _>(
            FutureRecord::to(&topic).payload("hello from async-std"),
            Duration::from_secs(0),
        )
        .await;
    if let Err((e, _)) = delivery_status {
        eprintln!("unable to send message: {}", e);
        process::exit(1);
    }

    let consumer: StreamConsumer<_, AsyncStdRuntime> = ClientConfig::new()
        .set("bootstrap.servers", brokers)
        .set("session.timeout.ms", "6000")
        .set("enable.auto.commit", "false")
        .set("auto.offset.reset", "earliest")
        .set("group.id", "rust-rdkafka-smol-runtime-example")
        .create()
        .expect("Consumer creation failed");
    consumer.subscribe(&[&topic]).unwrap();

    let mut stream = consumer.stream();
    let message = stream.next().await;
    match message {
        Some(Ok(message)) => println!(
            "Received message: {}",
            match message.payload_view::<str>() {
                None => "",
                Some(Ok(s)) => s,
                Some(Err(_)) => "<invalid utf-8>",
            }
        ),
        Some(Err(e)) => {
            eprintln!("Error receiving message: {}", e);
            process::exit(1);
        }
        None => {
            eprintln!("Consumer unexpectedly returned no messages");
            process::exit(1);
        }
    }
}