rust - 如何同时运行包含借来的TcpStream的 future ？

Question

我正在尝试使此代码段同时运行，而不是顺序运行，因为对等点的数量可能很大。我正在使用async_std 1.4和rust 1.41

pub struct Peer {
    pub peer_id: String,
    pub tcp_stream: Arc<TcpStream>,
    pub public_key: [u8; 32],
}

async fn send_to_all_peers(message: Protocol, peers: &HashMap<String,Peer>) -> Result<()> {
    for peer in peers.values() {
        let mut stream = &*peer.tcp_stream;
        stream.write_all(&bincode::serialize(&message)?).await?;
    }
    Ok(())
}

我尝试使用 futures::future::join_all方法没有任何运气，因为包装在 async_std::task::spawn中创建和使用的将来需要一个静态生命期。这是我尝试过的:

async fn send_to_all_peers(message: Protocol, peers: &HashMap<String,Peer>) {
    let handles = peers.values().into_iter().map(|peer| {
        task::spawn(
            async {
                let mut stream = &*peer.tcp_stream;
                if let Err(err) = stream
                    .write_all(&bincode::serialize(&message).unwrap())
                    .await
                {
                    error!("Error when writing to tcp_stream: {}", err);
                }
            }
        )
    });
    futures::future::join_all(handles).await;
}

我确定我缺少某种方法，谢谢您的帮助!

Answer 1

由于您尝试同时发送消息，因此每个任务都必须拥有自己的消息副本:

use async_std::{task, net::TcpStream};
use futures::{future, io::AsyncWriteExt};
use serde::Serialize;
use std::{
    collections::HashMap,
    error::Error,
    sync::Arc,
};

pub struct Peer {
    pub peer_id: String,
    pub tcp_stream: Arc<TcpStream>,
    pub public_key: [u8; 32],
}

#[derive(Serialize)]
struct Protocol;

async fn send_to_all_peers(
    message: Protocol,
    peers: &HashMap<String, Peer>)
    -> Result<(), Box<dyn Error>>
{
    let msg = bincode::serialize(&message)?;
    let handles = peers.values()
        .map(|peer| {
            let msg = msg.clone();
            let socket = peer.tcp_stream.clone();
            task::spawn(async move {
                let mut socket = &*socket;
                socket.write_all(&msg).await
            })
        });

    future::try_join_all(handles).await?;
    Ok(())
}