Rust: example of using channels to communicate between threads (mutiple producers, single consumer)

main.rs

use std::sync::mpsc::channel;

use chrono::{DateTime, Local};
use threadpool::ThreadPool;

#[derive(Debug)]
struct Site {
    id: String,
    url: String,
    changed: Option<bool>,
    changed_date: Option<DateTime<Local>>
}

#[derive(Debug)]
struct Group {
    ids: Vec<String>,
    changed: Option<bool>,
    changed_date: Option<DateTime<Local>>
}

#[derive(Debug)]
struct Plan {
    sites: Vec<Site>,
    groups: Vec<Group>
}


fn main() {
    let pool = ThreadPool::new(4);

    let mut plan = Plan {
        sites: vec![
            Site { id: "1qwe".to_string(), url: "http 1".to_string(), changed: None, changed_date: None },
            Site { id: "3sdf".to_string(), url: "http 2".to_string(), changed: None, changed_date: None },
            Site { id: "4321".to_string(), url: "http 3".to_string(), changed: None, changed_date: None },
        ],
        groups: vec![
            Group { ids: vec!["1qwe".to_string(), "4321".to_string()], changed: None, changed_date: None }
        ]
    };
    let n_sites = plan.sites.len();

    let (tx, rx) = channel();

    for mut site in plan.sites.into_iter() {
        let _tx = tx.clone();
        pool.execute(move || {

            /* some heavy work to determine if website has changed */
            let changed = true;

            if changed {
                site.changed = Option::from(true);
                site.changed_date = Option::from(Local::now());
            }
            _tx.send(site).unwrap();
        });
    }

    plan.sites = rx.iter()
        .take(n_sites)
        .collect();

    println!("{:?}", plan);
}