Multithread HTTP server with crossbeam

crossbeam_http_server.rs

// Try with
// RUST_LOG=debug cargo run
// [dependencies]
// crossbeam = "0.8.1"
// crossbeam-utils = "0.8.10"
// crossbeam-channel = "0.5"
// log = "0.4.17"
// env_logger = "0.9.0"

use crossbeam;
use crossbeam_utils::atomic::AtomicCell;
use log::{debug, info};
use std::fmt::Error;
use std::io::{BufRead, BufReader, Write};
use std::net::{Ipv4Addr, SocketAddrV4, TcpListener, TcpStream};

fn handle_connection(mut tcp_stream: TcpStream) {
    let socket_addr = tcp_stream.peer_addr().unwrap();

    let mut reader = BufReader::new(&tcp_stream);
    let mut buf = String::new();
    reader.read_line(&mut buf).unwrap();

    let contents = "Hello darkness!";
    let response = format!(
        "{}\r\nContent-Length: {}\r\n\r\n{}",
        "HTTP/1.1 200 OK",
        contents.len(),
        contents
    );

    debug!(
        "Remote address:\n{}\nRequest:\n{}\nResponse:\n{}\n",
        socket_addr.to_string(),
        buf,
        response
    );
    tcp_stream.write(response.as_bytes()).unwrap();
    tcp_stream.flush().unwrap();
}

fn main() -> Result<(), Error> {
    env_logger::init();

    let loopback = "127.0.0.1".parse::<Ipv4Addr>().unwrap();
    let socket = SocketAddrV4::new(loopback, 8080);
    let listener = TcpListener::bind(socket).unwrap();
    let port = listener.local_addr().unwrap();
    info!("Listening on: {}", port);

    const THREAD_THRESHOLD: u32 = 10;
    let thread_count = AtomicCell::new(THREAD_THRESHOLD);
    thread_count.store(0);

    crossbeam::scope(|s| loop {
        if thread_count.load() < 10 {
            for stream in listener.incoming() {
                s.spawn(|_| {
                    thread_count.store(thread_count.load() + 1);
                    info!("Activated thread: {}", thread_count.load());
                    handle_connection(stream.unwrap());
                    thread_count.store(thread_count.load() - 1);
                });
            }
        }
    })
    .unwrap();
    Ok(())
}