smarm/tests/shutdown.rs

//! Graceful shutdown — `request_shutdown` (OTP `exit(Pid, shutdown)`).
//!
//! `request_stop` is `exit(Pid, kill)`: an uncatchable unwind at the target's
//! next observation point. `request_shutdown` is the polite form:
//!   - a target that is NOT trapping exits is stopped exactly as by
//!     `request_stop` (OTP's rule: don't trap, you die);
//!   - a target that IS trapping receives an `ExitSignal { reason: Shutdown }`
//!     on its trap inbox and keeps running — it is expected to wind down and
//!     exit normally on its own.

use smarm::{monitor, request_shutdown, run, self_pid, sleep, spawn, trap_exit, DownReason, Pid};
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::{mpsc, Arc};
use std::thread;
use std::time::Duration;

const WATCHDOG: Duration = Duration::from_secs(10);

#[test]
fn request_shutdown_stops_a_non_trapping_actor() {
    run(|| {
        let h = spawn(|| sleep(Duration::from_secs(3600)));
        let mon = monitor(h.pid());
        request_shutdown(h.pid());
        let down = mon.rx.recv().expect("down");
        assert_eq!(down.reason, DownReason::Stopped);
    });
}

#[test]
fn request_shutdown_is_a_message_to_a_trapping_actor() {
    let unwound = Arc::new(AtomicBool::new(false));
    let u = unwound.clone();
    run(move || {
        struct Unwound(Arc<AtomicBool>);
        impl Drop for Unwound {
            fn drop(&mut self) {
                if std::thread::panicking() {
                    self.0.store(true, Ordering::SeqCst);
                }
            }
        }
        let (tx, rx) = smarm::channel::<(Pid, DownReason)>();
        let (ready_tx, ready_rx) = smarm::channel::<()>();
        let h = spawn(move || {
            let _g = Unwound(u);
            let inbox = trap_exit();
            let _ = ready_tx.send(());
            let sig = inbox.recv().expect("exit signal");
            let _ = tx.send((sig.from, sig.reason));
            // Keep doing work after the request: shutdown is advisory.
            sleep(Duration::from_millis(20));
        });
        // Trapping is set by the target itself; a request that beats it is a
        // plain stop (same window as OTP's exit-before-process_flag).
        ready_rx.recv().expect("ready");
        let me = self_pid();
        let mon = monitor(h.pid());
        request_shutdown(h.pid());
        let (from, reason) = rx.recv().expect("relayed");
        assert_eq!(from, me);
        assert_eq!(reason, DownReason::Shutdown);
        let down = mon.rx.recv().expect("down");
        assert_eq!(
            down.reason,
            DownReason::Exit,
            "target exited normally, not stopped"
        );
    });
    assert!(
        !unwound.load(Ordering::SeqCst),
        "trapping target must not be unwound"
    );
}

#[test]
fn request_shutdown_on_dead_pid_is_a_no_op() {
    run(|| {
        let h = spawn(|| {});
        let pid = h.pid();
        let _ = h.join();
        request_shutdown(pid); // must not panic
    });
}

#[test]
fn handle_request_shutdown_from_foreign_thread() {
    let rt = smarm::init(smarm::Config::exact(2));
    let handle = rt.handle();

    let (pid_tx, pid_rx) = mpsc::channel::<Pid>();
    let requester = thread::spawn(move || {
        let pid = pid_rx.recv().expect("pid");
        thread::sleep(Duration::from_millis(50));
        handle.request_shutdown(pid);
    });

    let (done_tx, done_rx) = mpsc::channel();
    thread::spawn(move || {
        rt.run(move || {
            let (tx, rx) = smarm::channel::<DownReason>();
            let (ready_tx, ready_rx) = smarm::channel::<()>();
            let h = spawn(move || {
                let inbox = trap_exit();
                let _ = ready_tx.send(());
                let sig = inbox.recv().expect("exit signal");
                let _ = tx.send(sig.reason);
            });
            ready_rx.recv().expect("ready");
            pid_tx.send(h.pid()).expect("send pid");
            let reason = rx.recv().expect("relayed");
            assert_eq!(reason, DownReason::Shutdown);
            let _ = h.join();
        });
        let _ = done_tx.send(());
    });

    done_rx
        .recv_timeout(WATCHDOG)
        .expect("run did not return: foreign-thread request_shutdown never reached the target");
    requester.join().expect("requester thread");
}