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use std::sync::atomic::AtomicBool;
use std::sync::atomic::Ordering;
use std::sync::Arc;
use crossbeam_channel::unbounded;
use crossbeam_channel::Receiver;
use crossbeam_channel::Select;
use crossbeam_channel::Sender;
use humthreads::ErrorKind as HumthreadsErrorKind;
use humthreads::MapThread;
use humthreads::Thread;
use signal_hook::SigId;
use slog::debug;
use slog::o;
use slog::warn;
use slog::Discard;
use slog::Logger;
use replicante_util_failure::capture_fail;
use replicante_util_failure::failure_info;
/// Block the calling thread until shutdown is requested.
///
/// Shutdown is requested when:
///
/// * The process receives SIGINT.
/// * A registered thread panics.
/// * A required thread exists (optional threads are allowed to exit gracefully).
///
/// # Shutdown Flow
///
/// 1. Request all registered threads to shutdown.
/// 2. Execute all on_shutdown callbacks.
/// 3 Wait for all registered threads to exit.
///
/// Threads and handlers are iterated on in registration order.
///
/// # Signal Handling
/// When a process is sent SIGINT the shutdown flow begins.
/// The process is allowed to take as long as it wants to shutdown.
///
/// If a second SIGINT is received while the process is shutting down
/// it will instead exit immediately.
///
/// # Example
/// ```no_run
/// # use replicante_util_upkeep::Upkeep;
/// let mut up = Upkeep::new();
/// up.on_shutdown(|| println!("Bye :wave:"));
/// up.keepalive();
/// ```
pub struct Upkeep {
callbacks: Vec<Box<dyn Fn()>>,
logger: Logger,
registered_signals: Vec<SigId>,
signal_flag: Arc<AtomicBool>,
signal_receiver: Receiver<()>,
signal_sender: Option<Sender<()>>,
threads: Vec<ThreadMeta>,
}
impl Upkeep {
pub fn new() -> Upkeep {
let (signal_sender, signal_receiver) = unbounded();
let signal_sender = Some(signal_sender);
Upkeep {
callbacks: Vec::new(),
logger: Logger::root(Discard, o!()),
registered_signals: Vec::new(),
signal_flag: Arc::new(AtomicBool::new(false)),
signal_receiver,
signal_sender,
threads: Vec::new(),
}
}
/// Block the calling thread waiting for the process to shutdown.
///
/// # Returns
/// This method returns `true` if the process shuts down cleanly.
pub fn keepalive(&mut self) -> bool {
// Use crossbeam_channel::Select to poll for signals or thread exists:
//
// - Generate a Select set to wait on.
// - Use the ready API to wait (select API seems to deadlock unless with timeout).
// - When a thread joins remove it from the vector.
let mut clean_exit = true;
loop {
let mut set = self.select_set();
let index = set.ready();
match index {
0 => {
warn!(self.logger, "Shutdown: signal received");
break;
}
n => {
let thread = &self.threads[n - 1];
let paniced = match thread.handle.join() {
Ok(()) => false,
Err(error) => match error.kind() {
HumthreadsErrorKind::Join(_) => {
capture_fail!(
&error,
self.logger,
"Thread paniced";
failure_info(&error),
);
clean_exit = false;
true
}
_ => false,
},
};
if paniced {
warn!(self.logger, "Shutdown: thread paniced");
break;
}
if thread.required {
warn!(self.logger, "Shutdown: thread exited");
break;
}
}
};
// Can reach here only if an optional thread exited without a panic.
drop(set);
self.threads.remove(index - 1);
}
self.shutdown();
self.join_threads() && clean_exit
}
/// Register a callback to be executed when a shutdown request is received.
pub fn on_shutdown<F>(&mut self, callback: F)
where
F: Fn() + 'static,
{
self.callbacks.push(Box::new(callback))
}
/// Register signal handers for SIGINT and SIGTERM.
pub fn register_signal(&mut self) -> Result<(), ::std::io::Error> {
let sender = match self.signal_sender.take() {
Some(sender) => sender,
None => return Ok(()),
};
let signals = vec![signal_hook::SIGINT, signal_hook::SIGTERM];
for signal in signals.into_iter() {
let signal_flag = Arc::clone(&self.signal_flag);
let signal_sender = sender.clone();
let callback = move || {
if signal_flag.load(Ordering::Relaxed) {
::std::process::exit(1);
}
signal_flag.store(true, Ordering::Relaxed);
let _ = signal_sender.send(());
};
let signal_id = unsafe { signal_hook::register(signal, callback) }?;
self.registered_signals.push(signal_id);
}
Ok(())
}
/// Register a [`Thread`] for shutdown.
///
/// Threads are politely asked to stop work and then joined.
/// Threads MUST join for the process to exit correctly.
///
/// If a [`Thread`] registered with this function panics or exits
/// the shutdown procedure for all other threads begins.
///
/// [`Thread`]: https://docs.rs/humthreads/0.1.2/humthreads/struct.Thread.html
pub fn register_thread<T: Send + 'static>(&mut self, thread: Thread<T>) {
let thread = ThreadMeta {
handle: thread.map(|_| ()),
required: true,
};
self.threads.push(thread);
}
/// Similar to [`Upkeep::register_thread`] but clean exists do not shutdown the process.
///
/// [`Upkeep::register_thread`]: #method.register_thread
pub fn register_thread_optional<T: Send + 'static>(&mut self, thread: Thread<T>) {
let thread = ThreadMeta {
handle: thread.map(|_| ()),
required: false,
};
self.threads.push(thread);
}
/// Set the logger to be used by the `Upkeep` instance.
pub fn set_logger(&mut self, logger: Logger) {
self.logger = logger;
}
/// Wait for each thread to join.
fn join_threads(&mut self) -> bool {
debug!(self.logger, "Joining with registered threads");
let mut clean_exit = true;
for thread in self.threads.drain(..) {
if let Err(error) = thread.handle.join() {
if let HumthreadsErrorKind::JoinedAlready = error.kind() {
debug!(self.logger, "Joined thread twice");
continue;
}
capture_fail!(&error, self.logger, "Thread paniced"; failure_info(&error));
clean_exit = false;
}
}
clean_exit
}
/// Return a crossbeam_channel::Select set to wait for signals or threads.
///
/// The returned set has the following propertied:
///
/// - idx 0 == signals receiver
/// - idx n == self.threads.get(n - 1)
fn select_set<'a, 'b: 'a>(&'b self) -> Select<'a> {
let mut set = Select::new();
set.recv(&self.signal_receiver);
for thread in &self.threads {
thread.handle.select_add(&mut set);
}
set
}
/// Handle process shutdown and trigger callback notifications.
fn shutdown(&mut self) {
debug!(self.logger, "Requesting shutdowns for registered threads");
for thread in &self.threads {
thread.handle.request_shutdown();
}
debug!(self.logger, "Executing shutdown callbacks");
for callback in &self.callbacks {
callback();
}
}
}
impl Default for Upkeep {
fn default() -> Upkeep {
Upkeep::new()
}
}
impl Drop for Upkeep {
fn drop(&mut self) {
for signal in self.registered_signals.drain(..) {
signal_hook::unregister(signal);
}
}
}
struct ThreadMeta {
handle: MapThread<()>,
required: bool,
}
#[cfg(test)]
mod tests {
use std::sync::atomic::AtomicBool;
use std::sync::atomic::AtomicUsize;
use std::sync::atomic::Ordering;
use std::sync::Arc;
use std::time::Duration;
use humthreads::Builder;
use super::Upkeep;
#[test]
fn callback() {
let flag = Arc::new(AtomicBool::new(false));
let mut up = Upkeep::new();
let inner_flag = Arc::clone(&flag);
up.on_shutdown(move || inner_flag.store(true, Ordering::Relaxed));
up.shutdown();
assert_eq!(true, flag.load(Ordering::Relaxed));
}
#[test]
fn thread_optional() {
let count = Arc::new(AtomicUsize::new(0));
let inner_count = Arc::clone(&count);
let mut up = Upkeep::new();
let optional = Builder::new("thread_optional_two")
.spawn(|_| ::std::thread::sleep(Duration::from_millis(10)))
.expect("to spawn test thread");
up.register_thread_optional(optional);
let thread = Builder::new("thread_optional_one")
.spawn(move |scope| {
for _ in 0..5 {
::std::thread::sleep(Duration::from_millis(10));
if scope.should_shutdown() {
break;
}
inner_count.fetch_add(1, Ordering::Relaxed);
}
})
.expect("to spawn test thread");
up.register_thread(thread);
let clean = up.keepalive();
assert_eq!(true, clean);
assert_eq!(5, count.load(Ordering::Relaxed));
}
#[test]
fn thread_panics() {
let flag = Arc::new(AtomicBool::new(false));
let inner_flag = Arc::clone(&flag);
let mut up = Upkeep::new();
let thread = Builder::new("thread_panics")
.spawn(move |_| {
inner_flag.store(true, Ordering::Relaxed);
panic!("this panic is expected");
})
.expect("to spawn test thread");
up.register_thread(thread);
let clean = up.keepalive();
assert_eq!(true, flag.load(Ordering::Relaxed));
assert_eq!(false, clean);
}
#[test]
fn thread_shuts_down() {
let flag = Arc::new(AtomicBool::new(false));
let inner_flag = Arc::clone(&flag);
let thread = Builder::new("thread_shuts_down")
.spawn(move |scope| {
loop {
::std::thread::sleep(Duration::from_millis(10));
if scope.should_shutdown() {
break;
}
}
inner_flag.store(true, Ordering::Relaxed);
})
.expect("to spawn test thread");
let mut up = Upkeep::new();
up.register_thread(thread);
up.shutdown();
let clean = up.keepalive();
assert_eq!(true, flag.load(Ordering::Relaxed));
assert_eq!(true, clean);
}
// Tests below are commented out because they cause undefined behaviours.
// Running this test as well as other can lead to a panic from the inners of stdlib threads:
//use nix::sys::signal::kill;
//use nix::sys::signal::SIGINT;
//use nix::unistd::Pid;
//#[test]
// ```
// thread '<unnamed>' panicked at 'assertion failed: c.borrow().is_none()', src/libstd/sys_common/thread_info.rs:37:26
// test tests::signal ... ok
// stack backtrace:
// 0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
// at src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:39
// 1: std::sys_common::backtrace::_print
// at src/libstd/sys_common/backtrace.rs:70
// 2: std::panicking::default_hook::{{closure}}
// at src/libstd/sys_common/backtrace.rs:58
// at src/libstd/panicking.rs:200
// 3: std::panicking::default_hook
// at src/libstd/panicking.rs:215
// 4: std::panicking::rust_panic_with_hook
// at src/libstd/panicking.rs:478
// 5: std::panicking::begin_panic
// at src/libstd/panicking.rs:412
// 6: std::sys_common::thread_info::set
// at src/libstd/sys_common/thread_info.rs:37
// at src/libstd/thread/local.rs:300
// at src/libstd/thread/local.rs:246
// at src/libstd/sys_common/thread_info.rs:37
// 7: std::thread::Builder::spawn_unchecked::{{closure}}
// at /rustc/91856ed52c58aa5ba66a015354d1cc69e9779bdf/src/libstd/thread/mod.rs:466
// 8: <F as alloc::boxed::FnBox<A>>::call_box
// at /rustc/91856ed52c58aa5ba66a015354d1cc69e9779bdf/src/liballoc/boxed.rs:749
// 9: std::sys::unix::thread::Thread::new::thread_start
// at /rustc/91856ed52c58aa5ba66a015354d1cc69e9779bdf/src/liballoc/boxed.rs:759
// at src/libstd/sys_common/thread.rs:14
// at src/libstd/sys/unix/thread.rs:81
// 10: start_thread
// 11: clone
// fatal runtime error: failed to initiate panic, error 5
// error: process didn't exit successfully: `replicante_util_upkeep-3a7217a487d2749e` (signal: 6, SIGABRT: process abort signal)
// ```
//
// Use the below command (after un-commenting this code) to see the error:
// ```
// for i in `seq 1 100`; do RUST_BACKTRACE=1 cargo test -p replicante_util_upkeep || break; done
// ```
//fn signal() {
// let flag = Arc::new(AtomicBool::new(false));
// let mut up = Upkeep::new();
// let inner_flag = Arc::clone(&flag);
// up.register_signal().unwrap();
// up.on_shutdown(move || inner_flag.store(true, Ordering::Relaxed));
// kill(Pid::this(), SIGINT).unwrap();
// let clean = up.keepalive();
// assert_eq!(true, flag.load(Ordering::Relaxed));
// assert_eq!(true, clean);
//}
// This test aborts the entrie tests process.
// On one hand: yey it works! On the other: can't test really.
//#[test]
//fn signal_kill() {
// let mut up = Upkeep::new();
// up.register_signal().unwrap();
// kill(Pid::this(), SIGINT).unwrap();
// kill(Pid::this(), SIGINT).unwrap();
//}
}