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use std::{
future::Future,
io, mem,
num::NonZeroUsize,
pin::Pin,
rc::Rc,
sync::{
atomic::{AtomicUsize, Ordering},
Arc,
},
task::{Context, Poll},
time::Duration,
};
use actix_rt::{
spawn,
time::{sleep, Instant, Sleep},
Arbiter, ArbiterHandle, System,
};
use futures_core::{future::LocalBoxFuture, ready};
use tokio::sync::{
mpsc::{unbounded_channel, UnboundedReceiver, UnboundedSender},
oneshot,
};
use tracing::{error, info, trace};
use crate::{
service::{BoxedServerService, InternalServiceFactory},
socket::MioStream,
waker_queue::{WakerInterest, WakerQueue},
};
/// Stop worker message. Returns `true` on successful graceful shutdown
/// and `false` if some connections still alive when shutdown execute.
pub(crate) struct Stop {
graceful: bool,
tx: oneshot::Sender<bool>,
}
#[derive(Debug)]
pub(crate) struct Conn {
pub io: MioStream,
pub token: usize,
}
/// Create accept and server worker handles.
fn handle_pair(
idx: usize,
conn_tx: UnboundedSender<Conn>,
stop_tx: UnboundedSender<Stop>,
counter: Counter,
) -> (WorkerHandleAccept, WorkerHandleServer) {
let accept = WorkerHandleAccept {
idx,
conn_tx,
counter,
};
let server = WorkerHandleServer { idx, stop_tx };
(accept, server)
}
/// counter: Arc<AtomicUsize> field is owned by `Accept` thread and `ServerWorker` thread.
///
/// `Accept` would increment the counter and `ServerWorker` would decrement it.
///
/// # Atomic Ordering:
///
/// `Accept` always look into it's cached `Availability` field for `ServerWorker` state.
/// It lazily increment counter after successful dispatching new work to `ServerWorker`.
/// On reaching counter limit `Accept` update it's cached `Availability` and mark worker as
/// unable to accept any work.
///
/// `ServerWorker` always decrement the counter when every work received from `Accept` is done.
/// On reaching counter limit worker would use `mio::Waker` and `WakerQueue` to wake up `Accept`
/// and notify it to update cached `Availability` again to mark worker as able to accept work again.
///
/// Hence, a wake up would only happen after `Accept` increment it to limit.
/// And a decrement to limit always wake up `Accept`.
#[derive(Clone)]
pub(crate) struct Counter {
counter: Arc<AtomicUsize>,
limit: usize,
}
impl Counter {
pub(crate) fn new(limit: usize) -> Self {
Self {
counter: Arc::new(AtomicUsize::new(1)),
limit,
}
}
/// Increment counter by 1 and return true when hitting limit
#[inline(always)]
pub(crate) fn inc(&self) -> bool {
self.counter.fetch_add(1, Ordering::Relaxed) != self.limit
}
/// Decrement counter by 1 and return true if crossing limit.
#[inline(always)]
pub(crate) fn dec(&self) -> bool {
self.counter.fetch_sub(1, Ordering::Relaxed) == self.limit
}
pub(crate) fn total(&self) -> usize {
self.counter.load(Ordering::SeqCst) - 1
}
}
pub(crate) struct WorkerCounter {
idx: usize,
inner: Rc<(WakerQueue, Counter)>,
}
impl Clone for WorkerCounter {
fn clone(&self) -> Self {
Self {
idx: self.idx,
inner: self.inner.clone(),
}
}
}
impl WorkerCounter {
pub(crate) fn new(idx: usize, waker_queue: WakerQueue, counter: Counter) -> Self {
Self {
idx,
inner: Rc::new((waker_queue, counter)),
}
}
#[inline(always)]
pub(crate) fn guard(&self) -> WorkerCounterGuard {
WorkerCounterGuard(self.clone())
}
fn total(&self) -> usize {
self.inner.1.total()
}
}
pub(crate) struct WorkerCounterGuard(WorkerCounter);
impl Drop for WorkerCounterGuard {
fn drop(&mut self) {
let (waker_queue, counter) = &*self.0.inner;
if counter.dec() {
waker_queue.wake(WakerInterest::WorkerAvailable(self.0.idx));
}
}
}
/// Handle to worker that can send connection message to worker and share the availability of worker
/// to other threads.
///
/// Held by [Accept](crate::accept::Accept).
pub(crate) struct WorkerHandleAccept {
idx: usize,
conn_tx: UnboundedSender<Conn>,
counter: Counter,
}
impl WorkerHandleAccept {
#[inline(always)]
pub(crate) fn idx(&self) -> usize {
self.idx
}
#[inline(always)]
pub(crate) fn send(&self, conn: Conn) -> Result<(), Conn> {
self.conn_tx.send(conn).map_err(|msg| msg.0)
}
#[inline(always)]
pub(crate) fn inc_counter(&self) -> bool {
self.counter.inc()
}
}
/// Handle to worker than can send stop message to worker.
///
/// Held by [ServerBuilder](crate::builder::ServerBuilder).
#[derive(Debug)]
pub(crate) struct WorkerHandleServer {
pub(crate) idx: usize,
stop_tx: UnboundedSender<Stop>,
}
impl WorkerHandleServer {
pub(crate) fn stop(&self, graceful: bool) -> oneshot::Receiver<bool> {
let (tx, rx) = oneshot::channel();
let _ = self.stop_tx.send(Stop { graceful, tx });
rx
}
}
/// Service worker.
///
/// Worker accepts Socket objects via unbounded channel and starts stream processing.
pub(crate) struct ServerWorker {
// UnboundedReceiver<Conn> should always be the first field.
// It must be dropped as soon as ServerWorker dropping.
conn_rx: UnboundedReceiver<Conn>,
stop_rx: UnboundedReceiver<Stop>,
counter: WorkerCounter,
services: Box<[WorkerService]>,
factories: Box<[Box<dyn InternalServiceFactory>]>,
state: WorkerState,
shutdown_timeout: Duration,
}
struct WorkerService {
factory_idx: usize,
status: WorkerServiceStatus,
service: BoxedServerService,
}
impl WorkerService {
fn created(&mut self, service: BoxedServerService) {
self.service = service;
self.status = WorkerServiceStatus::Unavailable;
}
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum WorkerServiceStatus {
Available,
Unavailable,
Failed,
Restarting,
Stopping,
Stopped,
}
impl Default for WorkerServiceStatus {
fn default() -> Self {
Self::Unavailable
}
}
/// Config for worker behavior passed down from server builder.
#[derive(Debug, Clone, Copy)]
pub(crate) struct ServerWorkerConfig {
shutdown_timeout: Duration,
max_blocking_threads: usize,
max_concurrent_connections: usize,
}
impl Default for ServerWorkerConfig {
fn default() -> Self {
let parallelism = std::thread::available_parallelism().map_or(2, NonZeroUsize::get);
// 512 is the default max blocking thread count of a Tokio runtime.
let max_blocking_threads = std::cmp::max(512 / parallelism, 1);
Self {
shutdown_timeout: Duration::from_secs(30),
max_blocking_threads,
max_concurrent_connections: 25600,
}
}
}
impl ServerWorkerConfig {
pub(crate) fn max_blocking_threads(&mut self, num: usize) {
self.max_blocking_threads = num;
}
pub(crate) fn max_concurrent_connections(&mut self, num: usize) {
self.max_concurrent_connections = num;
}
pub(crate) fn shutdown_timeout(&mut self, dur: Duration) {
self.shutdown_timeout = dur;
}
}
impl ServerWorker {
pub(crate) fn start(
idx: usize,
factories: Vec<Box<dyn InternalServiceFactory>>,
waker_queue: WakerQueue,
config: ServerWorkerConfig,
) -> io::Result<(WorkerHandleAccept, WorkerHandleServer)> {
trace!("starting server worker {}", idx);
let (tx1, conn_rx) = unbounded_channel();
let (tx2, stop_rx) = unbounded_channel();
let counter = Counter::new(config.max_concurrent_connections);
let pair = handle_pair(idx, tx1, tx2, counter.clone());
// get actix system context if it is set
let actix_system = System::try_current();
// get tokio runtime handle if it is set
let tokio_handle = tokio::runtime::Handle::try_current().ok();
// service factories initialization channel
let (factory_tx, factory_rx) = std::sync::mpsc::sync_channel::<io::Result<()>>(1);
// outline of following code:
//
// if system exists
// if uring enabled
// start arbiter using uring method
// else
// start arbiter with regular tokio
// else
// if uring enabled
// start uring in spawned thread
// else
// start regular tokio in spawned thread
// every worker runs in it's own thread and tokio runtime.
// use a custom tokio runtime builder to change the settings of runtime.
match (actix_system, tokio_handle) {
(None, None) => {
panic!("No runtime detected. Start a Tokio (or Actix) runtime.");
}
// no actix system
(None, Some(rt_handle)) => {
std::thread::Builder::new()
.name(format!("actix-server worker {}", idx))
.spawn(move || {
let (worker_stopped_tx, worker_stopped_rx) = oneshot::channel();
// local set for running service init futures and worker services
let ls = tokio::task::LocalSet::new();
// init services using existing Tokio runtime (so probably on main thread)
let services = rt_handle.block_on(ls.run_until(async {
let mut services = Vec::new();
for (idx, factory) in factories.iter().enumerate() {
match factory.create().await {
Ok((token, svc)) => services.push((idx, token, svc)),
Err(err) => {
error!("can not start worker: {:?}", err);
return Err(io::Error::new(
io::ErrorKind::Other,
format!("can not start server service {}", idx),
));
}
}
}
Ok(services)
}));
let services = match services {
Ok(services) => {
factory_tx.send(Ok(())).unwrap();
services
}
Err(err) => {
factory_tx.send(Err(err)).unwrap();
return;
}
};
let worker_services = wrap_worker_services(services);
let worker_fut = async move {
// spawn to make sure ServerWorker runs as non boxed future.
spawn(async move {
ServerWorker {
conn_rx,
stop_rx,
services: worker_services.into_boxed_slice(),
counter: WorkerCounter::new(idx, waker_queue, counter),
factories: factories.into_boxed_slice(),
state: WorkerState::default(),
shutdown_timeout: config.shutdown_timeout,
}
.await;
// wake up outermost task waiting for shutdown
worker_stopped_tx.send(()).unwrap();
});
worker_stopped_rx.await.unwrap();
};
#[cfg(all(target_os = "linux", feature = "io-uring"))]
{
// TODO: pass max blocking thread config when tokio-uring enable configuration
// on building runtime.
let _ = config.max_blocking_threads;
tokio_uring::start(worker_fut);
}
#[cfg(not(all(target_os = "linux", feature = "io-uring")))]
{
let rt = tokio::runtime::Builder::new_current_thread()
.enable_all()
.max_blocking_threads(config.max_blocking_threads)
.build()
.unwrap();
rt.block_on(ls.run_until(worker_fut));
}
})
.expect("cannot spawn server worker thread");
}
// with actix system
(Some(_sys), _) => {
#[cfg(all(target_os = "linux", feature = "io-uring"))]
let arbiter = {
// TODO: pass max blocking thread config when tokio-uring enable configuration
// on building runtime.
let _ = config.max_blocking_threads;
Arbiter::new()
};
#[cfg(not(all(target_os = "linux", feature = "io-uring")))]
let arbiter = {
Arbiter::with_tokio_rt(move || {
tokio::runtime::Builder::new_current_thread()
.enable_all()
.max_blocking_threads(config.max_blocking_threads)
.build()
.unwrap()
})
};
arbiter.spawn(async move {
// spawn_local to run !Send future tasks.
spawn(async move {
let mut services = Vec::new();
for (idx, factory) in factories.iter().enumerate() {
match factory.create().await {
Ok((token, svc)) => services.push((idx, token, svc)),
Err(err) => {
error!("can not start worker: {:?}", err);
Arbiter::current().stop();
factory_tx
.send(Err(io::Error::new(
io::ErrorKind::Other,
format!("can not start server service {}", idx),
)))
.unwrap();
return;
}
}
}
factory_tx.send(Ok(())).unwrap();
let worker_services = wrap_worker_services(services);
// spawn to make sure ServerWorker runs as non boxed future.
spawn(ServerWorker {
conn_rx,
stop_rx,
services: worker_services.into_boxed_slice(),
counter: WorkerCounter::new(idx, waker_queue, counter),
factories: factories.into_boxed_slice(),
state: Default::default(),
shutdown_timeout: config.shutdown_timeout,
});
});
});
}
};
// wait for service factories initialization
factory_rx.recv().unwrap()?;
Ok(pair)
}
fn restart_service(&mut self, idx: usize, factory_id: usize) {
let factory = &self.factories[factory_id];
trace!("service {:?} failed, restarting", factory.name(idx));
self.services[idx].status = WorkerServiceStatus::Restarting;
self.state = WorkerState::Restarting(Restart {
factory_id,
token: idx,
fut: factory.create(),
});
}
fn shutdown(&mut self, force: bool) {
self.services
.iter_mut()
.filter(|srv| srv.status == WorkerServiceStatus::Available)
.for_each(|srv| {
srv.status = if force {
WorkerServiceStatus::Stopped
} else {
WorkerServiceStatus::Stopping
};
});
}
fn check_readiness(&mut self, cx: &mut Context<'_>) -> Result<bool, (usize, usize)> {
let mut ready = true;
for (idx, srv) in self.services.iter_mut().enumerate() {
if srv.status == WorkerServiceStatus::Available
|| srv.status == WorkerServiceStatus::Unavailable
{
match srv.service.poll_ready(cx) {
Poll::Ready(Ok(_)) => {
if srv.status == WorkerServiceStatus::Unavailable {
trace!(
"service {:?} is available",
self.factories[srv.factory_idx].name(idx)
);
srv.status = WorkerServiceStatus::Available;
}
}
Poll::Pending => {
ready = false;
if srv.status == WorkerServiceStatus::Available {
trace!(
"service {:?} is unavailable",
self.factories[srv.factory_idx].name(idx)
);
srv.status = WorkerServiceStatus::Unavailable;
}
}
Poll::Ready(Err(_)) => {
error!(
"service {:?} readiness check returned error, restarting",
self.factories[srv.factory_idx].name(idx)
);
srv.status = WorkerServiceStatus::Failed;
return Err((idx, srv.factory_idx));
}
}
}
}
Ok(ready)
}
}
enum WorkerState {
Available,
Unavailable,
Restarting(Restart),
Shutdown(Shutdown),
}
struct Restart {
factory_id: usize,
token: usize,
fut: LocalBoxFuture<'static, Result<(usize, BoxedServerService), ()>>,
}
/// State necessary for server shutdown.
struct Shutdown {
// Interval for checking the shutdown progress.
timer: Pin<Box<Sleep>>,
/// Start time of shutdown.
start_from: Instant,
/// Notify caller of the shutdown outcome (graceful/force).
tx: oneshot::Sender<bool>,
}
impl Default for WorkerState {
fn default() -> Self {
Self::Unavailable
}
}
impl Drop for ServerWorker {
fn drop(&mut self) {
Arbiter::try_current().as_ref().map(ArbiterHandle::stop);
}
}
impl Future for ServerWorker {
type Output = ();
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
let this = self.as_mut().get_mut();
// `StopWorker` message handler
if let Poll::Ready(Some(Stop { graceful, tx })) = this.stop_rx.poll_recv(cx) {
let num = this.counter.total();
if num == 0 {
info!("shutting down idle worker");
let _ = tx.send(true);
return Poll::Ready(());
} else if graceful {
info!("graceful worker shutdown; finishing {} connections", num);
this.shutdown(false);
this.state = WorkerState::Shutdown(Shutdown {
timer: Box::pin(sleep(Duration::from_secs(1))),
start_from: Instant::now(),
tx,
});
} else {
info!("force shutdown worker, closing {} connections", num);
this.shutdown(true);
let _ = tx.send(false);
return Poll::Ready(());
}
}
match this.state {
WorkerState::Unavailable => match this.check_readiness(cx) {
Ok(true) => {
this.state = WorkerState::Available;
self.poll(cx)
}
Ok(false) => Poll::Pending,
Err((token, idx)) => {
this.restart_service(token, idx);
self.poll(cx)
}
},
WorkerState::Restarting(ref mut restart) => {
let factory_id = restart.factory_id;
let token = restart.token;
let (token_new, service) =
ready!(restart.fut.as_mut().poll(cx)).unwrap_or_else(|_| {
panic!(
"Can not restart {:?} service",
this.factories[factory_id].name(token)
)
});
assert_eq!(token, token_new);
trace!(
"service {:?} has been restarted",
this.factories[factory_id].name(token)
);
this.services[token].created(service);
this.state = WorkerState::Unavailable;
self.poll(cx)
}
WorkerState::Shutdown(ref mut shutdown) => {
// drop all pending connections in rx channel.
while let Poll::Ready(Some(conn)) = this.conn_rx.poll_recv(cx) {
// WorkerCounterGuard is needed as Accept thread has incremented counter.
// It's guard's job to decrement the counter together with drop of Conn.
let guard = this.counter.guard();
drop((conn, guard));
}
// wait for 1 second
ready!(shutdown.timer.as_mut().poll(cx));
if this.counter.total() == 0 {
// graceful shutdown
if let WorkerState::Shutdown(shutdown) = mem::take(&mut this.state) {
let _ = shutdown.tx.send(true);
}
Poll::Ready(())
} else if shutdown.start_from.elapsed() >= this.shutdown_timeout {
// timeout forceful shutdown
if let WorkerState::Shutdown(shutdown) = mem::take(&mut this.state) {
let _ = shutdown.tx.send(false);
}
Poll::Ready(())
} else {
// reset timer and wait for 1 second
let time = Instant::now() + Duration::from_secs(1);
shutdown.timer.as_mut().reset(time);
shutdown.timer.as_mut().poll(cx)
}
}
// actively poll stream and handle worker command
WorkerState::Available => loop {
match this.check_readiness(cx) {
Ok(true) => {}
Ok(false) => {
trace!("worker is unavailable");
this.state = WorkerState::Unavailable;
return self.poll(cx);
}
Err((token, idx)) => {
this.restart_service(token, idx);
return self.poll(cx);
}
}
// handle incoming io stream
match ready!(this.conn_rx.poll_recv(cx)) {
Some(msg) => {
let guard = this.counter.guard();
let _ = this.services[msg.token]
.service
.call((guard, msg.io))
.into_inner();
}
None => return Poll::Ready(()),
};
},
}
}
}
fn wrap_worker_services(services: Vec<(usize, usize, BoxedServerService)>) -> Vec<WorkerService> {
services
.into_iter()
.fold(Vec::new(), |mut services, (idx, token, service)| {
assert_eq!(token, services.len());
services.push(WorkerService {
factory_idx: idx,
service,
status: WorkerServiceStatus::Unavailable,
});
services
})
}