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|
//! Job runner for futures and async functions
use core::future::Future;
use std::pin::Pin;
use std::sync::Arc;
use std::time::Duration;
use futures::future::*;
use futures::select;
use tokio::sync::{mpsc, watch, Mutex};
use crate::error::Error;
type JobOutput = Result<(), Error>;
type Job = Pin<Box<dyn Future<Output = JobOutput> + Send>>;
/// Job runner for futures and async functions
pub struct BackgroundRunner {
stop_signal: watch::Receiver<bool>,
queue_in: mpsc::UnboundedSender<(Job, bool)>,
worker_in: mpsc::UnboundedSender<tokio::task::JoinHandle<()>>,
}
impl BackgroundRunner {
/// Create a new BackgroundRunner
pub fn new(
n_runners: usize,
stop_signal: watch::Receiver<bool>,
) -> (Arc<Self>, tokio::task::JoinHandle<()>) {
let (worker_in, mut worker_out) = mpsc::unbounded_channel();
let stop_signal_2 = stop_signal.clone();
let await_all_done = tokio::spawn(async move {
loop {
let wkr = {
select! {
item = worker_out.recv().fuse() => {
match item {
Some(x) => x,
None => break,
}
}
_ = tokio::time::sleep(Duration::from_secs(5)).fuse() => {
if *stop_signal_2.borrow() {
break;
} else {
continue;
}
}
}
};
if let Err(e) = wkr.await {
error!("Error while awaiting for worker: {}", e);
}
}
});
let (queue_in, queue_out) = mpsc::unbounded_channel();
let queue_out = Arc::new(Mutex::new(queue_out));
for i in 0..n_runners {
let queue_out = queue_out.clone();
let stop_signal = stop_signal.clone();
worker_in
.send(tokio::spawn(async move {
loop {
let (job, cancellable) = {
select! {
item = wait_job(&queue_out).fuse() => match item {
// We received a task, process it
Some(x) => x,
// We received a signal that no more tasks will ever be sent
// because the sending side was dropped. Exit now.
None => break,
},
_ = tokio::time::sleep(Duration::from_secs(5)).fuse() => {
if *stop_signal.borrow() {
// Nothing has been going on for 5 secs, and we are shutting
// down. Exit now.
break;
} else {
// Nothing is going on but we don't want to exit.
continue;
}
}
}
};
if cancellable && *stop_signal.borrow() {
continue;
}
if let Err(e) = job.await {
error!("Job failed: {}", e)
}
}
info!("Background worker {} exiting", i);
}))
.unwrap();
}
let bgrunner = Arc::new(Self {
stop_signal,
queue_in,
worker_in,
});
(bgrunner, await_all_done)
}
/// Spawn a task to be run in background
pub fn spawn<T>(&self, job: T)
where
T: Future<Output = JobOutput> + Send + 'static,
{
let boxed: Job = Box::pin(job);
self.queue_in
.send((boxed, false))
.map_err(|_| "could not put job in queue")
.unwrap();
}
/// Spawn a task to be run in background. It may get discarded before running if spawned while
/// the runner is stopping
pub fn spawn_cancellable<T>(&self, job: T)
where
T: Future<Output = JobOutput> + Send + 'static,
{
let boxed: Job = Box::pin(job);
self.queue_in
.send((boxed, true))
.map_err(|_| "could not put job in queue")
.unwrap();
}
pub fn spawn_worker<F, T>(&self, name: String, worker: F)
where
F: FnOnce(watch::Receiver<bool>) -> T + Send + 'static,
T: Future<Output = ()> + Send + 'static,
{
let stop_signal = self.stop_signal.clone();
let task = tokio::spawn(async move {
info!("Worker started: {}", name);
worker(stop_signal).await;
info!("Worker exited: {}", name);
});
self.worker_in
.send(task)
.map_err(|_| "could not put job in queue")
.unwrap();
}
}
async fn wait_job(q: &Mutex<mpsc::UnboundedReceiver<(Job, bool)>>) -> Option<(Job, bool)> {
q.lock().await.recv().await
}
|
