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-rw-r--r--src/util/background.rs124
1 files changed, 124 insertions, 0 deletions
diff --git a/src/util/background.rs b/src/util/background.rs
new file mode 100644
index 00000000..937062dd
--- /dev/null
+++ b/src/util/background.rs
@@ -0,0 +1,124 @@
+use core::future::Future;
+use std::pin::Pin;
+
+use futures::future::join_all;
+use futures::select;
+use futures_util::future::*;
+use std::sync::Arc;
+use tokio::sync::Mutex;
+use tokio::sync::{mpsc, watch, Notify};
+
+use crate::error::Error;
+
+type JobOutput = Result<(), Error>;
+type Job = Pin<Box<dyn Future<Output = JobOutput> + Send>>;
+
+pub struct BackgroundRunner {
+ n_runners: usize,
+ pub stop_signal: watch::Receiver<bool>,
+
+ queue_in: mpsc::UnboundedSender<(Job, bool)>,
+ queue_out: Mutex<mpsc::UnboundedReceiver<(Job, bool)>>,
+ job_notify: Notify,
+
+ workers: Mutex<Vec<tokio::task::JoinHandle<()>>>,
+}
+
+impl BackgroundRunner {
+ pub fn new(n_runners: usize, stop_signal: watch::Receiver<bool>) -> Arc<Self> {
+ let (queue_in, queue_out) = mpsc::unbounded_channel();
+ Arc::new(Self {
+ n_runners,
+ stop_signal,
+ queue_in,
+ queue_out: Mutex::new(queue_out),
+ job_notify: Notify::new(),
+ workers: Mutex::new(Vec::new()),
+ })
+ }
+
+ pub async fn run(self: Arc<Self>) {
+ let mut workers = self.workers.lock().await;
+ for i in 0..self.n_runners {
+ workers.push(tokio::spawn(self.clone().runner(i)));
+ }
+ drop(workers);
+
+ let mut stop_signal = self.stop_signal.clone();
+ while let Some(exit_now) = stop_signal.recv().await {
+ if exit_now {
+ let mut workers = self.workers.lock().await;
+ let workers_vec = workers.drain(..).collect::<Vec<_>>();
+ join_all(workers_vec).await;
+ return;
+ }
+ }
+ }
+
+ pub fn spawn<T>(&self, job: T)
+ where
+ T: Future<Output = JobOutput> + Send + 'static,
+ {
+ let boxed: Job = Box::pin(job);
+ let _: Result<_, _> = self.queue_in.clone().send((boxed, false));
+ self.job_notify.notify();
+ }
+
+ pub fn spawn_cancellable<T>(&self, job: T)
+ where
+ T: Future<Output = JobOutput> + Send + 'static,
+ {
+ let boxed: Job = Box::pin(job);
+ let _: Result<_, _> = self.queue_in.clone().send((boxed, true));
+ self.job_notify.notify();
+ }
+
+ pub async fn spawn_worker<F, T>(&self, name: String, worker: F)
+ where
+ F: FnOnce(watch::Receiver<bool>) -> T + Send + 'static,
+ T: Future<Output = JobOutput> + Send + 'static,
+ {
+ let mut workers = self.workers.lock().await;
+ let stop_signal = self.stop_signal.clone();
+ workers.push(tokio::spawn(async move {
+ if let Err(e) = worker(stop_signal).await {
+ error!("Worker stopped with error: {}, error: {}", name, e);
+ } else {
+ info!("Worker exited successfully: {}", name);
+ }
+ }));
+ }
+
+ async fn runner(self: Arc<Self>, i: usize) {
+ let mut stop_signal = self.stop_signal.clone();
+ loop {
+ let must_exit: bool = *stop_signal.borrow();
+ if let Some(job) = self.dequeue_job(must_exit).await {
+ if let Err(e) = job.await {
+ error!("Job failed: {}", e)
+ }
+ } else {
+ if must_exit {
+ info!("Background runner {} exiting", i);
+ return;
+ }
+ select! {
+ _ = self.job_notify.notified().fuse() => (),
+ _ = stop_signal.recv().fuse() => (),
+ }
+ }
+ }
+ }
+
+ async fn dequeue_job(&self, must_exit: bool) -> Option<Job> {
+ let mut queue = self.queue_out.lock().await;
+ while let Ok((job, cancellable)) = queue.try_recv() {
+ if cancellable && must_exit {
+ continue;
+ } else {
+ return Some(job);
+ }
+ }
+ None
+ }
+}