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fix(Turborepo): Make package discovery async, and apply a debouncer (v…
…ercel#8058) ### Description - move the debouncer to its own module so that it is reusable - apply the debouncer to package discovery - make package discovery async so it doesn't block the file watching channel ### Testing Instructions Existing test suite. Fixes vercel#3455 Closes TURBO-2909 --------- Co-authored-by: Greg Soltis <Greg Soltis> Co-authored-by: Alexander Lyon <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,127 @@ | ||
| use std::{fmt::Debug, sync::Mutex, time::Duration}; | ||
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| use tokio::{select, sync, time::Instant}; | ||
| use tracing::trace; | ||
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| pub(crate) struct Debouncer { | ||
| bump: sync::Notify, | ||
| serial: Mutex<Option<usize>>, | ||
| timeout: Duration, | ||
| } | ||
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| const DEFAULT_DEBOUNCE_TIMEOUT: Duration = Duration::from_millis(10); | ||
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| impl Default for Debouncer { | ||
| fn default() -> Self { | ||
| Self::new(DEFAULT_DEBOUNCE_TIMEOUT) | ||
| } | ||
| } | ||
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| impl Debug for Debouncer { | ||
| fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { | ||
| let serial = { self.serial.lock().expect("lock is valid") }; | ||
| f.debug_struct("Debouncer") | ||
| .field("is_pending", &serial.is_some()) | ||
| .field("timeout", &self.timeout) | ||
| .finish() | ||
| } | ||
| } | ||
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| impl Debouncer { | ||
| pub(crate) fn new(timeout: Duration) -> Self { | ||
| let bump = sync::Notify::new(); | ||
| let serial = Mutex::new(Some(0)); | ||
| Self { | ||
| bump, | ||
| serial, | ||
| timeout, | ||
| } | ||
| } | ||
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| pub(crate) fn bump(&self) -> bool { | ||
| let mut serial = self.serial.lock().expect("lock is valid"); | ||
| match *serial { | ||
| None => false, | ||
| Some(previous) => { | ||
| *serial = Some(previous + 1); | ||
| self.bump.notify_one(); | ||
| true | ||
| } | ||
| } | ||
| } | ||
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| pub(crate) async fn debounce(&self) { | ||
| let mut serial = { | ||
| self.serial | ||
| .lock() | ||
| .expect("lock is valid") | ||
| .expect("only this thread sets the value to None") | ||
| }; | ||
| let mut deadline = Instant::now() + self.timeout; | ||
| loop { | ||
| let timeout = tokio::time::sleep_until(deadline); | ||
| select! { | ||
| _ = self.bump.notified() => { | ||
| trace!("debouncer notified"); | ||
| // reset timeout | ||
| let current_serial = self.serial.lock().expect("lock is valid").expect("only this thread sets the value to None"); | ||
| if current_serial == serial { | ||
| // we timed out between the serial update and the notification. | ||
| // ignore this notification, we've already bumped the timer | ||
| continue; | ||
| } else { | ||
| serial = current_serial; | ||
| deadline = Instant::now() + self.timeout; | ||
| } | ||
| } | ||
| _ = timeout => { | ||
| // check if serial is still valid. It's possible a bump came in before the timeout, | ||
| // but we haven't been notified yet. | ||
| let mut current_serial_opt = self.serial.lock().expect("lock is valid"); | ||
| let current_serial = current_serial_opt.expect("only this thread sets the value to None"); | ||
| if current_serial == serial { | ||
| // if the serial is what we last observed, and the timer expired, we timed out. | ||
| // we're done. Mark that we won't accept any more bumps and return | ||
| *current_serial_opt = None; | ||
| return; | ||
| } else { | ||
| serial = current_serial; | ||
| deadline = Instant::now() + self.timeout; | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| #[cfg(test)] | ||
| mod tests { | ||
| use std::{ | ||
| sync::Arc, | ||
| time::{Duration, Instant}, | ||
| }; | ||
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| use crate::debouncer::Debouncer; | ||
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| #[tokio::test] | ||
| async fn test_debouncer() { | ||
| let debouncer = Arc::new(Debouncer::new(Duration::from_millis(10))); | ||
| let debouncer_copy = debouncer.clone(); | ||
| let handle = tokio::task::spawn(async move { | ||
| debouncer_copy.debounce().await; | ||
| }); | ||
| for _ in 0..10 { | ||
| // assert that we can continue bumping it past the original timeout | ||
| tokio::time::sleep(Duration::from_millis(2)).await; | ||
| assert!(debouncer.bump()); | ||
| } | ||
| let start = Instant::now(); | ||
| handle.await.unwrap(); | ||
| let end = Instant::now(); | ||
| // give some wiggle room to account for race conditions, but assert that we | ||
| // didn't immediately complete after the last bump | ||
| assert!(end - start > Duration::from_millis(5)); | ||
| // we shouldn't be able to bump it after it's run out it's timeout | ||
| assert!(!debouncer.bump()); | ||
| } | ||
| } |
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