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Decrease lock period while reloading templates. 

Previously, an `rx` lock was held for the entirety of the check period,
effectively making request handling serial. The implementation also held
a `write` lock to templating context while an expensive user-callback
was called, limiting template-related concurrency during that period.
This was changed so no lock is held during that period and a write-lock
is held only for the duration of the context field write.
This commit is contained in:
Sergio Benitez 2021-03-11 02:24:21 -08:00
parent e532f4e2b3
commit 4b09e77ccb
1 changed files with 21 additions and 29 deletions
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26
contrib/lib/src/templates/fairing.rs
View File

@ -49,7 +49,7 @@ mod context {
/// The current template context, inside an RwLock so it can be updated.
context: RwLock<Context>,
/// A filesystem watcher and the receive queue for its events.
watcher: Option<Mutex<(RecommendedWatcher, Receiver<RawEvent>)>>,
watcher: Option<(RecommendedWatcher, Mutex<Receiver<RawEvent>>)>,
}
impl ContextManager {
@ -61,7 +61,7 @@ mod context {
});
let watcher = match watcher {
Ok(watcher) => Some(Mutex::new((watcher, rx))),
Ok(watcher) => Some((watcher, Mutex::new(rx))),
Err(e) => {
warn!("Failed to enable live template reloading: {}", e);
debug_!("Reload error: {:?}", e);
@ -70,10 +70,7 @@ mod context {
}
};
ContextManager {
watcher,
context: RwLock::new(ctxt),
}
ContextManager { watcher, context: RwLock::new(ctxt), }
}
pub fn context(&self) -> impl Deref<Target=Context> + '_ {
@ -93,19 +90,15 @@ mod context {
/// reinitialized from disk and the user's customization callback is run
/// again.
pub fn reload_if_needed(&self, callback: &Callback) {
self.watcher.as_ref().map(|w| {
let rx_lock = w.lock().expect("receive queue lock");
let mut changed = false;
while let Ok(_) = rx_lock.1.try_recv() {
changed = true;
}
let templates_changes = self.watcher.as_ref()
.map(|(_, rx)| rx.lock().expect("fsevents lock").try_iter().count() > 0);
if changed {
if let Some(true) = templates_changes {
info_!("Change detected: reloading templates.");
let mut ctxt = self.context_mut();
if let Some(mut new_ctxt) = Context::initialize(&ctxt.root) {
let root = self.context().root.clone();
if let Some(mut new_ctxt) = Context::initialize(&root) {
match callback(&mut new_ctxt.engines) {
Ok(()) => *ctxt = new_ctxt,
Ok(()) => *self.context_mut() = new_ctxt,
Err(e) => {
warn_!("The template customization callback returned an error:");
warn_!("{}", e);
@ -117,7 +110,6 @@ mod context {
warn_!("The existing templates will remain active.");
};
}
});
}
}
}