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Merge pull request #1692 from mozilla-services/fix/threadpool-metrics-STOR-201
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fix: avoid underflow of the queued_tasks metric
This commit is contained in:
Philip Jenvey 2025-04-23 15:25:30 -07:00 committed by GitHub
commit 1d355ec7b5
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1 changed files with 12 additions and 9 deletions
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21
syncserver-common/src/lib.rs
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@ -130,18 +130,18 @@ impl BlockingThreadpool {
T: Send + 'static,
E: fmt::Debug + Send + InternalError + 'static,
{
self.spawned_tasks.fetch_add(1, Ordering::SeqCst);
self.spawned_tasks.fetch_add(1, Ordering::Relaxed);
// Ensure the counter's always decremented (whether the task completed,
// was cancelled or panicked)
scopeguard::defer! {
self.spawned_tasks.fetch_sub(1, Ordering::SeqCst);
self.spawned_tasks.fetch_sub(1, Ordering::Relaxed);
}
let active_threads = Arc::clone(&self.active_threads);
let f_with_metrics = move || {
active_threads.fetch_add(1, Ordering::SeqCst);
active_threads.fetch_add(1, Ordering::Relaxed);
scopeguard::defer! {
active_threads.fetch_sub(1, Ordering::SeqCst);
active_threads.fetch_sub(1, Ordering::Relaxed);
}
f()
};
@ -154,11 +154,14 @@ impl BlockingThreadpool {
/// Return the pool's current metrics
pub fn metrics(&self) -> BlockingThreadpoolMetrics {
// active_threads is decremented on a separate thread so we need a
// strong Ordering to ensure it's in sync w/ spawned_tasks (otherwise
// it could underflow queued_tasks)
let spawned_tasks = self.spawned_tasks.load(Ordering::SeqCst);
let active_threads = self.active_threads.load(Ordering::SeqCst);
let spawned_tasks = self.spawned_tasks.load(Ordering::Relaxed);
// active_threads is decremented on a separate thread so there's no
// Drop order guarantee of spawned_tasks decrementing before it does:
// catch the case where active_threads is larger
let active_threads = self
.active_threads
.load(Ordering::Relaxed)
.min(spawned_tasks);
BlockingThreadpoolMetrics {
queued_tasks: spawned_tasks - active_threads,
active_threads,