fix: only drain workers on graceful shutdown (#1405)

* Only drains workers on shutdown.

* trigger build

* Marks func as experimental.

---------

Co-authored-by: Alliballibaba <alliballibaba@gmail.com>

Author: AlliBalliBaba

caddy/caddy.go

@@ -113,7 +113,7 @@ func (f *FrankenPHPApp) Stop() error {
 	// note: Exiting() is currently marked as 'experimental'
 	// https://github.com/caddyserver/caddy/blob/e76405d55058b0a3e5ba222b44b5ef00516116aa/caddy.go#L810
 	if caddy.Exiting() {
-		frankenphp.Shutdown()
+		frankenphp.DrainWorkers()
 	}
 
 	// reset configuration so it doesn't bleed into later tests

frankenphp.go

@@ -374,7 +374,7 @@ func Shutdown() {
 		return
 	}
 
-	drainWorkers()
+	drainWatcher()
 	drainAutoScaling()
 	drainPHPThreads()
 

metrics.go

@@ -380,9 +380,9 @@ func (m *PrometheusMetrics) Shutdown() {
 	}
 
 	if err := m.registry.Register(m.queueDepth); err != nil &&
-        !errors.As(err, &prometheus.AlreadyRegisteredError{}) {
-        panic(err)
-    }
+		!errors.As(err, &prometheus.AlreadyRegisteredError{}) {
+		panic(err)
+	}
 }
 
 func getWorkerNameForMetrics(name string) string {
@@ -432,9 +432,9 @@ func NewPrometheusMetrics(registry prometheus.Registerer) *PrometheusMetrics {
 	}
 
 	if err := m.registry.Register(m.queueDepth); err != nil &&
-        !errors.As(err, &prometheus.AlreadyRegisteredError{}) {
-        panic(err)
-    }
+		!errors.As(err, &prometheus.AlreadyRegisteredError{}) {
+		panic(err)
+	}
 
 	return m
 }

worker.go

@@ -86,18 +86,14 @@ func newWorker(o workerOpt) (*worker, error) {
 	return w, nil
 }
 
-func drainWorkers() {
-	watcher.DrainWatcher()
+// EXPERIMENTAL: DrainWorkers finishes all worker scripts before a graceful shutdown
+func DrainWorkers() {
+	_ = drainWorkerThreads()
 }
 
-// RestartWorkers attempts to restart all workers gracefully
-func RestartWorkers() {
-	// disallow scaling threads while restarting workers
-	scalingMu.Lock()
-	defer scalingMu.Unlock()
-
+func drainWorkerThreads() []*phpThread {
 	ready := sync.WaitGroup{}
-	threadsToRestart := make([]*phpThread, 0)
+	drainedThreads := make([]*phpThread, 0)
 	for _, worker := range workers {
 		worker.threadMutex.RLock()
 		ready.Add(len(worker.threads))
@@ -108,17 +104,33 @@ func RestartWorkers() {
 				continue
 			}
 			close(thread.drainChan)
-			threadsToRestart = append(threadsToRestart, thread)
+			drainedThreads = append(drainedThreads, thread)
 			go func(thread *phpThread) {
 				thread.state.waitFor(stateYielding)
 				ready.Done()
 			}(thread)
 		}
 		worker.threadMutex.RUnlock()
 	}
-
 	ready.Wait()
 
+	return drainedThreads
+}
+
+func drainWatcher() {
+	if watcherIsEnabled {
+		watcher.DrainWatcher()
+	}
+}
+
+// RestartWorkers attempts to restart all workers gracefully
+func RestartWorkers() {
+	// disallow scaling threads while restarting workers
+	scalingMu.Lock()
+	defer scalingMu.Unlock()
+
+	threadsToRestart := drainWorkerThreads()
+
 	for _, thread := range threadsToRestart {
 		thread.drainChan = make(chan struct{})
 		thread.state.set(stateReady)