fix: graceful shutdown (#1242)

* Shuts caddy down gracefully.

* Moves isRunning to the very end.

* Changes check to Exiting().

caddy/caddy.go

@@ -40,22 +40,8 @@ func init() {
 	httpcaddyfile.RegisterDirectiveOrder("php_server", "before", "file_server")
 }
 
-type mainPHPinterpreterKeyType int
-
-var mainPHPInterpreterKey mainPHPinterpreterKeyType
-
-var phpInterpreter = caddy.NewUsagePool()
-
 var metrics = frankenphp.NewPrometheusMetrics(prometheus.DefaultRegisterer)
 
-type phpInterpreterDestructor struct{}
-
-func (phpInterpreterDestructor) Destruct() error {
-	frankenphp.Shutdown()
-
-	return nil
-}
-
 type workerConfig struct {
 	// FileName sets the path to the worker script.
 	FileName string `json:"file_name,omitempty"`
@@ -91,29 +77,24 @@ func (f *FrankenPHPApp) Start() error {
 		opts = append(opts, frankenphp.WithWorkers(repl.ReplaceKnown(w.FileName, ""), w.Num, w.Env, w.Watch))
 	}
 
-	_, loaded, err := phpInterpreter.LoadOrNew(mainPHPInterpreterKey, func() (caddy.Destructor, error) {
-		if err := frankenphp.Init(opts...); err != nil {
-			return nil, err
-		}
-
-		return phpInterpreterDestructor{}, nil
-	})
-	if err != nil {
+	frankenphp.Shutdown()
+	if err := frankenphp.Init(opts...); err != nil {
 		return err
 	}
 
-	if loaded {
-		frankenphp.Shutdown()
-		if err := frankenphp.Init(opts...); err != nil {
-			return err
-		}
-	}
-
 	return nil
 }
 
 func (f *FrankenPHPApp) Stop() error {
 	caddy.Log().Info("FrankenPHP stopped 🐘")
+
+	// attempt a graceful shutdown if caddy is exiting
+	// note: Exiting() is currently marked as 'experimental'
+	// https://github.com/caddyserver/caddy/blob/e76405d55058b0a3e5ba222b44b5ef00516116aa/caddy.go#L810
+	if caddy.Exiting() {
+		frankenphp.Shutdown()
+	}
+
 	// reset configuration so it doesn't bleed into later tests
 	f.Workers = nil
 	f.NumThreads = 0

frankenphp.go

@@ -64,6 +64,7 @@ var (
 	ScriptExecutionError        = errors.New("error during PHP script execution")
 
 	requestChan chan *http.Request
+	isRunning   bool
 
 	loggerMu sync.RWMutex
 	logger   *zap.Logger
@@ -275,9 +276,10 @@ func calculateMaxThreads(opt *opt) (int, int, error) {
 
 // Init starts the PHP runtime and the configured workers.
 func Init(options ...Option) error {
-	if requestChan != nil {
+	if isRunning {
 		return AlreadyStartedError
 	}
+	isRunning = true
 
 	// Ignore all SIGPIPE signals to prevent weird issues with systemd: https://github.com/dunglas/frankenphp/issues/1020
 	// Docker/Moby has a similar hack: https://github.com/moby/moby/blob/d828b032a87606ae34267e349bf7f7ccb1f6495a/cmd/dockerd/docker.go#L87-L90
@@ -357,6 +359,10 @@ func Init(options ...Option) error {
 
 // Shutdown stops the workers and the PHP runtime.
 func Shutdown() {
+	if !isRunning {
+		return
+	}
+
 	drainWorkers()
 	drainPHPThreads()
 	metrics.Shutdown()
@@ -368,6 +374,7 @@ func Shutdown() {
 	}
 
 	logger.Debug("FrankenPHP shut down")
+	isRunning = false
 }
 
 func getLogger() *zap.Logger {