1 files changed, 131 insertions, 0 deletions
diff --git a/libpod/shutdown/handler.go b/libpod/shutdown/handler.go
new file mode 100644
index 000000000..87538dec9
--- /dev/null
+++ b/libpod/shutdown/handler.go
@@ -0,0 +1,131 @@
+package shutdown
+
+import (
+	"os"
+	"os/signal"
+	"sync"
+	"syscall"
+
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
+)
+
+var (
+	stopped    bool
+	sigChan    chan os.Signal
+	cancelChan chan bool
+	// Definitions of all on-shutdown handlers
+	handlers map[string]func(os.Signal) error
+	// Ordering that on-shutdown handlers will be invoked.
+	handlerOrder    []string
+	shutdownInhibit sync.RWMutex
+)
+
+// Start begins handling SIGTERM and SIGINT and will run the given on-signal
+// handlers when one is called. This can be cancelled by calling Stop().
+func Start() error {
+	if sigChan != nil {
+		// Already running, do nothing.
+		return nil
+	}
+
+	sigChan = make(chan os.Signal, 1)
+	cancelChan = make(chan bool, 1)
+	stopped = false
+
+	signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)
+
+	go func() {
+		select {
+		case <-cancelChan:
+			signal.Stop(sigChan)
+			close(sigChan)
+			close(cancelChan)
+			stopped = true
+			return
+		case sig := <-sigChan:
+			logrus.Infof("Received shutdown signal %v, terminating!", sig)
+			shutdownInhibit.Lock()
+			for _, name := range handlerOrder {
+				handler, ok := handlers[name]
+				if !ok {
+					logrus.Errorf("Shutdown handler %s definition not found!", name)
+					continue
+				}
+				logrus.Infof("Invoking shutdown handler %s", name)
+				if err := handler(sig); err != nil {
+					logrus.Errorf("Error running shutdown handler %s: %v", name, err)
+				}
+			}
+			shutdownInhibit.Unlock()
+			return
+		}
+	}()
+
+	return nil
+}
+
+// Stop the shutdown signal handler.
+func Stop() error {
+	if cancelChan == nil {
+		return errors.New("shutdown signal handler has not yet been started")
+	}
+	if stopped {
+		return nil
+	}
+
+	cancelChan <- true
+
+	return nil
+}
+
+// Temporarily inhibit signals from shutting down Libpod.
+func Inhibit() {
+	shutdownInhibit.RLock()
+}
+
+// Stop inhibiting signals from shutting down Libpod.
+func Uninhibit() {
+	shutdownInhibit.RUnlock()
+}
+
+// Register registers a function that will be executed when Podman is terminated
+// by a signal. Handlers are invoked LIFO - the last handler registered is the
+// first run.
+func Register(name string, handler func(os.Signal) error) error {
+	if handlers == nil {
+		handlers = make(map[string]func(os.Signal) error)
+	}
+
+	if _, ok := handlers[name]; ok {
+		return errors.Errorf("handler with name %s already exists", name)
+	}
+
+	handlers[name] = handler
+	handlerOrder = append([]string{name}, handlerOrder...)
+
+	return nil
+}
+
+// Unregister un-registers a given shutdown handler.
+func Unregister(name string) error {
+	if handlers == nil {
+		return nil
+	}
+
+	if _, ok := handlers[name]; !ok {
+		return nil
+	}
+
+	delete(handlers, name)
+
+	newOrder := []string{}
+	for _, checkName := range handlerOrder {
+		if checkName != name {
+			newOrder = append(newOrder, checkName)
+		}
+	}
+	handlerOrder = newOrder
+
+	return nil
+}