add signals based on controller-runtime signals handler

signals/signal.go

@@ -0,0 +1,52 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package signals
+
+import (
+	"context"
+	"os"
+	"os/signal"
+)
+
+var onlyOneSignalHandler = make(chan struct{})
+
+// SetupSignalHandler registers for SIGTERM and SIGINT. A context is returned
+// which is canceled on one of these signals. If a second signal is caught, the program
+// is terminated with exit code 1.
+func SetupSignalHandler() context.Context {
+	return SetupSignalHandlerWithContext(context.Background())
+}
+
+// SetupSignalHandlerWithContext registers for SIGTERM and SIGINT. A context using the
+// given context as parent is returned which is canceled on one of these signals.
+// If a second signal is caught, the program is terminated with exit code 1.
+func SetupSignalHandlerWithContext(ctx context.Context) context.Context {
+	close(onlyOneSignalHandler) // panics when called twice
+
+	ctx, cancel := context.WithCancel(ctx)
+
+	c := make(chan os.Signal, 2)
+	signal.Notify(c, shutdownSignals...)
+	go func() {
+		<-c
+		cancel()
+		<-c
+		os.Exit(1) // second signal. Exit directly.
+	}()
+
+	return ctx
+}