TUN-528: Move cloudflared into a separate repo

cmd/cloudflared/signal.go

@@ -0,0 +1,79 @@
+package main
+
+import (
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+)
+
+// waitForSignal notifies all routines to shutdownC immediately by closing the
+// shutdownC when one of the routines in main exits, or when this process receives
+// SIGTERM/SIGINT
+func waitForSignal(errC chan error, shutdownC chan struct{}) error {
+	signals := make(chan os.Signal, 10)
+	signal.Notify(signals, syscall.SIGTERM, syscall.SIGINT)
+	defer signal.Stop(signals)
+
+	select {
+	case err := <-errC:
+		close(shutdownC)
+		return err
+	case <-signals:
+		close(shutdownC)
+	case <-shutdownC:
+	}
+	return nil
+}
+
+// waitForSignalWithGraceShutdown notifies all routines to shutdown immediately
+// by closing the shutdownC when one of the routines in main exits.
+// When this process recieves SIGTERM/SIGINT, it closes the graceShutdownC to
+// notify certain routines to start graceful shutdown. When grace period is over,
+// or when some routine exits, it notifies the rest of the routines to shutdown
+// immediately by closing shutdownC.
+// In the case of handling commands from Windows Service Manager, closing graceShutdownC
+// initiate graceful shutdown.
+func waitForSignalWithGraceShutdown(errC chan error,
+	shutdownC, graceShutdownC chan struct{},
+	gracePeriod time.Duration,
+) error {
+	signals := make(chan os.Signal, 10)
+	signal.Notify(signals, syscall.SIGTERM, syscall.SIGINT)
+	defer signal.Stop(signals)
+
+	select {
+	case err := <-errC:
+		close(graceShutdownC)
+		close(shutdownC)
+		return err
+	case <-signals:
+		close(graceShutdownC)
+		waitForGracePeriod(signals, errC, shutdownC, gracePeriod)
+	case <-graceShutdownC:
+		waitForGracePeriod(signals, errC, shutdownC, gracePeriod)
+	case <-shutdownC:
+		close(graceShutdownC)
+	}
+
+	return nil
+}
+
+func waitForGracePeriod(signals chan os.Signal,
+	errC chan error,
+	shutdownC chan struct{},
+	gracePeriod time.Duration,
+) {
+	logger.Infof("Initiating graceful shutdown...")
+	// Unregister signal handler early, so the client can send a second SIGTERM/SIGINT
+	// to force shutdown cloudflared
+	signal.Stop(signals)
+	graceTimerTick := time.Tick(gracePeriod)
+	// send close signal via shutdownC when grace period expires or when an
+	// error is encountered.
+	select {
+	case <-graceTimerTick:
+	case <-errC:
+	}
+	close(shutdownC)
+}