Bug 1817075: MCC & MCO don't free leader leases during shut down -> 10 minutes of leader election timeouts

cmd/common/helpers.go

@@ -2,6 +2,8 @@ package common
 
 import (
 	"os"
+	"os/signal"
+	"syscall"
 
 	"github.com/golang/glog"
 	"github.com/openshift/machine-config-operator/internal/clients"
@@ -69,3 +71,23 @@ func GetLeaderElectionConfig(restcfg *rest.Config) configv1.LeaderElection {
 
 	return defaultLeaderElection
 }
+
+// SignalHandler catches SIGINT/SIGTERM signals and makes sure the passed context gets cancelled when those signals happen. This allows us to use a
+// context to shut down our operations cleanly when we are signalled to shutdown.
+func SignalHandler(runCancel context.CancelFunc) {
+
+	// make a signal handling channel for os signals
+	ch := make(chan os.Signal, 1)
+	// stop listening for signals when we leave this function
+	defer func() { signal.Stop(ch) }()
+	// catch SIGINT and SIGTERM
+	signal.Notify(ch, os.Interrupt, syscall.SIGTERM)
+	sig := <-ch
+	glog.Infof("Shutting down due to: %s", sig)
+	// if we're shutting down, cancel the context so everything else will stop
+	runCancel()
+	glog.Infof("Context cancelled")
+	sig = <-ch
+	glog.Fatalf("Received shutdown signal twice, exiting: %s", sig)
+
+}

cmd/machine-config-controller/start.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"flag"
 	"fmt"
+	"os"
 
 	"github.com/golang/glog"
 	"github.com/openshift/machine-config-operator/cmd/common"
@@ -48,6 +49,10 @@ func runStartCmd(cmd *cobra.Command, args []string) {
 	flag.Set("logtostderr", "true")
 	flag.Parse()
 
+	// This is 'main' context that we thread through the controller context and
+	// the leader elections. Cancelling this is "stop everything, we are shutting down".
+	runContext, runCancel := context.WithCancel(context.Background())
+
 	// To help debugging, immediately log version
 	glog.Infof("Version: %+v (%s)", version.Raw, version.Hash)
 
@@ -56,6 +61,8 @@ func runStartCmd(cmd *cobra.Command, args []string) {
 		ctrlcommon.WriteTerminationError(fmt.Errorf("creating clients: %w", err))
 	}
 	run := func(ctx context.Context) {
+		go common.SignalHandler(runCancel)
+
 		ctrlctx := ctrlcommon.CreateControllerContext(cb, ctx.Done(), componentName)
 
 		// Start the metrics handler
@@ -82,20 +89,23 @@ func runStartCmd(cmd *cobra.Command, args []string) {
 		}
 		go draincontroller.Run(5, ctrlctx.Stop)
 
-		select {}
+		// wait here in this function until the context gets cancelled (which tells us whe were being shut down)
+		<-ctx.Done()
 	}
 
 	leaderElectionCfg := common.GetLeaderElectionConfig(cb.GetBuilderConfig())
 
-	leaderelection.RunOrDie(context.TODO(), leaderelection.LeaderElectionConfig{
-		Lock:          common.CreateResourceLock(cb, startOpts.resourceLockNamespace, componentName),
-		LeaseDuration: leaderElectionCfg.LeaseDuration.Duration,
-		RenewDeadline: leaderElectionCfg.RenewDeadline.Duration,
-		RetryPeriod:   leaderElectionCfg.RetryPeriod.Duration,
+	leaderelection.RunOrDie(runContext, leaderelection.LeaderElectionConfig{
+		Lock:            common.CreateResourceLock(cb, startOpts.resourceLockNamespace, componentName),
+		ReleaseOnCancel: true,
+		LeaseDuration:   leaderElectionCfg.LeaseDuration.Duration,
+		RenewDeadline:   leaderElectionCfg.RenewDeadline.Duration,
+		RetryPeriod:     leaderElectionCfg.RetryPeriod.Duration,
 		Callbacks: leaderelection.LeaderCallbacks{
 			OnStartedLeading: run,
 			OnStoppedLeading: func() {
-				glog.Fatalf("leaderelection lost")
+				glog.Infof("Stopped leading. Terminating.")
+				os.Exit(0)
 			},
 		},
 	})

cmd/machine-config-operator/start.go

@@ -39,6 +39,10 @@ func runStartCmd(cmd *cobra.Command, args []string) {
 	flag.Set("logtostderr", "true")
 	flag.Parse()
 
+	// This is 'main' context that we thread through the controller context and
+	// the leader elections. Cancelling this is "stop everything, we are shutting down".
+	runContext, runCancel := context.WithCancel(context.Background())
+
 	// To help debugging, immediately log version
 	glog.Infof("Version: %s (Raw: %s, Hash: %s)", os.Getenv("RELEASE_VERSION"), version.Raw, version.Hash)
 
@@ -51,6 +55,8 @@ func runStartCmd(cmd *cobra.Command, args []string) {
 		glog.Fatalf("error creating clients: %v", err)
 	}
 	run := func(ctx context.Context) {
+		go common.SignalHandler(runCancel)
+
 		ctrlctx := ctrlcommon.CreateControllerContext(cb, ctx.Done(), ctrlcommon.MCONamespace)
 		controller := operator.New(
 			ctrlcommon.MCONamespace, componentName,
@@ -91,20 +97,23 @@ func runStartCmd(cmd *cobra.Command, args []string) {
 
 		go controller.Run(2, ctrlctx.Stop)
 
-		select {}
+		// wait here in this function until the context gets cancelled (which tells us whe were being shut down)
+		<-ctx.Done()
 	}
 
 	leaderElectionCfg := common.GetLeaderElectionConfig(cb.GetBuilderConfig())
 
-	leaderelection.RunOrDie(context.TODO(), leaderelection.LeaderElectionConfig{
-		Lock:          common.CreateResourceLock(cb, ctrlcommon.MCONamespace, componentName),
-		LeaseDuration: leaderElectionCfg.LeaseDuration.Duration,
-		RenewDeadline: leaderElectionCfg.RenewDeadline.Duration,
-		RetryPeriod:   leaderElectionCfg.RetryPeriod.Duration,
+	leaderelection.RunOrDie(runContext, leaderelection.LeaderElectionConfig{
+		Lock:            common.CreateResourceLock(cb, ctrlcommon.MCONamespace, componentName),
+		ReleaseOnCancel: true,
+		LeaseDuration:   leaderElectionCfg.LeaseDuration.Duration,
+		RenewDeadline:   leaderElectionCfg.RenewDeadline.Duration,
+		RetryPeriod:     leaderElectionCfg.RetryPeriod.Duration,
 		Callbacks: leaderelection.LeaderCallbacks{
 			OnStartedLeading: run,
 			OnStoppedLeading: func() {
-				glog.Fatalf("leaderelection lost")
+				glog.Info("Stopped leading. Terminating.")
+				os.Exit(0)
 			},
 		},
 	})

pkg/controller/common/metrics.go

@@ -62,7 +62,12 @@ func StartMetricsListener(addr string, stopCh <-chan struct{}) {
 		}
 	}()
 	<-stopCh
-	if err := s.Shutdown(context.Background()); err != http.ErrServerClosed {
-		glog.Errorf("error stopping metrics listener: %v", err)
+	if err := s.Shutdown(context.Background()); err != nil {
+		if err != http.ErrServerClosed {
+			glog.Errorf("error stopping metrics listener: %v", err)
+		}
+	} else {
+		glog.Infof("Metrics listener successfully stopped")
 	}
+
 }