replace glog with simpler home-grown debug logging

Gopkg.toml

@@ -33,10 +33,6 @@ ignored = ["k8s.io/code-generator"]
   non-go = false
   unused-packages = false
 
-[[constraint]]
-  branch = "master"
-  name = "github.com/golang/glog"
-
 [[constraint]]
   name = "google.golang.org/grpc"
   version = "1.11.0"

Makefile

@@ -21,7 +21,7 @@ ifndef WHAT
 	@$(GO) test -race -coverprofile=coverage.txt -covermode=atomic $(pkgs)
 else
 	@cd $(WHAT) && \
-            $(GO) test -v -cover -coverprofile cover.out -args -logtostderr -v 2 || rc=1; \
+            $(GO) test -v -cover -coverprofile cover.out || rc=1; \
             $(GO) tool cover -html=cover.out -o coverage.html; \
             rm cover.out; \
             echo "Coverage report: file://$$(realpath coverage.html)"; \

build/docker/intel-fpga-plugin.Dockerfile

@@ -7,4 +7,4 @@ RUN chmod a+x /go/bin/fpga_plugin
 
 FROM alpine
 COPY --from=builder /go/bin/fpga_plugin /usr/bin/intel_fpga_device_plugin
-CMD ["/usr/bin/intel_fpga_device_plugin", "-logtostderr"]
+CMD ["/usr/bin/intel_fpga_device_plugin"]

cmd/fpga_admissionwebhook/controller.go

@@ -18,7 +18,6 @@ import (
 	"fmt"
 	"time"
 
-	"github.com/golang/glog"
 	"github.com/pkg/errors"
 
 	k8serrors "k8s.io/apimachinery/pkg/api/errors"
@@ -31,6 +30,7 @@ import (
 	clientset "github.com/intel/intel-device-plugins-for-kubernetes/pkg/client/clientset/versioned"
 	informers "github.com/intel/intel-device-plugins-for-kubernetes/pkg/client/informers/externalversions"
 	listers "github.com/intel/intel-device-plugins-for-kubernetes/pkg/client/listers/fpga.intel.com/v1"
+	"github.com/intel/intel-device-plugins-for-kubernetes/pkg/debug"
 )
 
 const (
@@ -89,7 +89,7 @@ func (c *controller) run(threadiness int) error {
 	defer runtime.HandleCrash()
 	defer c.queue.ShutDown()
 
-	glog.Info("Starting controller")
+	fmt.Println("Starting controller")
 
 	go c.informerFactory.Start(c.stopCh)
 
@@ -153,7 +153,7 @@ func (c *controller) processNextWorkItem() bool {
 		// Finally, if no error occurs we Forget this item so it does not
 		// get queued again until another change happens.
 		c.queue.Forget(obj)
-		glog.V(2).Infof("Successfully synced '%s'", key)
+		debug.Printf("Successfully synced '%s'", key)
 		return nil
 	}(obj)
 
@@ -180,7 +180,7 @@ func (c *controller) syncAfHandler(key string) error {
 		// processing.
 		if k8serrors.IsNotFound(err) {
 			runtime.HandleError(errors.Errorf("accelerated function '%s' in work queue no longer exists", key))
-			glog.V(2).Infof("AF '%s' no longer exists", key)
+			debug.Printf("AF '%s' no longer exists", key)
 			c.patcher.removeAf(name)
 			return nil
 		}
@@ -188,7 +188,7 @@ func (c *controller) syncAfHandler(key string) error {
 		return err
 	}
 
-	glog.V(2).Info("Received ", af)
+	debug.Print("Received", af)
 	c.patcher.addAf(af)
 	return nil
 }
@@ -208,7 +208,7 @@ func (c *controller) syncRegionHandler(key string) error {
 		// processing.
 		if k8serrors.IsNotFound(err) {
 			runtime.HandleError(errors.Errorf("FPGA region '%s' in work queue no longer exists", key))
-			glog.V(2).Infof("Region '%s' no longer exists", key)
+			debug.Printf("Region '%s' no longer exists", key)
 			c.patcher.removeRegion(name)
 			return nil
 		}
@@ -216,7 +216,7 @@ func (c *controller) syncRegionHandler(key string) error {
 		return err
 	}
 
-	glog.V(2).Info("Received ", region)
+	debug.Print("Received", region)
 	c.patcher.addRegion(region)
 	return nil
 }

cmd/fpga_admissionwebhook/controller_test.go

@@ -25,6 +25,7 @@ import (
 
 	v1 "github.com/intel/intel-device-plugins-for-kubernetes/pkg/apis/fpga.intel.com/v1"
 	listers "github.com/intel/intel-device-plugins-for-kubernetes/pkg/client/listers/fpga.intel.com/v1"
+	"github.com/intel/intel-device-plugins-for-kubernetes/pkg/debug"
 )
 
 type fakeAfNamespaceLister struct {
@@ -32,6 +33,10 @@ type fakeAfNamespaceLister struct {
 	err error
 }
 
+func init() {
+	debug.Activate()
+}
+
 func (nl *fakeAfNamespaceLister) Get(name string) (*v1.AcceleratorFunction, error) {
 	return nl.af, nl.err
 }

cmd/fpga_admissionwebhook/fpga_admissionwebhook.go

@@ -24,7 +24,6 @@ import (
 	"os"
 	"strings"
 
-	"github.com/golang/glog"
 	"github.com/pkg/errors"
 
 	"k8s.io/api/admission/v1beta1"
@@ -36,6 +35,8 @@ import (
 	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/clientcmd"
+
+	"github.com/intel/intel-device-plugins-for-kubernetes/pkg/debug"
 )
 
 const (
@@ -71,11 +72,11 @@ func getTLSConfig(certFile string, keyFile string) *tls.Config {
 func mutatePods(ar v1beta1.AdmissionReview, p *patcher) *v1beta1.AdmissionResponse {
 	var ops []string
 
-	glog.V(2).Info("mutating pods")
+	debug.Print("mutating pods")
 
 	podResource := metav1.GroupVersionResource{Group: "", Version: "v1", Resource: "pods"}
 	if ar.Request.Resource != podResource {
-		glog.Errorf("expect resource to be %s", podResource)
+		fmt.Printf("WARNING: Unexpected resource type %s\n", ar.Request.Resource)
 		return nil
 	}
 
@@ -128,7 +129,7 @@ func serve(w http.ResponseWriter, r *http.Request, admit admitFunc) {
 	}
 
 	if len(body) == 0 {
-		glog.Error("No body in request")
+		debug.Print("No body in request")
 		w.WriteHeader(http.StatusBadRequest)
 		return
 	}
@@ -136,16 +137,16 @@ func serve(w http.ResponseWriter, r *http.Request, admit admitFunc) {
 	// verify the content type is accurate
 	contentType := r.Header.Get("Content-Type")
 	if contentType != "application/json" {
-		glog.Errorf("contentType=%s, expect application/json", contentType)
+		debug.Printf("contentType=%s, expect application/json", contentType)
 		w.WriteHeader(http.StatusBadRequest)
 		return
 	}
 
-	glog.V(2).Info(fmt.Sprintf("handling request: %s", string(body)))
+	debug.Printf("handling request: %s", string(body))
 	ar := v1beta1.AdmissionReview{}
 	deserializer := codecs.UniversalDeserializer()
 	if _, _, err := deserializer.Decode(body, nil, &ar); err != nil {
-		glog.Error(err)
+		fmt.Printf("ERROR: %+v\n", err)
 		reviewResponse = toAdmissionResponse(err)
 	} else {
 		if ar.Request == nil {
@@ -156,7 +157,7 @@ func serve(w http.ResponseWriter, r *http.Request, admit admitFunc) {
 			reviewResponse = admit(ar)
 		}
 	}
-	glog.V(2).Info(fmt.Sprintf("sending response: %v", reviewResponse))
+	debug.Print("sending response", reviewResponse)
 
 	response := v1beta1.AdmissionReview{}
 	if reviewResponse != nil {
@@ -172,11 +173,11 @@ func serve(w http.ResponseWriter, r *http.Request, admit admitFunc) {
 
 	resp, err := json.Marshal(response)
 	if err != nil {
-		glog.Error(err)
+		fmt.Println("ERROR:", err)
 		return
 	}
 	if _, err := w.Write(resp); err != nil {
-		glog.Error(err)
+		fmt.Println("ERROR:", err)
 	}
 }
 
@@ -201,6 +202,7 @@ func main() {
 	var mode string
 	var config *rest.Config
 	var err error
+	var debugEnabled bool
 
 	flag.StringVar(&kubeconfig, "kubeconfig", "", "absolute path to the kubeconfig file")
 	flag.StringVar(&master, "master", "", "master url")
@@ -208,25 +210,30 @@ func main() {
 		"File containing the x509 Certificate for HTTPS. (CA cert, if any, concatenated after server cert).")
 	flag.StringVar(&keyFile, "tls-private-key-file", keyFile, "File containing the x509 private key matching --tls-cert-file.")
 	flag.StringVar(&mode, "mode", preprogrammed, fmt.Sprintf("webhook mode: '%s' (default) or '%s'", preprogrammed, orchestrated))
+	flag.BoolVar(&debugEnabled, "debug", false, "enable debug output")
 	flag.Parse()
 
+	if debugEnabled {
+		debug.Activate()
+	}
+
 	if certFile == "" {
-		glog.Error("TLS certificate file is not set")
+		fmt.Println("TLS certificate file is not set")
 		os.Exit(1)
 	}
 
 	if keyFile == "" {
-		glog.Error("TLS private key is not set")
+		fmt.Println("TLS private key is not set")
 		os.Exit(1)
 	}
 
 	if _, err = os.Stat(certFile); err != nil {
-		glog.Error("TLS certificate not found")
+		fmt.Println("TLS certificate not found")
 		os.Exit(1)
 	}
 
 	if _, err = os.Stat(keyFile); err != nil {
-		glog.Error("TLS private key not found")
+		fmt.Println("TLS private key not found")
 		os.Exit(1)
 	}
 
@@ -236,7 +243,7 @@ func main() {
 		config, err = clientcmd.BuildConfigFromFlags(master, kubeconfig)
 	}
 	if err != nil {
-		glog.Error("Failed to get cluster config ", err)
+		fmt.Println("Failed to get cluster config ", err)
 		os.Exit(1)
 	}
 
@@ -253,7 +260,7 @@ func main() {
 
 	http.HandleFunc("/pods", makePodsHandler(patcher))
 
-	glog.V(2).Info("Webhook started")
+	debug.Print("Webhook started")
 
 	server := &http.Server{
 		Addr:      ":443",

cmd/fpga_admissionwebhook/fpga_admissionwebhook_test.go

@@ -28,8 +28,14 @@ import (
 	"k8s.io/apimachinery/pkg/api/resource"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
+
+	"github.com/intel/intel-device-plugins-for-kubernetes/pkg/debug"
 )
 
+func init() {
+	debug.Activate()
+}
+
 func fakeMutatePods(ar v1beta1.AdmissionReview) *v1beta1.AdmissionResponse {
 	reviewResponse := v1beta1.AdmissionResponse{}
 	return &reviewResponse

cmd/fpga_admissionwebhook/patcher_test.go

@@ -22,8 +22,13 @@ import (
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 
 	fpgav1 "github.com/intel/intel-device-plugins-for-kubernetes/pkg/apis/fpga.intel.com/v1"
+	"github.com/intel/intel-device-plugins-for-kubernetes/pkg/debug"
 )
 
+func init() {
+	debug.Activate()
+}
+
 func TestPatcherStorageFunctions(t *testing.T) {
 	af := &fpgav1.AcceleratorFunction{
 		ObjectMeta: metav1.ObjectMeta{

cmd/fpga_crihook/main_test.go

@@ -22,8 +22,14 @@ import (
 
 	"k8s.io/utils/exec"
 	fakeexec "k8s.io/utils/exec/testing"
+
+	"github.com/intel/intel-device-plugins-for-kubernetes/pkg/debug"
 )
 
+func init() {
+	debug.Activate()
+}
+
 func TestGetFPGAParams(t *testing.T) {
 	tcases := []struct {
 		stdinJSON         string

cmd/fpga_plugin/fpga_plugin.go

@@ -24,7 +24,6 @@ import (
 	"strings"
 	"time"
 
-	"github.com/golang/glog"
 	"github.com/pkg/errors"
 
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -35,6 +34,7 @@ import (
 	utilnode "k8s.io/kubernetes/pkg/util/node"
 
 	dpapi "github.com/intel/intel-device-plugins-for-kubernetes/internal/deviceplugin"
+	"github.com/intel/intel-device-plugins-for-kubernetes/pkg/debug"
 )
 
 const (
@@ -237,7 +237,7 @@ func (dp *devicePlugin) getDevNode(devName string) (string, error) {
 func (dp *devicePlugin) scanFPGAs() (dpapi.DeviceTree, error) {
 	var devices []device
 
-	glog.V(2).Info("Start new FPGA scan")
+	debug.Print("Start new FPGA scan")
 
 	fpgaFiles, err := ioutil.ReadDir(dp.sysfsDir)
 	if err != nil {
@@ -340,13 +340,19 @@ func main() {
 	var master string
 	var config *rest.Config
 	var err error
+	var debugEnabled bool
 
 	flag.StringVar(&kubeconfig, "kubeconfig", "", "absolute path to the kubeconfig file")
 	flag.StringVar(&master, "master", "", "master url")
 	flag.StringVar(&mode, "mode", string(afMode),
 		fmt.Sprintf("device plugin mode: '%s' (default), '%s' or '%s'", afMode, regionMode, regionDevelMode))
+	flag.BoolVar(&debugEnabled, "debug", false, "enable debug output")
 	flag.Parse()
 
+	if debugEnabled {
+		debug.Activate()
+	}
+
 	if kubeconfig == "" {
 		config, err = rest.InClusterConfig()
 	} else {
@@ -370,7 +376,7 @@ func main() {
 	}
 
 	if nodeMode, ok := node.ObjectMeta.Annotations["fpga.intel.com/device-plugin-mode"]; ok {
-		glog.Info("Overriding mode to ", nodeMode)
+		fmt.Println("Overriding mode to ", nodeMode)
 		mode = nodeMode
 	}
 
@@ -379,7 +385,7 @@ func main() {
 		fatal(err)
 	}
 
-	glog.Info("FPGA device plugin started in ", mode, " mode")
+	fmt.Println("FPGA device plugin started in ", mode, " mode")
 
 	manager := dpapi.NewManager(namespace, plugin)
 	manager.Run()

cmd/fpga_plugin/fpga_plugin_test.go

@@ -29,8 +29,13 @@ import (
 	pluginapi "k8s.io/kubernetes/pkg/kubelet/apis/deviceplugin/v1beta1"
 
 	dpapi "github.com/intel/intel-device-plugins-for-kubernetes/internal/deviceplugin"
+	"github.com/intel/intel-device-plugins-for-kubernetes/pkg/debug"
 )
 
+func init() {
+	debug.Activate()
+}
+
 func createTestDirs(devfs, sysfs string, devfsDirs, sysfsDirs []string, sysfsFiles map[string][]byte) error {
 	var err error
 

cmd/gpu_plugin/gpu_plugin.go

@@ -24,12 +24,12 @@ import (
 	"strings"
 	"time"
 
-	"github.com/golang/glog"
 	"github.com/pkg/errors"
 
 	pluginapi "k8s.io/kubernetes/pkg/kubelet/apis/deviceplugin/v1beta1"
 
 	dpapi "github.com/intel/intel-device-plugins-for-kubernetes/internal/deviceplugin"
+	"github.com/intel/intel-device-plugins-for-kubernetes/pkg/debug"
 )
 
 const (
@@ -88,7 +88,7 @@ func (dp *devicePlugin) scan() (dpapi.DeviceTree, error) {
 		if dp.gpuDeviceReg.MatchString(f.Name()) {
 			dat, err := ioutil.ReadFile(path.Join(dp.sysfsDir, f.Name(), "device/vendor"))
 			if err != nil {
-				glog.Warning("Skipping. Can't read vendor file: ", err)
+				fmt.Println("WARNING: Skipping. Can't read vendor file: ", err)
 				continue
 			}
 
@@ -110,7 +110,7 @@ func (dp *devicePlugin) scan() (dpapi.DeviceTree, error) {
 						continue
 					}
 
-					glog.V(2).Info("Adding ", devPath, " to GPU ", f.Name())
+					debug.Printf("Adding %s to GPU %s", devPath, f.Name())
 					nodes = append(nodes, devPath)
 				}
 
@@ -134,16 +134,22 @@ func (dp *devicePlugin) scan() (dpapi.DeviceTree, error) {
 
 func main() {
 	var sharedDevNum int
+	var debugEnabled bool
 
 	flag.IntVar(&sharedDevNum, "shared-dev-num", 1, "number of containers sharing the same GPU device")
+	flag.BoolVar(&debugEnabled, "debug", false, "enable debug output")
 	flag.Parse()
 
+	if debugEnabled {
+		debug.Activate()
+	}
+
 	if sharedDevNum < 1 {
-		glog.Error("The number of containers sharing the same GPU must greater than zero")
+		fmt.Println("The number of containers sharing the same GPU must greater than zero")
 		os.Exit(1)
 	}
 
-	glog.Info("GPU device plugin started")
+	fmt.Println("GPU device plugin started")
 
 	plugin := newDevicePlugin(sysfsDrmDirectory, devfsDriDirectory, sharedDevNum)
 	manager := dpapi.NewManager(namespace, plugin)

cmd/gpu_plugin/gpu_plugin_test.go

@@ -21,8 +21,14 @@ import (
 	"path"
 	"testing"
 	"time"
+
+	"github.com/intel/intel-device-plugins-for-kubernetes/pkg/debug"
 )
 
+func init() {
+	debug.Activate()
+}
+
 func TestScan(t *testing.T) {
 	tmpdir := fmt.Sprintf("/tmp/gpuplugin-test-%d", time.Now().Unix())
 	sysfs := path.Join(tmpdir, "sysfs")

cmd/qat_plugin/README.md

@@ -35,7 +35,7 @@ $ ls /var/lib/kubelet/device-plugins/kubelet.sock
 ### Deploy QAT device plugin directly on the host:
 ```
 $ sudo $GOPATH/src/github.com/intel/intel-device-plugins-for-kubernetes/cmd/qat_plugin/qat_plugin \
--dpdk-driver igb_uio -kernel-vf-drivers dh895xccvf -max-num-devices 10 -v 10 logtostderr
+-dpdk-driver igb_uio -kernel-vf-drivers dh895xccvf -max-num-devices 10 -debug
 QAT device plugin started
 Discovered Devices below:
 03:01.0 device: corresponding DPDK device detected is uio0

cmd/qat_plugin/qat_plugin.go

@@ -25,12 +25,12 @@ import (
 	"strings"
 	"time"
 
-	"github.com/golang/glog"
 	"github.com/pkg/errors"
 
 	pluginapi "k8s.io/kubernetes/pkg/kubelet/apis/deviceplugin/v1beta1"
 
 	"github.com/intel/intel-device-plugins-for-kubernetes/internal/deviceplugin"
+	"github.com/intel/intel-device-plugins-for-kubernetes/pkg/debug"
 )
 
 const (
@@ -263,9 +263,14 @@ func main() {
 	dpdkDriver := flag.String("dpdk-driver", "igb_uio", "DPDK Device driver for configuring the QAT device")
 	kernelVfDrivers := flag.String("kernel-vf-drivers", "dh895xccvf,c6xxvf,c3xxxvf,d15xxvf", "Comma separated VF Device Driver of the QuickAssist Devices in the system. Devices supported: DH895xCC,C62x,C3xxx and D15xx")
 	maxNumDevices := flag.Int("max-num-devices", 32, "maximum number of QAT devices to be provided to the QuickAssist device plugin")
+	debugEnabled := flag.Bool("debug", false, "enable debug output")
 	flag.Parse()
 	fmt.Println("QAT device plugin started")
 
+	if *debugEnabled {
+		debug.Activate()
+	}
+
 	if !isValidDpdkDeviceDriver(*dpdkDriver) {
 		fmt.Println("Wrong DPDK device driver:", *dpdkDriver)
 		os.Exit(1)

cmd/qat_plugin/qat_plugin_test.go

@@ -23,8 +23,14 @@ import (
 	"time"
 
 	"github.com/pkg/errors"
+
+	"github.com/intel/intel-device-plugins-for-kubernetes/pkg/debug"
 )
 
+func init() {
+	debug.Activate()
+}
+
 func createTestFiles(prefix string, dirs []string, files map[string][]byte) error {
 	for _, dir := range dirs {
 		err := os.MkdirAll(path.Join(prefix, dir), 0755)

deployments/fpga_admissionwebhook/deployment-tpl.yaml

@@ -21,9 +21,7 @@ spec:
             - -tls-cert-file=/etc/webhook/certs/cert.pem
             - -tls-private-key-file=/etc/webhook/certs/key.pem
             - -mode={MODE}
-            - -alsologtostderr
-            - -v=2
-            - 2>&1
+            - -debug
           volumeMounts:
             - name: webhook-certs
               mountPath: /etc/webhook/certs

internal/deviceplugin/manager.go

@@ -19,9 +19,9 @@ import (
 	"os"
 	"reflect"
 
-	"github.com/golang/glog"
-
 	pluginapi "k8s.io/kubernetes/pkg/kubelet/apis/deviceplugin/v1beta1"
+
+	"github.com/intel/intel-device-plugins-for-kubernetes/pkg/debug"
 )
 
 // updateInfo contains info for added, updated and deleted devices.
@@ -107,7 +107,7 @@ func (m *Manager) Run() {
 }
 
 func (m *Manager) handleUpdate(update updateInfo) {
-	glog.V(2).Info("Received dev updates: ", update)
+	debug.Print("Received dev updates:", update)
 	for devType, devices := range update.Added {
 		var postAllocate func(*pluginapi.AllocateResponse) error
 

internal/deviceplugin/manager_test.go

@@ -18,8 +18,14 @@ import (
 	"testing"
 
 	pluginapi "k8s.io/kubernetes/pkg/kubelet/apis/deviceplugin/v1beta1"
+
+	"github.com/intel/intel-device-plugins-for-kubernetes/pkg/debug"
 )
 
+func init() {
+	debug.Activate()
+}
+
 func TestNotify(t *testing.T) {
 	tcases := []struct {
 		name            string

internal/deviceplugin/server.go

@@ -24,11 +24,12 @@ import (
 	"time"
 
 	"github.com/fsnotify/fsnotify"
-	"github.com/golang/glog"
 	"github.com/pkg/errors"
 	"google.golang.org/grpc"
 
 	pluginapi "k8s.io/kubernetes/pkg/kubelet/apis/deviceplugin/v1beta1"
+
+	"github.com/intel/intel-device-plugins-for-kubernetes/pkg/debug"
 )
 
 // devicePluginServer maintains a gRPC server satisfying
@@ -69,7 +70,7 @@ func (srv *server) sendDevices(stream pluginapi.DevicePlugin_ListAndWatchServer)
 	for id, device := range srv.devices {
 		resp.Devices = append(resp.Devices, &pluginapi.Device{id, device.State})
 	}
-	glog.V(2).Info("Sending to kubelet ", resp.Devices)
+	debug.Print("Sending to kubelet", resp.Devices)
 	if err := stream.Send(resp); err != nil {
 		srv.Stop()
 		return errors.Wrapf(err, "Cannot update device list")
@@ -79,7 +80,7 @@ func (srv *server) sendDevices(stream pluginapi.DevicePlugin_ListAndWatchServer)
 }
 
 func (srv *server) ListAndWatch(empty *pluginapi.Empty, stream pluginapi.DevicePlugin_ListAndWatchServer) error {
-	glog.V(2).Info("Started ListAndWatch for ", srv.devType)
+	debug.Print("Started ListAndWatch for", srv.devType)
 
 	if err := srv.sendDevices(stream); err != nil {
 		return err
@@ -187,7 +188,7 @@ func (srv *server) setupAndServe(namespace string, devicePluginPath string, kube
 
 		// Starts device plugin service.
 		go func() {
-			fmt.Printf("device-plugin start server at: %s\n", pluginSocket)
+			fmt.Printf("Start server for %s at: %s\n", srv.devType, pluginSocket)
 			srv.grpcServer.Serve(lis)
 		}()
 
@@ -201,16 +202,14 @@ func (srv *server) setupAndServe(namespace string, devicePluginPath string, kube
 		if err != nil {
 			return err
 		}
-		fmt.Println("device-plugin registered")
+		fmt.Printf("Device plugin for %s registered\n", srv.devType)
 
 		// Kubelet removes plugin socket when it (re)starts
 		// plugin must restart in this case
 		if err = watchFile(pluginSocket); err != nil {
 			return err
 		}
-		fmt.Printf("socket %s removed, restarting", pluginSocket)
-
-		fmt.Println("stop GRPC server")
+		fmt.Printf("Socket %s removed, restarting\n", pluginSocket)
 
 		srv.grpcServer.Stop()
 		os.Remove(pluginSocket)

internal/deviceplugin/server_test.go

@@ -29,6 +29,7 @@ import (
 
 	pluginapi "k8s.io/kubernetes/pkg/kubelet/apis/deviceplugin/v1beta1"
 
+	"github.com/intel/intel-device-plugins-for-kubernetes/pkg/debug"
 	"github.com/pkg/errors"
 )
 
@@ -47,6 +48,10 @@ type kubeletStub struct {
 	server         *grpc.Server
 }
 
+func init() {
+	debug.Activate()
+}
+
 // newKubeletStub returns an initialized kubeletStub for testing purpose.
 func newKubeletStub(socket string) *kubeletStub {
 	return &kubeletStub{

pkg/debug/debug.go

@@ -0,0 +1,57 @@
+// Copyright 2018 Intel Corporation. All Rights Reserved.
+//
+// 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 debug
+
+import (
+	"fmt"
+	"runtime"
+	"strings"
+)
+
+const (
+	prefix = "DEBUG"
+)
+
+var (
+	isEnabled bool
+)
+
+func getFileAndLine() string {
+	_, file, line, ok := runtime.Caller(2)
+	if !ok {
+		return "???:0"
+	}
+	parts := strings.Split(file, "/")
+	return fmt.Sprintf("%s:%d", parts[len(parts)-1], line)
+}
+
+// Activate activates debugging output
+func Activate() {
+	isEnabled = true
+}
+
+// Print prints its arguments with fmt.Println() if debug output is activated
+func Print(obj ...interface{}) {
+	if isEnabled {
+		fmt.Println(append([]interface{}{prefix, getFileAndLine()}, obj...)...)
+	}
+}
+
+// Printf prints its arguments with fmt.Printf() if debug output is activated
+func Printf(pattern string, obj ...interface{}) {
+	if isEnabled {
+		fmt.Printf(strings.Join([]string{prefix, getFileAndLine(), pattern + "\n"}, " "), obj...)
+	}
+}