Repository: kubernetes-csi/external-snapshotter (go)

Issue:
http-endpoint and metrics server seem not to be working in snapshot-controller
Hi,
I just tried to enable the http-endpoint on the `snapshot-controller:v4.1.1` deployment as described [in the docs](https://github.com/kubernetes-csi/external-snapshotter/tree/v4.1.1#snapshot-controller-command-line-options). The resulting manifest currently looks like this:

```yaml
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: snapshot-controller
  namespace: kube-system
spec:
  minReadySeconds: 15
  replicas: 2
  selector:
    matchLabels:
      app: snapshot-controller
  strategy:
    rollingUpdate:
      maxSurge: 0
      maxUnavailable: 1
    type: RollingUpdate
  template:
    metadata:
      labels:
        app: snapshot-controller
    spec:
      containers:
      - args:
        - --v=5
        - --leader-election=true
        - --http-endpoint=:8080
        - --metrics-path=/metrics
        image: k8s.gcr.io/sig-storage/snapshot-controller:v4.1.1
        imagePullPolicy: IfNotPresent
        name: snapshot-controller
        ports:
        - containerPort: 8080
          name: http
      serviceAccount: snapshot-controller
```

The logs indicate that the server was started:

```
I0806 07:32:03.910275       1 main.go:113] Version: v4.1.1                                                                                    
I0806 07:32:03.911956       1 main.go:156] Metrics server successfully started on :8080, /metrics
I0806 07:32:03.912124       1 main.go:162] Start NewCSISnapshotController with kubeconfig [] resyncPeriod [15m0s]  
```

But when i port-forward port `8080` I get the following responses:

```console
❯ curl -v localhost:8080/metrics
*   Trying 127.0.0.1:8080...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 8080 (#0)
> GET /metrics HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.68.0
> Accept: */*
> 
* Mark bundle as not supporting multiuse
< HTTP/1.1 200 OK
< Content-Type: text/plain; version=0.0.4; charset=utf-8
< Date: Fri, 06 Aug 2021 07:33:26 GMT
< Content-Length: 0
< 
* Connection #0 to host localhost left intact
```
```console
❯ curl -v localhost:8080/healthz/leader-election
*   Trying 127.0.0.1:8080...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 8080 (#0)
> GET /healthz/leader-election HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.68.0
> Accept: */*
> 
* Mark bundle as not supporting multiuse
< HTTP/1.1 404 Not Found
< Content-Type: text/plain; charset=utf-8
< X-Content-Type-Options: nosniff
< Date: Fri, 06 Aug 2021 07:34:19 GMT
< Content-Length: 19
< 
404 page not found
* Connection #0 to host localhost left intact
```

Is there anythin I'm missing in my setup?

Pull request description:
Refactor http server and register leaderelection health check

Signed-off-by: Grant Griffiths <ggriffiths@purestorage.com>

**What type of PR is this?**
/kind bug

**What this PR does / why we need it**:
- Needed to start the http server outside of pkg/metric for the snapshot controller
- We needed this because we want to add other endpoints to the server

**Which issue(s) this PR fixes**:
Fixes #572 

**Special notes for your reviewer**:

**Does this PR introduce a user-facing change?**:
```release-note
Adds the leader election health check for the snapshot controller at `/healthz/leader-election`
```


Patch:
diff --git a/cmd/snapshot-controller/main.go b/cmd/snapshot-controller/main.go
index ff78b9eea..10c85eedf 100644
--- a/cmd/snapshot-controller/main.go
+++ b/cmd/snapshot-controller/main.go
@@ -20,6 +20,8 @@ import (
 	"context"
 	"flag"
 	"fmt"
+	"net"
+	"net/http"
 	"os"
 	"os/signal"
 	"sync"
@@ -143,23 +145,15 @@ func main() {
 	// Create and register metrics manager
 	metricsManager := metrics.NewMetricsManager()
 	wg := &sync.WaitGroup{}
-	wg.Add(1)
+
+	mux := http.NewServeMux()
 	if *httpEndpoint != "" {
-		srv, err := metricsManager.StartMetricsEndpoint(*metricsPath, *httpEndpoint, promklog{}, wg)
+		err := metricsManager.PrepareMetricsPath(mux, *metricsPath, promklog{})
 		if err != nil {
-			klog.Errorf("Failed to start metrics server: %s", err.Error())
+			klog.Errorf("Failed to prepare metrics path: %s", err.Error())
 			os.Exit(1)
 		}
-		defer func() {
-			err := srv.Shutdown(context.Background())
-			if err != nil {
-				klog.Errorf("Failed to shutdown metrics server: %s", err.Error())
-			}
-
-			klog.Infof("Metrics server successfully shutdown")
-			wg.Done()
-		}()
-		klog.Infof("Metrics server successfully started on %s, %s", *httpEndpoint, *metricsPath)
+		klog.Infof("Metrics path successfully registered at %s", *metricsPath)
 	}
 
 	// Add Snapshot types to the default Kubernetes so events can be logged for them
@@ -199,6 +193,32 @@ func main() {
 		close(stopCh)
 	}
 
+	// start listening & serving http endpoint if set
+	if *httpEndpoint != "" {
+		l, err := net.Listen("tcp", *httpEndpoint)
+		if err != nil {
+			klog.Fatalf("failed to listen on address[%s], error[%v]", *httpEndpoint, err)
+		}
+		srv := &http.Server{Addr: l.Addr().String(), Handler: mux}
+		go func() {
+			defer wg.Done()
+			if err := srv.Serve(l); err != http.ErrServerClosed {
+				klog.Fatalf("failed to start endpoint at:%s/%s, error: %v", *httpEndpoint, *metricsPath, err)
+			}
+		}()
+		klog.Infof("Metrics http server successfully started on %s, %s", *httpEndpoint, *metricsPath)
+
+		defer func() {
+			err := srv.Shutdown(context.Background())
+			if err != nil {
+				klog.Errorf("Failed to shutdown metrics server: %s", err.Error())
+			}
+
+			klog.Infof("Metrics server successfully shutdown")
+			wg.Done()
+		}()
+	}
+
 	if !*leaderElection {
 		run(context.TODO())
 	} else {
@@ -210,6 +230,10 @@ func main() {
 			klog.Fatalf("failed to create leaderelection client: %v", err)
 		}
 		le := leaderelection.NewLeaderElection(leClientset, lockName, run)
+		if *httpEndpoint != "" {
+			le.PrepareHealthCheck(mux, leaderelection.DefaultHealthCheckTimeout)
+		}
+
 		if *leaderElectionNamespace != "" {
 			le.WithNamespace(*leaderElectionNamespace)
 		}
diff --git a/pkg/metrics/metrics.go b/pkg/metrics/metrics.go
index 92bb07364..c7f5f8950 100644
--- a/pkg/metrics/metrics.go
+++ b/pkg/metrics/metrics.go
@@ -17,8 +17,6 @@ limitations under the License.
 package metrics
 
 import (
-	"fmt"
-	"net"
 	"net/http"
 	"sync"
 	"time"
@@ -26,7 +24,6 @@ import (
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"k8s.io/apimachinery/pkg/types"
 	k8smetrics "k8s.io/component-base/metrics"
-	klog "k8s.io/klog/v2"
 )
 
 const (
@@ -89,12 +86,11 @@ type OperationStatus interface {
 var metricBuckets = []float64{0.1, 0.25, 0.5, 1, 2.5, 5, 10, 15, 30, 60, 120, 300, 600}
 
 type MetricsManager interface {
-	// StartMetricsEndpoint starts the metrics endpoint at the specified addr/pattern for
-	// metrics managed by this MetricsManager. It spawns a goroutine to listen to
-	// and serve HTTP requests received on addr/pattern.
-	// If the "pattern" is empty (i.e., ""), no endpoint will be started.
+	// PrepareMetricsPath prepares the metrics path the specified pattern for
+	// metrics managed by this MetricsManager.
+	// If the "pattern" is empty (i.e., ""), it will not be registered.
 	// An error will be returned if there is any.
-	StartMetricsEndpoint(pattern, addr string, logger promhttp.Logger, wg *sync.WaitGroup) (*http.Server, error)
+	PrepareMetricsPath(mux *http.ServeMux, pattern string, logger promhttp.Logger) error
 
 	// OperationStart takes in an operation and caches its start time.
 	// if the operation already exists, it's an no-op.
@@ -304,31 +300,15 @@ func (opMgr *operationMetricsManager) scheduleOpsInFlightMetric() {
 	}
 }
 
-func (opMgr *operationMetricsManager) StartMetricsEndpoint(pattern, addr string, logger promhttp.Logger, wg *sync.WaitGroup) (*http.Server, error) {
-	if addr == "" {
-		return nil, fmt.Errorf("metrics endpoint will not be started as endpoint address is not specified")
-	}
-	// start listening
-	l, err := net.Listen("tcp", addr)
-	if err != nil {
-		return nil, fmt.Errorf("failed to listen on address[%s], error[%v]", addr, err)
-	}
-	mux := http.NewServeMux()
+func (opMgr *operationMetricsManager) PrepareMetricsPath(mux *http.ServeMux, pattern string, logger promhttp.Logger) error {
 	mux.Handle(pattern, k8smetrics.HandlerFor(
 		opMgr.registry,
 		k8smetrics.HandlerOpts{
 			ErrorLog:      logger,
 			ErrorHandling: k8smetrics.ContinueOnError,
 		}))
-	srv := &http.Server{Addr: l.Addr().String(), Handler: mux}
-	// start serving the endpoint
-	go func() {
-		defer wg.Done()
-		if err := srv.Serve(l); err != http.ErrServerClosed {
-			klog.Fatalf("failed to start endpoint at:%s/%s, error: %v", addr, pattern, err)
-		}
-	}()
-	return srv, nil
+
+	return nil
 }
 
 func (opMgr *operationMetricsManager) GetRegistry() k8smetrics.KubeRegistry {
diff --git a/pkg/sidecar-controller/snapshot_controller_base.go b/pkg/sidecar-controller/snapshot_controller_base.go
index 0d2030652..07876a189 100644
--- a/pkg/sidecar-controller/snapshot_controller_base.go
+++ b/pkg/sidecar-controller/snapshot_controller_base.go
@@ -26,7 +26,7 @@ import (
 	storagelisters "github.com/kubernetes-csi/external-snapshotter/client/v4/listers/volumesnapshot/v1"
 	"github.com/kubernetes-csi/external-snapshotter/v4/pkg/snapshotter"
 
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/apimachinery/pkg/labels"
 	"k8s.io/apimachinery/pkg/util/wait"


Test patch:
diff --git a/pkg/common-controller/framework_test.go b/pkg/common-controller/framework_test.go
index 414cfcc42..c0093f008 100644
--- a/pkg/common-controller/framework_test.go
+++ b/pkg/common-controller/framework_test.go
@@ -19,7 +19,7 @@ package common_controller
 import (
 	"errors"
 	"fmt"
-	"k8s.io/client-go/util/workqueue"
+	"net/http"
 	"reflect"
 	sysruntime "runtime"
 	"strconv"
@@ -29,6 +29,8 @@ import (
 	"testing"
 	"time"
 
+	"k8s.io/client-go/util/workqueue"
+
 	crdv1 "github.com/kubernetes-csi/external-snapshotter/client/v4/apis/volumesnapshot/v1"
 	clientset "github.com/kubernetes-csi/external-snapshotter/client/v4/clientset/versioned"
 	"github.com/kubernetes-csi/external-snapshotter/client/v4/clientset/versioned/fake"
@@ -737,9 +739,14 @@ func newTestController(kubeClient kubernetes.Interface, clientset clientset.Inte
 
 	coreFactory := coreinformers.NewSharedInformerFactory(kubeClient, utils.NoResyncPeriodFunc())
 	metricsManager := metrics.NewMetricsManager()
-	wg := &sync.WaitGroup{}
-	wg.Add(1)
-	metricsManager.StartMetricsEndpoint("/metrics", "localhost:0", nil, wg)
+	mux := http.NewServeMux()
+	metricsManager.PrepareMetricsPath(mux, "/metrics", nil)
+	go func() {
+		err := http.ListenAndServe("localhost:0", mux)
+		if err != nil {
+			t.Errorf("failed to prepare metrics path: %v", err)
+		}
+	}()
 
 	ctrl := NewCSISnapshotCommonController(
 		clientset,
diff --git a/pkg/metrics/metrics_test.go b/pkg/metrics/metrics_test.go
index c16fe971e..bb840a038 100644
--- a/pkg/metrics/metrics_test.go
+++ b/pkg/metrics/metrics_test.go
@@ -22,6 +22,7 @@ import (
 	"io"
 	"io/ioutil"
 	"log"
+	"net"
 	"net/http"
 	"reflect"
 	"sort"
@@ -60,35 +61,44 @@ func (s *fakeOpStatus) String() string {
 	return "Unknown"
 }
 
-func initMgr() (MetricsManager, *sync.WaitGroup, *http.Server) {
-	wg := &sync.WaitGroup{}
-	wg.Add(1)
+func initMgr() (MetricsManager, *http.Server) {
 	mgr := NewMetricsManager()
-	srv, err := mgr.StartMetricsEndpoint(httpPattern, addr, nil, wg)
+	mux := http.NewServeMux()
+	err := mgr.PrepareMetricsPath(mux, httpPattern, nil)
 	if err != nil {
 		log.Fatalf("failed to start serving [%v]", err)
 	}
-	return mgr, wg, srv
+	l, err := net.Listen("tcp", addr)
+	if err != nil {
+		log.Fatalf("failed to listen on address[%s], error[%v]", addr, err)
+	}
+	srv := &http.Server{Addr: l.Addr().String(), Handler: mux}
+	go func() {
+		if err := srv.Serve(l); err != http.ErrServerClosed {
+			log.Fatalf("failed to start endpoint at:%s/%s, error: %v", addr, httpPattern, err)
+		}
+	}()
+
+	return mgr, srv
 }
 
-func shutdown(srv *http.Server, wg *sync.WaitGroup) {
+func shutdown(srv *http.Server) {
 	if err := srv.Shutdown(context.Background()); err != nil {
 		panic(err)
 	}
-	wg.Wait()
 }
 
 func TestNew(t *testing.T) {
-	mgr, wg, srv := initMgr()
-	defer shutdown(srv, wg)
+	mgr, srv := initMgr()
+	defer shutdown(srv)
 	if mgr == nil {
 		t.Errorf("failed testing new")
 	}
 }
 
 func TestDropNonExistingOperation(t *testing.T) {
-	mgr, wg, srv := initMgr()
-	defer shutdown(srv, wg)
+	mgr, srv := initMgr()
+	defer shutdown(srv)
 	op := OperationKey{
 		Name:       "drop-non-existing-operation-should-be-noop",
 		ResourceID: types.UID("uid"),
@@ -97,9 +107,9 @@ func TestDropNonExistingOperation(t *testing.T) {
 }
 
 func TestRecordMetricsForNonExistingOperation(t *testing.T) {
-	mgr, wg, srv := initMgr()
+	mgr, srv := initMgr()
 	srvAddr := "http://" + srv.Addr + httpPattern
-	defer shutdown(srv, wg)
+	defer shutdown(srv)
 	opKey := OperationKey{
 		Name:       "no-metrics-should-be-recorded-as-operation-did-not-start",
 		ResourceID: types.UID("uid"),
@@ -119,9 +129,9 @@ func TestRecordMetricsForNonExistingOperation(t *testing.T) {
 }
 
 func TestDropOperation(t *testing.T) {
-	mgr, wg, srv := initMgr()
+	mgr, srv := initMgr()
 	srvAddr := "http://" + srv.Addr + httpPattern
-	defer shutdown(srv, wg)
+	defer shutdown(srv)
 	opKey := OperationKey{
 		Name:       "should-have-been-dropped",
 		ResourceID: types.UID("uid"),
@@ -176,9 +186,9 @@ snapshot_controller_operation_total_seconds_count{driver_name="driver",operation
 }
 
 func TestUnknownStatus(t *testing.T) {
-	mgr, wg, srv := initMgr()
+	mgr, srv := initMgr()
 	srvAddr := "http://" + srv.Addr + httpPattern
-	defer shutdown(srv, wg)
+	defer shutdown(srv)
 	opKey := OperationKey{
 		Name:       "unknown-status-operation",
 		ResourceID: types.UID("uid"),
@@ -214,9 +224,9 @@ snapshot_controller_operation_total_seconds_count{driver_name="driver",operation
 }
 
 func TestRecordMetrics(t *testing.T) {
-	mgr, wg, srv := initMgr()
+	mgr, srv := initMgr()
 	srvAddr := "http://" + srv.Addr + httpPattern
-	defer shutdown(srv, wg)
+	defer shutdown(srv)
 	// add an operation
 	opKey := OperationKey{
 		Name:       "op1",
@@ -284,9 +294,9 @@ snapshot_controller_operation_total_seconds_count{driver_name="driver2",operatio
 }
 
 func TestConcurrency(t *testing.T) {
-	mgr, wg, srv := initMgr()
+	mgr, srv := initMgr()
 	srvAddr := "http://" + srv.Addr + httpPattern
-	defer shutdown(srv, wg)
+	defer shutdown(srv)
 	success := &fakeOpStatus{
 		statusCode: 0,
 	}
@@ -482,8 +492,8 @@ snapshot_controller_operation_total_seconds_count{driver_name="driver5",operatio
 func TestInFlightMetric(t *testing.T) {
 	inFlightCheckInterval = time.Millisecond * 50
 
-	mgr, wg, srv := initMgr()
-	defer shutdown(srv, wg)
+	mgr, srv := initMgr()
+	defer shutdown(srv)
 	srvAddr := "http://" + srv.Addr + httpPattern
 
 	//  Start first operation, should be 1
@@ -710,8 +720,8 @@ func containsMetrics(expectedMfs, gotMfs []*cmg.MetricFamily) bool {
 }
 
 func TestProcessStartTimeMetricExist(t *testing.T) {
-	mgr, wg, srv := initMgr()
-	defer shutdown(srv, wg)
+	mgr, srv := initMgr()
+	defer shutdown(srv)
 	metricsFamilies, err := mgr.GetRegistry().Gather()
 	if err != nil {
 		t.Fatalf("Error fetching metrics: %v", err)