exec credential provider: add rest_client_exec_plugin_call_total metric

Signed-off-by: Andrew Keesler <akeesler@vmware.com>

Kubernetes-commit: 31eec29b098f790cd96fd6d2441e68938f15363b

plugin/pkg/client/auth/exec/metrics_test.go

@@ -17,8 +17,14 @@ limitations under the License.
 package exec
 
 import (
+	"fmt"
 	"testing"
 	"time"
+
+	"github.com/google/go-cmp/cmp"
+	"k8s.io/client-go/pkg/apis/clientauthentication"
+	"k8s.io/client-go/tools/clientcmd/api"
+	"k8s.io/client-go/tools/metrics"
 )
 
 type mockExpiryGauge struct {
@@ -94,3 +100,98 @@ func TestCertificateExpirationTracker(t *testing.T) {
 		})
 	}
 }
+
+type mockCallsMetric struct {
+	exitCode  int
+	errorType string
+}
+
+type mockCallsMetricCounter struct {
+	calls []mockCallsMetric
+}
+
+func (f *mockCallsMetricCounter) Increment(exitCode int, errorType string) {
+	f.calls = append(f.calls, mockCallsMetric{exitCode: exitCode, errorType: errorType})
+}
+
+func TestCallsMetric(t *testing.T) {
+	const (
+		goodOutput = `{
+			"kind": "ExecCredential",
+			"apiVersion": "client.authentication.k8s.io/v1beta1",
+			"status": {
+				"token": "foo-bar"
+			}
+		}`
+	)
+
+	callsMetricCounter := &mockCallsMetricCounter{}
+	originalExecPluginCalls := metrics.ExecPluginCalls
+	t.Cleanup(func() { metrics.ExecPluginCalls = originalExecPluginCalls })
+	metrics.ExecPluginCalls = callsMetricCounter
+
+	exitCodes := []int{0, 1, 2, 0}
+	var wantCallsMetrics []mockCallsMetric
+	for _, exitCode := range exitCodes {
+		c := api.ExecConfig{
+			Command:    "./testdata/test-plugin.sh",
+			APIVersion: "client.authentication.k8s.io/v1beta1",
+			Env: []api.ExecEnvVar{
+				{Name: "TEST_EXIT_CODE", Value: fmt.Sprintf("%d", exitCode)},
+				{Name: "TEST_OUTPUT", Value: goodOutput},
+			},
+		}
+
+		a, err := newAuthenticator(newCache(), &c, nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		// Run refresh creds twice so that our test validates that the metrics are set correctly twice
+		// in a row with the same authenticator.
+		refreshCreds := func() {
+			if err := a.refreshCredsLocked(&clientauthentication.Response{}); (err == nil) != (exitCode == 0) {
+				if err != nil {
+					t.Fatalf("wanted no error, but got %q", err.Error())
+				} else {
+					t.Fatal("wanted error, but got nil")
+				}
+			}
+			mockCallsMetric := mockCallsMetric{exitCode: exitCode, errorType: "no_error"}
+			if exitCode != 0 {
+				mockCallsMetric.errorType = "plugin_execution_error"
+			}
+			wantCallsMetrics = append(wantCallsMetrics, mockCallsMetric)
+		}
+		refreshCreds()
+		refreshCreds()
+	}
+
+	// Run some iterations of the authenticator where the exec plugin fails to run to test special
+	// metric values.
+	refreshCreds := func(command string) {
+		c := api.ExecConfig{
+			Command:    "does not exist",
+			APIVersion: "client.authentication.k8s.io/v1beta1",
+		}
+		a, err := newAuthenticator(newCache(), &c, nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if err := a.refreshCredsLocked(&clientauthentication.Response{}); err == nil {
+			t.Fatal("expected the authenticator to fail because the plugin does not exist")
+		}
+		wantCallsMetrics = append(wantCallsMetrics, mockCallsMetric{exitCode: 1, errorType: "plugin_not_found_error"})
+	}
+	refreshCreds("does not exist without path slashes")
+	refreshCreds("./does/not/exist/with/relative/path")
+	refreshCreds("/does/not/exist/with/absolute/path")
+
+	callsMetricComparer := cmp.Comparer(func(a, b mockCallsMetric) bool {
+		return a.exitCode == b.exitCode && a.errorType == b.errorType
+	})
+	actuallCallsMetrics := callsMetricCounter.calls
+	if diff := cmp.Diff(wantCallsMetrics, actuallCallsMetrics, callsMetricComparer); diff != "" {
+		t.Fatalf("got unexpected metrics calls; -want, +got:\n%s", diff)
+	}
+}