cmd: silence warnings in kube-controller-manager/kube-apiserver, dedupe/color warnings in kubectl

cmd/kube-apiserver/app/server.go

@@ -53,6 +53,7 @@ import (
 	"k8s.io/apiserver/pkg/util/webhook"
 	clientgoinformers "k8s.io/client-go/informers"
 	clientgoclientset "k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/rest"
 	"k8s.io/client-go/util/keyutil"
 	cloudprovider "k8s.io/cloud-provider"
 	cliflag "k8s.io/component-base/cli/flag"
@@ -100,6 +101,12 @@ cluster's shared state through which all other components interact.`,
 
 		// stop printing usage when the command errors
 		SilenceUsage: true,
+		PersistentPreRunE: func(*cobra.Command, []string) error {
+			// silence client-go warnings.
+			// kube-apiserver loopback clients should not log self-issued warnings.
+			rest.SetDefaultWarningHandler(rest.NoWarnings{})
+			return nil
+		},
 		RunE: func(cmd *cobra.Command, args []string) error {
 			verflag.PrintAndExitIfRequested()
 			cliflag.PrintFlags(cmd.Flags())

cmd/kube-controller-manager/app/controllermanager.go

@@ -104,6 +104,13 @@ state of the cluster through the apiserver and makes changes attempting to move
 current state towards the desired state. Examples of controllers that ship with
 Kubernetes today are the replication controller, endpoints controller, namespace
 controller, and serviceaccounts controller.`,
+		PersistentPreRunE: func(*cobra.Command, []string) error {
+			// silence client-go warnings.
+			// kube-controller-manager generically watches APIs (including deprecated ones),
+			// and CI ensures it works properly against matching kube-apiserver versions.
+			restclient.SetDefaultWarningHandler(restclient.NoWarnings{})
+			return nil
+		},
 		Run: func(cmd *cobra.Command, args []string) {
 			verflag.PrintAndExitIfRequested()
 			cliflag.PrintFlags(cmd.Flags())

pkg/kubectl/cmd/cmd.go

@@ -28,6 +28,7 @@ import (
 
 	"github.com/spf13/cobra"
 
+	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/clientcmd"
 	cliflag "k8s.io/component-base/cli/flag"
 	cmdpkg "k8s.io/kubectl/pkg/cmd"
@@ -69,6 +70,7 @@ import (
 	"k8s.io/kubectl/pkg/cmd/wait"
 	"k8s.io/kubectl/pkg/util/i18n"
 	"k8s.io/kubectl/pkg/util/templates"
+	"k8s.io/kubectl/pkg/util/term"
 	"k8s.io/kubernetes/pkg/kubectl/cmd/auth"
 	"k8s.io/kubernetes/pkg/kubectl/cmd/convert"
 	"k8s.io/kubernetes/pkg/kubectl/cmd/cp"
@@ -428,6 +430,9 @@ func HandlePluginCommand(pluginHandler PluginHandler, cmdArgs []string) error {
 
 // NewKubectlCommand creates the `kubectl` command and its nested children.
 func NewKubectlCommand(in io.Reader, out, err io.Writer) *cobra.Command {
+	warningHandler := rest.NewWarningWriter(err, rest.WarningWriterOptions{Deduplicate: true, Color: term.AllowsColorOutput(err)})
+	warningsAsErrors := false
+
 	// Parent command to which all subcommands are added.
 	cmds := &cobra.Command{
 		Use:   "kubectl",
@@ -441,10 +446,25 @@ func NewKubectlCommand(in io.Reader, out, err io.Writer) *cobra.Command {
 		// Hook before and after Run initialize and write profiles to disk,
 		// respectively.
 		PersistentPreRunE: func(*cobra.Command, []string) error {
+			rest.SetDefaultWarningHandler(warningHandler)
 			return initProfiling()
 		},
 		PersistentPostRunE: func(*cobra.Command, []string) error {
-			return flushProfiling()
+			if err := flushProfiling(); err != nil {
+				return err
+			}
+			if warningsAsErrors {
+				count := warningHandler.WarningCount()
+				switch count {
+				case 0:
+					// no warnings
+				case 1:
+					return fmt.Errorf("%d warning received", count)
+				default:
+					return fmt.Errorf("%d warnings received", count)
+				}
+			}
+			return nil
 		},
 		BashCompletionFunction: bashCompletionFunc,
 	}
@@ -458,6 +478,8 @@ func NewKubectlCommand(in io.Reader, out, err io.Writer) *cobra.Command {
 
 	addProfilingFlags(flags)
 
+	flags.BoolVar(&warningsAsErrors, "warnings-as-errors", warningsAsErrors, "Treat warnings received from the server as errors and exit with a non-zero exit code")
+
 	kubeConfigFlags := genericclioptions.NewConfigFlags(true).WithDeprecatedPasswordFlag()
 	kubeConfigFlags.AddFlags(flags)
 	matchVersionKubeConfigFlags := cmdutil.NewMatchVersionFlags(kubeConfigFlags)

staging/src/k8s.io/kubectl/pkg/util/term/term.go

@@ -19,6 +19,7 @@ package term
 import (
 	"io"
 	"os"
+	"runtime"
 
 	"github.com/moby/term"
 
@@ -70,6 +71,32 @@ func IsTerminal(i interface{}) bool {
 	return terminal
 }
 
+// AllowsColorOutput returns true if the specified writer is a terminal and
+// the process environment indicates color output is supported and desired.
+func AllowsColorOutput(w io.Writer) bool {
+	if !IsTerminal(w) {
+		return false
+	}
+
+	// https://en.wikipedia.org/wiki/Computer_terminal#Dumb_terminals
+	if os.Getenv("TERM") == "dumb" {
+		return false
+	}
+
+	// https://no-color.org/
+	if _, nocolor := os.LookupEnv("NO_COLOR"); nocolor {
+		return false
+	}
+
+	// On Windows WT_SESSION is set by the modern terminal component.
+	// Older terminals have poor support for UTF-8, VT escape codes, etc.
+	if runtime.GOOS == "windows" && os.Getenv("WT_SESSION") == "" {
+		return false
+	}
+
+	return true
+}
+
 // Safe invokes the provided function and will attempt to ensure that when the
 // function returns (or a termination signal is sent) that the terminal state
 // is reset to the condition it was in prior to the function being invoked. If

test/cmd/rbac.sh

@@ -145,6 +145,14 @@ run_role_tests() {
   create_and_use_new_namespace
   kube::log::status "Testing role"
 
+  # Test deprecated API request output
+  # TODO(liggitt): switch this to a custom deprecated resource once CRDs support marking versions as deprecated
+  output_message=$(kubectl get roles.v1beta1.rbac.authorization.k8s.io 2>&1 "${kube_flags[@]}")
+  kube::test::if_has_string "${output_message}" 'Role is deprecated'
+  output_message=$(! kubectl get roles.v1beta1.rbac.authorization.k8s.io --warnings-as-errors 2>&1 "${kube_flags[@]}")
+  kube::test::if_has_string "${output_message}" 'Role is deprecated'
+  kube::test::if_has_string "${output_message}" 'Error: 1 warning received'
+
   # Dry-run create
   kubectl create "${kube_flags[@]}" role pod-admin --dry-run=client --verb=* --resource=pods
   kubectl create "${kube_flags[@]}" role pod-admin --dry-run=server --verb=* --resource=pods