feat: Disable any logging from go-client's klog

This PR disables warnings from go-client. Unfortunately this is not
sufficient to also supress the warning about deprecated auth plugins,
therefore the need for klog output code too.

But in general direct logging from 3rd-party libs is undesirable, and
this configures K8S's go-client klog to discard any logs.

I've added some tests to cover some unexpected 3rd-party output, but as
this depends on the environment and kubeconfig config, incl. providers,
and is noteasily reproducible, this should be covered by integration
test, as the current test do not fully cover this. Opened #406.

fixes #402

cmd/kubent/main.go

@@ -1,7 +1,9 @@
 package main
 
 import (
+	"flag"
 	"fmt"
+	"io"
 	"os"
 
 	"github.com/doitintl/kube-no-trouble/pkg/collector"
@@ -16,6 +18,7 @@ import (
 	_ "k8s.io/client-go/plugin/pkg/client/auth/azure"
 	_ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
 	_ "k8s.io/client-go/plugin/pkg/client/auth/oidc"
+	"k8s.io/klog/v2"
 )
 
 var (
@@ -97,6 +100,13 @@ func main() {
 
 	log.Logger = log.Output(zerolog.ConsoleWriter{Out: os.Stderr})
 
+	// disable any logging from K8S go-client
+	// unfortunately restConfig.WarningHandler does not handle auth plugins
+	klog.SetOutput(io.Discard)
+	flags := &flag.FlagSet{}
+	klog.InitFlags(flags)
+	flags.Set("logtostderr", "false")
+
 	config, err := config.NewFromFlags()
 	if err != nil {
 		log.Fatal().Err(err).Msg("failed to parse config flags")

cmd/kubent/main_test.go

@@ -117,20 +117,22 @@ func TestMainExitCodes(t *testing.T) {
 		expected    int      // expected exit code
 		stdout      string   // expected stdout
 		outFileName string
+		emptyStderr bool
 	}{
-		{"success", []string{clusterFlagDisabled, helm3FlagDisabled}, 0, "", ""},
-		{"errorBadFlag", []string{"-c=not-boolean"}, 2, "", ""},
-		{"successFound", []string{"-o=json", clusterFlagDisabled, helm3FlagDisabled, "-f=" + filepath.Join(FIXTURES_DIR, "deployment-v1beta1.yaml")}, 0, string(expectedJsonOutput), ""},
-		{"exitErrorFlagNone", []string{clusterFlagDisabled, helm3FlagDisabled, "-e"}, 0, "", ""},
-		{"exitErrorFlagFound", []string{clusterFlagDisabled, helm3FlagDisabled, "-e", "-f=" + filepath.Join(FIXTURES_DIR, "deployment-v1beta1.yaml")}, 200, "", ""},
-		{"version short flag set", []string{"-v"}, 0, "", ""},
-		{"version long flag set", []string{"--version"}, 0, "", ""},
-		{"empty text output", []string{clusterFlagDisabled, helm3FlagDisabled}, 0, "", ""},
-		{"empty json output", []string{"-o=json", clusterFlagDisabled, helm3FlagDisabled}, 0, "[]\n", ""},
-		{"json-file", []string{"-o=json", clusterFlagDisabled, helm3FlagDisabled, "-f=" + filepath.Join(FIXTURES_DIR, "deployment-v1beta1.yaml")}, 0, "", filepath.Join(tmpDir, "json-file.out")},
-		{"text-file", []string{"-o=json", clusterFlagDisabled, helm3FlagDisabled, "-f=" + filepath.Join(FIXTURES_DIR, "deployment-v1beta1.yaml")}, 0, "", filepath.Join(tmpDir, "text-file.out")},
-		{"json-stdout", []string{"-o=json", clusterFlagDisabled, helm3FlagDisabled, "-f=" + filepath.Join(FIXTURES_DIR, "deployment-v1beta1.yaml")}, 0, string(expectedJsonOutput), "-"},
-		{"error-bad-file", []string{clusterFlagDisabled, helm3FlagDisabled}, 1, "", "/this/dir/is/unlikely/to/exist"},
+		{"success", []string{clusterFlagDisabled, helm3FlagDisabled}, 0, "", "", false},
+		{"errorBadFlag", []string{"-c=not-boolean"}, 2, "", "", false},
+		{"successFound", []string{"-o=json", clusterFlagDisabled, helm3FlagDisabled, "-f=" + filepath.Join(FIXTURES_DIR, "deployment-v1beta1.yaml")}, 0, string(expectedJsonOutput), "", false},
+		{"exitErrorFlagNone", []string{clusterFlagDisabled, helm3FlagDisabled, "-e"}, 0, "", "", false},
+		{"exitErrorFlagFound", []string{clusterFlagDisabled, helm3FlagDisabled, "-e", "-f=" + filepath.Join(FIXTURES_DIR, "deployment-v1beta1.yaml")}, 200, "", "", false},
+		{"version short flag set", []string{"-v"}, 0, "", "", false},
+		{"version long flag set", []string{"--version"}, 0, "", "", false},
+		{"empty text output", []string{clusterFlagDisabled, helm3FlagDisabled}, 0, "", "", false},
+		{"empty json output", []string{"-o=json", clusterFlagDisabled, helm3FlagDisabled}, 0, "[]\n", "", false},
+		{"json-file", []string{"-o=json", clusterFlagDisabled, helm3FlagDisabled, "-f=" + filepath.Join(FIXTURES_DIR, "deployment-v1beta1.yaml")}, 0, "", filepath.Join(tmpDir, "json-file.out"), false},
+		{"text-file", []string{"-o=text", clusterFlagDisabled, helm3FlagDisabled, "-f=" + filepath.Join(FIXTURES_DIR, "deployment-v1beta1.yaml")}, 0, "", filepath.Join(tmpDir, "text-file.out"), false},
+		{"json-stdout", []string{"-o=json", clusterFlagDisabled, helm3FlagDisabled, "-f=" + filepath.Join(FIXTURES_DIR, "deployment-v1beta1.yaml")}, 0, string(expectedJsonOutput), "-", false},
+		{"error-bad-file", []string{clusterFlagDisabled, helm3FlagDisabled}, 1, "", "/this/dir/is/unlikely/to/exist", false},
+		{"no-3rdparty-output", []string{clusterFlagDisabled, helm3FlagDisabled, "-l=disabled"}, 0, "", "", true},
 	}
 
 	if os.Getenv("TEST_EXIT_CODE") == "1" {
@@ -150,11 +152,18 @@ func TestMainExitCodes(t *testing.T) {
 			}
 			base64Args, _ := encodeBase64(tc.args)
 
+			var stdout, stderr bytes.Buffer
+
 			cmd := exec.Command(os.Args[0], "-test.run=TestMainExitCodes")
 			cmd.Env = append(os.Environ(),
 				"TEST_EXIT_CODE=1",
 				"TEST_ARGS="+base64Args)
-			out, err := cmd.Output()
+			cmd.Stdout = &stdout
+			cmd.Stderr = &stderr
+			err := cmd.Run()
+
+			outStr := stdout.String()
+			errStr := stderr.String()
 
 			if tc.expected == 0 && err != nil {
 				t.Fatalf("expected to succeed with exit code %d, failed with %v", tc.expected, err)
@@ -171,16 +180,19 @@ func TestMainExitCodes(t *testing.T) {
 					t.Fatalf("expected to get exit code %d, failed with %v", tc.expected, err)
 				}
 			}
-			if tc.expected == 0 && err == nil && tc.stdout != string(out) {
-				t.Fatalf("expected to get stdout as %s, instead got %s", tc.stdout, out)
+			if tc.expected == 0 && err == nil && tc.stdout != outStr {
+				t.Fatalf("expected to get stdout as %s, instead got %s", tc.stdout, outStr)
 			}
 
 			if tc.expected == 0 && err == nil && tc.outFileName != "" && tc.outFileName != "-" {
 				if fs, err := os.Stat(tc.outFileName); err != nil || fs.Size() == 0 {
-					t.Fatalf("expected non-empty outputdile: %s, got error: %v", tc.outFileName, err)
+					t.Fatalf("expected non-empty outputfile: %s, got error: %v", tc.outFileName, err)
 				}
 			}
 
+			if tc.emptyStderr && errStr != "" {
+				t.Fatalf("expected empty stderr, got: %s", errStr)
+			}
 		})
 	}
 }

go.mod

@@ -6,11 +6,12 @@ require (
 	github.com/ghodss/yaml v1.0.0
 	github.com/hashicorp/go-version v1.3.0
 	github.com/open-policy-agent/opa v0.34.2
-	github.com/rs/zerolog v1.21.1-0.20210413053206-582f0cf0e39b
+	github.com/rs/zerolog v1.26.1
 	github.com/spf13/pflag v1.0.5
 	helm.sh/helm/v3 v3.10.2
 	k8s.io/apimachinery v0.25.4
 	k8s.io/client-go v0.25.4
+	k8s.io/klog/v2 v2.70.1
 )
 
 require (
@@ -75,7 +76,6 @@ require (
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 	k8s.io/api v0.25.4 // indirect
 	k8s.io/apiextensions-apiserver v0.25.2 // indirect
-	k8s.io/klog/v2 v2.70.1 // indirect
 	k8s.io/kube-openapi v0.0.0-20220803162953-67bda5d908f1 // indirect
 	k8s.io/utils v0.0.0-20220728103510-ee6ede2d64ed // indirect
 	sigs.k8s.io/json v0.0.0-20220713155537-f223a00ba0e2 // indirect

go.sum

@@ -114,7 +114,6 @@ github.com/coreos/etcd v3.3.10+incompatible/go.mod h1:uF7uidLiAD3TWHmW31ZFd/JWoc
 github.com/coreos/go-etcd v2.0.0+incompatible/go.mod h1:Jez6KQU2B/sWsbdaef3ED8NzMklzPG4d5KIOhIy30Tk=
 github.com/coreos/go-semver v0.2.0/go.mod h1:nnelYz7RCh+5ahJtPPxZlU+153eP4D4r3EedlOD2RNk=
 github.com/coreos/go-semver v0.3.0/go.mod h1:nnelYz7RCh+5ahJtPPxZlU+153eP4D4r3EedlOD2RNk=
-github.com/coreos/go-systemd v0.0.0-20190321100706-95778dfbb74e/go.mod h1:F5haX7vjVVG0kc13fIWeqUViNPyEJxv/OmvnBo0Yme4=
 github.com/coreos/go-systemd/v22 v22.3.2/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSVTIJ3seZv2GcEnc=
 github.com/cpuguy83/go-md2man v1.0.10/go.mod h1:SmD6nW6nTyfqj6ABTjUi3V3JVMnlJmwcJI5acqYI6dE=
 github.com/cpuguy83/go-md2man/v2 v2.0.0/go.mod h1:maD7wRr/U5Z6m/iR4s+kqSMx2CaBsrgA7czyZG/E6dU=
@@ -447,9 +446,9 @@ github.com/rcrowley/go-metrics v0.0.0-20200313005456-10cdbea86bc0/go.mod h1:bCqn
 github.com/rogpeppe/fastuuid v1.2.0/go.mod h1:jVj6XXZzXRy/MSR5jhDC/2q6DgLz+nrA6LYCDYWNEvQ=
 github.com/rogpeppe/go-internal v1.3.0/go.mod h1:M8bDsm7K2OlrFYOpmOWEs/qY81heoFRclV5y23lUDJ4=
 github.com/rogpeppe/go-internal v1.8.0/go.mod h1:WmiCO8CzOY8rg0OYDC4/i/2WRWAB6poM+XZ2dLUbcbE=
-github.com/rs/xid v1.2.1/go.mod h1:+uKXf+4Djp6Md1KODXJxgGQPKngRmWyn10oCKFzNHOQ=
-github.com/rs/zerolog v1.21.1-0.20210413053206-582f0cf0e39b h1:lZjlZ6/ExLhIqPOmlh0dVJnBbiKokcjffr022PlkSSo=
-github.com/rs/zerolog v1.21.1-0.20210413053206-582f0cf0e39b/go.mod h1:ZPhntP/xmq1nnND05hhpAh2QMhSsA4UN3MGZ6O2J3hM=
+github.com/rs/xid v1.3.0/go.mod h1:trrq9SKmegXys3aeAKXMUTdJsYXVwGY3RLcfgqegfbg=
+github.com/rs/zerolog v1.26.1 h1:/ihwxqH+4z8UxyI70wM1z9yCvkWcfz/a3mj48k/Zngc=
+github.com/rs/zerolog v1.26.1/go.mod h1:/wSSJWX7lVrsOwlbyTRSOJvqRlc+WjWlfes+CiJ+tmc=
 github.com/rubenv/sql-migrate v1.1.2 h1:9M6oj4e//owVVHYrFISmY9LBRw6gzkCNmD9MV36tZeQ=
 github.com/rubenv/sql-migrate v1.1.2/go.mod h1:/7TZymwxN8VWumcIxw1jjHEcR1djpdkMHQPT4FWdnbQ=
 github.com/russross/blackfriday v1.5.2/go.mod h1:JO/DiYxRf+HjHt06OyowR9PTA263kcR/rfWxYHBV53g=
@@ -539,6 +538,7 @@ golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPh
 golang.org/x/crypto v0.0.0-20200820211705-5c72a883971a/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
 golang.org/x/crypto v0.0.0-20211215153901-e495a2d5b3d3/go.mod h1:IxCIyHEi3zRg3s0A5j5BB6A9Jmi73HwBIUl50j+osU4=
+golang.org/x/crypto v0.0.0-20211215165025-cf75a172585e/go.mod h1:P+XmwS30IXTQdn5tA2iutPOUgjI07+tq3H3K9MVA1s8=
 golang.org/x/crypto v0.0.0-20220525230936-793ad666bf5e h1:T8NU3HyQ8ClP4SEE+KbFlg6n0NhuTsN4MyznaarGsZM=
 golang.org/x/crypto v0.0.0-20220525230936-793ad666bf5e/go.mod h1:IxCIyHEi3zRg3s0A5j5BB6A9Jmi73HwBIUl50j+osU4=
 golang.org/x/exp v0.0.0-20190121172915-509febef88a4/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=

pkg/collector/kube.go

@@ -38,6 +38,7 @@ func newClientRestConfig(kubeconfig string, kubecontext string, inClusterFn func
 	if kubeconfig == "" {
 		if restConfig, err := inClusterFn(); err == nil {
 			restConfig.UserAgent = userAgent
+			restConfig.WarningHandler = rest.NoWarnings{}
 			return restConfig, nil
 		}
 	}
@@ -64,6 +65,7 @@ func newClientRestConfig(kubeconfig string, kubecontext string, inClusterFn func
 	}
 
 	restConfig.UserAgent = userAgent
+	restConfig.WarningHandler = rest.NoWarnings{}
 	return restConfig, nil
 }
 

pkg/collector/kube_test.go

@@ -3,6 +3,7 @@ package collector
 import (
 	"os"
 	"path/filepath"
+	"reflect"
 	"testing"
 
 	"k8s.io/client-go/rest"
@@ -141,6 +142,14 @@ func TestNewClientRestConfigWithContext(t *testing.T) {
 	if config.Host != expectedHost {
 		t.Fatalf("Expected host from context %s to be: %s, got %s instead", expectedContext, expectedHost, config.Host)
 	}
+
+	if config.UserAgent != USER_AGENT {
+		t.Fatalf("Expected %s UserAgent, instead got: %s", USER_AGENT, config.UserAgent)
+	}
+
+	if _, ok := config.WarningHandler.(rest.NoWarnings); !ok {
+		t.Fatalf("Expected NoWarnings warnings handler, instead got: %s", reflect.TypeOf(config.WarningHandler).Name())
+	}
 }
 
 func TestNewClientRestConfigContextMissing(t *testing.T) {
@@ -165,6 +174,12 @@ func TestNewClientRestConfigInCluster(t *testing.T) {
 	if cfg.Host != expectedHost {
 		t.Fatalf("Expected %s host, instead got: %s", expectedHost, cfg.Host)
 	}
+	if cfg.UserAgent != USER_AGENT {
+		t.Fatalf("Expected %s UserAgent, instead got: %s", USER_AGENT, cfg.UserAgent)
+	}
+	if _, ok := cfg.WarningHandler.(rest.NoWarnings); !ok {
+		t.Fatalf("Expected NoWarnings warnings handler, instead got: %s", reflect.TypeOf(cfg.WarningHandler).Name())
+	}
 }
 
 type env struct {