k8s.io/component-base/logs: allow overriding os.Stdout and os.Stderr

This is useful for tests which need to discard or capture the output.

staging/src/k8s.io/component-base/logs/api/v1/options.go

@@ -19,7 +19,9 @@ package v1
 import (
 	"flag"
 	"fmt"
+	"io"
 	"math"
+	"os"
 	"strings"
 	"time"
 
@@ -63,18 +65,41 @@ func NewLoggingConfiguration() *LoggingConfiguration {
 // The optional FeatureGate controls logging features. If nil, the default for
 // these features is used.
 func ValidateAndApply(c *LoggingConfiguration, featureGate featuregate.FeatureGate) error {
-	return ValidateAndApplyAsField(c, featureGate, nil)
+	return validateAndApply(c, nil, featureGate, nil)
+}
+
+// ValidateAndApplyWithOptions is a variant of ValidateAndApply which accepts
+// additional options beyond those that can be configured through the API. This
+// is meant for testing.
+func ValidateAndApplyWithOptions(c *LoggingConfiguration, options *LoggingOptions, featureGate featuregate.FeatureGate) error {
+	return validateAndApply(c, options, featureGate, nil)
+}
+
+// +k8s:deepcopy-gen=false
+
+// LoggingOptions can be used with ValidateAndApplyWithOptions to override
+// certain global defaults.
+type LoggingOptions struct {
+	// ErrorStream can be used to override the os.Stderr default.
+	ErrorStream io.Writer
+
+	// InfoStream can be used to override the os.Stdout default.
+	InfoStream io.Writer
 }
 
 // ValidateAndApplyAsField is a variant of ValidateAndApply that should be used
 // when the LoggingConfiguration is embedded in some larger configuration
 // structure.
 func ValidateAndApplyAsField(c *LoggingConfiguration, featureGate featuregate.FeatureGate, fldPath *field.Path) error {
+	return validateAndApply(c, nil, featureGate, fldPath)
+}
+
+func validateAndApply(c *LoggingConfiguration, options *LoggingOptions, featureGate featuregate.FeatureGate, fldPath *field.Path) error {
 	errs := Validate(c, featureGate, fldPath)
 	if len(errs) > 0 {
 		return errs.ToAggregate()
 	}
-	return apply(c, featureGate)
+	return apply(c, options, featureGate)
 }
 
 // Validate can be used to check for invalid settings without applying them.
@@ -157,7 +182,7 @@ func featureEnabled(featureGate featuregate.FeatureGate, feature featuregate.Fea
 	return enabled
 }
 
-func apply(c *LoggingConfiguration, featureGate featuregate.FeatureGate) error {
+func apply(c *LoggingConfiguration, options *LoggingOptions, featureGate featuregate.FeatureGate) error {
 	contextualLoggingEnabled := contextualLoggingDefault
 	if featureGate != nil {
 		contextualLoggingEnabled = featureGate.Enabled(ContextualLogging)
@@ -168,7 +193,13 @@ func apply(c *LoggingConfiguration, featureGate featuregate.FeatureGate) error {
 	if format.factory == nil {
 		klog.ClearLogger()
 	} else {
-		log, control := format.factory.Create(*c)
+		if options == nil {
+			options = &LoggingOptions{
+				ErrorStream: os.Stderr,
+				InfoStream:  os.Stdout,
+			}
+		}
+		log, control := format.factory.Create(*c, *options)
 		if control.SetVerbosityLevel != nil {
 			setverbositylevel.Mutex.Lock()
 			defer setverbositylevel.Mutex.Unlock()

staging/src/k8s.io/component-base/logs/api/v1/registry.go

@@ -61,7 +61,7 @@ type RuntimeControl struct {
 // non-default log format.
 type LogFormatFactory interface {
 	// Create returns a logger with the requested configuration.
-	Create(c LoggingConfiguration) (logr.Logger, RuntimeControl)
+	Create(c LoggingConfiguration, o LoggingOptions) (logr.Logger, RuntimeControl)
 }
 
 // RegisterLogFormat registers support for a new logging format. This must be called

staging/src/k8s.io/component-base/logs/json/json.go

@@ -18,7 +18,6 @@ package json
 
 import (
 	"io"
-	"os"
 	"sync/atomic"
 	"time"
 
@@ -116,7 +115,7 @@ func (f Factory) Feature() featuregate.Feature {
 	return logsapi.LoggingBetaOptions
 }
 
-func (f Factory) Create(c logsapi.LoggingConfiguration) (logr.Logger, logsapi.RuntimeControl) {
+func (f Factory) Create(c logsapi.LoggingConfiguration, o logsapi.LoggingOptions) (logr.Logger, logsapi.RuntimeControl) {
 	// We intentionally avoid all os.File.Sync calls. Output is unbuffered,
 	// therefore we don't need to flush, and calling the underlying fsync
 	// would just slow down writing.
@@ -125,9 +124,9 @@ func (f Factory) Create(c logsapi.LoggingConfiguration) (logr.Logger, logsapi.Ru
 	// written to the output stream before the process terminates, but
 	// doesn't need to worry about data not being written because of a
 	// system crash or powerloss.
-	stderr := zapcore.Lock(AddNopSync(os.Stderr))
+	stderr := zapcore.Lock(AddNopSync(o.ErrorStream))
 	if c.Options.JSON.SplitStream {
-		stdout := zapcore.Lock(AddNopSync(os.Stdout))
+		stdout := zapcore.Lock(AddNopSync(o.InfoStream))
 		size := c.Options.JSON.InfoBufferSize.Value()
 		if size > 0 {
 			// Prevent integer overflow.

test/integration/logs/benchmark/benchmark_test.go

@@ -32,7 +32,6 @@ import (
 	"testing"
 	"time"
 
-	"github.com/go-logr/logr"
 	logsapi "k8s.io/component-base/logs/api/v1"
 	logsjson "k8s.io/component-base/logs/json"
 	"k8s.io/klog/v2"
@@ -175,9 +174,6 @@ func benchmarkOutputFormats(b *testing.B, config loadGeneratorConfig, discard bo
 		generateOutput(b, config, nil, out)
 	})
 	b.Run("JSON", func(b *testing.B) {
-		c := logsapi.NewLoggingConfiguration()
-		var logger logr.Logger
-		var flush func()
 		var out1, out2 *os.File
 		if !discard {
 			var err error
@@ -192,46 +188,30 @@ func benchmarkOutputFormats(b *testing.B, config loadGeneratorConfig, discard bo
 			}
 			defer out2.Close()
 		}
+		o := logsapi.LoggingOptions{}
+		if discard {
+			o.ErrorStream = io.Discard
+			o.InfoStream = io.Discard
+		} else {
+			o.ErrorStream = out1
+			o.InfoStream = out1
+		}
+
 		b.Run("single-stream", func(b *testing.B) {
-			if discard {
-				l, control := logsjson.NewJSONLogger(c.Verbosity, logsjson.AddNopSync(&output), nil, nil)
-				logger = l
-				flush = control.Flush
-			} else {
-				stderr := os.Stderr
-				os.Stderr = out1
-				defer func() {
-					os.Stderr = stderr
-				}()
-				l, control := logsjson.Factory{}.Create(*c)
-				logger = l
-				flush = control.Flush
-			}
+			c := logsapi.NewLoggingConfiguration()
+			logger, control := logsjson.Factory{}.Create(*c, o)
 			klog.SetLogger(logger)
 			defer klog.ClearLogger()
-			generateOutput(b, config, flush, out1)
+			generateOutput(b, config, control.Flush, out1)
 		})
 
 		b.Run("split-stream", func(b *testing.B) {
-			if discard {
-				l, control := logsjson.NewJSONLogger(c.Verbosity, logsjson.AddNopSync(&output), logsjson.AddNopSync(&output), nil)
-				logger = l
-				flush = control.Flush
-			} else {
-				stdout, stderr := os.Stdout, os.Stderr
-				os.Stdout, os.Stderr = out1, out2
-				defer func() {
-					os.Stdout, os.Stderr = stdout, stderr
-				}()
-				c := logsapi.NewLoggingConfiguration()
-				c.Options.JSON.SplitStream = true
-				l, control := logsjson.Factory{}.Create(*c)
-				logger = l
-				flush = control.Flush
-			}
+			c := logsapi.NewLoggingConfiguration()
+			c.Options.JSON.SplitStream = true
+			logger, control := logsjson.Factory{}.Create(*c, o)
 			klog.SetLogger(logger)
 			defer klog.ClearLogger()
-			generateOutput(b, config, flush, out1, out2)
+			generateOutput(b, config, control.Flush, out1, out2)
 		})
 	})
 }