Make audit batch webhook backend configurable

cmd/kube-apiserver/app/options/BUILD

@@ -74,6 +74,7 @@ go_test(
         "//vendor/k8s.io/apiserver/pkg/server/options:go_default_library",
         "//vendor/k8s.io/apiserver/pkg/storage/storagebackend:go_default_library",
         "//vendor/k8s.io/apiserver/pkg/util/flag:go_default_library",
+        "//vendor/k8s.io/apiserver/plugin/pkg/audit/webhook:go_default_library",
         "//vendor/k8s.io/client-go/rest:go_default_library",
     ],
 )

cmd/kube-apiserver/app/options/options_test.go

@@ -28,6 +28,7 @@ import (
 	apiserveroptions "k8s.io/apiserver/pkg/server/options"
 	"k8s.io/apiserver/pkg/storage/storagebackend"
 	utilconfig "k8s.io/apiserver/pkg/util/flag"
+	auditwebhook "k8s.io/apiserver/plugin/pkg/audit/webhook"
 	restclient "k8s.io/client-go/rest"
 	"k8s.io/kubernetes/pkg/api/legacyscheme"
 	kapi "k8s.io/kubernetes/pkg/apis/core"
@@ -55,6 +56,12 @@ func TestAddFlags(t *testing.T) {
 		"--audit-policy-file=/policy",
 		"--audit-webhook-config-file=/webhook-config",
 		"--audit-webhook-mode=blocking",
+		"--audit-webhook-batch-buffer-size=42",
+		"--audit-webhook-batch-max-size=43",
+		"--audit-webhook-batch-max-wait=1s",
+		"--audit-webhook-batch-throttle-qps=43.5",
+		"--audit-webhook-batch-throttle-burst=44",
+		"--audit-webhook-batch-initial-backoff=2s",
 		"--authentication-token-webhook-cache-ttl=3m",
 		"--authentication-token-webhook-config-file=/token-webhook-config",
 		"--authorization-mode=AlwaysDeny",
@@ -170,6 +177,14 @@ func TestAddFlags(t *testing.T) {
 			WebhookOptions: apiserveroptions.AuditWebhookOptions{
 				Mode:       "blocking",
 				ConfigFile: "/webhook-config",
+				BatchConfig: auditwebhook.BatchBackendConfig{
+					BufferSize:     42,
+					MaxBatchSize:   43,
+					MaxBatchWait:   1 * time.Second,
+					ThrottleQPS:    43.5,
+					ThrottleBurst:  44,
+					InitialBackoff: 2 * time.Second,
+				},
 			},
 			PolicyFile: "/policy",
 		},

staging/src/k8s.io/apiserver/pkg/server/options/audit.go

@@ -77,12 +77,17 @@ type AuditWebhookOptions struct {
 	//
 	// Defaults to asynchronous batch events.
 	Mode string
+	// Configuration for batching webhook. Only used in batch mode.
+	BatchConfig pluginwebhook.BatchBackendConfig
 }
 
 func NewAuditOptions() *AuditOptions {
 	return &AuditOptions{
-		WebhookOptions: AuditWebhookOptions{Mode: pluginwebhook.ModeBatch},
-		LogOptions:     AuditLogOptions{Format: pluginlog.FormatJson},
+		WebhookOptions: AuditWebhookOptions{
+			Mode:        pluginwebhook.ModeBatch,
+			BatchConfig: pluginwebhook.NewDefaultBatchBackendConfig(),
+		},
+		LogOptions: AuditLogOptions{Format: pluginlog.FormatJson},
 	}
 }
 
@@ -102,7 +107,7 @@ func (o *AuditOptions) Validate() []error {
 			allErrors = append(allErrors, fmt.Errorf("feature '%s' must be enabled to set option --audit-webhook-config-file", features.AdvancedAuditing))
 		}
 	} else {
-		// check webhook mode
+		// Check webhook mode
 		validMode := false
 		for _, m := range pluginwebhook.AllowedModes {
 			if m == o.WebhookOptions.Mode {
@@ -114,7 +119,21 @@ func (o *AuditOptions) Validate() []error {
 			allErrors = append(allErrors, fmt.Errorf("invalid audit webhook mode %s, allowed modes are %q", o.WebhookOptions.Mode, strings.Join(pluginwebhook.AllowedModes, ",")))
 		}
 
-		// check log format
+		// Check webhook batch configuration
+		if o.WebhookOptions.BatchConfig.BufferSize <= 0 {
+			allErrors = append(allErrors, fmt.Errorf("invalid audit batch webhook buffer size %v, must be a positive number", o.WebhookOptions.BatchConfig.BufferSize))
+		}
+		if o.WebhookOptions.BatchConfig.MaxBatchSize <= 0 {
+			allErrors = append(allErrors, fmt.Errorf("invalid audit batch webhook max batch size %v, must be a positive number", o.WebhookOptions.BatchConfig.MaxBatchSize))
+		}
+		if o.WebhookOptions.BatchConfig.ThrottleQPS <= 0 {
+			allErrors = append(allErrors, fmt.Errorf("invalid audit batch webhook throttle QPS %v, must be a positive number", o.WebhookOptions.BatchConfig.ThrottleQPS))
+		}
+		if o.WebhookOptions.BatchConfig.ThrottleBurst <= 0 {
+			allErrors = append(allErrors, fmt.Errorf("invalid audit batch webhook throttle burst %v, must be a positive number", o.WebhookOptions.BatchConfig.ThrottleBurst))
+		}
+
+		// Check log format
 		validFormat := false
 		for _, f := range pluginlog.AllowedFormats {
 			if f == o.LogOptions.Format {
@@ -249,6 +268,24 @@ func (o *AuditWebhookOptions) AddFlags(fs *pflag.FlagSet) {
 		"Strategy for sending audit events. Blocking indicates sending events should block"+
 			" server responses. Batch causes the webhook to buffer and send events"+
 			" asynchronously. Known modes are "+strings.Join(pluginwebhook.AllowedModes, ",")+".")
+	fs.IntVar(&o.BatchConfig.BufferSize, "audit-webhook-batch-buffer-size",
+		o.BatchConfig.BufferSize, "The size of the buffer to store events before "+
+			"batching and sending to the webhook. Only used in batch mode.")
+	fs.IntVar(&o.BatchConfig.MaxBatchSize, "audit-webhook-batch-max-size",
+		o.BatchConfig.MaxBatchSize, "The maximum size of a batch sent to the webhook. "+
+			"Only used in batch mode.")
+	fs.DurationVar(&o.BatchConfig.MaxBatchWait, "audit-webhook-batch-max-wait",
+		o.BatchConfig.MaxBatchWait, "The amount of time to wait before force sending the "+
+			"batch that hadn't reached the max size. Only used in batch mode.")
+	fs.Float32Var(&o.BatchConfig.ThrottleQPS, "audit-webhook-batch-throttle-qps",
+		o.BatchConfig.ThrottleQPS, "Maximum average number of requests per second. "+
+			"Only used in batch mode.")
+	fs.IntVar(&o.BatchConfig.ThrottleBurst, "audit-webhook-batch-throttle-burst",
+		o.BatchConfig.ThrottleBurst, "Maximum number of requests sent at the same "+
+			"moment if ThrottleQPS was not utilized before. Only used in batch mode.")
+	fs.DurationVar(&o.BatchConfig.InitialBackoff, "audit-webhook-batch-initial-backoff",
+		o.BatchConfig.InitialBackoff, "The amount of time to wait before retrying the "+
+			"first failed requests. Only used in batch mode.")
 }
 
 func (o *AuditWebhookOptions) applyTo(c *server.Config) error {
@@ -256,7 +293,7 @@ func (o *AuditWebhookOptions) applyTo(c *server.Config) error {
 		return nil
 	}
 
-	webhook, err := pluginwebhook.NewBackend(o.ConfigFile, o.Mode, auditv1beta1.SchemeGroupVersion)
+	webhook, err := pluginwebhook.NewBackend(o.ConfigFile, o.Mode, auditv1beta1.SchemeGroupVersion, o.BatchConfig)
 	if err != nil {
 		return fmt.Errorf("initializing audit webhook: %v", err)
 	}

staging/src/k8s.io/apiserver/plugin/pkg/audit/webhook/webhook.go

@@ -57,9 +57,6 @@ var AllowedModes = []string{
 
 const (
 	// Default configuration values for ModeBatch.
-	//
-	// TODO(ericchiang): Make these value configurable. Maybe through a
-	// kubeconfig extension?
 	defaultBatchBufferSize = 10000            // Buffer up to 10000 events before starting discarding.
 	defaultBatchMaxSize    = 400              // Only send up to 400 events at a time.
 	defaultBatchMaxWait    = 30 * time.Second // Send events at least twice a minute.
@@ -72,13 +69,49 @@ const (
 // The plugin name reported in error metrics.
 const pluginName = "webhook"
 
+// BatchBackendConfig represents batching webhook audit backend configuration.
+type BatchBackendConfig struct {
+	// BufferSize defines a size of the buffering queue.
+	BufferSize int
+	// MaxBatchSize defines maximum size of a batch.
+	MaxBatchSize int
+	// MaxBatchWait defines maximum amount of time to wait for MaxBatchSize
+	// events to be accumulated in the buffer before forcibly sending what's
+	// being accumulated.
+	MaxBatchWait time.Duration
+
+	// ThrottleQPS defines the allowed rate of batches per second sent to the webhook.
+	ThrottleQPS float32
+	// ThrottleBurst defines the maximum rate of batches per second sent to the webhook in case
+	// the capacity defined by ThrottleQPS was not utilized.
+	ThrottleBurst int
+
+	// InitialBackoff defines the amount of time to wait before retrying the requests
+	// to the webhook for the first time.
+	InitialBackoff time.Duration
+}
+
+// NewDefaultBatchBackendConfig returns new BatchBackendConfig objects populated by default values.
+func NewDefaultBatchBackendConfig() BatchBackendConfig {
+	return BatchBackendConfig{
+		BufferSize:   defaultBatchBufferSize,
+		MaxBatchSize: defaultBatchMaxSize,
+		MaxBatchWait: defaultBatchMaxWait,
+
+		ThrottleQPS:   defaultBatchThrottleQPS,
+		ThrottleBurst: defaultBatchThrottleBurst,
+
+		InitialBackoff: defaultInitialBackoff,
+	}
+}
+
 // NewBackend returns an audit backend that sends events over HTTP to an external service.
 // The mode indicates the caching behavior of the webhook. Either blocking (ModeBlocking)
 // or buffered with batch POSTs (ModeBatch).
-func NewBackend(kubeConfigFile string, mode string, groupVersion schema.GroupVersion) (audit.Backend, error) {
+func NewBackend(kubeConfigFile string, mode string, groupVersion schema.GroupVersion, config BatchBackendConfig) (audit.Backend, error) {
 	switch mode {
 	case ModeBatch:
-		return newBatchWebhook(kubeConfigFile, groupVersion)
+		return newBatchWebhook(kubeConfigFile, groupVersion, config)
 	case ModeBlocking:
 		return newBlockingWebhook(kubeConfigFile, groupVersion)
 	default:
@@ -105,13 +138,13 @@ func init() {
 	install.Install(groupFactoryRegistry, registry, audit.Scheme)
 }
 
-func loadWebhook(configFile string, groupVersion schema.GroupVersion) (*webhook.GenericWebhook, error) {
+func loadWebhook(configFile string, groupVersion schema.GroupVersion, initialBackoff time.Duration) (*webhook.GenericWebhook, error) {
 	return webhook.NewGenericWebhook(registry, audit.Codecs, configFile,
-		[]schema.GroupVersion{groupVersion}, defaultInitialBackoff)
+		[]schema.GroupVersion{groupVersion}, initialBackoff)
 }
 
 func newBlockingWebhook(configFile string, groupVersion schema.GroupVersion) (*blockingBackend, error) {
-	w, err := loadWebhook(configFile, groupVersion)
+	w, err := loadWebhook(configFile, groupVersion, defaultInitialBackoff)
 	if err != nil {
 		return nil, err
 	}
@@ -146,19 +179,19 @@ func (b *blockingBackend) processEvents(ev ...*auditinternal.Event) error {
 	return b.w.RestClient.Post().Body(&list).Do().Error()
 }
 
-func newBatchWebhook(configFile string, groupVersion schema.GroupVersion) (*batchBackend, error) {
-	w, err := loadWebhook(configFile, groupVersion)
+func newBatchWebhook(configFile string, groupVersion schema.GroupVersion, config BatchBackendConfig) (*batchBackend, error) {
+	w, err := loadWebhook(configFile, groupVersion, config.InitialBackoff)
 	if err != nil {
 		return nil, err
 	}
 
 	return &batchBackend{
 		w:            w,
-		buffer:       make(chan *auditinternal.Event, defaultBatchBufferSize),
-		maxBatchSize: defaultBatchMaxSize,
-		maxBatchWait: defaultBatchMaxWait,
+		buffer:       make(chan *auditinternal.Event, config.BufferSize),
+		maxBatchSize: config.MaxBatchSize,
+		maxBatchWait: config.MaxBatchWait,
 		shutdownCh:   make(chan struct{}),
-		throttle:     flowcontrol.NewTokenBucketRateLimiter(defaultBatchThrottleQPS, defaultBatchThrottleBurst),
+		throttle:     flowcontrol.NewTokenBucketRateLimiter(config.ThrottleQPS, config.ThrottleBurst),
 	}, nil
 }
 

staging/src/k8s.io/apiserver/plugin/pkg/audit/webhook/webhook_test.go

@@ -116,7 +116,7 @@ func newWebhook(t *testing.T, endpoint string, mode string, groupVersion schema.
 	// NOTE(ericchiang): Do we need to use a proper serializer?
 	require.NoError(t, stdjson.NewEncoder(f).Encode(config), "writing kubeconfig")
 
-	backend, err := NewBackend(f.Name(), mode, groupVersion)
+	backend, err := NewBackend(f.Name(), mode, groupVersion, NewDefaultBatchBackendConfig())
 	require.NoError(t, err, "initializing backend")
 
 	return backend