DelegatingAuthenticationOptions TokenReview request timeout

it turns out that setting a timeout on HTTP client affect watch requests made by the delegated authentication component.
with a 10 second timeout watch requests are being re-established exactly after 10 seconds even though the default request timeout for them is ~5 minutes.

this is because if multiple timeouts were set, the stdlib picks the smaller timeout to be applied, leaving other useless.
for more details see a937729c2c/src/net/http/client.go (L364)

instead of setting a timeout on the HTTP client we should use context for cancellation.

Kubernetes-commit: d690d71d27c78f2f7981b286f5b584455ff30246

pkg/authentication/authenticatorfactory/delegating.go

@@ -44,6 +44,9 @@ type DelegatingAuthenticatorConfig struct {
 	// TokenAccessReviewClient is a client to do token review. It can be nil. Then every token is ignored.
 	TokenAccessReviewClient authenticationclient.TokenReviewInterface
 
+	// TokenAccessReviewTimeout specifies a time limit for requests made by the authorization webhook client.
+	TokenAccessReviewTimeout time.Duration
+
 	// WebhookRetryBackoff specifies the backoff parameters for the authentication webhook retry logic.
 	// This allows us to configure the sleep time at each iteration and the maximum number of retries allowed
 	// before we fail the webhook call in order to limit the fan out that ensues when the system is degraded.
@@ -88,7 +91,7 @@ func (c DelegatingAuthenticatorConfig) New() (authenticator.Request, *spec.Secur
 		if c.WebhookRetryBackoff == nil {
 			return nil, nil, errors.New("retry backoff parameters for delegating authentication webhook has not been specified")
 		}
-		tokenAuth, err := webhooktoken.NewFromInterface(c.TokenAccessReviewClient, c.APIAudiences, *c.WebhookRetryBackoff)
+		tokenAuth, err := webhooktoken.NewFromInterface(c.TokenAccessReviewClient, c.APIAudiences, *c.WebhookRetryBackoff, c.TokenAccessReviewTimeout)
 		if err != nil {
 			return nil, nil, err
 		}

pkg/server/options/authentication.go

@@ -195,9 +195,9 @@ type DelegatingAuthenticationOptions struct {
 	// before we fail the webhook call in order to limit the fan out that ensues when the system is degraded.
 	WebhookRetryBackoff *wait.Backoff
 
-	// ClientTimeout specifies a time limit for requests made by the authorization webhook client.
+	// TokenRequestTimeout specifies a time limit for requests made by the authorization webhook client.
 	// The default value is set to 10 seconds.
-	ClientTimeout time.Duration
+	TokenRequestTimeout time.Duration
 
 	// CustomRoundTripperFn allows for specifying a middleware function for custom HTTP behaviour for the authentication webhook client.
 	CustomRoundTripperFn transport.WrapperFunc
@@ -214,7 +214,7 @@ func NewDelegatingAuthenticationOptions() *DelegatingAuthenticationOptions {
 			ExtraHeaderPrefixes: []string{"x-remote-extra-"},
 		},
 		WebhookRetryBackoff: DefaultAuthWebhookRetryBackoff(),
-		ClientTimeout:       10 * time.Second,
+		TokenRequestTimeout: 10 * time.Second,
 	}
 }
 
@@ -223,9 +223,9 @@ func (s *DelegatingAuthenticationOptions) WithCustomRetryBackoff(backoff wait.Ba
 	s.WebhookRetryBackoff = &backoff
 }
 
-// WithClientTimeout sets the given timeout for the authentication webhook client.
-func (s *DelegatingAuthenticationOptions) WithClientTimeout(timeout time.Duration) {
-	s.ClientTimeout = timeout
+// WithRequestTimeout sets the given timeout for requests made by the authentication webhook client.
+func (s *DelegatingAuthenticationOptions) WithRequestTimeout(timeout time.Duration) {
+	s.TokenRequestTimeout = timeout
 }
 
 // WithCustomRoundTripper allows for specifying a middleware function for custom HTTP behaviour for the authentication webhook client.
@@ -282,9 +282,10 @@ func (s *DelegatingAuthenticationOptions) ApplyTo(authenticationInfo *server.Aut
 	}
 
 	cfg := authenticatorfactory.DelegatingAuthenticatorConfig{
-		Anonymous:           true,
-		CacheTTL:            s.CacheTTL,
-		WebhookRetryBackoff: s.WebhookRetryBackoff,
+		Anonymous:                true,
+		CacheTTL:                 s.CacheTTL,
+		WebhookRetryBackoff:      s.WebhookRetryBackoff,
+		TokenAccessReviewTimeout: s.TokenRequestTimeout,
 	}
 
 	client, err := s.getClient()
@@ -427,7 +428,10 @@ func (s *DelegatingAuthenticationOptions) getClient() (kubernetes.Interface, err
 	// set high qps/burst limits since this will effectively limit API server responsiveness
 	clientConfig.QPS = 200
 	clientConfig.Burst = 400
-	clientConfig.Timeout = s.ClientTimeout
+	// do not set a timeout on the http client, instead use context for cancellation
+	// if multiple timeouts were set, the request will pick the smaller timeout to be applied, leaving other useless.
+	//
+	// see https://github.com/golang/go/blob/a937729c2c2f6950a32bc5cd0f5b88700882f078/src/net/http/client.go#L364
 	if s.CustomRoundTripperFn != nil {
 		clientConfig.Wrap(s.CustomRoundTripperFn)
 	}

plugin/pkg/authenticator/token/webhook/webhook.go

@@ -52,17 +52,18 @@ type tokenReviewer interface {
 }
 
 type WebhookTokenAuthenticator struct {
-	tokenReview  tokenReviewer
-	retryBackoff wait.Backoff
-	implicitAuds authenticator.Audiences
+	tokenReview    tokenReviewer
+	retryBackoff   wait.Backoff
+	implicitAuds   authenticator.Audiences
+	requestTimeout time.Duration
 }
 
 // NewFromInterface creates a webhook authenticator using the given tokenReview
 // client. It is recommend to wrap this authenticator with the token cache
 // authenticator implemented in
 // k8s.io/apiserver/pkg/authentication/token/cache.
-func NewFromInterface(tokenReview authenticationv1client.TokenReviewInterface, implicitAuds authenticator.Audiences, retryBackoff wait.Backoff) (*WebhookTokenAuthenticator, error) {
-	return newWithBackoff(tokenReview, retryBackoff, implicitAuds)
+func NewFromInterface(tokenReview authenticationv1client.TokenReviewInterface, implicitAuds authenticator.Audiences, retryBackoff wait.Backoff, requestTimeout time.Duration) (*WebhookTokenAuthenticator, error) {
+	return newWithBackoff(tokenReview, retryBackoff, implicitAuds, requestTimeout)
 }
 
 // New creates a new WebhookTokenAuthenticator from the provided kubeconfig
@@ -74,12 +75,12 @@ func New(kubeConfigFile string, version string, implicitAuds authenticator.Audie
 	if err != nil {
 		return nil, err
 	}
-	return newWithBackoff(tokenReview, retryBackoff, implicitAuds)
+	return newWithBackoff(tokenReview, retryBackoff, implicitAuds, time.Duration(0))
 }
 
 // newWithBackoff allows tests to skip the sleep.
-func newWithBackoff(tokenReview tokenReviewer, retryBackoff wait.Backoff, implicitAuds authenticator.Audiences) (*WebhookTokenAuthenticator, error) {
-	return &WebhookTokenAuthenticator{tokenReview, retryBackoff, implicitAuds}, nil
+func newWithBackoff(tokenReview tokenReviewer, retryBackoff wait.Backoff, implicitAuds authenticator.Audiences, requestTimeout time.Duration) (*WebhookTokenAuthenticator, error) {
+	return &WebhookTokenAuthenticator{tokenReview, retryBackoff, implicitAuds, requestTimeout}, nil
 }
 
 // AuthenticateToken implements the authenticator.Token interface.
@@ -105,7 +106,17 @@ func (w *WebhookTokenAuthenticator) AuthenticateToken(ctx context.Context, token
 	var (
 		result *authenticationv1.TokenReview
 		auds   authenticator.Audiences
+		cancel context.CancelFunc
 	)
+
+	// set a hard timeout if it was defined
+	// if the child has a shorter deadline then it will expire first,
+	// otherwise if the parent has a shorter deadline then the parent will expire and it will be propagate to the child
+	if w.requestTimeout > 0 {
+		ctx, cancel = context.WithTimeout(ctx, w.requestTimeout)
+		defer cancel()
+	}
+
 	// WithExponentialBackoff will return tokenreview create error (tokenReviewErr) if any.
 	if err := webhook.WithExponentialBackoff(ctx, w.retryBackoff, func() error {
 		var tokenReviewErr error

plugin/pkg/authenticator/token/webhook/webhook_v1_test.go

@@ -206,7 +206,7 @@ func newV1TokenAuthenticator(serverURL string, clientCert, clientKey, ca []byte,
 		return nil, err
 	}
 
-	authn, err := newWithBackoff(c, testRetryBackoff, implicitAuds)
+	authn, err := newWithBackoff(c, testRetryBackoff, implicitAuds, 10*time.Second)
 	if err != nil {
 		return nil, err
 	}

plugin/pkg/authenticator/token/webhook/webhook_v1beta1_test.go

@@ -200,7 +200,7 @@ func newV1beta1TokenAuthenticator(serverURL string, clientCert, clientKey, ca []
 		return nil, err
 	}
 
-	authn, err := newWithBackoff(c, testRetryBackoff, implicitAuds)
+	authn, err := newWithBackoff(c, testRetryBackoff, implicitAuds, 10*time.Second)
 	if err != nil {
 		return nil, err
 	}