🐛 DynamicRestMapper: return NoMatchError when resource doesn't exist

Author: timebertt

pkg/client/apiutil/dynamicrestmapper.go

@@ -31,6 +31,10 @@ import (
 
 // ErrRateLimited is returned by a RESTMapper method if the number of API
 // calls has exceeded a limit within a certain time period.
+//
+// Deprecated: as the dynamic RESTMapper now returns NoMatch errors directly
+// instead of RateLimited errors, it is meaningless and only kept for the sake
+// of backwards-compatibility.
 type ErrRateLimited struct {
 	// Duration to wait until the next API call can be made.
 	Delay time.Duration
@@ -43,6 +47,10 @@ func (e ErrRateLimited) Error() string {
 // DelayIfRateLimited returns the delay time until the next API call is
 // allowed and true if err is of type ErrRateLimited. The zero
 // time.Duration value and false are returned if err is not a ErrRateLimited.
+//
+// Deprecated: as the dynamic RESTMapper now returns NoMatch errors directly
+// instead of RateLimited errors, it is meaningless and only kept for the sake
+// of backwards-compatibility.
 func DelayIfRateLimited(err error) (time.Duration, bool) {
 	var rlerr ErrRateLimited
 	if errors.As(err, &rlerr) {
@@ -56,7 +64,7 @@ func DelayIfRateLimited(err error) (time.Duration, bool) {
 type dynamicRESTMapper struct {
 	mu           sync.RWMutex // protects the following fields
 	staticMapper meta.RESTMapper
-	limiter      *dynamicLimiter
+	limiter      *rate.Limiter
 	newMapper    func() (meta.RESTMapper, error)
 
 	lazy bool
@@ -70,7 +78,7 @@ type DynamicRESTMapperOption func(*dynamicRESTMapper) error
 // WithLimiter sets the RESTMapper's underlying limiter to lim.
 func WithLimiter(lim *rate.Limiter) DynamicRESTMapperOption {
 	return func(drm *dynamicRESTMapper) error {
-		drm.limiter = &dynamicLimiter{lim}
+		drm.limiter = lim
 		return nil
 	}
 }
@@ -103,9 +111,7 @@ func NewDynamicRESTMapper(cfg *rest.Config, opts ...DynamicRESTMapperOption) (me
 		return nil, err
 	}
 	drm := &dynamicRESTMapper{
-		limiter: &dynamicLimiter{
-			rate.NewLimiter(rate.Limit(defaultRefillRate), defaultLimitSize),
-		},
+		limiter: rate.NewLimiter(rate.Limit(defaultRefillRate), defaultLimitSize),
 		newMapper: func() (meta.RESTMapper, error) {
 			groupResources, err := restmapper.GetAPIGroupResources(client)
 			if err != nil {
@@ -161,12 +167,13 @@ func (drm *dynamicRESTMapper) init() (err error) {
 // checkAndReload attempts to call the given callback, which is assumed to be dependent
 // on the data in the restmapper.
 //
-// If the callback returns a NoKindMatchError, it will attempt to reload
+// If the callback returns an error that matches the given error, it will attempt to reload
 // the RESTMapper's data and re-call the callback once that's occurred.
 // If the callback returns any other error, the function will return immediately regardless.
 //
-// It will take care
-// ensuring that reloads are rate-limitted and that extraneous calls aren't made.
+// It will take care of ensuring that reloads are rate-limited and that extraneous calls
+// aren't made. If a reload would exceed the limiters rate, it returns the error return by
+// the callback.
 // It's thread-safe, and worries about thread-safety for the callback (so the callback does
 // not need to attempt to lock the restmapper).
 func (drm *dynamicRESTMapper) checkAndReload(needsReloadErr error, checkNeedsReload func() error) error {
@@ -199,7 +206,9 @@ func (drm *dynamicRESTMapper) checkAndReload(needsReloadErr error, checkNeedsRel
 	}
 
 	// we're still stale, so grab a rate-limit token if we can...
-	if err := drm.limiter.checkRate(); err != nil {
+	if !drm.limiter.Allow() {
+		// return error from static mapper here, we have refreshed often enough (exceeding rate of provided limiter)
+		// so that client's can handle this the same way as a "normal" NoResourceMatchError / NoKindMatchError
 		return err
 	}
 
@@ -305,19 +314,3 @@ func (drm *dynamicRESTMapper) ResourceSingularizer(resource string) (string, err
 	})
 	return singular, err
 }
-
-// dynamicLimiter holds a rate limiter used to throttle chatty RESTMapper users.
-type dynamicLimiter struct {
-	*rate.Limiter
-}
-
-// checkRate returns an ErrRateLimited if too many API calls have been made
-// within the set limit.
-func (b *dynamicLimiter) checkRate() error {
-	res := b.Reserve()
-	if res.Delay() == 0 {
-		return nil
-	}
-	res.Cancel()
-	return ErrRateLimited{res.Delay()}
-}

pkg/client/apiutil/dynamicrestmapper_test.go

@@ -1,11 +1,12 @@
 package apiutil_test
 
 import (
-	"errors"
 	"time"
 
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
+	"github.com/onsi/gomega/format"
+	"github.com/onsi/gomega/types"
 	"golang.org/x/time/rate"
 	"k8s.io/apimachinery/pkg/api/meta"
 	"k8s.io/apimachinery/pkg/runtime/schema"
@@ -57,53 +58,49 @@ var _ = Describe("Dynamic REST Mapper", func() {
 		})
 
 		It("should reload if not present in the cache", func() {
-			By("reading successfully once")
+			By("reading target successfully once")
 			Expect(callWithTarget()).To(Succeed())
-			Expect(callWithOther()).NotTo(Succeed())
 
-			By("asking for a something that didn't exist previously after adding it to the mapper")
+			By("reading other not successfully")
+			count := 0
 			addToMapper = func(baseMapper *meta.DefaultRESTMapper) {
+				count++
 				baseMapper.Add(targetGVK, meta.RESTScopeNamespace)
-				baseMapper.Add(secondGVK, meta.RESTScopeNamespace)
 			}
-			Expect(callWithOther()).To(Succeed())
-			Expect(callWithTarget()).To(Succeed())
-		})
+			Expect(callWithOther()).To(beNoMatchError())
+			Expect(count).To(Equal(1), "should reload exactly once")
 
-		It("should rate-limit reloads so that we don't get more than a certain number per second", func() {
-			By("setting a small limit")
-			*lim = *rate.NewLimiter(rate.Limit(1), 1)
-
-			By("forcing a reload after changing the mapper")
+			By("reading both successfully now")
 			addToMapper = func(baseMapper *meta.DefaultRESTMapper) {
+				baseMapper.Add(targetGVK, meta.RESTScopeNamespace)
 				baseMapper.Add(secondGVK, meta.RESTScopeNamespace)
 			}
 			Expect(callWithOther()).To(Succeed())
-
-			By("calling another time that would need a requery and failing")
-			Eventually(func() bool {
-				return errors.As(callWithTarget(), &apiutil.ErrRateLimited{})
-			}, "10s").Should(BeTrue())
+			Expect(callWithTarget()).To(Succeed())
 		})
 
-		It("should rate-limit then allow more at 1rps", func() {
+		It("should rate-limit then allow more at configured rate", func() {
 			By("setting a small limit")
-			*lim = *rate.NewLimiter(rate.Limit(1), 1)
+			*lim = *rate.NewLimiter(rate.Every(100*time.Millisecond), 1)
 
 			By("forcing a reload after changing the mapper")
 			addToMapper = func(baseMapper *meta.DefaultRESTMapper) {
 				baseMapper.Add(secondGVK, meta.RESTScopeNamespace)
 			}
-
-			By("calling twice to trigger rate limiting")
 			Expect(callWithOther()).To(Succeed())
-			Expect(callWithTarget()).NotTo(Succeed())
 
-			// by 2nd call loop should succeed because we canceled our 1st rate-limited token, then waited a full second
-			By("calling until no longer rate-limited, 2nd call should succeed")
-			Eventually(func() bool {
-				return errors.As(callWithTarget(), &apiutil.ErrRateLimited{})
-			}, "2.5s", "1s").Should(BeFalse())
+			By("calling another time to trigger rate limiting")
+			addToMapper = func(baseMapper *meta.DefaultRESTMapper) {
+				baseMapper.Add(targetGVK, meta.RESTScopeNamespace)
+			}
+			// if call consistently fails, we are sure, that it was rate-limited,
+			// otherwise it would have reloaded and succeeded
+			Consistently(callWithTarget, "90ms", "10ms").Should(beNoMatchError())
+
+			By("calling until no longer rate-limited")
+			// once call succeeds, we are sure, that it was no longer rate-limited,
+			// as it was allowed to reload and found matching kind/resource
+			Eventually(callWithTarget, "30ms", "10ms").Should(And(Succeed(), Not(beNoMatchError())))
 		})
 
 		It("should avoid reloading twice if two requests for the same thing come in", func() {
@@ -251,3 +248,25 @@ var _ = Describe("Dynamic REST Mapper", func() {
 		})
 	})
 })
+
+func beNoMatchError() types.GomegaMatcher {
+	return noMatchErrorMatcher{}
+}
+
+type noMatchErrorMatcher struct{}
+
+func (k noMatchErrorMatcher) Match(actual interface{}) (success bool, err error) {
+	actualErr, actualOk := actual.(error)
+	if !actualOk {
+		return false, nil
+	}
+
+	return meta.IsNoMatchError(actualErr), nil
+}
+
+func (k noMatchErrorMatcher) FailureMessage(actual interface{}) (message string) {
+	return format.Message(actual, "to be a NoMatchError")
+}
+func (k noMatchErrorMatcher) NegatedFailureMessage(actual interface{}) (message string) {
+	return format.Message(actual, "not to be a NoMatchError")
+}