Fixed: 22422 use singleflight to alleviate simultaneous calls to #112696

aimuz · 2022-09-23T07:27:10Z

Signed-off-by: aimuz mr.imuz@gmail.com

What type of PR is this?

/kind bug

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #22422

Special notes for your reviewer:

Does this PR introduce a user-facing change?

Fixed: #22422 Admission controllers can cause unnecessary significant load on apiserver

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

k8s-ci-robot · 2022-09-23T07:27:18Z

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k8s-ci-robot · 2022-09-23T07:27:19Z

Hi @aimuz. Thanks for your PR.

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aimuz · 2022-09-23T07:29:47Z

/sig scalability

aojea · 2022-09-23T07:54:55Z

plugin/pkg/admission/limitranger/admission.go

-			// throttling - see #22422 for details.
-			liveList, err := l.client.CoreV1().LimitRanges(a.GetNamespace()).List(context.TODO(), metav1.ListOptions{})
+			// Fixed: #22422
+			// use singleflight to alleviate simultaneous calls to


there should be a regression test verifying the fix

I have added a test, please help me to see if this matches @aojea

aojea · 2022-09-23T11:28:27Z

plugin/pkg/admission/limitranger/admission_test.go

+		go func(wg *sync.WaitGroup) {
+			_, err := handler.GetLimitRanges(attributes)
+			if err != nil {
+				t.Errorf("unexpected error: %v", err)
+			}
+			wg.Done()
+		}(&wg)


do you need to pass the wg var as parameter?

Suggested change

go func(wg *sync.WaitGroup) {

_, err := handler.GetLimitRanges(attributes)

if err != nil {

t.Errorf("unexpected error: %v", err)

}

wg.Done()

}(&wg)

go func() {

defer wg.Done()

_, err := handler.GetLimitRanges(attributes)

if err != nil {

t.Errorf("unexpected error: %v", err)

}

}()

nit, defer wg.Done() use to be more idiomatic

aojea · 2022-09-23T11:29:12Z

plugin/pkg/admission/limitranger/admission_test.go

+			limitRangeList.Items = append(limitRangeList.Items, value)
+		}
+		// Set the latency to simulate the real environment
+		time.Sleep(200 * time.Millisecond)


this is a low value and can flake, just set 1*time.Second

hmm, I think we can do this more reliable if we add a select and block on a channel

that you signal before the wg.Wait(), so you guarantee that all the request were sent

aojea · 2022-09-23T11:30:29Z

plugin/pkg/admission/limitranger/admission_test.go

+	count := 0
+	mockClient := &fake.Clientset{}
+	mockClient.AddReactor("list", "limitranges", func(action core.Action) (bool, runtime.Object, error) {
+		count++


without the singleflight this will race, you can use an atomic counter
var count int64
atomic.AddInt64(&count,1)

aojea · 2022-09-23T11:33:42Z

plugin/pkg/admission/limitranger/admission_test.go

+	if count != 1 {
+		t.Errorf("Expected 1 limit range, got %d", count)
+	}
+}


I would add another

_, err := handler.GetLimitRanges(attributes) if err != nil { t.Errorf("unexpected error: %v", err) }

and check that count == 2

aimuz · 2022-10-20T03:30:36Z

/retest

liggitt · 2022-10-20T13:59:16Z

plugin/pkg/admission/limitranger/admission.go

-			liveList, err := l.client.CoreV1().LimitRanges(a.GetNamespace()).List(context.TODO(), metav1.ListOptions{})
+			// Fixed: #22422
+			// use singleflight to alleviate simultaneous calls to
+			lruItemObj, err, _ = l.group.Do(a.GetNamespace(), func() (interface{}, error) {


if I switch this to partition on a constant string "x" instead of the namespace, the added unit test still passes, so the test is not effectively verifying this is correct

If the constant string x will be used, then he will partition all calls. If there are two concurrent calls with different namespaces, he will only call them once until the call returns. This should be the wrong behavior.

Currently using namespaces as partitions, this is partitioning a set of calls with the same namespace. This is the same behavior as using namespaces as keys for LRU caching before
@liggitt

using a constant string "x" here would be a bug, since it would make calls from different namespaces share a single lookup and use the same retrieved result. The unit test should fail under those circumstances, and it does not.

If you use the constant string x, the test will block

that's not what I'm seeing:

git diff

diff --git a/plugin/pkg/admission/limitranger/admission.go b/plugin/pkg/admission/limitranger/admission.go index 4525463d2e6..907a28bda32 100644 --- a/plugin/pkg/admission/limitranger/admission.go +++ b/plugin/pkg/admission/limitranger/admission.go @@ -165,7 +165,7 @@ func (l *LimitRanger) GetLimitRanges(a admission.Attributes) ([]*corev1.LimitRan if !ok || lruItemObj.(liveLookupEntry).expiry.Before(time.Now()) { // Fixed: #22422 // use singleflight to alleviate simultaneous calls to - lruItemObj, err, _ = l.group.Do(a.GetNamespace(), func() (interface{}, error) { + lruItemObj, err, _ = l.group.Do("x", func() (interface{}, error) { liveList, err := l.client.CoreV1().LimitRanges(a.GetNamespace()).List(context.TODO(), metav1.ListOptions{}) if err != nil { return nil, admission.NewForbidden(a, err)

go test ./plugin/pkg/admission/limitranger -count=1 -v -run TestLimitRanger_GetLimitRangesFixed22422 === RUN TestLimitRanger_GetLimitRangesFixed22422 --- PASS: TestLimitRanger_GetLimitRangesFixed22422 (0.00s) PASS ok k8s.io/kubernetes/plugin/pkg/admission/limitranger 0.800s

I just updated it and the problem should be fixed, Please look at the

go test ./plugin/pkg/admission/limitranger -count=1 -v -run TestLimitRanger_GetLimitRangesFixed22422 === RUN TestLimitRanger_GetLimitRangesFixed22422 admission_test.go:910: Expected test namespace, got test1 admission_test.go:910: Expected test namespace, got test1 admission_test.go:910: Expected test namespace, got test1 admission_test.go:910: Expected test namespace, got test1 admission_test.go:910: Expected test namespace, got test1 admission_test.go:910: Expected test namespace, got test1 admission_test.go:910: Expected test namespace, got test1 admission_test.go:910: Expected test namespace, got test1 admission_test.go:910: Expected test namespace, got test1 --- FAIL: TestLimitRanger_GetLimitRangesFixed22422 (0.00s) FAIL FAIL k8s.io/kubernetes/plugin/pkg/admission/limitranger 0.792s FAIL

aimuz · 2022-10-21T01:48:48Z

plugin/pkg/admission/limitranger/admission_test.go

+	// since all the calls with the same namespace will be holded, they must be catched on the singleflight group,
+	// There are two different sets of namespace calls
+	// hence only 2
+	if count != 2 {


It actually shows up in the test, in the loop I turned on two different sets of namespace calls and he also correctly increased the count to 2, so I don't think it's a problem. @liggitt

aimuz · 2022-10-21T01:49:29Z

plugin/pkg/admission/limitranger/admission_test.go

+		// simulating concurrent calls after a cache failure
+		go func() {
+			defer wg.Done()
+			_, err := handler.GetLimitRanges(attributes)
+			if err != nil {
+				t.Errorf("unexpected error: %v", err)
+			}
+		}()
+
+		// simulation of different namespaces is not a call
+		go func() {
+			defer wg.Done()
+			_, err := handler.GetLimitRanges(attributesTest1)
+			if err != nil {
+				t.Errorf("unexpected error: %v", err)
+			}
+		}()


Two different sets of namespace calls are initiated here

Signed-off-by: aimuz <mr.imuz@gmail.com>

aimuz · 2022-10-21T19:54:48Z

/retest

liggitt · 2022-10-24T14:08:39Z

/lgtm
/approve

k8s-ci-robot · 2022-10-24T14:09:13Z

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aimuz, liggitt

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

~~plugin/pkg/admission/OWNERS~~ [liggitt]

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aimuz · 2022-10-25T01:16:46Z

/retest

aimuz · 2022-10-25T01:19:33Z

Thanks, this PR has benefited me a lot @aojea @liggitt

k8s-ci-robot requested review from deads2k and derekwaynecarr September 23, 2022 07:27

k8s-ci-robot added do-not-merge/needs-sig Indicates an issue or PR lacks a `sig/foo` label and requires one. needs-triage Indicates an issue or PR lacks a `triage/foo` label and requires one. labels Sep 23, 2022

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aimuz force-pushed the fix-22422 branch from 2566de2 to 9816fcc Compare September 23, 2022 07:28

aimuz changed the title ~~Fixed: #22422 use singleflight to alleviate simultaneous calls to~~ Fixed: 22422 use singleflight to alleviate simultaneous calls to Sep 23, 2022

k8s-ci-robot removed the do-not-merge/invalid-commit-message Indicates that a PR should not merge because it has an invalid commit message. label Sep 23, 2022

k8s-ci-robot added sig/scalability Categorizes an issue or PR as relevant to SIG Scalability. and removed do-not-merge/needs-sig Indicates an issue or PR lacks a `sig/foo` label and requires one. labels Sep 23, 2022

aimuz force-pushed the fix-22422 branch from 9816fcc to 203b933 Compare September 23, 2022 07:32

aojea reviewed Sep 23, 2022

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aimuz force-pushed the fix-22422 branch 2 times, most recently from 37a3006 to 4192b79 Compare September 23, 2022 09:03

aimuz requested review from aojea and removed request for derekwaynecarr and deads2k September 23, 2022 09:05

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aimuz requested review from aojea and liggitt and removed request for liggitt and aojea October 20, 2022 02:27

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aimuz commented Oct 21, 2022

View reviewed changes

Fixed: 22422 use singleflight to alleviate simultaneous calls to

bd441d0

Signed-off-by: aimuz <mr.imuz@gmail.com>

aimuz force-pushed the fix-22422 branch from bf4d7c8 to bd441d0 Compare October 21, 2022 16:16

aimuz requested review from liggitt and aojea and removed request for aojea and liggitt October 21, 2022 16:23

aimuz requested review from liggitt and removed request for aojea October 21, 2022 19:57

k8s-ci-robot added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Oct 24, 2022

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k8s-ci-robot merged commit b932a3a into kubernetes:master Oct 25, 2022

k8s-ci-robot added this to the v1.26 milestone Oct 25, 2022

This was referenced Oct 27, 2022

TestLimitRanger_GetLimitRangesFixed22422 flakes #113377

Closed

REQUEST: New membership for @aimuz kubernetes/org#3794

Closed

DrAuYueng mentioned this pull request Jan 9, 2023

Reduce simultaneous calls to quota queries #114919

Closed

flavianmissi mentioned this pull request Apr 3, 2024

resourcequota: use singleflight.Group to reduce apiserver load #124163

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Fixed: 22422 use singleflight to alleviate simultaneous calls to #112696

Fixed: 22422 use singleflight to alleviate simultaneous calls to #112696

aimuz commented Sep 23, 2022 •

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Fixed: 22422 use singleflight to alleviate simultaneous calls to #112696

Fixed: 22422 use singleflight to alleviate simultaneous calls to #112696

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aimuz commented Sep 23, 2022 • edited

What type of PR is this?

What this PR does / why we need it:

Which issue(s) this PR fixes:

Special notes for your reviewer:

Does this PR introduce a user-facing change?

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

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