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Ingress-NGINX Controller for Kubernetes
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Pointing to an ExternalName service without a DNS record can overload the DNS service #6523

Open lucianjon opened 3 years ago

lucianjon commented 3 years ago

NGINX Ingress controller version: v0.41.2

Kubernetes version (use kubectl version): 

Client Version: version.Info{Major:"1", Minor:"16", GitVersion:"v1.16.10", GitCommit:"f3add640dbcd4f3c33a7749f38baaac0b3fe810d", GitTreeState:"clean", BuildDate:"2020-05-20T14:00:52Z", GoVersion:"go1.13.9", Compiler:"gc", Platform:"darwin/amd64"}
Server Version: version.Info{Major:"1", Minor:"18", GitVersion:"v1.18.9", GitCommit:"94f372e501c973a7fa9eb40ec9ebd2fe7ca69848", GitTreeState:"clean", BuildDate:"2020-09-16T13:47:43Z", GoVersion:"go1.13.15", Compiler:"gc", Platform:"linux/amd64"}

Environment:

What happened:

If an ingress definition is created that points to an ExternalName service, which in turn produces a DNS lookup error, an endless loop of DNS requests is created that can bring the system down.

We noticed this when migrating from v0.19.0 -> v0.41.2, we have both controllers running in parallel. One of our teams was prepping for this and creating routes that pointed to yet to be created DNS records. It appears the old controllers were unaffected but there was huge amounts of DNS lookups generated by the routes on the new controller. It doesn't require actual requests to the routes, just creating the ingress and service definition is enough.

Eventually this overwhelmed dnsmasq and brought down our cluster's DNS, the concurrent requests were limited by dnsmasq but we were looking at thousands of requests per second. Was there some behaviour change between the two versions that could introduce this behaviour and is this expected? My naive guess is there would typically be some kind of exponential backoff on a DNS lookup error.

This is the error produced by the controller:

2020/11/25 20:18:52 [error] 1707#1707: *51723 [lua] dns.lua:152: dns_lookup(): failed to query the DNS server for foo.unknown.com:
server returned error code: 3: name error
server returned error code: 3: name error, context: ngx.timer

What you expected to happen:

DNS lookup failures to be handled with some form of backoff.

How to reproduce it:

These two definitions should be enough to reproduce the issue, assuming a proper class and namespace:

---
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: dns-issue-repro
  namespace: default
  annotations:
    kubernetes.io/ingress.provider: "nginx"
    kubernetes.io/ingress.class: "external"
spec:
  rules:
    - host: foo.unknown.com
      http:
        paths:
          - path: /
            backend:
              serviceName: bad-svc
              servicePort: 80

---
apiVersion: v1
kind: Service
metadata:
  name: bad-svc
  namespace: default
spec:
  type: ExternalName
  externalName: foo.unknown.com

/kind bug

aledbf commented 3 years ago

The behavior changed here https://github.com/kubernetes/ingress-nginx/pull/4671

fejta-bot commented 3 years ago

Issues go stale after 90d of inactivity. Mark the issue as fresh with /remove-lifecycle stale. Stale issues rot after an additional 30d of inactivity and eventually close.

If this issue is safe to close now please do so with /close.

Send feedback to sig-contributor-experience at kubernetes/community. /lifecycle stale

fejta-bot commented 3 years ago

Stale issues rot after 30d of inactivity. Mark the issue as fresh with /remove-lifecycle rotten. Rotten issues close after an additional 30d of inactivity.

If this issue is safe to close now please do so with /close.

Send feedback to sig-contributor-experience at kubernetes/community. /lifecycle rotten

fejta-bot commented 3 years ago

Rotten issues close after 30d of inactivity. Reopen the issue with /reopen. Mark the issue as fresh with /remove-lifecycle rotten.

Send feedback to sig-contributor-experience at kubernetes/community. /close

k8s-ci-robot commented 3 years ago

@fejta-bot: Closing this issue.

In response to [this](https://github.com/kubernetes/ingress-nginx/issues/6523#issuecomment-826161992): >Rotten issues close after 30d of inactivity. >Reopen the issue with `/reopen`. >Mark the issue as fresh with `/remove-lifecycle rotten`. > >Send feedback to sig-contributor-experience at [kubernetes/community](https://github.com/kubernetes/community). >/close Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.
adamcharnock commented 2 years ago

Yep, this just got me too while working on a new cluster. Nginx Ingress essentially DOSed CoreDNS, which caused all kinds of wierdness in the cluster.

Edit: Running k8s.gcr.io/ingress-nginx/controller:v1.1.1

unnikm8 commented 2 years ago

I am getting this issue too.

Running k8s.gcr.io/ingress-nginx/controller:v1.1.0

VsevolodSauta commented 2 years ago

I'm also affected by this issue. Hope on some activity on it. /reopen

k8s-ci-robot commented 2 years ago

@VsevolodSauta: You can't reopen an issue/PR unless you authored it or you are a collaborator.

In response to [this](https://github.com/kubernetes/ingress-nginx/issues/6523#issuecomment-1090065024): >I'm also affected by this issue. Hope on some activity on it. >/reopen Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.
javimosch commented 1 year ago

I'm also getting this issue: k8s.gcr.io/ingress-nginx/controller:v1.2.0

karlhaworth commented 1 year ago

Same issue.

dexterlakin-bdm commented 1 year ago

Why is this closed?

I am also seeing the same issue - has anyone here resolved it or has a workaround?

longwuyuan commented 1 year ago

Even without kubernetes, if a process makes calls to unresolvable hostname in a infinite loop, then there will be impact.

Thanks, ; Long

On Mon, 3 Oct, 2022, 4:32 PM dexterlakin-bdm, @.***> wrote:

Why is this closed?

I am also seeing the same issue - has anyone here resolved it or has a workaround?

— Reply to this email directly, view it on GitHub https://github.com/kubernetes/ingress-nginx/issues/6523#issuecomment-1265275394, or unsubscribe https://github.com/notifications/unsubscribe-auth/ABGZVWUGAXBN7GR4KZYGANLWBK4L7ANCNFSM4UC4AJOQ . You are receiving this because you are subscribed to this thread.Message ID: @.***>

sravanakinapally commented 1 year ago

Same issue dns.lua:152: dns_lookup(): failed to query the DNS server for

ahmad-sharif commented 1 year ago

I am also having the same issue with v1.3.1 in some clusters

qixiaobo commented 1 year ago

Same problem, keep watching

alv91 commented 1 year ago

+1

fuog commented 10 months ago

We are experiencing identical issues on both GKE and AKS clusters while using ingress-nginx versions 1.9.1 and 1.9.3.

Occasionally, we encounter situations where the backend resides outside the cluster. The "ExternalName" record is dynamically resolved using endpoints controlled by Consul. However, if it happens to be a single backend service or the last one, and it deregisters due to reasons such as a reboot, the "ExternalName" encounters a non-existing CNAME record. This, in turn, causes ingress-nginx to goes completely crazy with such errors:

2023/10/26 18:16:18 [error] 432#432: *18134 [lua] dns.lua:152: dns_lookup(): failed to query the DNS server for my-not-existing-record.example.com:
server returned error code: 3: name error
server returned error code: 3: name error, context: ngx.timer

In situations where there are only a few occurrences, this behavior can sometimes be obscured by the sheer volume of logs. However, when a substantial number of endpoints become unreachable all at once, compounded by the current scale of Ingress-NGINX pods (which, in our scenario, includes both internal and external-facing ingress classes), the problem escalates significantly and places a severe burden on our coreDNS server, potentially overwhelming them.

What I would like to see is a restriction on the number of resolve attempts / limiting resolve-retry rates or, even more desirable, the implementation of a back-off mechanism.

mjozefcz commented 10 months ago

We're experiencing same behavior. With a few 'invalid' or 'temporaty invalid' svc ExternalName backend configurations we noticed a tons of messages like this and huge amount of DNS calls.

We tested the same scenario with traefik as a ingress controller - no issue at all, just 502 response on the client call.

tao12345666333 commented 7 months ago

/reopen

k8s-ci-robot commented 7 months ago

@tao12345666333: Reopened this issue.

In response to [this](https://github.com/kubernetes/ingress-nginx/issues/6523#issuecomment-1949935389): >/reopen > Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.
k8s-ci-robot commented 7 months ago

This issue is currently awaiting triage.

If Ingress contributors determines this is a relevant issue, they will accept it by applying the triage/accepted label and provide further guidance.

The triage/accepted label can be added by org members by writing /triage accepted in a comment.

Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.
k8s-triage-robot commented 6 months ago

The Kubernetes project currently lacks enough active contributors to adequately respond to all issues and PRs.

This bot triages issues according to the following rules:

You can:

Please send feedback to sig-contributor-experience at kubernetes/community.

/close not-planned

k8s-ci-robot commented 6 months ago

@k8s-triage-robot: Closing this issue, marking it as "Not Planned".

In response to [this](https://github.com/kubernetes/ingress-nginx/issues/6523#issuecomment-2003685663): >The Kubernetes project currently lacks enough active contributors to adequately respond to all issues and PRs. > >This bot triages issues according to the following rules: >- After 90d of inactivity, `lifecycle/stale` is applied >- After 30d of inactivity since `lifecycle/stale` was applied, `lifecycle/rotten` is applied >- After 30d of inactivity since `lifecycle/rotten` was applied, the issue is closed > >You can: >- Reopen this issue with `/reopen` >- Mark this issue as fresh with `/remove-lifecycle rotten` >- Offer to help out with [Issue Triage][1] > >Please send feedback to sig-contributor-experience at [kubernetes/community](https://github.com/kubernetes/community). > >/close not-planned > >[1]: https://www.kubernetes.dev/docs/guide/issue-triage/ Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.
neerfri commented 2 days ago

/reopen

k8s-ci-robot commented 2 days ago

@neerfri: You can't reopen an issue/PR unless you authored it or you are a collaborator.

In response to [this](https://github.com/kubernetes/ingress-nginx/issues/6523#issuecomment-2355074977): >/reopen Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes-sigs/prow](https://github.com/kubernetes-sigs/prow/issues/new?title=Prow%20issue:) repository.
neerfri commented 2 days ago

@tao12345666333 if you can please reopen the ticket.

I have a PR to fix this that is almost ready to be merged waiting for approval from @grounded042 https://github.com/kubernetes/ingress-nginx/pull/10989

Thanks!

longwuyuan commented 2 days ago

/reopen

On Tue, 17 Sept, 2024, 15:37 Neer Friedman, @.***> wrote:

@tao12345666333 https://github.com/tao12345666333 if you can please reopen the ticket.

I have a PR to fix this that is almost ready to be merged waiting for approval from @grounded042 https://github.com/grounded042

10989 https://github.com/kubernetes/ingress-nginx/pull/10989

Thanks!

— Reply to this email directly, view it on GitHub https://github.com/kubernetes/ingress-nginx/issues/6523#issuecomment-2355163847, or unsubscribe https://github.com/notifications/unsubscribe-auth/ABGZVWR3OK2UZAWMOCEARVDZW75P7AVCNFSM4UC4AJO2U5DIOJSWCZC7NNSXTN2JONZXKZKDN5WW2ZLOOQ5TEMZVGUYTMMZYGQ3Q . You are receiving this because you commented.Message ID: @.***>

k8s-ci-robot commented 2 days ago

@longwuyuan: Reopened this issue.

In response to [this](https://github.com/kubernetes/ingress-nginx/issues/6523#issuecomment-2355215187): >/reopen > >On Tue, 17 Sept, 2024, 15:37 Neer Friedman, ***@***.***> >wrote: > >> @tao12345666333 if you can please >> reopen the ticket. >> >> I have a PR to fix this that is almost ready to be merged waiting for >> approval from @grounded042 >> #10989 >> >> Thanks! >> >> — >> Reply to this email directly, view it on GitHub >> , >> or unsubscribe >> >> . >> You are receiving this because you commented.Message ID: >> ***@***.***> >> > Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes-sigs/prow](https://github.com/kubernetes-sigs/prow/issues/new?title=Prow%20issue:) repository.