Documentation for new feature setHostnameAsFQDN #21210

javidiaz · 2020-05-26T19:12:54Z

This change documents how to use a new feature introduced by KEP kubernetes/enhancements#1797 and kubernetes/enhancements#1792. The PR of the code change is kubernetes/kubernetes#91699

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k8sio-netlify-preview-bot · 2020-05-26T19:13:37Z

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sftim

Hi. Here's some early feedback on this draft PR.

content/en/docs/concepts/services-networking/dns-pod-service.md

content/en/docs/reference/command-line-tools-reference/feature-gates.md

content/en/docs/reference/command-line-tools-reference/kube-apiserver.md

savitharaghunathan · 2020-05-26T22:32:45Z

/milestone 1.19

k8s-ci-robot · 2020-05-26T22:32:47Z

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savitharaghunathan · 2020-05-26T22:39:18Z

/milestone 1.19

Hi @sftim , when you get a moment can you add milestone label to this PR, please?

savitharaghunathan · 2020-05-27T00:51:50Z

/milestone 1.19

javidiaz · 2020-06-02T19:27:20Z

@savitharaghunathan @sftim Thanks for the feedback! I will work on fixing this.

We were thinking to include an admission controller example (code and yaml files) and reference it from these docs. Where should I put those files?

javidiaz · 2020-06-02T19:31:31Z

Hi @thockin, I was thinking to put the information about the HostnameFQDN feature in https://deploy-preview-21210--kubernetes-io-vnext-staging.netlify.app/docs/concepts/services-networking/dns-pod-service/#pod-hostnamefqdn-field

That page is about networking concepts, but I think it is the only place in docs where Pod FQDN are discussed. Are you OK with adding this section to that page? do you have suggestions for a better location?

javidiaz · 2020-06-19T14:12:11Z

/assign @xiangpengzhao

content/en/docs/concepts/services-networking/dns-pod-service.md

sftim

Preview

Markdown looks good to me.

javidiaz · 2020-06-25T17:01:34Z

@thockin @dchen1107 Could you please have a look at this doc PR? This is related to the SetHostnameAsFQDN feature kubernetes/kubernetes#91699 I think need a lgtm from one of you. thanks!

kbhawkey · 2020-06-25T17:31:32Z

content/en/docs/concepts/services-networking/dns-pod-service.md

+{{< note >}}
+In Linux, the hostname field of the kernel (the `nodename` field of `struct utsname`) is limited to 64 characters.
+
+If a Pod enables this feature and its FQDN is longer than 64 character, it will fail to start. The Pod will remain in `Pending` status (`ContainerCreating` as seen by `kubectl`) generating error events regarding its FQDN length. One way of improving user experience for this scenario is to create an [admission webhook controller](/docs/reference/access-authn-authz/extensible-admission-controllers/#admission-webhooks) to control FQDN size when users create top level objects, for example, Deployment.


Is this page relevant:
https://kubernetes.io/docs/concepts/overview/working-with-objects/names/#dns-label-names

I am not sure we should link to that page, it might be confusing for users. That page is mentioning that some k8s objects follow the same regex as DNS for naming. In this page we are discussing networking concepts, which are not really k8s objects.

👍 I guess I found this phrase confusing:
If a Pod enables this feature and its FQDN is longer than 64 character,
I'll see if the KEPs add clarification.
OK. This makes sense.

dashpole · 2020-06-30T17:53:45Z

/cc

dashpole

one optional suggestion. lgtm otherwise

dashpole · 2020-07-06T23:47:02Z

content/en/docs/concepts/services-networking/dns-pod-service.md

+{{< note >}}
+In Linux, the hostname field of the kernel (the `nodename` field of `struct utsname`) is limited to 64 characters.
+
+If a Pod enables this feature and its FQDN is longer than 64 character, it will fail to start. The Pod will remain in `Pending` status (`ContainerCreating` as seen by `kubectl`) generating error events regarding its FQDN length. One way of improving user experience for this scenario is to create an [admission webhook controller](/docs/reference/access-authn-authz/extensible-admission-controllers/#admission-webhooks) to control FQDN size when users create top level objects, for example, Deployment.


It may be helpful to know the name of the failure event.

Thanks @dashpole, good idea. I changed sentence to add example.

dashpole · 2020-07-07T20:10:30Z

/lgtm

KEP: kubernetes/enhancements#1797 and kubernetes/enhancements#1792 Code PR: kubernetes/kubernetes#91699

javidiaz · 2020-07-07T20:44:40Z

@dashpole can you lgtm again please? I had to rebase. thanks!

dashpole · 2020-07-07T20:53:53Z

/lgtm

sftim · 2020-07-08T12:58:41Z

Preview

Markdown looks good to me.

savitharaghunathan

/lgtm
/approve

k8s-ci-robot · 2020-07-08T14:00:49Z

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alculquicondor · 2020-07-24T16:08:03Z

content/en/docs/concepts/services-networking/dns-pod-service.md

@@ -157,6 +157,18 @@ pointing to the Pod's IP address. Also, Pod needs to become ready in order to ha
 record unless `publishNotReadyAddresses=True` is set on the Service.
 {{< /note >}}

+### Pod's setHostnameAsFQDN field {#pod-sethostnameasfqdn-field}
+
+When a Pod is configured to have fully qualified domain name (FQDN), its hostname is the short hostname. For example, if you have a Pod with the fully qualified domain name `busybox-1.default-subdomain.my-namespace.svc.cluster-domain.example`, then by default the `hostname` command inside that Pod returns `busybox-1` and  the `hostname --fqdn` command returns the FQDN.


This is lacking an alpha notice.

{{< feature-state for_k8s_version="v1.19" state="alpha" >}}

A mention of the Feature gate would be useful too.

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javidiaz force-pushed the hostnamefqdn branch from b18388b to 0e42f1d Compare May 26, 2020 19:32

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This was referenced Jun 2, 2020

Add new PodSpec field hostnameFQDN kubernetes/kubernetes#91697

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Allow setting FQDN in hostname kubernetes/kubernetes#91699

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javidiaz force-pushed the hostnamefqdn branch from 0e42f1d to b3770dd Compare June 19, 2020 14:07

javidiaz marked this pull request as ready for review June 19, 2020 14:11

k8s-ci-robot assigned xiangpengzhao Jun 19, 2020

javidiaz changed the title ~~[WIP] Documentation for new feature hostnameFQDN~~ Documentation for new feature setHostnameAsFQDN Jun 19, 2020

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javidiaz force-pushed the hostnamefqdn branch from b3770dd to c39bba8 Compare June 19, 2020 20:06

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javidiaz force-pushed the hostnamefqdn branch from c39bba8 to 279f15c Compare June 21, 2020 15:50

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javidiaz mentioned this pull request Jun 30, 2020

Allow users to set a pod’s hostname to its Fully Qualified Domain Name (FQDN) kubernetes/enhancements#1797

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javidiaz force-pushed the hostnamefqdn branch 3 times, most recently from 544442a to c9a4ed4 Compare July 7, 2020 15:58

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Documenting setHostnameAsFQDN feature

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KEP: kubernetes/enhancements#1797 and kubernetes/enhancements#1792 Code PR: kubernetes/kubernetes#91699

javidiaz force-pushed the hostnamefqdn branch from c9a4ed4 to 64422b1 Compare July 7, 2020 20:43

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Allow setting FQDN as hostname of pods. kubernetes/kubernetes#91036

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Adding feature status and prerequisite to new feature. #22712

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Documentation for new feature setHostnameAsFQDN #21210

Documentation for new feature setHostnameAsFQDN #21210

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Documentation for new feature setHostnameAsFQDN #21210

Documentation for new feature setHostnameAsFQDN #21210

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