Release 1.8 (#5659)
* GC now supports non-core resources * Add two examples about how to analysis audits of kube-apiserver (#4264) * Deprecate system:nodes binding * [1.8] StatefulSet `initialized` annotation is now ignored. * inits the kubeadm upgrade docs addresses kubernetes/kubernetes.github.io/issues/4689 * adds kubeadm upgrade cmd to ToC addresses kubernetes/kubernetes.github.io/issues/4689 * add workload placement docs * ScaleIO - document udpate for 1.8 * Add documentation on storageClass.mountOptions and PV.mountOptions (#5254) * Add documentation on storageClass.mountOptions and PV.mountOptions * convert notes into callouts * Add docs for CustomResource validation add info about supported fields * advanced audit beta features (#5300) * Update job workload doc with backoff failure policy (#5319) Add to the Jobs documentation how to use the new backoffLimit field that limit the number of Pod failure before considering the Job as failed. * Documented additional AWS Service annotations (#4864) * Add device plugin doc under concepts/cluster-administration. (#5261) * Add device plugin doc under concepts/cluster-administration. * Update device-plugins.md * Update device-plugins.md Add meta description. Fix typo. Change bare metal deployment to manual deployment. * Update device-plugins.md Fix typo again. * Update page.version. (#5341) * Add documentation on storageClass.reclaimPolicy (#5171) * [Advanced audit] use new herf for audit-api (#5349) This tag contains all the changes in v1beta1 version. Update it now. * Added documentation around creating the InitializerConfiguration for the persistent volume label controller in the cloud-controller-manager (#5255) * Documentation for kubectl plugins (#5294) * Documentation for kubectl plugins * Update kubectl-plugins.md * Update kubectl-plugins.md * Updated CPU manager docs to match implementation. (#5332) * Noted limitation of alpha static cpumanager. * Updated CPU manager docs to match implementation. - Removed references to CPU pressure node condition and evictions. - Added note about new --cpu-manager-reconcile-period flag. - Added note about node allocatable requirements for static policy. - Noted limitation of alpha static cpumanager. * Move cpu-manager task link to rsc mgmt section. * init containers annotation removed in 1.8 (#5390) * Add documentation for TaintNodesByCondition (#5352) * Add documentation for TaintNodesByCondition * Update nodes.md * Update taint-and-toleration.md * Update daemonset.md * Update nodes.md * Update taint-and-toleration.md * Update daemonset.md * Fix deployments (#5421) * Document extended resources and OIR deprecation. (#5399) * Document extended resources and OIR deprecation. * Updated extended resources doc per reviews. * reverts extra spacing in _data/tasks.yml * addresses `kubeadm upgrade` review comments Feedback from @chenopis, @luxas, and @steveperry-53 addressed with this commit * HugePages documentation (#5419) * Update cpu-management-policies.md (#5407) Fixed the bad link. Modified "cpu" to "CPU". Added more 'yaml' as supplement. * Update RBAC docs for v1 (#5445) * Add user docs for pod priority and preemption (#5328) * Add user docs for pod priority and preemption * Update pod-priority-preemption.md * More updates * Update docs/admin/kubeadm.md for 1.8 (#5440) - Made a couple of minor wording changes (not strictly 1.8 related). - Did some reformatting (not strictly 1.8 related). - Updated references to the default token TTL (was infinite, now 24 hours). - Documented the new `--discovery-token-ca-cert-hash` and `--discovery-token-unsafe-skip-ca-verification` flags for `kubeadm join`. - Added references to the new `--discovery-token-ca-cert-hash` flag in all the default examples. - Added a new _Security model_ section that describes the security tradeoffs of the various discovery modes. - Documented the new `--groups` flag for `kubeadm token create`. - Added a note of caution under _Automating kubeadm_ that references the _Security model_ section. - Updated the component version table to drop 1.6 and add 1.8. - Update `_data/reference.yml` to try to get the sidebar fixed up and more consistent with `kubefed`. * Update StatefulSet Basics for 1.8 release (#5398) * addresses `kubeadm upgrade` review comments 2nd iteration review comments by @luxas * adds kubelet upgrade section to kubeadm upgrade * Fix a bulleted list on docs/admin/kubeadm.md. (#5458) I updated this doc yesterday and I was absolutely sure I fixed this, but I just saw that this commit got lost somehow. This was introduced recently in https://github.com/kubernetes/kubernetes.github.io/pull/5440. * Clarify the API to check for device plugins * Moving Flexvolume to separate out-of-tree section * addresses `kubeadm upgrade` review comments CC: @luxas * fixes kubeadm upgrade index * Update Stackdriver Logging documentation (#5495) * Re-update WordPress and MySQL PV doc to use apps/v1beta2 APIs (#5526) * Update statefulset concepts doc to use apps/v1beta2 APIs (#5420) * add document on kubectl's behavior regarding initializers (#5505) * Update docs/admin/kubeadm.md to cover self-hosting in 1.8. (#5497) This is a new beta feature in 1.8. * Update kubectl patch doc to use apps/v1beta2 APIs (#5422) * [1.8] Update "Run Applications" tasks to apps/v1beta2. (#5525) * Update replicated stateful application task for 1.8. * Update single instance stateful app task for 1.8. * Update stateless app task for 1.8. * Update kubectl patch task for 1.8. * fix the link of persistent storage (#5515) * update the admission-controllers.md index.md what-is-kubernetes.md link * fix the link of persistent storage * Add quota support for local ephemeral storage (#5493) * Add quota support for local ephemeral storage update the doc to this alpha feature * Update resource-quotas.md * Updated Deployments concepts doc (#5491) * Updated Deployments concepts doc * Addressed comments * Addressed more comments * Modify allocatable storage to ephemeral-storage (#5490) Update the doc to use ephemeral-storage instead of storage * Revamped concepts doc for ReplicaSet (#5463) * Revamped concepts doc for ReplicaSet * Minor changes to call out specific versions for selector defaulting and immutability * Addressed doc review comments * Remove petset documentations (#5395) * Update docs to use batch/v1beta1 cronjobs (#5475) * add federation job doc (#5485) * add federation job doc * Update job.md Edits for clarity and consistency * Update job.md Fixed a typo * update DaemonSet concept for 1.8 release (#5397) * update DaemonSet concept for 1.8 release * Update daemonset.md Fix typo. than -> then * Update bootstrap tokens doc for 1.8. (#5479) * Update bootstrap tokens doc for 1.8. This has some changes I missed when I was updating the main kubeadm documention: - Bootstrap tokens are now beta, not alpha (https://github.com/kubernetes/features/issues/130) - The apiserver flag to enable the authenticator changedin 1.8 (https://github.com/kubernetes/kubernetes/pull/51198) - Added `auth-extra-groups` documentaion (https://github.com/kubernetes/kubernetes/pull/50933) - Updated the _Token Management with `kubeadm`_ section to link to the main kubeadm docs, since it was just duplicated information. * Update bootstrap-tokens.md * Updated the Cassandra tutorial to use apps/v1beta2 (#5548) * add docs for AllowPrivilegeEscalation (#5448) Signed-off-by: Jess Frazelle <acidburn@microsoft.com> * Add local ephemeral storage alpha feature in managing compute resource (#5522) * Add local ephemeral storage alpha feature in managing compute resource Since 1.8, we add the local ephemeral storage alpha feature as one resource type to manage. Add this feature into the doc. * Update manage-compute-resources-container.md * Update manage-compute-resources-container.md * Update manage-compute-resources-container.md * Update manage-compute-resources-container.md * Update manage-compute-resources-container.md * Update manage-compute-resources-container.md * Added documentation for Metrics Server (#5560) * authorization: improve authorization debugging docs (#5549) * Document mount propagation (#5544) * Update /docs/setup/independent/create-cluster-kubeadm.md for 1.8. (#5524) This introduction needed a couple of small tweaks to cover the `--discovery-token-ca-cert-hash` flag added in https://github.com/kubernetes/kubernetes/pull/49520 and some version bumps. * Add task doc for alpha dynamic kubelet configuration (#5523) * Fix input/output of selfsubjectaccess review (#5593) * Add docs for implementing resize (#5528) * Add docs for implementing resize * Update admission-controllers.md * Added link to PVC section * minor typo fixes * Update NetworkPolicy concept guide with egress and CIDR changes (#5529) * update zookeeper tutorial for 1.8 release * add doc for hostpath type (#5503) * Federated Hpa feature doc (#5487) * Federated Hpa feature doc * Federated Hpa feature doc review fixes * Update hpa.md * Update hpa.md * update cloud controller manager docs for v1.8 * Update cronjob with defaults information (#5556) * Kubernetes 1.8 reference docs (#5632) * Kubernetes 1.8 reference docs * Kubectl reference docs for 1.8 * Update side bar with 1.8 kubectl and api ref docs links * remove petset.md * update on state of HostAlias in 1.8 with hostNetwork Pod support (#5644) * Fix cron job deletion section (#5655) * update imported docs (#5656) * Add documentation for certificate rotation. (#5639) * Link to using kubeadm page * fix the command output fix the command output * fix typo in api/resources reference: "Worloads" * Add documentation for certificate rotation. * Create TOC entry for cloud controller manager. (#5662) * Updates for new versions of API types * Followup 5655: fix link to garbage collection (#5666) * Temporarily redirect resources-reference to api-reference. (#5668) * Update config for 1.8 release. (#5661) * Update config for 1.8 release. * Address reviewer comments. * Switch references in HPA docs from alpha to beta (#5671) The HPA docs still referenced the alpha version. This switches them to talk about v2beta1, which is the appropriate version for Kubernetes 1.8 * Deprecate openstack heat (#5670) * Fix typo in pod preset conflict example Move container port definition to the correct line. * Highlight openstack-heat provider deprecation The openstack-heat provider for kube-up is being deprecated and will be removed in a future release. * Temporarily fix broken links by redirecting. (#5672) * Fix broken links. (#5675) * Fix render of code block (#5674) * Fix broken links. (#5677) * Add a small note about auto-bootstrapped CSR ClusterRoles (#5660) * Update kubeadm install doc for v1.8 (#5676) * add draft workloads api content for 1.8 (#5650) * add draft workloads api content for 1.8 * edits per review, add tables, for 1.8 workloads api doc * fix typo * Minor fixes to kubeadm 1.8 upgrade guide. (#5678) - The kubelet upgrade instructions should be done on every host, not just worker nodes. - We should just upgrade all packages, instead of calling out kubelet specifically. This will also upgrade kubectl, kubeadm, and kubernetes-cni, if installed. - Draining nodes should also ignore daemonsets, and master errors can be ignored. - Make sure that the new kubeadm download is chmoded correctly. - Add a step to run `kubeadm version` to verify after downloading. - Manually approve new kubelet CSRs if rotation is enabled (known issue). * Release 1.8 (#5680) * Fix versions for 1.8 API ref docs * Updates for 1.8 kubectl reference docs * Kubeadm /docs/admin/kubeadm.md cleanup, editing. (#5681) * Update docs/admin/kubeadm.md (mostly 1.8 related). This is Fabrizio's work, which I'm committing along with my edits (in a commit on top of this). * A few of my own edits to clarify and clean up some Markdown.
This commit is contained in:
Steve Perry
@@ -22,8 +22,10 @@ on a given schedule, written in [Cron](https://en.wikipedia.org/wiki/Cron) forma
|
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**Note:** The question mark (`?`) in the schedule has the same meaning as an asterisk `*`,
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that is, it stands for any of available value for a given field.
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|
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**Note:** ScheduledJob resource was introduced in Kubernetes version 1.4, but starting
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from version 1.5 its current name is CronJob.
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**Note:** CronJob resource in `batch/v2alpha1` API group has been deprecated starting
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from cluster version 1.8. You should switch to using `batch/v1beta1`, instead, which is
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enabled by default in the API server. Further in this document, we will be using
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`batch/v1beta1` in all the examples.
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|
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A typical use case is:
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|
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@@ -32,8 +34,8 @@ A typical use case is:
|
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|
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### Prerequisites
|
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|
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You need a working Kubernetes cluster at version >= 1.4 (for ScheduledJob), >= 1.5 (for CronJob),
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with batch/v2alpha1 API turned on by passing `--runtime-config=batch/v2alpha1=true` while bringing up
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You need a working Kubernetes cluster at version >= 1.8 (for CronJob). For previous versions of cluster (< 1.8)
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you need to explicitly enable `batch/v2alpha1` API by passing `--runtime-config=batch/v2alpha1=true` to
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the API server (see [Turn on or off an API version for your cluster](/docs/admin/cluster-management/#turn-on-or-off-an-api-version-for-your-cluster)
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for more).
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|
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@@ -111,25 +113,8 @@ $ kubectl delete cronjob hello
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cronjob "hello" deleted
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```
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This stops new jobs from being created. However, running jobs won't be stopped, and no jobs or their pods will
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be deleted. To clean up those jobs and pods, you need to list all jobs created by the cron job, and delete them all:
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```shell
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$ kubectl get jobs
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NAME DESIRED SUCCESSFUL AGE
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hello-1201907962 1 1 11m
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hello-1202039034 1 1 8m
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...
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$ kubectl delete jobs hello-1201907962 hello-1202039034 ...
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job "hello-1201907962" deleted
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job "hello-1202039034" deleted
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...
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```
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Once the jobs are deleted, the pods created by them are deleted as well. Note that all jobs created by cron
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job "hello" will be prefixed "hello-". You can delete them at once with `kubectl delete jobs --all`, if you want to
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delete all jobs in the current namespace (not just the ones created by "hello").
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This stops new jobs from being created and removes all the jobs and pods created by this cronjob.
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You can read more about it in [garbage collection section](/docs/concepts/workloads/controllers/garbage-collection/).
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## Cron Job Limitations
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@@ -187,6 +172,7 @@ apply to already started executions. Defaults to false.
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### Jobs History Limits
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The `.spec.successfulJobsHistoryLimit` and `.spec.failedJobsHistoryLimit` fields are optional. These fields specify how many completed and failed jobs should be kept.
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By default, there are no limits, and all successful and failed jobs are kept. However, jobs can pile up quickly when running a cron job, and setting these fields is recommended. Setting a limit to `0` corresponds to keeping none of the corresponding kind of jobs after they finish.
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The `.spec.successfulJobsHistoryLimit` and `.spec.failedJobsHistoryLimit` fields are optional.
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These fields specify how many completed and failed jobs should be kept. By default, they are
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set to 3 and 1 respectively. Setting a limit to `0` corresponds to keeping none of the corresponding
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kind of jobs after they finish.
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@@ -1,4 +1,4 @@
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apiVersion: batch/v2alpha1
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apiVersion: batch/v1beta1
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kind: CronJob
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metadata:
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name: hello
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@@ -1,6 +1,10 @@
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---
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approvers:
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- enisoc
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- erictune
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- foxish
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- janetkuo
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- kow3ns
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title: Daemon Sets
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---
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||||
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@@ -9,9 +13,9 @@ title: Daemon Sets
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## What is a DaemonSet?
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A _DaemonSet_ ensures that all (or some) nodes run a copy of a pod. As nodes are added to the
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cluster, pods are added to them. As nodes are removed from the cluster, those pods are garbage
|
||||
collected. Deleting a DaemonSet will clean up the pods it created.
|
||||
A _DaemonSet_ ensures that all (or some) Nodes run a copy of a Pod. As nodes are added to the
|
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cluster, Pods are added to them. As nodes are removed from the cluster, those Pods are garbage
|
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collected. Deleting a DaemonSet will clean up the Pods it created.
|
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|
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Some typical uses of a DaemonSet are:
|
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|
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@@ -47,20 +51,26 @@ A DaemonSet also needs a [`.spec`](https://git.k8s.io/community/contributors/dev
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|
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### Pod Template
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The `.spec.template` is the only required field of the `.spec`.
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The `.spec.template` is one of the required fields in `.spec`.
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The `.spec.template` is a [pod template](/docs/concepts/workloads/pods/pod-overview/#pod-templates). It has exactly the same schema as a [pod](/docs/concepts/workloads/pods/pod/), except it is nested and does not have an `apiVersion` or `kind`.
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The `.spec.template` is a [pod template](/docs/concepts/workloads/pods/pod-overview/#pod-templates). It has exactly the same schema as a [Pod](/docs/concepts/workloads/pods/pod/), except it is nested and does not have an `apiVersion` or `kind`.
|
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|
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In addition to required fields for a pod, a pod template in a DaemonSet has to specify appropriate
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In addition to required fields for a Pod, a Pod template in a DaemonSet has to specify appropriate
|
||||
labels (see [pod selector](#pod-selector)).
|
||||
|
||||
A pod template in a DaemonSet must have a [`RestartPolicy`](/docs/user-guide/pod-states)
|
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A Pod Template in a DaemonSet must have a [`RestartPolicy`](/docs/user-guide/pod-states)
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||||
equal to `Always`, or be unspecified, which defaults to `Always`.
|
||||
|
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### Pod Selector
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||||
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The `.spec.selector` field is a pod selector. It works the same as the `.spec.selector` of
|
||||
a [Job](/docs/concepts/jobs/run-to-completion-finite-workloads/) or other new resources.
|
||||
a [Job](/docs/concepts/jobs/run-to-completion-finite-workloads/).
|
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|
||||
As of Kubernetes 1.8, you must specify a pod selector that matches the labels of the
|
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`.spec.template`. The pod selector will no longer be defaulted when left empty. Selector
|
||||
defaulting was not compatible with `kubectl apply`. Also, once a DaemonSet is created,
|
||||
its `spec.selector` can not be mutated. Mutating the pod selector can lead to the
|
||||
unintentional orphaning of Pods, and it was found to be confusing to users.
|
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|
||||
The `spec.selector` is an object consisting of two fields:
|
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|
||||
@@ -73,53 +83,58 @@ When the two are specified the result is ANDed.
|
||||
If the `.spec.selector` is specified, it must match the `.spec.template.metadata.labels`. If not
|
||||
specified, they are defaulted to be equal. Config with these not matching will be rejected by the API.
|
||||
|
||||
Also you should not normally create any pods whose labels match this selector, either directly, via
|
||||
another DaemonSet, or via other controller such as ReplicationController. Otherwise, the DaemonSet
|
||||
controller will think that those pods were created by it. Kubernetes will not stop you from doing
|
||||
this. One case where you might want to do this is manually create a pod with a different value on
|
||||
Also you should not normally create any Pods whose labels match this selector, either directly, via
|
||||
another DaemonSet, or via other controller such as ReplicaSet. Otherwise, the DaemonSet
|
||||
controller will think that those Pods were created by it. Kubernetes will not stop you from doing
|
||||
this. One case where you might want to do this is manually create a Pod with a different value on
|
||||
a node for testing.
|
||||
|
||||
If you attempt to create a DaemonSet such that
|
||||
|
||||
### Running Pods on Only Some Nodes
|
||||
|
||||
If you specify a `.spec.template.spec.nodeSelector`, then the DaemonSet controller will
|
||||
create pods on nodes which match that [node
|
||||
create Pods on nodes which match that [node
|
||||
selector](/docs/concepts/configuration/assign-pod-node/). Likewise if you specify a `.spec.template.spec.affinity`,
|
||||
then DaemonSet controller will create pods on nodes which match that [node affinity](/docs/concepts/configuration/assign-pod-node/).
|
||||
If you do not specify either, then the DaemonSet controller will create pods on all nodes.
|
||||
then DaemonSet controller will create Pods on nodes which match that [node affinity](/docs/concepts/configuration/assign-pod-node/).
|
||||
If you do not specify either, then the DaemonSet controller will create Pods on all nodes.
|
||||
|
||||
## How Daemon Pods are Scheduled
|
||||
|
||||
Normally, the machine that a pod runs on is selected by the Kubernetes scheduler. However, pods
|
||||
created by the Daemon controller have the machine already selected (`.spec.nodeName` is specified
|
||||
when the pod is created, so it is ignored by the scheduler). Therefore:
|
||||
Normally, the machine that a Pod runs on is selected by the Kubernetes scheduler. However, Pods
|
||||
created by the DaemonSet controller have the machine already selected (`.spec.nodeName` is specified
|
||||
when the Pod is created, so it is ignored by the scheduler). Therefore:
|
||||
|
||||
- The [`unschedulable`](/docs/admin/node/#manual-node-administration) field of a node is not respected
|
||||
by the DaemonSet controller.
|
||||
- DaemonSet controller can make pods even when the scheduler has not been started, which can help cluster
|
||||
- The DaemonSet controller can make Pods even when the scheduler has not been started, which can help cluster
|
||||
bootstrap.
|
||||
|
||||
Daemon pods do respect [taints and tolerations](/docs/concepts/configuration/assign-pod-node/#taints-and-tolerations-beta-feature),
|
||||
Daemon Pods do respect [taints and tolerations](/docs/concepts/configuration/assign-pod-node/#taints-and-tolerations-beta-feature),
|
||||
but they are created with `NoExecute` tolerations for the following taints with no `tolerationSeconds`:
|
||||
|
||||
- `node.alpha.kubernetes.io/notReady`
|
||||
- `node.alpha.kubernetes.io/unreachable`
|
||||
- `node.alpha.kubernetes.io/memoryPressure`
|
||||
- `node.alpha.kubernetes.io/diskPressure`
|
||||
|
||||
When the support to critical pods is enabled and the pods in a DaemonSet are
|
||||
labelled as critical, the Daemon pods are created with an additional
|
||||
`NoExecute` toleration for the `node.alpha.kubernetes.io/outOfDisk` taint with
|
||||
no `tolerationSeconds`.
|
||||
|
||||
This ensures that when the `TaintBasedEvictions` alpha feature is enabled,
|
||||
they will not be evicted when there are node problems such as a network partition. (When the
|
||||
`TaintBasedEvictions` feature is not enabled, they are also not evicted in these scenarios, but
|
||||
due to hard-coded behavior of the NodeController rather than due to tolerations).
|
||||
|
||||
They also tolerate following `NoSchedule` taints:
|
||||
|
||||
- `node.kubernetes.io/memory-pressure`
|
||||
- `node.kubernetes.io/disk-pressure`
|
||||
|
||||
When the support to critical pods is enabled and the pods in a DaemonSet are
|
||||
labelled as critical, the Daemon pods are created with an additional
|
||||
`NoSchedule` toleration for the `node.kubernetes.io/out-of-disk` taint.
|
||||
|
||||
Note that all above `NoSchedule` taints above are created only in version 1.8 or later if the alpha feature `TaintNodesByCondition` is enabled.
|
||||
|
||||
## Communicating with Daemon Pods
|
||||
|
||||
Some possible patterns for communicating with pods in a DaemonSet are:
|
||||
Some possible patterns for communicating with Pods in a DaemonSet are:
|
||||
|
||||
- **Push**: Pods in the DaemonSet are configured to send updates to another service, such
|
||||
as a stats database. They do not have clients.
|
||||
@@ -127,24 +142,24 @@ Some possible patterns for communicating with pods in a DaemonSet are:
|
||||
- **DNS**: Create a [headless service](/docs/concepts/services-networking/service/#headless-services) with the same pod selector,
|
||||
and then discover DaemonSets using the `endpoints` resource or retrieve multiple A records from
|
||||
DNS.
|
||||
- **Service**: Create a service with the same pod selector, and use the service to reach a
|
||||
- **Service**: Create a service with the same Pod selector, and use the service to reach a
|
||||
daemon on a random node. (No way to reach specific node.)
|
||||
|
||||
## Updating a DaemonSet
|
||||
|
||||
If node labels are changed, the DaemonSet will promptly add pods to newly matching nodes and delete
|
||||
pods from newly not-matching nodes.
|
||||
If node labels are changed, the DaemonSet will promptly add Pods to newly matching nodes and delete
|
||||
Pods from newly not-matching nodes.
|
||||
|
||||
You can modify the pods that a DaemonSet creates. However, pods do not allow all
|
||||
You can modify the Pods that a DaemonSet creates. However, Pods do not allow all
|
||||
fields to be updated. Also, the DaemonSet controller will use the original template the next
|
||||
time a node (even with the same name) is created.
|
||||
|
||||
|
||||
You can delete a DaemonSet. If you specify `--cascade=false` with `kubectl`, then the pods
|
||||
You can delete a DaemonSet. If you specify `--cascade=false` with `kubectl`, then the Pods
|
||||
will be left on the nodes. You can then create a new DaemonSet with a different template.
|
||||
the new DaemonSet with the different template will recognize all the existing pods as having
|
||||
matching labels. It will not modify or delete them despite a mismatch in the pod template.
|
||||
You will need to force new pod creation by deleting the pod or deleting the node.
|
||||
The new DaemonSet with the different template will recognize all the existing Pods as having
|
||||
matching labels. It will not modify or delete them despite a mismatch in the Pod template.
|
||||
You will need to force new Pod creation by deleting the Pod or deleting the node.
|
||||
|
||||
In Kubernetes version 1.6 and later, you can [perform a rolling update](/docs/tasks/manage-daemon/update-daemon-set/) on a DaemonSet.
|
||||
|
||||
@@ -159,35 +174,35 @@ It is certainly possible to run daemon processes by directly starting them on a
|
||||
running such processes via a DaemonSet:
|
||||
|
||||
- Ability to monitor and manage logs for daemons in the same way as applications.
|
||||
- Same config language and tools (e.g. pod templates, `kubectl`) for daemons and applications.
|
||||
- Same config language and tools (e.g. Pod templates, `kubectl`) for daemons and applications.
|
||||
- Future versions of Kubernetes will likely support integration between DaemonSet-created
|
||||
pods and node upgrade workflows.
|
||||
Pods and node upgrade workflows.
|
||||
- Running daemons in containers with resource limits increases isolation between daemons from app
|
||||
containers. However, this can also be accomplished by running the daemons in a container but not in a pod
|
||||
containers. However, this can also be accomplished by running the daemons in a container but not in a Pod
|
||||
(e.g. start directly via Docker).
|
||||
|
||||
### Bare Pods
|
||||
|
||||
It is possible to create pods directly which specify a particular node to run on. However,
|
||||
a DaemonSet replaces pods that are deleted or terminated for any reason, such as in the case of
|
||||
It is possible to create Pods directly which specify a particular node to run on. However,
|
||||
a DaemonSet replaces Pods that are deleted or terminated for any reason, such as in the case of
|
||||
node failure or disruptive node maintenance, such as a kernel upgrade. For this reason, you should
|
||||
use a DaemonSet rather than creating individual pods.
|
||||
use a DaemonSet rather than creating individual Pods.
|
||||
|
||||
### Static Pods
|
||||
|
||||
It is possible to create pods by writing a file to a certain directory watched by Kubelet. These
|
||||
It is possible to create Pods by writing a file to a certain directory watched by Kubelet. These
|
||||
are called [static pods](/docs/concepts/cluster-administration/static-pod/).
|
||||
Unlike DaemonSet, static pods cannot be managed with kubectl
|
||||
or other Kubernetes API clients. Static pods do not depend on the apiserver, making them useful
|
||||
in cluster bootstrapping cases. Also, static pods may be deprecated in the future.
|
||||
Unlike DaemonSet, static Pods cannot be managed with kubectl
|
||||
or other Kubernetes API clients. Static Pods do not depend on the apiserver, making them useful
|
||||
in cluster bootstrapping cases. Also, static Pods may be deprecated in the future.
|
||||
|
||||
### Replication Controller
|
||||
### Deployments
|
||||
|
||||
DaemonSet are similar to [Replication Controllers](/docs/user-guide/replication-controller) in that
|
||||
they both create pods, and those pods have processes which are not expected to terminate (e.g. web servers,
|
||||
DaemonSets are similar to [Deployments](/docs/concepts/workloads/controllers/deployment.md) in that
|
||||
they both create Pods, and those Pods have processes which are not expected to terminate (e.g. web servers,
|
||||
storage servers).
|
||||
|
||||
Use a replication controller for stateless services, like frontends, where scaling up and down the
|
||||
Use a Deployment for stateless services, like frontends, where scaling up and down the
|
||||
number of replicas and rolling out updates are more important than controlling exactly which host
|
||||
the pod runs on. Use a Daemon Controller when it is important that a copy of a pod always run on
|
||||
all or certain hosts, and when it needs to start before other pods.
|
||||
the Pod runs on. Use a DaemonSet when it is important that a copy of a Pod always run on
|
||||
all or certain hosts, and when it needs to start before other Pods.
|
||||
|
||||
@@ -1,4 +1,4 @@
|
||||
apiVersion: extensions/v1beta1
|
||||
apiVersion: apps/v1beta2
|
||||
kind: DaemonSet
|
||||
metadata:
|
||||
name: fluentd-elasticsearch
|
||||
@@ -6,6 +6,9 @@ metadata:
|
||||
labels:
|
||||
k8s-app: fluentd-logging
|
||||
spec:
|
||||
selector:
|
||||
matchLabels:
|
||||
name: fluentd-elasticsearch
|
||||
template:
|
||||
metadata:
|
||||
labels:
|
||||
@@ -33,4 +36,4 @@ spec:
|
||||
path: /var/log
|
||||
- name: varlibdockercontainers
|
||||
hostPath:
|
||||
path: /var/lib/docker/containers
|
||||
path: /var/lib/docker/containers
|
||||
|
||||
@@ -288,6 +288,9 @@ It is generally discouraged to make label selector updates and it is suggested t
|
||||
In any case, if you need to perform a label selector update, exercise great caution and make sure you have grasped
|
||||
all of the implications.
|
||||
|
||||
**Note:** In API version `apps/v1beta2`, a Deployment's label selector is immutable after it gets created.
|
||||
{: .note}
|
||||
|
||||
* Selector additions require the pod template labels in the Deployment spec to be updated with the new label too,
|
||||
otherwise a validation error is returned. This change is a non-overlapping one, meaning that the new selector does
|
||||
not select ReplicaSets and Pods created with the old selector, resulting in orphaning all old ReplicaSets and
|
||||
@@ -850,9 +853,9 @@ allowed, which is the default if not specified.
|
||||
`.spec.selector` is an optional field that specifies a [label selector](/docs/concepts/overview/working-with-objects/labels/)
|
||||
for the Pods targeted by this deployment.
|
||||
|
||||
If specified, `.spec.selector` must match `.spec.template.metadata.labels`, or it will be rejected by
|
||||
the API. If `.spec.selector` is unspecified, `.spec.selector.matchLabels` defaults to
|
||||
`.spec.template.metadata.labels`.
|
||||
`.spec.selector` must match `.spec.template.metadata.labels`, or it will be rejected by the API.
|
||||
|
||||
In API version `apps/v1beta2`, `.spec.selector` and `.metadata.labels` no longer default to `.spec.template.metadata.labels` if not set. So they must be set explicitly. Also note that `.spec.selector` is immutable after creation of the Deployment in `apps/v1beta2`.
|
||||
|
||||
A Deployment may terminate Pods whose labels match the selector if their template is different
|
||||
from `.spec.template` or if the total number of such Pods exceeds `.spec.replicas`. It brings up new
|
||||
@@ -926,20 +929,7 @@ a Pod is considered ready, see [Container Probes](/docs/concepts/workloads/pods/
|
||||
|
||||
### Rollback To
|
||||
|
||||
`.spec.rollbackTo` is an optional field with the configuration the Deployment
|
||||
should roll back to. Setting this field triggers a rollback, and this field will
|
||||
be cleared by the server after a rollback is done.
|
||||
|
||||
Because this field will be cleared by the server, it should not be used
|
||||
declaratively. For example, you should not perform `kubectl apply` with a
|
||||
manifest with `.spec.rollbackTo` field set.
|
||||
|
||||
#### Revision
|
||||
|
||||
`.spec.rollbackTo.revision` is an optional field specifying the revision to roll
|
||||
back to. Setting to 0 means rolling back to the last revision in history;
|
||||
otherwise, means rolling back to the specified revision. This defaults to 0 when
|
||||
[`spec.rollbackTo`](#rollback-to) is set.
|
||||
Field `.spec.rollbackTo` has been deprecated in API versions `extensions/v1beta1` and `apps/v1beta1`, and is no longer supported in API version `apps/v1beta2`. Instead, `kubectl rollout undo` as introduced in [Rolling Back to a Previous Revision](#rolling-back-to-a-previous-revision) should be used.
|
||||
|
||||
### Revision History Limit
|
||||
|
||||
|
||||
@@ -1,20 +1,14 @@
|
||||
apiVersion: extensions/v1beta1
|
||||
apiVersion: apps/v1beta2 # for versions before 1.6.0 use extensions/v1beta1
|
||||
kind: ReplicaSet
|
||||
metadata:
|
||||
name: frontend
|
||||
# these labels can be applied automatically
|
||||
# from the labels in the pod template if not set
|
||||
# labels:
|
||||
# app: guestbook
|
||||
# tier: frontend
|
||||
labels:
|
||||
app: guestbook
|
||||
tier: frontend
|
||||
spec:
|
||||
# this replicas value is default
|
||||
# modify it according to your case
|
||||
replicas: 3
|
||||
# selector can be applied automatically
|
||||
# from the labels in the pod template if not set,
|
||||
# but we are specifying the selector here to
|
||||
# demonstrate its usage.
|
||||
selector:
|
||||
matchLabels:
|
||||
tier: frontend
|
||||
|
||||
@@ -155,11 +155,8 @@ is not used, only the ReplicaSets will be deleted, and the Pods will be orphaned
|
||||
See [kubeadm/#149](https://github.com/kubernetes/kubeadm/issues/149#issuecomment-284766613) for more information.
|
||||
|
||||
## Known issues
|
||||
* As of 1.7, garbage collection does not yet support
|
||||
[custom resources](/docs/concepts/api-extension/custom-resources/),
|
||||
such as those added through CustomResourceDefinition or aggregated API servers.
|
||||
|
||||
[Other known issues](https://github.com/kubernetes/kubernetes/issues/26120)
|
||||
Tracked at [#26120](https://github.com/kubernetes/kubernetes/issues/26120)
|
||||
|
||||
{% endcapture %}
|
||||
|
||||
|
||||
@@ -12,4 +12,5 @@ spec:
|
||||
image: perl
|
||||
command: ["perl", "-Mbignum=bpi", "-wle", "print bpi(2000)"]
|
||||
restartPolicy: Never
|
||||
backoffLimit: 4
|
||||
|
||||
|
||||
@@ -196,6 +196,12 @@ sometimes be started twice.
|
||||
If you do specify `.spec.parallelism` and `.spec.completions` both greater than 1, then there may be
|
||||
multiple pods running at once. Therefore, your pods must also be tolerant of concurrency.
|
||||
|
||||
### Pod Backoff failure policy
|
||||
|
||||
There are situations where you want to fail a Job after some amount of retries due to a logical error in configuration etc.
|
||||
To do so set `.spec.template.spec.backoffLimit` to specify the number of retries before considering a Job as failed.
|
||||
The back-off limit is set by default to 6. Failed Pods associated with the Job are recreated by the Job controller with an exponential back-off delay (10s, 20s, 40s ...) capped at six minutes, The back-off limit is reset if no new failed Pods appear before the Job's next status check.
|
||||
|
||||
## Job Termination and Cleanup
|
||||
|
||||
When a Job completes, no more Pods are created, but the Pods are not deleted either. Since they are terminated,
|
||||
@@ -230,6 +236,7 @@ spec:
|
||||
image: perl
|
||||
command: ["perl", "-Mbignum=bpi", "-wle", "print bpi(2000)"]
|
||||
restartPolicy: Never
|
||||
backoffLimit: 5
|
||||
```
|
||||
|
||||
Note that both the Job Spec and the Pod Template Spec within the Job have a field with the same name.
|
||||
|
||||
@@ -1,9 +1,14 @@
|
||||
apiVersion: apps/v1beta1 # for versions before 1.6.0 use extensions/v1beta1
|
||||
apiVersion: apps/v1beta2 # for versions before 1.7.0 use apps/v1beta1
|
||||
kind: Deployment
|
||||
metadata:
|
||||
name: nginx-deployment
|
||||
labels:
|
||||
app: nginx
|
||||
spec:
|
||||
replicas: 3
|
||||
selector:
|
||||
matchLabels:
|
||||
app: nginx
|
||||
template:
|
||||
metadata:
|
||||
labels:
|
||||
|
||||
@@ -1,441 +0,0 @@
|
||||
---
|
||||
approvers:
|
||||
- bprashanth
|
||||
- enisoc
|
||||
- erictune
|
||||
- foxish
|
||||
- janetkuo
|
||||
- kow3ns
|
||||
- smarterclayton
|
||||
title: PetSets
|
||||
---
|
||||
|
||||
__Warning:__ Starting in Kubernetes version 1.5, PetSet has been renamed to [StatefulSet](/docs/concepts/abstractions/controllers/statefulsets). To use (or continue to use) PetSet in Kubernetes 1.5, you _must_ [migrate](/docs/tasks/manage-stateful-set/upgrade-pet-set-to-stateful-set/) your existing PetSets to StatefulSets. For information on working with StatefulSet, see the tutorial on [how to run replicated stateful applications](/docs/tasks/run-application/run-replicated-stateful-application/).
|
||||
|
||||
__This document has been deprecated__, but can still apply if you're using
|
||||
Kubernetes version 1.4 or earlier.
|
||||
|
||||
* TOC
|
||||
{:toc}
|
||||
|
||||
__Terminology__
|
||||
|
||||
Throughout this doc you will see a few terms that are sometimes used interchangeably elsewhere, that might cause confusion. This section attempts to clarify them.
|
||||
|
||||
* Node: A single virtual or physical machine in a Kubernetes cluster.
|
||||
* Cluster: A group of nodes in a single failure domain, unless mentioned otherwise.
|
||||
* Persistent Volume Claim (PVC): A request for storage, typically a [persistent volume](/docs/tasks/configure-pod-container/configure-persistent-volume-storage/).
|
||||
* Host name: The hostname attached to the UTS namespace of the pod, i.e. the output of `hostname` in the pod.
|
||||
* DNS/Domain name: A *cluster local* domain name resolvable using standard methods (e.g.: [gethostbyname](http://linux.die.net/man/3/gethostbyname)).
|
||||
* Ordinality: the property of being "ordinal", or occupying a position in a sequence.
|
||||
* Pet: a single member of a PetSet; more generally, a stateful application.
|
||||
* Peer: a process running a server, capable of communicating with other such processes.
|
||||
|
||||
__Prerequisites__
|
||||
|
||||
This doc assumes familiarity with the following Kubernetes concepts:
|
||||
|
||||
* [Pods](/docs/user-guide/pods/single-container/)
|
||||
* [Cluster DNS](/docs/concepts/services-networking/dns-pod-service/)
|
||||
* [Headless Services](/docs/concepts/services-networking/service/#headless-services)
|
||||
* [Persistent Volumes](/docs/concepts/storage/persistent-volumes/)
|
||||
* [Persistent Volume Provisioning](https://github.com/kubernetes/examples/tree/{{page.githubbranch}}/staging/persistent-volume-provisioning/README.md)
|
||||
|
||||
You need a working Kubernetes cluster at version >= 1.3, with a healthy DNS [cluster addon](http://releases.k8s.io/{{page.githubbranch}}/cluster/addons/README.md) at version >= 15. You cannot use PetSet on a hosted Kubernetes provider that has disabled `alpha` resources.
|
||||
|
||||
## What is a PetSet?
|
||||
|
||||
In Kubernetes, most pod management abstractions group them into disposable units of work that compose a micro service. Replication controllers for example, are designed with a weak guarantee - that there should be N replicas of a particular pod template. The pods are treated as stateless units, if one of them is unhealthy or superseded by a newer version, the system just disposes it.
|
||||
|
||||
```
|
||||
foo.default.svc.cluster.local
|
||||
|service|
|
||||
/ \
|
||||
| pod-asdf | | pod-zxcv |
|
||||
```
|
||||
|
||||
A PetSet, in contrast, is a group of stateful pods that require a stronger notion of identity. The document refers to these as "clustered applications".
|
||||
|
||||
```
|
||||
*.foo.default.svc.cluster.local
|
||||
| mysql-0 | <-> | mysql-1 |
|
||||
[pv 0] [pv 1]
|
||||
```
|
||||
|
||||
The co-ordinated deployment of clustered applications is notoriously hard. They require stronger notions of identity and membership, which they use in opaque internal protocols, and are especially prone to race conditions and deadlock. Traditionally administrators have deployed these applications by leveraging nodes as stable, long-lived entities with persistent storage and static ips.
|
||||
|
||||
The goal of PetSet is to decouple this dependency by assigning identities to individual instances of an application that are not anchored to the underlying physical infrastructure. For the rest of this document we will refer to these entities as "Pets". Our use of this term is predated by the "Pets vs Cattle" analogy.
|
||||
|
||||
__Relationship between Pets and Pods__: PetSet requires there be {0..N-1} Pets. Each Pet has a deterministic name - PetSetName-Ordinal, and a unique identity. Each Pet has at most one pod, and each PetSet has at most one Pet with a given identity.
|
||||
|
||||
## When to use PetSet?
|
||||
|
||||
A PetSet ensures that a specified number of "pets" with unique identities are running at any given time. The identity of a Pet is comprised of:
|
||||
|
||||
* a stable hostname, available in DNS
|
||||
* an ordinal index
|
||||
* stable storage: linked to the ordinal & hostname
|
||||
|
||||
These properties are useful in deploying stateful applications. However most stateful applications are also clustered, meaning they form groups with strict membership requirements that rely on stored state. PetSet also helps with the 2 most common problems encountered managing such clustered applications:
|
||||
|
||||
* discovery of peers for quorum
|
||||
* startup/teardown ordering
|
||||
|
||||
Only use PetSet if your application requires some or all of these properties. Managing pods as stateless replicas is vastly easier.
|
||||
|
||||
Example workloads for PetSet:
|
||||
|
||||
* Databases like MySQL or PostgreSQL that require a single instance attached to an NFS persistent volume at any time
|
||||
* Clustered software like Zookeeper, Etcd, or Elasticsearch that require stable membership.
|
||||
|
||||
## Alpha limitations
|
||||
|
||||
Before you start deploying applications as PetSets, there are a few limitations you should understand.
|
||||
|
||||
* PetSet is an *alpha* resource, not available in any Kubernetes release prior to 1.3.
|
||||
* As with all alpha/beta resources, it can be disabled through the `--runtime-config` option passed to the apiserver, and in fact most likely will be disabled on hosted offerings of Kubernetes.
|
||||
* The only updatable field on a PetSet is `replicas`.
|
||||
* The storage for a given pet must either be provisioned by a [persistent volume provisioner](https://github.com/kubernetes/examples/tree/{{page.githubbranch}}/staging/persistent-volume-provisioning/README.md) based on the requested `storage class`, or pre-provisioned by an admin. Note that persistent volume provisioning is also currently in alpha.
|
||||
* Deleting and/or scaling a PetSet down will *not* delete the volumes associated with the PetSet. This is done to ensure safety first, your data is more valuable than an auto purge of all related PetSet resources. **Deleting the Persistent Volume Claims will result in a deletion of the associated volumes**.
|
||||
* All PetSets currently require a "governing service", or a Service responsible for the network identity of the pets. The user is responsible for this Service.
|
||||
* Updating an existing PetSet is currently a manual process, meaning you either need to deploy a new PetSet with the new image version, or orphan Pets one by one, update their image, and join them back to the cluster.
|
||||
|
||||
## Example PetSet
|
||||
|
||||
We'll create a basic PetSet to demonstrate how Pets are assigned unique and "sticky" identities.
|
||||
|
||||
{% include code.html language="yaml" file="petset.yaml" ghlink="/docs/concepts/workloads/controllers/petset.yaml" %}
|
||||
|
||||
Saving this config into `petset.yaml` and submitting it to a Kubernetes cluster should create the defined PetSet and Pets it manages:
|
||||
|
||||
```shell
|
||||
$ kubectl create -f petset.yaml
|
||||
service "nginx" created
|
||||
petset "web" created
|
||||
```
|
||||
|
||||
## Pet Identity
|
||||
|
||||
The identity of a Pet sticks to it, regardless of which node it's (re) scheduled on. We can examine the identity of the pets we just created.
|
||||
|
||||
### Ordinal index
|
||||
|
||||
you should see 2 pods with predictable names formatted thus: `$(petset name)-$(ordinal index assigned by petset controller)`
|
||||
|
||||
```shell
|
||||
$ kubectl get po
|
||||
NAME READY STATUS RESTARTS AGE
|
||||
web-0 1/1 Running 0 10m
|
||||
web-1 1/1 Running 0 10m
|
||||
```
|
||||
|
||||
### Stable storage
|
||||
|
||||
2 persistent volumes, one per pod. This is auto created by the PetSet based on the `volumeClaimTemplate` field
|
||||
|
||||
```shell
|
||||
$ kubectl get pv
|
||||
NAME CAPACITY ACCESSMODES STATUS CLAIM REASON AGE
|
||||
pvc-90234946-3717-11e6-a46e-42010af00002 1Gi RWO Bound default/www-web-0 11m
|
||||
pvc-902733c2-3717-11e6-a46e-42010af00002 1Gi RWO Bound default/www-web-1 11m
|
||||
```
|
||||
|
||||
### Network identity
|
||||
|
||||
The network identity has 2 parts. First, we created a headless Service that controls the domain within which we create Pets. The domain managed by this Service takes the form: `$(service name).$(namespace).svc.cluster.local`, where "cluster.local" is the [cluster domain](/docs/concepts/services-networking/dns-pod-service/). As each pet is created, it gets a matching DNS subdomain, taking the form: `$(petname).$(governing service domain)`, where the governing service is defined by the `serviceName` field on the PetSet.
|
||||
|
||||
Here are some examples of choices for Cluster Domain, Service name, PetSet name, and how that affects the DNS names for the Pets and the hostnames in the Pet's pods:
|
||||
|
||||
Cluster Domain | Service (ns/name) | PetSet (ns/name) | PetSet Domain | Pet DNS | Pet Hostname |
|
||||
-------------- | ----------------- | ----------------- | -------------- | ------- | ------------ |
|
||||
cluster.local | default/nginx | default/web | nginx.default.svc.cluster.local | web-{0..N-1}.nginx.default.svc.cluster.local | web-{0..N-1} |
|
||||
cluster.local | foo/nginx | foo/web | nginx.foo.svc.cluster.local | web-{0..N-1}.nginx.foo.svc.cluster.local | web-{0..N-1} |
|
||||
kube.local | foo/nginx | foo/web | nginx.foo.svc.kube.local | web-{0..N-1}.nginx.foo.svc.kube.local | web-{0..N-1} |
|
||||
|
||||
Note that Cluster Domain will be set to `cluster.local` unless [otherwise configured](https://github.com/kubernetes/kubernetes/blob/master/examples/cluster-dns/README.md).
|
||||
|
||||
Let's verify our assertion with a simple test.
|
||||
|
||||
```shell
|
||||
$ kubectl get svc
|
||||
NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE
|
||||
nginx None <none> 80/TCP 12m
|
||||
...
|
||||
```
|
||||
|
||||
First, the PetSet provides a stable hostname:
|
||||
|
||||
```shell
|
||||
$ for i in 0 1; do kubectl exec web-$i -- sh -c 'hostname'; done
|
||||
web-0
|
||||
web-1
|
||||
```
|
||||
|
||||
And the hostname is linked to the in-cluster DNS address:
|
||||
|
||||
```shell
|
||||
$ kubectl run -i --tty --image busybox dns-test --restart=Never /bin/sh
|
||||
dns-test # nslookup web-0.nginx
|
||||
Server: 10.0.0.10
|
||||
Address 1: 10.0.0.10 kube-dns.kube-system.svc.cluster.local
|
||||
|
||||
Name: web-0.nginx
|
||||
Address 1: 10.180.3.5
|
||||
|
||||
dns-test # nslookup web-1.nginx
|
||||
Server: 10.0.0.10
|
||||
Address 1: 10.0.0.10 kube-dns.kube-system.svc.cluster.local
|
||||
|
||||
Name: web-1.nginx
|
||||
Address 1: 10.180.0.9
|
||||
```
|
||||
|
||||
The containers are running nginx webservers, which by default will look for an index.html file in `/usr/share/nginx/html/index.html`. That directory is backed by a `PersistentVolume` created by the PetSet. So let's write our hostname there:
|
||||
|
||||
```shell
|
||||
$ for i in 0 1; do
|
||||
kubectl exec web-$i -- sh -c 'echo $(hostname) > /usr/share/nginx/html/index.html';
|
||||
done
|
||||
```
|
||||
|
||||
And verify each webserver serves its own hostname:
|
||||
|
||||
```shell
|
||||
$ for i in 0 1; do kubectl exec -it web-$i -- curl localhost; done
|
||||
web-0
|
||||
web-1
|
||||
```
|
||||
|
||||
Now delete all pods in the petset:
|
||||
|
||||
```shell
|
||||
$ kubectl delete po -l app=nginx
|
||||
pod "web-0" deleted
|
||||
pod "web-1" deleted
|
||||
```
|
||||
|
||||
Wait for them to come back up, and try to retrieve the previously written hostname through the DNS name of the peer. They match, because the storage, DNS name, and hostname stick to the Pet no matter where it gets scheduled:
|
||||
|
||||
```shell
|
||||
$ kubectl exec -it web-1 -- curl web-0.nginx
|
||||
web-0
|
||||
$ kubectl exec -it web-0 -- curl web-1.nginx
|
||||
web-1
|
||||
```
|
||||
|
||||
## Peer discovery
|
||||
|
||||
A pet can piece together its own identity:
|
||||
|
||||
1. Use the [downward api](/docs/tasks/inject-data-application/downward-api-volume-expose-pod-information/) to find its pod name
|
||||
2. Run `hostname` to find its DNS name
|
||||
3. Run `mount` or `df` to find its volumes (usually this is unnecessary)
|
||||
|
||||
It's not necessary to "discover" the governing Service of a PetSet, since it's known at creation time you can simply pass it down through an [environment variable](/docs/user-guide/environment-guide).
|
||||
|
||||
Usually pets also need to find their peers. In the previous nginx example, we just used `kubectl` to get the names of existing pods, and as humans, we could tell which ones belonged to a given PetSet. Another way to find peers is by contacting the API server, just like `kubectl`, but that has several disadvantages (you end up implementing a Kubernetes specific init system that runs as pid 1 in your application container).
|
||||
|
||||
PetSet gives you a way to discover your peers using DNS records. To illustrate this we can use the previous example (note: one usually doesn't `apt-get` in a container).
|
||||
|
||||
```shell
|
||||
$ kubectl exec -it web-0 /bin/sh
|
||||
web-0 # apt-get update && apt-get install -y dnsutils
|
||||
...
|
||||
|
||||
web-0 # nslookup -type=srv nginx.default
|
||||
Server: 10.0.0.10
|
||||
Address: 10.0.0.10#53
|
||||
|
||||
nginx.default.svc.cluster.local service = 10 50 0 web-1.ub.default.svc.cluster.local.
|
||||
nginx.default.svc.cluster.local service = 10 50 0 web-0.ub.default.svc.cluster.local.
|
||||
```
|
||||
|
||||
## Updating a PetSet
|
||||
|
||||
You cannot update any field of the PetSet except `spec.replicas` and the `containers` in the podTemplate. Updating `spec.replicas` will scale the PetSet, updating `containers` will not have any effect till a Pet is deleted, at which time it is recreated with the modified podTemplate.
|
||||
|
||||
## Scaling a PetSet
|
||||
|
||||
You can scale a PetSet by updating the "replicas" field. Note however that the controller will only:
|
||||
|
||||
1. Create one pet at a time, in order from {0..N-1}, and wait till each one is in [Running and Ready](/docs/user-guide/pod-states) before creating the next
|
||||
2. Delete one pet at a time, in reverse order from {N-1..0}, and wait till each one is completely shutdown (past its [terminationGracePeriodSeconds](/docs/concepts/workloads/pods/pod/#termination-of-pods) before deleting the next
|
||||
|
||||
```shell
|
||||
$ kubectl get po
|
||||
NAME READY STATUS RESTARTS AGE
|
||||
web-0 1/1 Running 0 30s
|
||||
web-1 1/1 Running 0 36s
|
||||
|
||||
$ kubectl patch petset web -p '{"spec":{"replicas":3}}'
|
||||
petset "web" patched
|
||||
|
||||
$ kubectl get po
|
||||
NAME READY STATUS RESTARTS AGE
|
||||
web-0 1/1 Running 0 40s
|
||||
web-1 1/1 Running 0 46s
|
||||
web-2 1/1 Running 0 8s
|
||||
```
|
||||
|
||||
You can also use the `kubectl scale` command:
|
||||
|
||||
```shell
|
||||
$ kubectl get petset
|
||||
NAME DESIRED CURRENT AGE
|
||||
web 3 3 24m
|
||||
|
||||
$ kubectl scale petset web --replicas=5
|
||||
petset "web" scaled
|
||||
|
||||
$ kubectl get po --watch-only
|
||||
NAME READY STATUS RESTARTS AGE
|
||||
web-0 1/1 Running 0 10m
|
||||
web-1 1/1 Running 0 27m
|
||||
web-2 1/1 Running 0 10m
|
||||
web-3 1/1 Running 0 3m
|
||||
web-4 0/1 ContainerCreating 0 48s
|
||||
|
||||
$ kubectl get petset web
|
||||
NAME DESIRED CURRENT AGE
|
||||
web 5 5 30m
|
||||
```
|
||||
|
||||
Note however, that scaling up to N and back down to M *will not* delete the volumes of the M-N pets, as described in the section on [deletion](#deleting-a-petset), i.e. scaling back up to M creates new pets that use the same volumes. To see this in action, scale the PetSet back down to 3:
|
||||
|
||||
```shell
|
||||
$ kubectl get po --watch-only
|
||||
web-4 1/1 Terminating 0 4m
|
||||
web-4 1/1 Terminating 0 4m
|
||||
web-3 1/1 Terminating 0 6m
|
||||
web-3 1/1 Terminating 0 6m
|
||||
```
|
||||
|
||||
Note that we still have 5 pvcs:
|
||||
|
||||
```shell
|
||||
$ kubectl get pvc
|
||||
NAME STATUS VOLUME CAPACITY ACCESSMODES AGE
|
||||
www-web-0 Bound pvc-42ca5cef-8113-11e6-82f6-42010af00002 1Gi RWO 32m
|
||||
www-web-1 Bound pvc-42de30af-8113-11e6-82f6-42010af00002 1Gi RWO 32m
|
||||
www-web-2 Bound pvc-ba416413-8115-11e6-82f6-42010af00002 1Gi RWO 14m
|
||||
www-web-3 Bound pvc-ba45f19c-8115-11e6-82f6-42010af00002 1Gi RWO 14m
|
||||
www-web-4 Bound pvc-ba47674a-8115-11e6-82f6-42010af00002 1Gi RWO 14m
|
||||
```
|
||||
|
||||
This allows you to upgrade the image of a petset and have it come back up with the same data, as described in the next section.
|
||||
|
||||
## Image upgrades
|
||||
|
||||
PetSet currently *does not* support automated image upgrade as noted in the section on [limitations](#alpha-limitations), however you can update the `image` field of any container in the podTemplate and delete Pets one by one, the PetSet controller will recreate it with the new image.
|
||||
|
||||
Edit the image on the PetSet to `gcr.io/google_containers/nginx-slim:0.7` and delete 1 Pet:
|
||||
|
||||
```shell{% raw %}
|
||||
$ for p in 0 1 2; do kubectl get po web-$p --template '{{range $i, $c := .spec.containers}}{{$c.image}}{{end}}'; echo; done
|
||||
gcr.io/google_containers/nginx-slim:0.8
|
||||
gcr.io/google_containers/nginx-slim:0.8
|
||||
gcr.io/google_containers/nginx-slim:0.8
|
||||
|
||||
$ kubectl delete po web-0
|
||||
pod "web-0" deleted
|
||||
|
||||
$ for p in 0 1 2; do kubectl get po web-$p --template '{{range $i, $c := .spec.containers}}{{$c.image}}{{end}}'; echo; done
|
||||
gcr.io/google_containers/nginx-slim:0.7
|
||||
gcr.io/google_containers/nginx-slim:0.8
|
||||
gcr.io/google_containers/nginx-slim:0.8
|
||||
{% endraw %}```
|
||||
|
||||
Delete the remaining 2:
|
||||
|
||||
```shell
|
||||
$ kubectl delete po web-1 web-2
|
||||
pod "web-1" deleted
|
||||
pod "web-2" deleted
|
||||
```
|
||||
|
||||
Wait till the PetSet is stable and check the images:
|
||||
|
||||
```shell{% raw %}
|
||||
$ for p in 0 1 2; do kubectl get po web-$p --template '{{range $i, $c := .spec.containers}}{{$c.image}}{{end}}'; echo; done
|
||||
gcr.io/google_containers/nginx-slim:0.7
|
||||
gcr.io/google_containers/nginx-slim:0.7
|
||||
gcr.io/google_containers/nginx-slim:0.7
|
||||
{% endraw %}```
|
||||
|
||||
## Deleting a PetSet
|
||||
|
||||
Deleting a PetSet through kubectl will scale it down to 0, thereby deleting all the Pets. If you wish to delete just the PetSet and not the Pets, use `--cascade=false`:
|
||||
|
||||
```shell
|
||||
$ kubectl delete -f petset.yaml --cascade=false
|
||||
petset "web" deleted
|
||||
|
||||
$ kubectl get po -l app=nginx
|
||||
NAME READY STATUS RESTARTS AGE
|
||||
web-0 1/1 Running 0 21h
|
||||
web-1 1/1 Running 0 21h
|
||||
|
||||
$ kubectl delete po -l app=nginx
|
||||
pod "web-0" deleted
|
||||
pod "web-1" deleted
|
||||
```
|
||||
|
||||
Deleting the pods will *not* delete the volumes. Until we finalize the recycle policy for these volumes they will have to get cleaned up by an admin. This is to ensure that you have the chance to copy data off the volume before deleting it. Simply deleting the PVC after the pods have left the [terminating state](/docs/concepts/workloads/pods/pod/#termination-of-pods) should trigger deletion of the backing Persistent Volumes.
|
||||
|
||||
**Note: you will lose all your data once the PVC is deleted, do this with caution.**
|
||||
|
||||
```shell
|
||||
$ kubectl get po -l app=nginx
|
||||
$ kubectl get pvc -l app=nginx
|
||||
NAME STATUS VOLUME CAPACITY ACCESSMODES AGE
|
||||
www-web-0 Bound pvc-62d271cd-3822-11e6-b1b7-42010af00002 0 21h
|
||||
www-web-1 Bound pvc-62d6750e-3822-11e6-b1b7-42010af00002 0 21h
|
||||
|
||||
$ kubectl delete pvc -l app=nginx
|
||||
$ kubectl get pv
|
||||
```
|
||||
|
||||
If you simply want to clean everything:
|
||||
|
||||
```shell{% raw %}
|
||||
$ grace=$(kubectl get po web-0 --template '{{.spec.terminationGracePeriodSeconds}}')
|
||||
$ kubectl delete petset,po -l app=nginx
|
||||
$ sleep $grace
|
||||
$ kubectl delete pvc -l app=nginx
|
||||
{% endraw %}
|
||||
```
|
||||
|
||||
## Troubleshooting
|
||||
|
||||
You might have noticed an `annotations` field in all the PetSets shown above.
|
||||
|
||||
```yaml
|
||||
annotations:
|
||||
pod.alpha.kubernetes.io/initialized: "true"
|
||||
```
|
||||
|
||||
This field is a debugging hook. It pauses any scale up/down operations on the entire PetSet. If you'd like to pause a petset after each pet, set it to `false` in the template, wait for each pet to come up, verify it has initialized correctly, and then set it to `true` using `kubectl edit` on the pet (setting it to `false` on *any pet* is enough to pause the PetSet). If you don't need it, create the PetSet with it set to `true` as shown. This is surprisingly useful in debugging bootstrapping race conditions.
|
||||
|
||||
## Future Work
|
||||
|
||||
There are a LOT of planned improvements since PetSet is still in alpha.
|
||||
|
||||
* Data gravity and local storage
|
||||
* Richer notification events
|
||||
* Public network identities
|
||||
* WAN cluster deployments (multi-AZ/region/cloud provider)
|
||||
* Image and node upgrades
|
||||
|
||||
This list goes on, if you have examples, ideas or thoughts, please contribute.
|
||||
|
||||
## Alternatives
|
||||
|
||||
Deploying one RC of size 1/Service per pod is a popular alternative, as is simply deploying a DaemonSet that utilizes the identity of a Node.
|
||||
|
||||
## Next steps
|
||||
|
||||
* Learn about [StatefulSet](/docs/concepts/abstractions/controllers/statefulsets/),
|
||||
the replacement for PetSet introduced in Kubernetes version 1.5.
|
||||
* [Migrate your existing PetSets to StatefulSets](/docs/tasks/manage-stateful-set/upgrade-pet-set-to-stateful-set/)
|
||||
when upgrading to Kubernetes version 1.5 or higher.
|
||||
|
||||
@@ -1,51 +0,0 @@
|
||||
# A headless service to create DNS records
|
||||
apiVersion: v1
|
||||
kind: Service
|
||||
metadata:
|
||||
name: nginx
|
||||
labels:
|
||||
app: nginx
|
||||
spec:
|
||||
ports:
|
||||
- port: 80
|
||||
name: web
|
||||
# *.nginx.default.svc.cluster.local
|
||||
clusterIP: None
|
||||
selector:
|
||||
app: nginx
|
||||
---
|
||||
apiVersion: apps/v1alpha1
|
||||
kind: PetSet
|
||||
metadata:
|
||||
name: web
|
||||
spec:
|
||||
serviceName: "nginx"
|
||||
replicas: 2
|
||||
template:
|
||||
metadata:
|
||||
labels:
|
||||
app: nginx
|
||||
annotations:
|
||||
pod.alpha.kubernetes.io/initialized: "true"
|
||||
spec:
|
||||
terminationGracePeriodSeconds: 0
|
||||
containers:
|
||||
- name: nginx
|
||||
image: gcr.io/google_containers/nginx-slim:0.8
|
||||
ports:
|
||||
- containerPort: 80
|
||||
name: web
|
||||
volumeMounts:
|
||||
- name: www
|
||||
mountPath: /usr/share/nginx/html
|
||||
volumeClaimTemplates:
|
||||
- metadata:
|
||||
name: www
|
||||
annotations:
|
||||
volume.alpha.kubernetes.io/storage-class: anything
|
||||
spec:
|
||||
accessModes: [ "ReadWriteOnce" ]
|
||||
resources:
|
||||
requests:
|
||||
storage: 1Gi
|
||||
|
||||
@@ -17,7 +17,6 @@ whereas a Replication Controller only supports equality-based selector requireme
|
||||
|
||||
{% endcapture %}
|
||||
|
||||
|
||||
{% capture body %}
|
||||
|
||||
## How to use a ReplicaSet
|
||||
@@ -52,20 +51,21 @@ use a Deployment instead, and define your application in the spec section.
|
||||
|
||||
{% include code.html language="yaml" file="frontend.yaml" ghlink="/docs/concepts/workloads/controllers/frontend.yaml" %}
|
||||
|
||||
Saving this config into `frontend.yaml` and submitting it to a Kubernetes cluster should
|
||||
Saving this manifest into `frontend.yaml` and submitting it to a Kubernetes cluster should
|
||||
create the defined ReplicaSet and the pods that it manages.
|
||||
|
||||
```shell
|
||||
$ kubectl create -f frontend.yaml
|
||||
replicaset "frontend" created
|
||||
$ kubectl describe rs/frontend
|
||||
Name: frontend
|
||||
Namespace: default
|
||||
Selector: tier=frontend,tier in (frontend)
|
||||
Labels: app=guestbook,tier=frontend
|
||||
Annotations: <none>
|
||||
Replicas: 3 current / 3 desired
|
||||
Pods Status: 3 Running / 0 Waiting / 0 Succeeded / 0 Failed
|
||||
Name: frontend
|
||||
Namespace: default
|
||||
Selector: tier=frontend,tier in (frontend)
|
||||
Labels: app=guestbook
|
||||
tier=frontend
|
||||
Annotations: <none>
|
||||
Replicas: 3 current / 3 desired
|
||||
Pods Status: 3 Running / 0 Waiting / 0 Succeeded / 0 Failed
|
||||
Pod Template:
|
||||
Labels: app=guestbook
|
||||
tier=frontend
|
||||
@@ -93,7 +93,98 @@ frontend-dnjpy 1/1 Running 0 1m
|
||||
frontend-qhloh 1/1 Running 0 1m
|
||||
```
|
||||
|
||||
## ReplicaSet as an Horizontal Pod Autoscaler target
|
||||
## Writing a ReplicaSet Spec
|
||||
|
||||
As with all other Kubernetes API objects, a ReplicaSet needs the `apiVersion`, `kind`, and `metadata` fields. For
|
||||
general information about working with manifests, see [here](/docs/user-guide/simple-yaml/),
|
||||
[here](/docs/user-guide/configuring-containers/), and [here](/docs/concepts/tools/kubectl/object-management-overview/).
|
||||
|
||||
A ReplicaSet also needs a [`.spec` section](https://git.k8s.io/community/contributors/devel/api-conventions.md#spec-and-status).
|
||||
|
||||
### Pod Template
|
||||
|
||||
The `.spec.template` is the only required field of the `.spec`. The `.spec.template` is a
|
||||
[pod template](/docs/concepts/workloads/pods/pod-overview/#pod-templates). It has exactly the same schema as a
|
||||
[pod](/docs/concepts/workloads/pods/pod/), except that it is nested and does not have an `apiVersion` or `kind`.
|
||||
|
||||
In addition to required fields of a pod, a pod template in a ReplicaSet must specify appropriate
|
||||
labels and an appropriate restart policy.
|
||||
|
||||
For labels, make sure to not overlap with other controllers. For more information, see [pod selector](#pod-selector).
|
||||
|
||||
For [restart policy](/docs/concepts/workloads/pods/pod-lifecycle/), the only allowed value for `.spec.template.spec.restartPolicy` is `Always`, which is the default.
|
||||
|
||||
For local container restarts, ReplicaSet delegates to an agent on the node,
|
||||
for example the [Kubelet](/docs/admin/kubelet/) or Docker.
|
||||
|
||||
### Pod Selector
|
||||
|
||||
The `.spec.selector` field is a [label selector](/docs/user-guide/labels/#label-selectors). A ReplicaSet
|
||||
manages all the pods with labels that match the selector. It does not distinguish
|
||||
between pods that it created or deleted and pods that another person or process created or
|
||||
deleted. This allows the ReplicaSet to be replaced without affecting the running pods.
|
||||
|
||||
The `.spec.template.metadata.labels` must match the `.spec.selector`, or it will
|
||||
be rejected by the API.
|
||||
|
||||
In Kubernetes 1.8 the API version `apps/v1beta2` on the ReplicaSet kind is the current version and is enabled by default. The API version `extensions/v1beta1` is deprecated. In API version `apps/v1beta2`, `.spec.selector` and `.metadata.labels` no longer default to `.spec.template.metadata.labels` if not set. So they must be set explicitly. Also note that `.spec.selector` is immutable after creation starting in API version `apps/v1beta2`.
|
||||
|
||||
Also you should not normally create any pods whose labels match this selector, either directly, with
|
||||
another ReplicaSet, or with another controller such as a Deployment. If you do so, the ReplicaSet thinks that it
|
||||
created the other pods. Kubernetes does not stop you from doing this.
|
||||
|
||||
If you do end up with multiple controllers that have overlapping selectors, you
|
||||
will have to manage the deletion yourself.
|
||||
|
||||
### Labels on a ReplicaSet
|
||||
|
||||
The ReplicaSet can itself have labels (`.metadata.labels`). Typically, you
|
||||
would set these the same as the `.spec.template.metadata.labels`. However, they are allowed to be
|
||||
different, and the `.metadata.labels` do not affect the behavior of the ReplicaSet.
|
||||
|
||||
### Replicas
|
||||
|
||||
You can specify how many pods should run concurrently by setting `.spec.replicas`. The number running at any time may be higher
|
||||
or lower, such as if the replicas were just increased or decreased, or if a pod is gracefully
|
||||
shut down, and a replacement starts early.
|
||||
|
||||
If you do not specify `.spec.replicas`, then it defaults to 1.
|
||||
|
||||
## Working with ReplicaSets
|
||||
|
||||
### Deleting a ReplicaSet and its Pods
|
||||
|
||||
To delete a ReplicaSet and all its pods, use [`kubectl
|
||||
delete`](/docs/user-guide/kubectl/{{page.version}}/#delete). Kubectl will scale the ReplicaSet to zero and wait
|
||||
for it to delete each pod before deleting the ReplicaSet itself. If this kubectl command is interrupted, it can
|
||||
be restarted.
|
||||
|
||||
When using the REST API or go client library, you need to do the steps explicitly (scale replicas to
|
||||
0, wait for pod deletions, then delete the ReplicaSet).
|
||||
|
||||
### Deleting just a ReplicaSet
|
||||
|
||||
You can delete a ReplicaSet without affecting any of its pods, using [`kubectl delete`](/docs/user-guide/kubectl/{{page.version}}/#delete) with the `--cascade=false` option.
|
||||
|
||||
When using the REST API or go client library, simply delete the ReplicaSet object.
|
||||
|
||||
Once the original is deleted, you can create a new ReplicaSet to replace it. As long
|
||||
as the old and new `.spec.selector` are the same, then the new one will adopt the old pods.
|
||||
However, it will not make any effort to make existing pods match a new, different pod template.
|
||||
To update pods to a new spec in a controlled way, use a [rolling update](#rolling-updates).
|
||||
|
||||
### Isolating pods from a ReplicaSet
|
||||
|
||||
Pods may be removed from a ReplicaSet's target set by changing their labels. This technique may be used to remove pods
|
||||
from service for debugging, data recovery, etc. Pods that are removed in this way will be replaced automatically (
|
||||
assuming that the number of replicas is not also changed).
|
||||
|
||||
### Scaling a ReplicaSet
|
||||
|
||||
A ReplicaSet can be easily scaled up or down by simply updating the `.spec.replicas` field. The ReplicaSet controller
|
||||
ensures that that a desired number of pods with a matching label selector are available and operational.
|
||||
|
||||
### ReplicaSet as an Horizontal Pod Autoscaler Target
|
||||
|
||||
A ReplicaSet can also be a target for
|
||||
[Horizontal Pod Autoscalers (HPA)](/docs/tasks/run-application/horizontal-pod-autoscale/). That is,
|
||||
@@ -102,8 +193,7 @@ the ReplicaSet we created in the previous example.
|
||||
|
||||
{% include code.html language="yaml" file="hpa-rs.yaml" ghlink="/docs/concepts/workloads/controllers/hpa-rs.yaml" %}
|
||||
|
||||
|
||||
Saving this config into `hpa-rs.yaml` and submitting it to a Kubernetes cluster should
|
||||
Saving this manifest into `hpa-rs.yaml` and submitting it to a Kubernetes cluster should
|
||||
create the defined HPA that autoscales the target ReplicaSet depending on the CPU usage
|
||||
of the replicated pods.
|
||||
|
||||
@@ -118,6 +208,31 @@ Alternatively, you can use the `kubectl autoscale` command to accomplish the sam
|
||||
kubectl autoscale rs frontend
|
||||
```
|
||||
|
||||
## Alternatives to ReplicaSet
|
||||
|
||||
### Deployment (Recommended)
|
||||
|
||||
[`Deployment`](/docs/concepts/workloads/controllers/deployment/) is a higher-level API object that updates its underlying ReplicaSets and their Pods
|
||||
in a similar fashion as `kubectl rolling-update`. Deployments are recommended if you want this rolling update functionality,
|
||||
because unlike `kubectl rolling-update`, they are declarative, server-side, and have additional features. For more information on running a stateless
|
||||
application using a Deployment, please read [Run a Stateless Application Using a Deployment](/docs/tasks/run-application/run-stateless-application-deployment/).
|
||||
|
||||
### Bare Pods
|
||||
|
||||
Unlike the case where a user directly created pods, a ReplicaSet replaces pods that are deleted or terminated for any reason, such as in the case of node failure or disruptive node maintenance, such as a kernel upgrade. For this reason, we recommend that you use a ReplicaSet even if your application requires only a single pod. Think of it similarly to a process supervisor, only it supervises multiple pods across multiple nodes instead of individual processes on a single node. A ReplicaSet delegates local container restarts to some agent on the node (for example, Kubelet or Docker).
|
||||
|
||||
### Job
|
||||
|
||||
Use a [`Job`](/docs/concepts/jobs/run-to-completion-finite-workloads/) instead of a ReplicaSet for pods that are expected to terminate on their own
|
||||
(that is, batch jobs).
|
||||
|
||||
### DaemonSet
|
||||
|
||||
Use a [`DaemonSet`](/docs/concepts/workloads/controllers/daemonset/) instead of a ReplicaSet for pods that provide a
|
||||
machine-level function, such as machine monitoring or machine logging. These pods have a lifetime that is tied
|
||||
to a machine lifetime: the pod needs to be running on the machine before other pods start, and are
|
||||
safe to terminate when the machine is otherwise ready to be rebooted/shutdown.
|
||||
|
||||
{% endcapture %}
|
||||
|
||||
{% include templates/concept.md %}
|
||||
|
||||
@@ -10,10 +10,8 @@ title: StatefulSets
|
||||
---
|
||||
|
||||
{% capture overview %}
|
||||
**StatefulSets are a beta feature in 1.7. This feature replaces the
|
||||
PetSets feature from 1.4. Users of PetSets are referred to the 1.5
|
||||
[Upgrade Guide](/docs/tasks/run-application/upgrade-pet-set-to-stateful-set/)
|
||||
for further information on how to upgrade existing PetSets to StatefulSets.**
|
||||
**StatefulSet is the workload API object used to manage stateful applications.
|
||||
StatefulSets are beta in 1.8.**
|
||||
|
||||
{% include templates/glossary/snippet.md term="statefulset" length="long" %}
|
||||
{% endcapture %}
|
||||
@@ -51,8 +49,7 @@ The example below demonstrates the components of a StatefulSet.
|
||||
|
||||
* A Headless Service, named nginx, is used to control the network domain.
|
||||
* The StatefulSet, named web, has a Spec that indicates that 3 replicas of the nginx container will be launched in unique Pods.
|
||||
* The volumeClaimTemplates will provide stable storage using [PersistentVolumes](/docs/concepts/storage/volumes/) provisioned by a
|
||||
PersistentVolume Provisioner.
|
||||
* The volumeClaimTemplates will provide stable storage using [PersistentVolumes](/docs/concepts/storage/volumes/) provisioned by a PersistentVolume Provisioner.
|
||||
|
||||
```yaml
|
||||
apiVersion: v1
|
||||
@@ -69,17 +66,20 @@ spec:
|
||||
selector:
|
||||
app: nginx
|
||||
---
|
||||
apiVersion: apps/v1beta1
|
||||
apiVersion: apps/v1beta2
|
||||
kind: StatefulSet
|
||||
metadata:
|
||||
name: web
|
||||
spec:
|
||||
selector:
|
||||
matchLabels:
|
||||
app: nginx # has to match .spec.template.metadata.labels
|
||||
serviceName: "nginx"
|
||||
replicas: 3
|
||||
replicas: 3 # by default is 1
|
||||
template:
|
||||
metadata:
|
||||
labels:
|
||||
app: nginx
|
||||
app: nginx # has to match .spec.selector.matchLabels
|
||||
spec:
|
||||
terminationGracePeriodSeconds: 10
|
||||
containers:
|
||||
@@ -102,6 +102,9 @@ spec:
|
||||
storage: 1Gi
|
||||
```
|
||||
|
||||
## Pod Selector
|
||||
You must set the `spec.selector` field of a StatefulSet to match the labels of its `.spec.template.metadata.labels`. Prior to Kubernetes 1.8, the `spec.selector` field was defaulted when omitted. In 1.8 and later versions, failing to specify a matching Pod Selector will result in a validation error during StatefulSet creation.
|
||||
|
||||
## Pod Identity
|
||||
StatefulSet Pods have a unique identity that is comprised of an ordinal, a
|
||||
stable network identity, and stable storage. The identity sticks to the Pod,
|
||||
|
||||
Reference in New Issue
Block a user