Kubernetes Prow Robot
@@ -39,10 +39,18 @@ that provides a set of stateless replicas.
|
||||
|
||||
## Limitations
|
||||
|
||||
* The storage for a given Pod must either be provisioned by a [PersistentVolume Provisioner](https://github.com/kubernetes/examples/tree/master/staging/persistent-volume-provisioning/README.md) based on the requested `storage class`, or pre-provisioned by an admin.
|
||||
* Deleting and/or scaling a StatefulSet down will *not* delete the volumes associated with the StatefulSet. This is done to ensure data safety, which is generally more valuable than an automatic purge of all related StatefulSet resources.
|
||||
* StatefulSets currently require a [Headless Service](/docs/concepts/services-networking/service/#headless-services) to be responsible for the network identity of the Pods. You are responsible for creating this Service.
|
||||
* StatefulSets do not provide any guarantees on the termination of pods when a StatefulSet is deleted. To achieve ordered and graceful termination of the pods in the StatefulSet, it is possible to scale the StatefulSet down to 0 prior to deletion.
|
||||
* The storage for a given Pod must either be provisioned by a
|
||||
[PersistentVolume Provisioner](https://github.com/kubernetes/examples/tree/master/staging/persistent-volume-provisioning/README.md)
|
||||
based on the requested `storage class`, or pre-provisioned by an admin.
|
||||
* Deleting and/or scaling a StatefulSet down will *not* delete the volumes associated with the
|
||||
StatefulSet. This is done to ensure data safety, which is generally more valuable than an
|
||||
automatic purge of all related StatefulSet resources.
|
||||
* StatefulSets currently require a [Headless Service](/docs/concepts/services-networking/service/#headless-services)
|
||||
to be responsible for the network identity of the Pods. You are responsible for creating this
|
||||
Service.
|
||||
* StatefulSets do not provide any guarantees on the termination of pods when a StatefulSet is
|
||||
deleted. To achieve ordered and graceful termination of the pods in the StatefulSet, it is
|
||||
possible to scale the StatefulSet down to 0 prior to deletion.
|
||||
* When using [Rolling Updates](#rolling-updates) with the default
|
||||
[Pod Management Policy](#pod-management-policies) (`OrderedReady`),
|
||||
it's possible to get into a broken state that requires
|
||||
@@ -108,18 +116,24 @@ In the above example:
|
||||
|
||||
* 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/persistent-volumes/) provisioned by a PersistentVolume Provisioner.
|
||||
* The `volumeClaimTemplates` will provide stable storage using
|
||||
[PersistentVolumes](/docs/concepts/storage/persistent-volumes/) provisioned by a
|
||||
PersistentVolume Provisioner.
|
||||
|
||||
The name of a StatefulSet object must be a valid
|
||||
[DNS subdomain name](/docs/concepts/overview/working-with-objects/names#dns-subdomain-names).
|
||||
|
||||
### Pod Selector
|
||||
|
||||
You must set the `.spec.selector` field of a StatefulSet to match the labels of its `.spec.template.metadata.labels`. Failing to specify a matching Pod Selector will result in a validation error during StatefulSet creation.
|
||||
You must set the `.spec.selector` field of a StatefulSet to match the labels of its
|
||||
`.spec.template.metadata.labels`. Failing to specify a matching Pod Selector will result in a
|
||||
validation error during StatefulSet creation.
|
||||
|
||||
### Volume Claim Templates
|
||||
|
||||
You can set the `.spec.volumeClaimTemplates` which can provide stable storage using [PersistentVolumes](/docs/concepts/storage/persistent-volumes/) provisioned by a PersistentVolume Provisioner.
|
||||
You can set the `.spec.volumeClaimTemplates` which can provide stable storage using
|
||||
[PersistentVolumes](/docs/concepts/storage/persistent-volumes/) provisioned by a PersistentVolume
|
||||
Provisioner.
|
||||
|
||||
|
||||
### Minimum ready seconds
|
||||
@@ -128,9 +142,11 @@ You can set the `.spec.volumeClaimTemplates` which can provide stable storage u
|
||||
|
||||
`.spec.minReadySeconds` is an optional field that specifies the minimum number of seconds for which a newly
|
||||
created Pod should be ready without any of its containers crashing, for it to be considered available.
|
||||
Please note that this feature is beta and enabled by default. Please opt out by unsetting the StatefulSetMinReadySeconds flag, if you don't
|
||||
Please note that this feature is beta and enabled by default. Please opt out by unsetting the
|
||||
StatefulSetMinReadySeconds flag, if you don't
|
||||
want this feature to be enabled. This field defaults to 0 (the Pod will be considered
|
||||
available as soon as it is ready). To learn more about when a Pod is considered ready, see [Container Probes](/docs/concepts/workloads/pods/pod-lifecycle/#container-probes).
|
||||
available as soon as it is ready). To learn more about when a Pod is considered ready, see
|
||||
[Container Probes](/docs/concepts/workloads/pods/pod-lifecycle/#container-probes).
|
||||
|
||||
## Pod Identity
|
||||
|
||||
@@ -166,8 +182,8 @@ remembered and reused, even after the Pod is running, for at least a few seconds
|
||||
If you need to discover Pods promptly after they are created, you have a few options:
|
||||
|
||||
- Query the Kubernetes API directly (for example, using a watch) rather than relying on DNS lookups.
|
||||
- Decrease the time of caching in your Kubernetes DNS provider (typically this means editing the config map for CoreDNS, which currently caches for 30 seconds).
|
||||
|
||||
- Decrease the time of caching in your Kubernetes DNS provider (typically this means editing the
|
||||
config map for CoreDNS, which currently caches for 30 seconds).
|
||||
|
||||
As mentioned in the [limitations](#limitations) section, you are responsible for
|
||||
creating the [Headless Service](/docs/concepts/services-networking/service/#headless-services)
|
||||
@@ -189,7 +205,9 @@ Cluster Domain will be set to `cluster.local` unless
|
||||
|
||||
### Stable Storage
|
||||
|
||||
For each VolumeClaimTemplate entry defined in a StatefulSet, each Pod receives one PersistentVolumeClaim. In the nginx example above, each Pod receives a single PersistentVolume with a StorageClass of `my-storage-class` and 1 Gib of provisioned storage. If no StorageClass
|
||||
For each VolumeClaimTemplate entry defined in a StatefulSet, each Pod receives one
|
||||
PersistentVolumeClaim. In the nginx example above, each Pod receives a single PersistentVolume
|
||||
with a StorageClass of `my-storage-class` and 1 Gib of provisioned storage. If no StorageClass
|
||||
is specified, then the default StorageClass will be used. When a Pod is (re)scheduled
|
||||
onto a node, its `volumeMounts` mount the PersistentVolumes associated with its
|
||||
PersistentVolume Claims. Note that, the PersistentVolumes associated with the
|
||||
@@ -210,7 +228,9 @@ the StatefulSet.
|
||||
* Before a scaling operation is applied to a Pod, all of its predecessors must be Running and Ready.
|
||||
* Before a Pod is terminated, all of its successors must be completely shutdown.
|
||||
|
||||
The StatefulSet should not specify a `pod.Spec.TerminationGracePeriodSeconds` of 0. This practice is unsafe and strongly discouraged. For further explanation, please refer to [force deleting StatefulSet Pods](/docs/tasks/run-application/force-delete-stateful-set-pod/).
|
||||
The StatefulSet should not specify a `pod.Spec.TerminationGracePeriodSeconds` of 0. This practice
|
||||
is unsafe and strongly discouraged. For further explanation, please refer to
|
||||
[force deleting StatefulSet Pods](/docs/tasks/run-application/force-delete-stateful-set-pod/).
|
||||
|
||||
When the nginx example above is created, three Pods will be deployed in the order
|
||||
web-0, web-1, web-2. web-1 will not be deployed before web-0 is
|
||||
@@ -256,7 +276,8 @@ annotations for the Pods in a StatefulSet. There are two possible values:
|
||||
create new Pods that reflect modifications made to a StatefulSet's `.spec.template`.
|
||||
|
||||
`RollingUpdate`
|
||||
: The `RollingUpdate` update strategy implements automated, rolling update for the Pods in a StatefulSet. This is the default update strategy.
|
||||
: The `RollingUpdate` update strategy implements automated, rolling update for the Pods in a
|
||||
StatefulSet. This is the default update strategy.
|
||||
|
||||
## Rolling Updates
|
||||
|
||||
@@ -299,7 +320,7 @@ unavailable Pod in the range `0` to `replicas - 1`, it will be counted towards
|
||||
{{< note >}}
|
||||
The `maxUnavailable` field is in Alpha stage and it is honored only by API servers
|
||||
that are running with the `MaxUnavailableStatefulSet`
|
||||
[feature gate](/docs/reference/commmand-line-tools-reference/feature-gates/)
|
||||
[feature gate](/docs/reference/command-line-tools-reference/feature-gates/)
|
||||
enabled.
|
||||
{{< /note >}}
|
||||
|
||||
@@ -375,8 +396,8 @@ spec:
|
||||
...
|
||||
```
|
||||
|
||||
The StatefulSet {{<glossary_tooltip text="controller" term_id="controller">}} adds [owner
|
||||
references](/docs/concepts/overview/working-with-objects/owners-dependents/#owner-references-in-object-specifications)
|
||||
The StatefulSet {{<glossary_tooltip text="controller" term_id="controller">}} adds
|
||||
[owner references](/docs/concepts/overview/working-with-objects/owners-dependents/#owner-references-in-object-specifications)
|
||||
to its PVCs, which are then deleted by the {{<glossary_tooltip text="garbage collector"
|
||||
term_id="garbage-collection">}} after the Pod is terminated. This enables the Pod to
|
||||
cleanly unmount all volumes before the PVCs are deleted (and before the backing PV and
|
||||
|
||||
Reference in New Issue
Block a user