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Address editorial comments 

updates link to statefulset conept
reviewable/pr1803/r5
Kenneth Owens 2016-12-02 14:26:22 -08:00
parent 5e15fc667f
commit 00dea6eee1
1 changed files with 16 additions and 15 deletions
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docs/tutorials/stateful-application/basic-stateful-set.md
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@ -10,8 +10,8 @@ assignees:
--- ---
{% capture overview %} {% capture overview %}
This tutorial provides an introduction to the This tutorial provides an introduction to managing applications with
[StatefulSet](/docs/concepts/controllers/statefulsets/) concept. It [StatefulSets](/docs/concepts/abstractions/controllers/statefulsets/). It
demonstrates how to create, delete, scale, and update the container image of a demonstrates how to create, delete, scale, and update the container image of a
StatefulSet. StatefulSet.
{% endcapture %} {% endcapture %}
@ -25,7 +25,7 @@ following Kubernetes concepts.
* [Headless Services](/docs/user-guide/services/#headless-services) * [Headless Services](/docs/user-guide/services/#headless-services)
* [PersistentVolumes](/docs/user-guide/volumes/) * [PersistentVolumes](/docs/user-guide/volumes/)
* [PersistentVolume Provisioning](http://releases.k8s.io/{{page.githubbranch}}/examples/experimental/persistent-volume-provisioning/) * [PersistentVolume Provisioning](http://releases.k8s.io/{{page.githubbranch}}/examples/experimental/persistent-volume-provisioning/)
* [StatefulSets](/docs/concepts/controllers/statefulsets/) * [StatefulSets](/docs/concepts/abstractions/controllers/statefulsets/)
* [kubectl CLI](/docs/user-guide/kubectl) * [kubectl CLI](/docs/user-guide/kubectl)
This tutorial assumes that your cluster is configured to dynamically provision This tutorial assumes that your cluster is configured to dynamically provision
@ -55,7 +55,7 @@ After this tutorial, you will be familiar with the following.
Begin by creating a StatefulSet using the example below. It is similar to the Begin by creating a StatefulSet using the example below. It is similar to the
example presented in the example presented in the
[StatefulSets](/docs/concepts/controllers/statefulsets/) concept. It creates [StatefulSets](/docs/concepts/abstractions/controllers/statefulsets/) concept. It creates
a [Headless Service](/docs/user-guide/services/#headless-services), `nginx`, to a [Headless Service](/docs/user-guide/services/#headless-services), `nginx`, to
control the domain of the StatefulSet, `web`. control the domain of the StatefulSet, `web`.
@ -121,8 +121,10 @@ launching `web-1`. In fact, `web-1` is not launched until `web-0` is
[Running and Ready](/docs/user-guide/pod-states). [Running and Ready](/docs/user-guide/pod-states).
### Pods in a StatefulSet ### Pods in a StatefulSet
Unlike Pods in other controllers, the Pods in a StatefulSet have a unqiue
ordinal index and a stable network identity.
#### Ordinal Index #### Examining the Pod's Ordinal Index
Get the StatefulSet's Pods. Get the StatefulSet's Pods.
@ -134,14 +136,14 @@ web-1 1/1 Running 0 1m
``` ```
As mentioned in the [StatefulSets](/docs/concepts/controllers/statefulsets/) As mentioned in the [StatefulSets](/docs/concepts/abstractions/controllers/statefulsets/)
concept, the Pods in a StatefulSet have a sticky, unique identity. This identity concept, the Pods in a StatefulSet have a sticky, unique identity. This identity
is based on a unique ordinal index that is assigned to each Pod by the Stateful is based on a unique ordinal index that is assigned to each Pod by the Stateful
Set controller. The Pods' names take the form Set controller. The Pods' names take the form
`<statefulset name>-<ordinal index>`. Since the `web` StatefulSet has two `<statefulset name>-<ordinal index>`. Since the `web` StatefulSet has two
replicas, it creates two Pods, `web-0` and `web-1`. replicas, it creates two Pods, `web-0` and `web-1`.
#### Stable Network Identity #### Using Stable Network Identities
Each Pod has a stable hostname based on its ordinal index. Use Each Pod has a stable hostname based on its ordinal index. Use
[`kubectl exec`](/docs/user-guide/kubectl/kubectl_exec/) to execute the [`kubectl exec`](/docs/user-guide/kubectl/kubectl_exec/) to execute the
`hostname` command in each Pod. `hostname` command in each Pod.
@ -249,7 +251,7 @@ liveness and readiness, you should use the SRV records of the Pods in the
StatefulSet (e.g `web-0.nginx.default.svc.cluster.local`, StatefulSet (e.g `web-0.nginx.default.svc.cluster.local`,
`web-1.nginx.default.svc.cluster.local`). `web-1.nginx.default.svc.cluster.local`).
#### Stable Storage #### Writing to Stable Storage
Get the PersistentVolumeClaims for `web-0` and `web-1`. Get the PersistentVolumeClaims for `web-0` and `web-1`.
@ -323,9 +325,8 @@ and `web-1` are scheduled on, their PersistentVolumes will be mounted to the
appropriate mount points. appropriate mount points.
### Scaling a StatefulSet ### Scaling a StatefulSet
When we refer to scaling a StatefulSet, we mean increasing or decreasing the Scaling a StatefulSet refers to increasing or decreasing the number of replicas.
number of replicas in the StatefulSet. This is accomplished by updating This is accomplished by updating the `replicas` field. You can use either
the `replicas` field. You can use either
[`kubectl scale`](/docs/user-guide/kubectl/kubectl_scale/) or [`kubectl scale`](/docs/user-guide/kubectl/kubectl_scale/) or
[`kubectl patch`](/docs/user-guide/kubectl/kubectl_patch/) to scale a Stateful [`kubectl patch`](/docs/user-guide/kubectl/kubectl_patch/) to scale a Stateful
Set. Set.
@ -617,8 +618,8 @@ web-2 0/1 Terminating 0 3m
When the `web` StatefulSet was recreated, it first relaunched `web-0`. When the `web` StatefulSet was recreated, it first relaunched `web-0`.
Since `web-1` was already Running and Ready, when `web-0` transitioned to Since `web-1` was already Running and Ready, when `web-0` transitioned to
Running and Ready, it simply adopted this Pod. Since we recreated the Stateful Running and Ready, it simply adopted this Pod. Since you recreated the StatefulSet
Set with `replicas` equal to 2, once `web-0` had been recreated, and once with `replicas` equal to 2, once `web-0` had been recreated, and once
`web-1` had been determined to already be Running and Ready, `web-2` was `web-1` had been determined to already be Running and Ready, `web-2` was
terminated. terminated.
@ -631,7 +632,7 @@ web-0
web-1 web-1
``` ```
Even though we deleted both the StatefulSet and the `web-0` Pod, it still Even though you deleted both the StatefulSet and the `web-0` Pod, it still
serves the hostname originally entered into its `index.html` file. This is serves the hostname originally entered into its `index.html` file. This is
because the StatefulSet never deletes the PersistentVolumes associated with a because the StatefulSet never deletes the PersistentVolumes associated with a
Pod. When you recreated the StatefulSet and it relaunched `web-0`, its original Pod. When you recreated the StatefulSet and it relaunched `web-0`, its original
@ -672,7 +673,7 @@ web-1 0/1 Terminating 0 29m
``` ```
As we saw in the [Scaling Down](#ordered-pod-termination) section, the Pods As you saw in the [Scaling Down](#ordered-pod-termination) section, the Pods
are terminated one at a time, with respect to the reverse order of their ordinal are terminated one at a time, with respect to the reverse order of their ordinal
indices. Before terminating a Pod, the StatefulSet controller waits for indices. Before terminating a Pod, the StatefulSet controller waits for
the Pod's successor to be completely terminated. the Pod's successor to be completely terminated.