Add update to statefulset concepts and basic tutorial (#4174)

* Add update to statefulset concpets and basic tutorial

* Address tech comments.

docs/concepts/workloads/controllers/statefulset.md

@@ -1,6 +1,5 @@
 ---
 assignees:
-- bprashanth
 - enisoc
 - erictune
 - foxish
@@ -14,7 +13,7 @@ redirect_from:
 ---
 
 {% capture overview %}
-**StatefulSets are a beta feature in 1.5. This feature replaces the 
+**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/manage-stateful-set/upgrade-pet-set-to-stateful-set/)
 for further information on how to upgrade existing PetSets to StatefulSets.**
@@ -34,8 +33,9 @@ following.
 * Stable, persistent storage.
 * Ordered, graceful deployment and scaling.
 * Ordered, graceful deletion and termination.
+* Ordered, automated rolling updates.
 
-In the above, stable is synonymous with persistence across Pod (re)schedulings.
+In the above, stable is synonymous with persistence across Pod (re)scheduling.
 If an application doesn't require any stable identifiers or ordered deployment, 
 deletion, or scaling, you should deploy your application with a controller that 
 provides a set of stateless replicas. Controllers such as 
@@ -48,7 +48,6 @@ provides a set of stateless replicas. Controllers such as
 * The storage for a given Pod must either be provisioned by a [PersistentVolume Provisioner](http://releases.k8s.io/{{page.githubbranch}}/examples/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.
-* Updating an existing StatefulSet is currently a [manual process](/docs/tutorials/stateful-application/basic-stateful-set/#updating-containers).
 
 ## Components
 The example below demonstrates the components of a StatefulSet. 
@@ -59,7 +58,6 @@ The example below demonstrates the components of a StatefulSet.
  PersistentVolume Provisioner.
 
 ```yaml
----
 apiVersion: v1
 kind: Service
 metadata:
@@ -154,7 +152,7 @@ PersistentVolume Claims. Note that, the PersistentVolumes associated with the
 Pods' PersistentVolume Claims are not deleted when the Pods, or StatefulSet are deleted. 
 This must be done manually.
 
-## Deployment and Scaling Guarantee
+## Deployment and Scaling Guarantees
 
 * For a StatefulSet with N replicas, when Pods are being deployed, they are created sequentially, in order from {0..N-1}. 
 * When Pods are being deleted, they are terminated in reverse order, from {N-1..0}.
@@ -175,5 +173,62 @@ If a user were to scale the deployed example by patching the StatefulSet such th
 is fully shutdown and deleted. If web-0 were to fail after web-2 has been terminated and 
 is completely shutdown, but prior to web-1's termination, web-1 would not be terminated 
 until web-0 is Running and Ready.
+
+### Pod Management Policies
+In Kubernetes 1.7 and later, StatefulSet allows you to relax its ordering guarantees while 
+preserving its uniqueness and identity guarantees via its `.spec.podManagementPolicy` field.
+
+#### OrderedReady Pod Management
+
+`OrderedReady` pod management is the default for StatefulSets. It implements the behavior 
+described [above](#deployment-and-scaling-guarantees).
+
+#### Parallel Pod Management
+
+`Parallel` pod management tells the StatefulSet controller to launch or 
+terminate all Pods in parallel, and to not wait for Pods to become Running 
+and Ready or completely terminated prior to launching or terminating another 
+Pod.
+
+## Update Strategies
+
+In Kuberentes 1.7 and later, StatefulSet's `.spec.updateStrategy` field allows you to configure 
+and disable automated rolling updates for containers, labels, resource request/limits, and 
+annotations for the Pods in a StatefulSet.
+
+### On Delete
+
+The `OnDelete` update strategy implements the legacy (1.6 and prior) behavior. It is the default 
+strategy when `spec.updateStrategy` is left unspecified. When a StatefulSet's 
+`.spec.updateStrategy.type` is set to `OnDelete`, the StatefulSet controller will not automatically 
+update the Pods in a StatefulSet. Users must manually delete Pods to cause the controller to 
+create new Pods that reflect modifications made to a StatefulSet's `.spec.template`.
+
+### Rolling Updates
+
+The `RollingUpdate` update strategy implements automated, rolling update for the Pods in a 
+StatefulSet. When a StatefulSet's `.spec.updateStrategy.type` is set to `RollingUpdate`, the 
+StatefulSet controller will delete and recreate each Pod in the StatefulSet. It will proceed 
+in the same order as Pod termination (from the largest ordinal to the smallest), updating 
+each Pod one at a time. It will wait until an updated Pod is Running and Ready prior to 
+updating its predecessor.
+
+#### Partitions
+
+The `RollingUpdate` update strategy can be partitioned, by specifying a 
+`.spec.updateStrategy.rollingUpdate.partition`. If a partition is specified, all Pods with an 
+ordinal that is greater than or equal to the partition will be updated when the StatefulSet's 
+`.spec.template` is updated. All Pods with an ordinal that is less than the partition will not 
+be updated, and, even if they are deleted, they will be recreated at the previous version. If a 
+StatefulSet's `.spec.updateStrategy.rollingUpdate.partition` is greater than its `.spec.replicas`, 
+updates to its `.spec.template` will not be propagated to its Pods.
+In most cases you will not need to use a partition, but they are useful if you want to stage an 
+update, roll out a canary, or perform a phased roll out.
+
+{% endcapture %}
+{% capture whatsnext %}
+
+* Follow an example of [deploying a stateful application](/docs/tutorials/stateful-application/basic-stateful-set). 
+
 {% endcapture %}
 {% include templates/concept.md %}