Adds note callouts throughout
Implementing our new note callouts by way of experimentation. A couple other minor edits.
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@ -7,14 +7,13 @@ title: Deployments
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{% capture overview %}
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A _Deployment_ provides declarative updates for [Pods](/docs/concepts/workloads/pods/pod/) and
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[ReplicaSets](/docs/concepts/workloads/controllers/replicaset/) (the next-generation ReplicationController).
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You describe the desired state in a Deployment object, and the Deployment controller changes the actual state to the desired state at a controlled rate. You can define Deployments to
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create new ReplicaSets, or remove existing Deployments and adopt all their resources with new Deployments.
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A _Deployment_ controller provides declarative updates for [Pods](/docs/concepts/workloads/pods/pod/) and
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[ReplicaSets](/docs/concepts/workloads/controllers/replicaset/).
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**Note:** You should not manage ReplicaSets owned by a Deployment. If you do so, you are racing with the Deployment
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controller! All the use cases should be covered by manipulating the Deployment object. Consider opening
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an issue in the main Kubernetes repository if your use case is not covered below.
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You describe a _desired state_ in a Deployment object, and the Deployment controller changes the actual state to the desired state at a controlled rate. You can define Deployments to create new ReplicaSets, or to remove existing Deployments and adopt all their resources with new Deployments.
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**Note:** You should not manage ReplicaSets owned by a Deployment. All the use cases should be covered by manipulating the Deployment object. Consider opening an issue in the main Kubernetes repository if your use case is not covered below.
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{: .note}
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{% endcapture %}
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@ -23,7 +22,7 @@ an issue in the main Kubernetes repository if your use case is not covered below
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## Use Case
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A typical use case is:
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The following are typical use cases for Deployments:
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* [Create a Deployment to rollout a ReplicaSet](#creating-a-deployment). The ReplicaSet creates Pods in the background. Check the status of the rollout to see if it succeeds or not.
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* [Declare the new state of the Pods](#updating-a-deployment) by updating the PodTemplateSpec of the Deployment. A new ReplicaSet is created and the Deployment manages moving the Pods from the old ReplicaSet to the new one at a controlled rate. Each new ReplicaSet updates the revision of the Deployment.
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@ -106,10 +105,12 @@ The created ReplicaSet ensures that there are three nginx Pods at all times.
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StatefulSets, etc.). Kubernetes doesn't stop you from overlapping, and if multiple
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controllers have overlapping selectors, those controllers may fight with each other and won't behave
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correctly.
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{: .note}
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### Pod-template-hash label
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**Note:** This label is not meant to be changed by users!
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**Note:** Do not change this label.
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{: .note}
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Note the pod-template-hash label in the example output in the pod labels above. This label is added by the
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Deployment controller to every ReplicaSet that a Deployment creates or adopts. Its purpose is to make sure that child
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@ -121,6 +122,7 @@ and in any existing Pods that the ReplicaSet may have.
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**Note:** A Deployment's rollout is triggered if and only if the Deployment's pod template (that is, `.spec.template`)
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is changed, for example if the labels or container images of the template are updated. Other updates, such as scaling the Deployment, do not trigger a rollout.
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{: .note}
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Suppose that we now want to update the nginx Pods to use the `nginx:1.9.1` image
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instead of the `nginx:1.7.9` image.
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@ -268,6 +270,7 @@ for example if you update the labels or container images of the template. Other
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do not create a Deployment revision, so that we can facilitate simultaneous manual- or auto-scaling.
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This means that when you roll back to an earlier revision, only the Deployment's pod template part is
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rolled back.
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{: .note}
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Suppose that we made a typo while updating the Deployment, by putting the image name as `nginx:1.91` instead of `nginx:1.9.1`:
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@ -313,6 +316,7 @@ ReplicaSet. This depends on the rollingUpdate parameters (`maxUnavailable` speci
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Kubernetes by default sets the value to 1 and spec.replicas to 1 so if you haven't cared about setting those
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parameters, your Deployment can have 100% unavailability by default! This will be fixed in Kubernetes in a future
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version.
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{: .note}
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```shell
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$ kubectl describe deployment
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@ -579,6 +583,7 @@ nginx-3926361531 3 3 3 28s
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```
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**Note:** You cannot rollback a paused Deployment until you resume it.
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{: .note}
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## Deployment status
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@ -652,10 +657,12 @@ See the [Kubernetes API conventions](https://git.k8s.io/community/contributors/d
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**Note:** Kubernetes will take no action on a stalled Deployment other than to report a status condition with
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`Reason=ProgressDeadlineExceeded`. Higher level orchestrators can take advantage of it and act accordingly, for
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example, rollback the Deployment to its previous version.
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{: .note}
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**Note:** If you pause a Deployment, Kubernetes does not check progress against your specified deadline. You can
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safely pause a Deployment in the middle of a rollout and resume without triggering the condition for exceeding the
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deadline.
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{: .note}
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You may experience transient errors with your Deployments, either due to a low timeout that you have set or
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due to any other kind of error that can be treated as transient. For example, let's suppose you have
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@ -758,7 +765,7 @@ all revision history will be kept. In a future version, it will default to switc
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**Note:** Explicitly setting this field to 0, will result in cleaning up all the history of your Deployment
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thus that Deployment will not be able to roll back.
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{: .note}
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## Use Cases
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@ -809,6 +816,7 @@ Pods with `.spec.template` if the number of Pods is less than the desired number
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**Note:** You should not create other pods whose labels match this selector, either directly, by creating
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another Deployment, or by creating another controller such as a ReplicaSet or a ReplicationController. If you
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do so, the first Deployment thinks that it created these other pods. Kubernetes does not stop you from doing this.
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{: .note}
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If you have multiple controllers that have overlapping selectors, the controllers will fight with each
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other and won't behave correctly.
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