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Qiming Teng
2020-11-16 12:56:30 +08:00
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content/zh/docs/concepts/workloads/controllers/replicaset.md
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@@ -1,8 +1,17 @@
---
title: ReplicaSet
content_type: concept
weight: 10
weight: 20
---
<!--
reviewers:
- Kashomon
- bprashanth
- madhusudancs
title: ReplicaSet
content_type: concept
weight: 20
-->
<!-- overview -->
@@ -18,30 +27,25 @@ ReplicaSet 的目的是维护一组在任何时候都处于运行状态的 Pod
<!--
## How a ReplicaSet works
A ReplicaSet is defined with fields, including a selector that specifies how
to identify Pods it can acquire, a number of replicas indicating how many Pods
it should be maintaining, and a pod template specifying the data of new Pods
it should create to meet the number of replicas criteria. A ReplicaSet then
fulfills its purpose by creating and deleting Pods as needed to reach the
desired number. When a ReplicaSet needs to create new Pods, it uses its Pod
A ReplicaSet is defined with fields, including a selector that specifies how to identify Pods it can acquire, a number
of replicas indicating how many Pods it should be maintaining, and a pod template specifying the data of new Pods
it should create to meet the number of replicas criteria. A ReplicaSet then fulfills its purpose by creating
and deleting Pods as needed to reach the desired number. When a ReplicaSet needs to create new Pods, it uses its Pod
template.
-->
## ReplicaSet 的工作原理 {#how-a-replicaset-works}
RepicaSet 是通过一组字段来定义的，包括一个用来识别可获得的 Pod
的集合的选择算符，一个用来标明应该维护的副本个数的数值，一个用来指定应该创建新 Pod
以满足副本个数条件时要使用的 Pod 模板等等。每个 ReplicaSet 都通过根据需要创建和
删除 Pod 以使得副本个数达到期望值，进而实现其存在价值。当 ReplicaSet 需要创建
新的 Pod 时，会使用所提供的 Pod 模板。
的集合的选择算符、一个用来标明应该维护的副本个数的数值、一个用来指定应该创建新 Pod
以满足副本个数条件时要使用的 Pod 模板等等。
每个 ReplicaSet 都通过根据需要创建和 删除 Pod 以使得副本个数达到期望值，
进而实现其存在价值。当 ReplicaSet 需要创建新的 Pod 时，会使用所提供的 Pod 模板。
<!--
A ReplicaSet is linked to its Pods via the Pods'
[metadata.ownerReferences](/docs/concepts/workloads/controllers/garbage-collection/#owners-and-dependents)
field, which specifies what resource the current object is owned by. All Pods
acquired by a ReplicaSet have their owning ReplicaSet's identifying
information within their ownerReferences field. It's through this link that
the ReplicaSet knows of the state of the Pods it is maintaining and plans
accordingly.
A ReplicaSet is linked to its Pods via the Pods' [metadata.ownerReferences](/docs/concepts/workloads/controllers/garbage-collection/#owners-and-dependents)
field, which specifies what resource the current object is owned by. All Pods acquired by a ReplicaSet have their owning
ReplicaSet's identifying information within their ownerReferences field. It's through this link that the ReplicaSet
knows of the state of the Pods it is maintaining and plans accordingly.
-->
ReplicaSet 通过 Pod 上的
[metadata.ownerReferences](/zh/docs/concepts/workloads/controllers/garbage-collection/#owners-and-dependents)
@@ -51,41 +55,14 @@ ReplicaSet 所获得的 Pod 都在其 ownerReferences 字段中包含了属主 R
并据此计划其操作行为。
<!--
A ReplicaSet identifies new Pods to acquire by using its selector. If there is
a Pod that has no OwnerReference or the OwnerReference is not a {{<
glossary_tooltip term_id="controller" >}} and it matches a ReplicaSet's
selector, it will be immediately acquired by said ReplicaSet.
A ReplicaSet identifies new Pods to acquire by using its selector. If there is a Pod that has no OwnerReference or the
OwnerReference is not a {{< glossary_tooltip term_id="controller" >}} and it matches a ReplicaSet's selector, it will be immediately acquired by said ReplicaSet.
-->
ReplicaSet 使用其选择算符来辨识要获得的 Pod 集合。如果某个 Pod 没有
OwnerReference 或者其 OwnerReference 不是一个
{{< glossary_tooltip text="控制器" term_id="controller" >}}，且其匹配到
某 ReplicaSet 的选择算符，则该 Pod 立即被此 ReplicaSet 获得。
<!--
## How to use a ReplicaSet
Most [`kubectl`](/docs/user-guide/kubectl/) commands that support
Replication Controllers also support ReplicaSets. One exception is the
[`rolling-update`](/docs/reference/generated/kubectl/kubectl-commands#rolling-update) command. If
you want the rolling update functionality please consider using Deployments
instead. Also, the
[`rolling-update`](/docs/reference/generated/kubectl/kubectl-commands#rolling-update) command is
imperative whereas Deployments are declarative, so we recommend using Deployments
through the [`rollout`](/docs/reference/generated/kubectl/kubectl-commands#rollout) command.
While ReplicaSets can be used independently, today it's mainly used by
[Deployments](/docs/concepts/workloads/controllers/deployment/) as a mechanism to orchestrate pod
creation, deletion and updates. When you use Deployments you don't have to worry
about managing the ReplicaSets that they create. Deployments own and manage
their ReplicaSets.
-->
## 怎样使用 ReplicaSet {#how-to-use-a-replicaset}
大多数支持 Replication Controllers 的[`kubectl`](/zh/docs/reference/kubectl/kubectl/)命令也支持 ReplicaSets。但[`rolling-update`](/docs/reference/generated/kubectl/kubectl-commands#rolling-update) 命令是个例外。如果您想要滚动更新功能请考虑使用 Deployment。[`rolling-update`](/docs/reference/generated/kubectl/kubectl-commands#rolling-update) 命令是必需的，而 Deployment 是声明性的，因此我们建议通过 [`rollout`](/docs/reference/generated/kubectl/kubectl-commands#rollout)命令使用 Deployment。
虽然 ReplicaSets 可以独立使用，但今天它主要被[Deployments](/zh/docs/concepts/workloads/controllers/deployment/) 用作协调 Pod 创建、删除和更新的机制。
当您使用 Deployment 时，您不必担心还要管理它们创建的 ReplicaSet。Deployment 会拥有并管理它们的 ReplicaSet。
<!--
## When to use a ReplicaSet
@@ -98,14 +75,16 @@ you require custom update orchestration or don't require updates at all.
This actually means that you may never need to manipulate ReplicaSet objects:
use a Deployment instead, and define your application in the spec section.
-->
## 什么时候使用 ReplicaSet
## 何时使用 ReplicaSet
ReplicaSet 确保任何时间都有指定数量的 Pod 副本在运行。
然而，Deployment 是一个更高级的概念，它管理 ReplicaSet，并向 Pod 提供声明式的更新以及许多其他有用的功能。
因此，我们建议使用 Deployment 而不是直接使用 ReplicaSet，除非您需要自定义更新业务流程或根本不需要更新。
然而，Deployment 是一个更高级的概念，它管理 ReplicaSet，并向 Pod
提供声明式的更新以及许多其他有用的功能。
因此，我们建议使用 Deployment 而不是直接使用 ReplicaSet，除非
你需要自定义更新业务流程或根本不需要更新。
这实际上意味着，您可能永远不需要操作 ReplicaSet 对象：而是使用 Deployment，并在 spec 部分定义您的应用。
这实际上意味着，你可能永远不需要操作 ReplicaSet 对象：而是使用
Deployment，并在 spec 部分定义你的应用。
<!--
## Example
@@ -118,151 +97,349 @@ ReplicaSet 确保任何时间都有指定数量的 Pod 副本在运行。
Saving this manifest into `frontend.yaml` and submitting it to a Kubernetes cluster should
create the defined ReplicaSet and the pods that it manages.
-->
将此清单保存到 `frontend.yaml` 中，并将其提交到 Kubernetes 集群，
应该就能创建 yaml 文件所定义的 ReplicaSet 及其管理的 Pod。
将此清单保存到 `frontend.yaml` 中，并将其提交到 Kubernetes 集群，应该就能创建 yaml 文件所定义的 ReplicaSet 及其管理的 Pod。
```shell
$ kubectl create -f http://k8s.io/examples/controllers/frontend.yaml
replicaset.apps/frontend created
$ kubectl describe rs/frontend
kubectl apply -f https://kubernetes.io/examples/controllers/frontend.yaml
```
<!--
You can then get the current ReplicaSets deployed:
-->
你可以看到当前被部署的 ReplicaSet：
```shell
kubectl get rs
```
<!--
And see the frontend one you created:
-->
并看到你所创建的前端：
```
NAME DESIRED CURRENT READY AGE
frontend 3 3 3 6s
```
<!--
You can also check on the state of the ReplicaSet:
-->
你也可以查看 ReplicaSet 的状态：
```shell
kubectl describe rs/frontend
```
<!--
And you will see output similar to:
-->
你会看到类似如下的输出：
```
Name: frontend
Namespace: default
Selector: tier=frontend,tier in (frontend)
Selector: tier=frontend
Labels: app=guestbook
tier=frontend
Annotations: <none>
Annotations: kubectl.kubernetes.io/last-applied-configuration:
{"apiVersion":"apps/v1","kind":"ReplicaSet","metadata":{"annotations":{},"labels":{"app":"guestbook","tier":"frontend"},"name":"frontend",...
Replicas: 3 current / 3 desired
Pods Status: 3 Running / 0 Waiting / 0 Succeeded / 0 Failed
Pod Template:
Labels: app=guestbook
tier=frontend
Labels: tier=frontend
Containers:
php-redis:
Image: gcr.io/google_samples/gb-frontend:v3
Port: 80/TCP
Requests:
cpu: 100m
memory: 100Mi
Environment:
GET_HOSTS_FROM: dns
Port: <none>
Host Port: <none>
Environment: <none>
Mounts: <none>
Volumes: <none>
Events:
FirstSeen LastSeen Count From SubobjectPath Type Reason Message
--------- -------- ----- ---- ------------- -------- ------ -------
1m 1m 1 {replicaset-controller } Normal SuccessfulCreate Created pod: frontend-qhloh
1m 1m 1 {replicaset-controller } Normal SuccessfulCreate Created pod: frontend-dnjpy
1m 1m 1 {replicaset-controller } Normal SuccessfulCreate Created pod: frontend-9si5l
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
frontend-9si5l 1/1 Running 0 1m
frontend-dnjpy 1/1 Running 0 1m
frontend-qhloh 1/1 Running 0 1m
Type Reason Age From Message
---- ------ ---- ---- -------
Normal SuccessfulCreate 117s replicaset-controller Created pod: frontend-wtsmm
Normal SuccessfulCreate 116s replicaset-controller Created pod: frontend-b2zdv
Normal SuccessfulCreate 116s replicaset-controller Created pod: frontend-vcmts
```
<!--
And lastly you can check for the Pods brought up:
-->
最后可以查看启动了的 Pods：
```shell
kubectl get pods
```
<!--
You should see Pod information similar to:
-->
你会看到类似如下的 Pod 信息：
```
NAME READY STATUS RESTARTS AGE
frontend-b2zdv 1/1 Running 0 6m36s
frontend-vcmts 1/1 Running 0 6m36s
frontend-wtsmm 1/1 Running 0 6m36s
```
<!--
You can also verify that the owner reference of these pods is set to the frontend ReplicaSet.
To do this, get the yaml of one of the Pods running:
-->
你也可以查看 Pods 的属主引用被设置为前端的 ReplicaSet。
要实现这点，可取回运行中的 Pods 之一的 YAML：
```shell
kubectl get pods frontend-b2zdv -o yaml
```
<!--
The output will look similar to this, with the frontend ReplicaSet's info set in the metadata's ownerReferences field:
-->
输出将类似这样，frontend ReplicaSet 的信息被设置在 metadata 的
`ownerReferences` 字段中：
```yaml
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: "2020-02-12T07:06:16Z"
generateName: frontend-
labels:
tier: frontend
name: frontend-b2zdv
namespace: default
ownerReferences:
- apiVersion: apps/v1
blockOwnerDeletion: true
controller: true
kind: ReplicaSet
name: frontend
uid: f391f6db-bb9b-4c09-ae74-6a1f77f3d5cf
...
```
<!--
## Non-Template Pod acquisitions
While you can create bare Pods with no problems, it is strongly recommended to make sure that the bare Pods do not have
labels which match the selector of one of your ReplicaSets. The reason for this is because a ReplicaSet is not limited
to owning Pods specified by its template - it can acquire other Pods in the manner specified in the previous sections.
-->
## 非模板 Pod 的获得
<!--
While you can create bare Pods with no problems, it is strongly recommended to
make sure that the bare Pods do not have labels which match the selector of
one of your ReplicaSets. The reason for this is because a ReplicaSet is not
limited to owning Pods specified by its template - it can acquire other Pods
in the manner specified in the previous sections.
Take the previous frontend ReplicaSet example, and the Pods specified in the
following manifest:
-->
尽管你完全可以直接创建裸的 Pods，强烈建议你确保这些裸的 Pods 并不包含可能与你
的某个 ReplicaSet 的选择算符相匹配的标签。原因在于 ReplicaSet 并不仅限于拥有
在其模板中设置的 Pods，它还可以像前面小节中所描述的那样获得其他 Pods。
{{< codenew file="pods/pod-rs.yaml" >}}
<!--
As those Pods do not have a Controller (or any object) as their owner reference and match the selector of the frontend
ReplicaSet, they will immediately be acquired by it.
Suppose you create the Pods after the frontend ReplicaSet has been deployed and has set up its initial Pod replicas to
fulfill its replica count requirement:
-->
由于这些 Pod 没有控制器（Controller，或其他对象）作为其属主引用，并且
其标签与 frontend ReplicaSet 的选择算符匹配，它们会立即被该 ReplicaSet
获取。
假定你在 frontend ReplicaSet 已经被部署之后创建 Pods，并且你已经在 ReplicaSet
中设置了其初始的 Pod 副本数以满足其副本计数需要：
```shell
kubectl apply -f https://kubernetes.io/examples/pods/pod-rs.yaml
```
<!--
The new Pods will be acquired by the ReplicaSet, and then immediately terminated as the ReplicaSet would be over
its desired count.
Fetching the Pods:
-->
新的 Pods 会被该 ReplicaSet 获取，并立即被 ReplicaSet 终止，因为
它们的存在会使得 ReplicaSet 中 Pod 个数超出其期望值。
取回 Pods：
```shell
kubectl get pods
```
<!--
The output shows that the new Pods are either already terminated, or in the process of being terminated:
-->
输出显示新的 Pods 或者已经被终止，或者处于终止过程中：
```shell
NAME READY STATUS RESTARTS AGE
frontend-b2zdv 1/1 Running 0 10m
frontend-vcmts 1/1 Running 0 10m
frontend-wtsmm 1/1 Running 0 10m
pod1 0/1 Terminating 0 1s
pod2 0/1 Terminating 0 1s
```
<!--
If you create the Pods first:
-->
如果你先行创建 Pods：
```shell
kubectl apply -f https://kubernetes.io/examples/pods/pod-rs.yaml
```
<!--
And then create the ReplicaSet however:
-->
之后再创建 ReplicaSet：
```shell
kubectl apply -f https://kubernetes.io/examples/controllers/frontend.yaml
```
<!--
You shall see that the ReplicaSet has acquired the Pods and has only created new ones according to its spec until the
number of its new Pods and the original matches its desired count. As fetching the Pods:
-->
你会看到 ReplicaSet 已经获得了该 Pods，并仅根据其规约创建新的 Pods，直到
新的 Pods 和原来的 Pods 的总数达到其预期个数。
这时取回 Pods：
```shell
kubectl get pods
```
<!--
Will reveal in its output:
-->
将会生成下面的输出：
```
NAME READY STATUS RESTARTS AGE
frontend-hmmj2 1/1 Running 0 9s
pod1 1/1 Running 0 36s
pod2 1/1 Running 0 36s
```
采用这种方式，一个 ReplicaSet 中可以包含异质的 Pods 集合。
<!--
## 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 [object management using kubectl](/docs/concepts/overview/object-management-kubectl/overview/).
As with all other Kubernetes API objects, a ReplicaSet needs the `apiVersion`, `kind`, and `metadata` fields.
For ReplicaSets, the kind is always just ReplicaSet.
In Kubernetes 1.9 the API version `apps/v1` on the ReplicaSet kind is the current version and is enabled by default. The API version `apps/v1beta2` is deprecated.
Refer to the first lines of the `frontend.yaml` example for guidance.
The name of a ReplicaSet object must be a valid
[DNS subdomain name](/docs/concepts/overview/working-with-objects/names#dns-subdomain-names).
A ReplicaSet also needs a [`.spec` section](https://git.k8s.io/community/contributors/devel/api-conventions.md#spec-and-status).
-->
## 编写 ReplicaSet 的 spec
## 编写 ReplicaSet Spec
与所有其他 Kubernetes API 对象一样，ReplicaSet 也需要 `apiVersion`、`kind`、和 `metadata` 字段。
对于 ReplicaSets 而言，其 kind 始终是 ReplicaSet。
在 Kubernetes 1.9 中，ReplicaSet 上的 API 版本 `apps/v1` 是其当前版本，且被
默认启用。API 版本 `apps/v1beta2` 已被废弃。
参考 `frontend.yaml` 示例的第一行。
与所有其他 Kubernetes API 对象一样，ReplicaSet 也需要 `apiVersion`、`kind`、和 `metadata` 字段。有关使用清单的一般信息，请参见 [使用 kubectl 管理对象](/zh/docs/concepts/overview/working-with-objects/object-management/)。
ReplicaSet 对象的名称必须是合法的
[DNS 子域名](/zh/docs/concepts/overview/working-with-objects/names#dns-subdomain-names)。
ReplicaSet 也需要 [`.spec`](https://git.k8s.io/community/contributors/devel/api-conventions.md#spec-and-status) 部分。
ReplicaSet 也需要 [`.spec`](https://git.k8s.io/community/contributors/devel/api-conventions.md#spec-and-status)
部分。
<!--
### 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`.
The `.spec.template` is a [pod template](/docs/concepts/workloads/pods/#pod-templates) which is also
required to have labels in place. In our `frontend.yaml` example we had one label: `tier: frontend`.
Be careful not to overlap with the selectors of other controllers, lest they try to adopt this Pod.
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/#restart-policy), 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.
For the template's [restart policy](/docs/concepts/workloads/Pods/pod-lifecycle/#restart-policy) field,
`.spec.template.spec.restartPolicy`, the only allowed value is `Always`, which is the default.
-->
### Pod 模版
`.spec.template` 是 `.spec` 唯一需要的字段。`.spec.template` 是 [Pod 模版](/zh/docs/concepts/workloads/pods/#pod-templates)。它和 [Pod](/zh/docs/concepts/workloads/pods/) 的语法几乎完全一样，除了它是嵌套的并没有 `apiVersion` 和 `kind`。
`.spec.template` 是一个[Pod 模版](/zh/docs/concepts/workloads/pods/#pod-templates)，
要求设置标签。在 `frontend.yaml` 示例中，我们指定了标签 `tier: frontend`。
注意不要将标签与其他控制器的选择算符重叠，否则那些控制器会尝试收养此 Pod。
除了所需的 Pod 字段之外，ReplicaSet 中的 Pod 模板必须指定适当的标签和适当的重启策略。
对于标签，请确保不要与其他控制器重叠。更多信息请参考 [Pod 选择器](#pod-selector)。
对于 [重启策略](/zh/docs/concepts/workloads/pods/pod-lifecycle/#restart-policy)，`.spec.template.spec.restartPolicy` 唯一允许的取值是 `Always`，这也是默认值.
对于本地容器重新启动，ReplicaSet 委托给了节点上的代理去执行，例如[Kubelet](/zh/docs/reference/command-line-tools-reference/kubelet/) 或 Docker 去执行。
对于模板的[重启策略](/zh/docs/concepts/workloads/pods/pod-lifecycle/#restart-policy)
字段，`.spec.template.spec.restartPolicy`，唯一允许的取值是 `Always`，这也是默认值.
<!--
### Pod Selector
The `.spec.selector` field is a [label selector](/docs/concepts/overview/working-with-objects/labels/). 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.selector` field is a [label selector](/docs/concepts/overview/working-with-objects/labels/). As discussed
[earlier](#how-a-replicaset-works) these are the labels used to identify potential Pods to acquire. In our
`frontend.yaml` example, the selector was:
The `.spec.template.metadata.labels` must match the `.spec.selector`, or it will
```yaml
matchLabels:
tier: frontend
```
In the ReplicaSet, `.spec.template.metadata.labels` must match `spec.selector`, or it will
be rejected by the API.
In Kubernetes 1.9 the API version `apps/v1` on the ReplicaSet kind is the current version and is enabled by default. The API version `apps/v1beta2` is deprecated.
-->
### Pod 选择算符 {#pod-selector}
### Pod 选择器
`.spec.selector` 字段是一个[标签选择算符](/zh/docs/concepts/overview/working-with-objects/labels/)。
如前文中[所讨论的](how-a-replicaset-works)，这些是用来标识要被获取的 Pods
的标签。在签名的 `frontend.yaml` 示例中，选择算符为：
`.spec.selector` 字段是[标签选择器](/zh/docs/concepts/overview/working-with-objects/labels/)。ReplicaSet 管理所有标签匹配与标签选择器的 Pod。它不区分自己创建或删除的 Pod 和其他人或进程创建或删除的pod。这允许在不影响运行中的 Pod 的情况下替换副本集。
```yaml
matchLabels:
tier: frontend
```
`.spec.template.metadata.labels` 必须匹配 `.spec.selector`，否则它将被 API 拒绝。
在 ReplicaSet 中，`.spec.template.metadata.labels` 的值必须与 `spec.selector` 值
相匹配，否则该配置会被 API 拒绝。
Kubernetes 1.9 版本中，API 版本 `apps/v1` 中的 ReplicaSet 类型的版本是当前版本并默认开启。API 版本 `apps/v1beta2` 被弃用。
{{< note >}}
<!--
For 2 ReplicaSets specifying the same `.spec.selector` but different `.spec.template.metadata.labels` and `.spec.template.spec` fields, each ReplicaSet ignores the Pods created by the other ReplicaSet.
-->
对于设置了相同的 `.spec.selector`，但
`.spec.template.metadata.labels` 和 `.spec.template.spec` 字段不同的
两个 ReplicaSet 而言，每个 ReplicaSet 都会忽略被另一个 ReplicaSet 所
创建的 Pods。
{{< /note >}}
<!--
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.
-->
另外，通常您不应该创建标签与此选择器匹配的任何 Pod，或者直接与另一个 ReplicaSet 或另一个控制器（如 Deployment）标签匹配的任何 Pod。
如果你这样做，ReplicaSet 会认为它创造了其他 Pod。Kubernetes 并不会阻止您这样做。
如果您最终使用了多个具有重叠选择器的控制器，则必须自己负责删除。
<!--
### 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.
You can specify how many Pods should run concurrently by setting `.spec.replicas`. The ReplicaSet will create/delete
its Pods to match this number.
If you do not specify `.spec.replicas`, then it defaults to 1.
-->
### Replicas
通过设置 `.spec.replicas` 您可以指定要同时运行多少个 Pod。
在任何时间运行的 Pod 数量可能高于或低于 `.spec.replicas` 指定的数量，例如在副本刚刚被增加或减少后、或者 Pod 正在被优雅地关闭、以及替换提前开始。
你可以通过设置 `.spec.replicas` 来指定要同时运行的 Pod 个数。
ReplicaSet 创建、删除 Pods 以与此值匹配。
如果您没有指定 `.spec.replicas`, 那么默认值为 1。
如果你没有指定 `.spec.replicas`, 那么默认值为 1。
<!--
## Working with ReplicaSets
@@ -273,58 +450,63 @@ To delete a ReplicaSet and all of its Pods, use [`kubectl delete`](/docs/referen
When using the REST API or the `client-go` library, you must set `propagationPolicy` to `Background` or `Foreground` in delete option. e.g. :
-->
## 使用 ReplicaSets 的具体方法
## 使用 ReplicaSets
### 删除 ReplicaSet 和它的 Pod
要删除 ReplicaSet 和它的所有 Pod，使用[`kubectl delete`](/docs/reference/generated/kubectl/kubectl-commands#delete) 命令。
默认情况下，[垃圾收集器](/zh/docs/concepts/workloads/controllers/garbage-collection/) 自动删除所有依赖的 Pod。
要删除 ReplicaSet 和它的所有 Pod，使用
[`kubectl delete`](/docs/reference/generated/kubectl/kubectl-commands#delete) 命令。
默认情况下，[垃圾收集器](/zh/docs/concepts/workloads/controllers/garbage-collection/)
自动删除所有依赖的 Pod。
当使用 REST API 或 `client-go` 库时，您必须在删除选项中将 `propagationPolicy` 设置为 `Background` 或 `Foreground`。例如：
当使用 REST API 或 `client-go` 库时，你必须在删除选项中将 `propagationPolicy`
设置为 `Background` 或 `Foreground`。例如：
```shell
kubectl proxy --port=8080
curl -X DELETE 'localhost:8080/apis/apps/v1/namespaces/default/replicasets/frontend' \
> -d '{"kind":"DeleteOptions","apiVersion":"v1","propagationPolicy":"Foreground"}' \
> -H "Content-Type: application/json"
-d '{"kind":"DeleteOptions","apiVersion":"v1","propagationPolicy":"Foreground"}' \
-H "Content-Type: application/json"
```
<!--
### Deleting just a ReplicaSet
You can delete a ReplicaSet without affecting any of its pods using [`kubectl delete`](/docs/reference/generated/kubectl/kubectl-commands#delete) with the `--cascade=false` option.
When using the REST API or the `client-go` library, you must set `propagationPolicy` to `Orphan`, e.g. :
You can delete a ReplicaSet without affecting any of its pods using [`kubectl delete`](/docs/reference/generated/kubectl/kubectl-commands#delete) with the `-cascade=false` option.
When using the REST API or the `client-go` library, you must set `propagationPolicy` to `Orphan`.
For example:
-->
### 只删除 ReplicaSet
您可以只删除 ReplicaSet 而不影响它的 Pod，方法是使用[`kubectl delete`](/docs/reference/generated/kubectl/kubectl-commands#delete) 命令并设置 `--cascade=false` 选项。
你可以只删除 ReplicaSet 而不影响它的 Pod，方法是使用
[`kubectl delete`](/docs/reference/generated/kubectl/kubectl-commands#delete)
命令并设置 `--cascade=false` 选项。
当使用 REST API 或 `client-go` 库时，您必须将 `propagationPolicy` 设置为 `Orphan`。例如：
当使用 REST API 或 `client-go` 库时，你必须将 `propagationPolicy` 设置为 `Orphan`。
例如：
```shell
kubectl proxy --port=8080
curl -X DELETE 'localhost:8080/apis/apps/v1/namespaces/default/replicasets/frontend' \
> -d '{"kind":"DeleteOptions","apiVersion":"v1","propagationPolicy":"Orphan"}' \
> -H "Content-Type: application/json"
-d '{"kind":"DeleteOptions","apiVersion":"v1","propagationPolicy":"Orphan"}' \
-H "Content-Type: application/json"
```
<!--
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).
To update Pods to a new spec in a controlled way, use a
[Deployment](/docs/concepts/workloads/controllers/deployment/#creating-a-deployment), as ReplicaSets do not support a rolling update directly.
-->
一旦删除了原来的 ReplicaSet，就可以创建一个新的来替换它。
由于新旧 ReplicaSet 的 `.spec.selector` 是相同的，新的 ReplicaSet 将接管老的 Pod。
但是，它不会努力使现有的 Pod 与新的、不同的 Pod 模板匹配。
若想要以可控的方式将 Pod 更新到新的 spec，就要使用 [滚动更新](#rolling-updates)的方式。
若想要以可控的方式更新 Pod 的规约，可以使用
[Deployment](/zh/docs/concepts/workloads/controllers/deployment/#creating-a-deployment)
资源，因为 ReplicaSet 并不直接支持滚动更新。
<!--
### 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
@@ -332,10 +514,10 @@ from service for debugging, data recovery, etc. Pods that are removed in this wa
assuming that the number of replicas is not also changed).
-->
### 将 Pod 从 ReplicaSet 中隔离
可以通过改变标签来从 ReplicaSet 的目标集中移除 Pod。这种技术可以用来从服务中去除 Pod，以便进行排错、数据恢复等。
可以通过改变标签来从 ReplicaSet 的目标集中移除 Pod。
这种技术可以用来从服务中去除 Pod，以便进行排错、数据恢复等。
以这种方式移除的 Pod 将被自动替换（假设副本的数量没有改变）。
<!--
@@ -344,10 +526,10 @@ from service for debugging, data recovery, etc. Pods that are removed in this wa
A ReplicaSet can be easily scaled up or down by simply updating the `.spec.replicas` field. The ReplicaSet controller
ensures that a desired number of pods with a matching label selector are available and operational.
-->
### 缩放 RepliaSet
通过更新 `.spec.replicas` 字段，ReplicaSet 可以被轻松的进行缩放。ReplicaSet 控制器能确保匹配标签选择器的数量的 Pod 是可用的和可操作的。
通过更新 `.spec.replicas` 字段，ReplicaSet 可以被轻松的进行缩放。ReplicaSet
控制器能确保匹配标签选择器的数量的 Pod 是可用的和可操作的。
<!--
### ReplicaSet as an Horizontal Pod Autoscaler Target
@@ -357,13 +539,13 @@ A ReplicaSet can also be a target for
a ReplicaSet can be auto-scaled by an HPA. Here is an example HPA targeting
the ReplicaSet we created in the previous example.
-->
### ReplicaSet 作为水平的 Pod 自动缩放器目标
ReplicaSet 也可以作为 [水平的 Pod 缩放器 (HPA)](/docs/tasks/run-application/horizontal-pod-autoscale/) 的目标。也就是说，ReplicaSet 可以被 HPA 自动缩放。
ReplicaSet 也可以作为
[水平的 Pod 缩放器 (HPA)](/zh/docs/tasks/run-application/horizontal-pod-autoscale/)
的目标。也就是说，ReplicaSet 可以被 HPA 自动缩放。
以下是 HPA 以我们在前一个示例中创建的副本集为目标的示例。
{{< codenew file="controllers/hpa-rs.yaml" >}}
<!--
@@ -371,23 +553,21 @@ Saving this manifest into `hpa-rs.yaml` and submitting it to a Kubernetes cluste
create the defined HPA that autoscales the target ReplicaSet depending on the CPU usage
of the replicated pods.
-->
将这个列表保存到 `hpa-rs.yaml` 并提交到 Kubernetes 集群，就能创建它所定义的 HPA，进而就能根据复制的 Pod 的 CPU 利用率对目标 ReplicaSet进行自动缩放。
将这个列表保存到 `hpa-rs.yaml` 并提交到 Kubernetes 集群，就能创建它所定义的
HPA，进而就能根据复制的 Pod 的 CPU 利用率对目标 ReplicaSet进行自动缩放。
```shell
kubectl create -f https://k8s.io/examples/controllers/hpa-rs.yaml
kubectl apply -f https://k8s.io/examples/controllers/hpa-rs.yaml
```
<!--
Alternatively, you can use the `kubectl autoscale` command to accomplish the same
(and it's easier!)
-->
或者，可以使用 `kubectl autoscale` 命令完成相同的操作。
(而且它更简单！)
或者，可以使用 `kubectl autoscale` 命令完成相同的操作。 (而且它更简单！)
```shell
kubectl autoscale rs frontend
kubectl autoscale rs frontend --max=10 --min=3 --cpu-percent=50
```
<!--
@@ -395,43 +575,49 @@ kubectl autoscale rs frontend
### 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/).
[`Deployment`](/docs/concepts/workloads/controllers/deployment/) is an object which can own ReplicaSets and update
them and their Pods via declarative, server-side rolling updates.
While ReplicaSets can be used independently, today they're mainly used by Deployments as a mechanism to orchestrate Pod
creation, deletion and updates. When you use Deployments you don't have to worry about managing the ReplicaSets that
they create. Deployments own and manage their ReplicaSets.
As such, it is recommended to use Deployments when you want ReplicaSets.
-->
## ReplicaSet 的替代方案
### Deployment （推荐）
[`Deployment`](/zh/docs/concepts/workloads/controllers/deployment/) 是一个高级 API 对象，它以 `kubectl rolling-update` 的方式更新其底层副本集及其Pod。
如果您需要滚动更新功能，建议使用 Deployment，因为 Deployment 与 `kubectl rolling-update` 不同的是：它是声明式的、服务器端的、并且具有其他特性。
有关使用 Deployment 来运行无状态应用的更多信息，请参阅 [使用 Deployment 运行无状态应用](/zh/docs/tasks/run-application/run-stateless-application-deployment/)。
[`Deployment`](/zh/docs/concepts/workloads/controllers/deployment/) 是一个
可以拥有 ReplicaSet 并使用声明式方式在服务器端完成对 Pods 滚动更新的对象。
尽管 ReplicaSet 可以独立使用，目前它们的主要用途是提供给 Deployment 作为
编排 Pod 创建、删除和更新的一种机制。当使用 Deployment 时，你不必关心
如何管理它所创建的 ReplicaSet，Deployment 拥有并管理其 ReplicaSet。
因此，建议你在需要 ReplicaSet 时使用 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).
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).
-->
### 裸 Pod
与用户直接创建 Pod 的情况不同，ReplicaSet 会替换那些由于某些原因被删除或被终止的 Pod，例如在节点故障或破坏性的节点维护（如内核升级）的情况下。
因为这个好处，我们建议您使用 ReplicaSet，即使应用程序只需要一个 Pod。
想像一下，ReplicaSet 类似于进程监视器，只不过它在多个节点上监视多个 Pod，而不是在单个节点上监视单个进程。
与用户直接创建 Pod 的情况不同，ReplicaSet 会替换那些由于某些原因被删除或被终止的
Pod，例如在节点故障或破坏性的节点维护（如内核升级）的情况下。
因为这个原因，我们建议你使用 ReplicaSet，即使应用程序只需要一个 Pod。
想像一下，ReplicaSet 类似于进程监视器，只不过它在多个节点上监视多个 Pod，
而不是在单个节点上监视单个进程。
ReplicaSet 将本地容器重启的任务委托给了节点上的某个代理（例如，Kubelet 或 Docker）去完成。
<!--
### 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
Use a [`Job`](/docs/concepts/workloads/controllers/job/) instead of a ReplicaSet for Pods that are expected to terminate on their own
(that is, batch jobs).
-->
### Job
使用[`Job`](/zh/docs/concepts/workloads/controllers/job/) 代替ReplicaSet，可以用于那些期望自行终止的 Pod。
使用[`Job`](/zh/docs/concepts/workloads/controllers/job/) 代替ReplicaSet，
可以用于那些期望自行终止的 Pod。
<!--
### DaemonSet
@@ -441,11 +627,25 @@ machine-level function, such as machine monitoring or machine logging. These po
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.
-->
### DaemonSet
对于管理那些提供主机级别功能（如主机监控和主机日志）的容器，就要用[`DaemonSet`](/zh/docs/concepts/workloads/controllers/daemonset/) 而不用 ReplicaSet。
这些 Pod 的寿命与主机寿命有关：这些 Pod 需要先于主机上的其他 Pod 运行，并且在机器准备重新启动/关闭时安全地终止。
对于管理那些提供主机级别功能（如主机监控和主机日志）的容器，
就要用 [`DaemonSet`](/zh/docs/concepts/workloads/controllers/daemonset/)
而不用 ReplicaSet。
这些 Pod 的寿命与主机寿命有关：这些 Pod 需要先于主机上的其他 Pod 运行，
并且在机器准备重新启动/关闭时安全地终止。
### ReplicationController
<!--
ReplicaSets are the successors to [_ReplicationControllers_](/docs/concepts/workloads/controllers/replicationcontroller/).
The two serve the same purpose, and behave similarly, except that a ReplicationController does not support set-based
selector requirements as described in the [labels user guide](/docs/concepts/overview/working-with-objects/labels/#label-selectors).
As such, ReplicaSets are preferred over ReplicationControllers
-->
ReplicaSet 是 [ReplicationController](/zh/docs/concepts/workloads/controllers/replicationcontroller/)
的后继者。二者目的相同且行为类似，只是 ReplicationController 不支持
[标签用户指南](/zh/docs/concepts/overview/working-with-objects/labels/#label-selectors)
中讨论的基于集合的选择算符需求。
因此，相比于 ReplicationController，应优先考虑 ReplicaSet。