Kubernetes 简明教程

Kubernetes - Replication Controller

副本控制器是 Kubernetes 的一项主要特性，用于管理 Pod 生命周期。它的作用是确保在任何时间点都运行指定数量的副本 Pod。在希望确保运行指定数量的 Pod 或至少运行一个 Pod 时使用它。它具有增加或减少指定数量的 Pod 的能力。

Replication Controller is one of the key features of Kubernetes, which is responsible for managing the pod lifecycle. It is responsible for making sure that the specified number of pod replicas are running at any point of time. It is used in time when one wants to make sure that the specified number of pod or at least one pod is running. It has the capability to bring up or down the specified no of pod.

最好使用副本控制器管理 Pod 生命周期，而不是反复创建 Pod。

It is a best practice to use the replication controller to manage the pod life cycle rather than creating a pod again and again.

apiVersion: v1
kind: ReplicationController --------------------------> 1
metadata:
   name: Tomcat-ReplicationController --------------------------> 2
spec:
   replicas: 3 ------------------------> 3
   template:
      metadata:
         name: Tomcat-ReplicationController
      labels:
         app: App
         component: neo4j
      spec:
         containers:
         - name: Tomcat- -----------------------> 4
         image: tomcat: 8.0
         ports:
            - containerPort: 7474 ------------------------> 5

Setup Details

  1. Kind: ReplicationController → In the above code, we have defined the kind as replication controller which tells the kubectl that the yaml file is going to be used for creating the replication controller.

  2. name: Tomcat-ReplicationController → This helps in identifying the name with which the replication controller will be created. If we run the kubctl, get rc < Tomcat-ReplicationController > it will show the replication controller details.

  3. replicas: 3 → This helps the replication controller to understand that it needs to maintain three replicas of a pod at any point of time in the pod lifecycle.

  4. name: Tomcat → In the spec section, we have defined the name as tomcat which will tell the replication controller that the container present inside the pods is tomcat.

  5. containerPort: 7474 → It helps in making sure that all the nodes in the cluster where the pod is running the container inside the pod will be exposed on the same port 7474.

kube service replicas

在此处，Kubernetes 服务充当三个 tomcat 副本的负载均衡器。

Here, the Kubernetes service is working as a load balancer for three tomcat replicas.