Kubernetes 简明教程

Kubernetes - Replica Sets

副本集确保应该运行多少副本的 Pod。可以将其视为副本控制器的替代方案。副本集与副本控制器之间的主要区别是，副本控制器仅支持基于等式的选择器，而副本集支持基于集合的选择器。

Replica Set ensures how many replica of pod should be running. It can be considered as a replacement of replication controller. The key difference between the replica set and the replication controller is, the replication controller only supports equality-based selector whereas the replica set supports set-based selector.

apiVersion: extensions/v1beta1 --------------------->1
kind: ReplicaSet --------------------------> 2
metadata:
   name: Tomcat-ReplicaSet
spec:
   replicas: 3
   selector:
      matchLables:
         tier: Backend ------------------> 3
      matchExpression:
{ key: tier, operation: In, values: [Backend]} --------------> 4
template:
   metadata:
      lables:
         app: Tomcat-ReplicaSet
         tier: Backend
      labels:
         app: App
         component: neo4j
   spec:
      containers:
      - name: Tomcat
      image: tomcat: 8.0
      ports:
      - containerPort: 7474

Setup Details

  1. apiVersion: extensions/v1beta1 → In the above code, the API version is the advanced beta version of Kubernetes which supports the concept of replica set.

  2. kind: ReplicaSet → We have defined the kind as the replica set which helps kubectl to understand that the file is used to create a replica set.

  3. tier: Backend → We have defined the label tier as backend which creates a matching selector.

  4. {key: tier, operation: In, values: [Backend]} → This will help matchExpression to understand the matching condition we have defined and in the operation which is used by matchlabel to find details.

使用 kubectl 运行上述文件，并使用 yaml 文件中提供的定义创建后端副本集。

Run the above file using kubectl and create the backend replica set with the provided definition in the yaml file.

kube service backend replicaset