k8s practice (d): Controller

Environment Description:

CPU name	Operating system version	ip	docker version	omelets version	Configuration	Remark
master	Centos 06/07/1810	172.27.9.131	Docker 18.09.6	V1.14.2	2C2G	Remark
node01	Centos 06/07/1810	172.27.9.135	Docker 18.09.6	V1.14.2	2C2G	Remark
node02	Centos 06/07/1810	172.27.9.136	Docker 18.09.6	V1.14.2	2C2G	Remark

 

k8s cluster deployment see: Centos7.6 deployment k8s (v1.14.2) cluster
k8s learning materials See: basic concepts, kubectl command and information sharing

 

A, Kubernetes core components

1. Core Component Overview

Kubernetes mainly consists of the following core components:

• etcd saves the state of the entire cluster;
• apiserver provides the only entrance resources operations, and to provide authentication, authorization, access control, API registration and discovery mechanisms;
• controller manager responsible for maintaining the state of the cluster, such as fault detection, automatic extension, rollover, etc.;
• the scheduler is responsible for scheduling resources according to a predetermined scheduling policy to schedule the Pod corresponding machine;
• kubelet responsible for maintaining the life cycle of the container, it is also responsible for managing Volume (CVI) and network (CNI) of;
• Container runtime is responsible for image management and Pod and containers actually run (CRI);
• kube-proxy cluster is responsible for providing internal services for the Service Discovery and Load Balancing

Deployment Process

2. Check the core components

Kubelet is the only component that has to run as a regular component of the system, which the other components to run as a pod.

2.1 View Kubelet

master node and the node can be viewed

[root@master ~]# systemctl status kubelet

2.2 View other components

[root@master ~]# kubectl get po -o custom-columns=POD:metadata.name,NODE:spec.nodeName --sort-by spec.nodeName -n kube-system

!

This article focuses on the core components of controller manager
 
each resource shorthand View:

[root@master ~]# kubectl api-resources 

二、Controller Manager

1 Introduction

    Controller Manager由kube-controller-manager和cloud-controller-manager组成，是Kubernetes的大脑，它通过apiserver监控维护整个集群的状态，比如故障检测、自动扩展、滚动更新等并确保集群处于预期的工作状态。

    cloud-controller-manager 在 Kubernetes 启用 Cloud Provider 的时候才需要，用来配合云服务提供商的控制，如：Node Controller、Route Controller、Service Controller。

2. 原理

    Controller Manager是Kubernetes集群内部的管理控制中心， 负责Kubernetes集群内的Node、 Pod、服务端点、 服务、 资源配额、 命名空间 、服务账号等资源的管理 、 自动化部署、健康监测， 并对异常资源执行自动化修复， 确保集群各资源始终处于预期的工作状态 。 比如， 当某个Node意外若机时，Controller Manager会根据资源调度策略选择集群内其他节点自动部署原右机节点上的Pod副本 。
    Controller Manager是 一 个控制器集合， 包含Replication Controller、Deployment Controller、RelicaSet、StatefulSet Controller、Daemon Controller、CronJob Controller、Node Controller、Resourcequota Controller 、Namespace Controller 、ServiceAccount Controller 、Token Controller、Service Controller及Endpoint Controller等多个控制器，Controller Manager是这些控制器的核心管理者。 一般来说， 智能系统和自动系统通常会通过一个操纵系统来不断修正系统的状态。 在Kubernetes集群中， 每个控制器的核心工作原理就是：每个控制器通过API服务器来查看系统的运行状态， 并尝试着将系统状态从“ 现有状态 ”修正到“期望状态”。

三、ReplicationController

1. 简介

ReplicationController会持续监控正在运行的pod列表，确保pod的数量始终与其标签选择器匹配，ReplicationController由三部分组成：

• label selector(标签选择器),用于确定ReplicationController作用域中有哪些pod
• replica count(副本个数),指定应运行的pod 数量
• pod template(pod模板),用于创建新的pod 副本

2. 创建ReplicationController

[root@master ~]# more nginx-rc.yaml 
apiVersion: v1
kind: ReplicationController    #类型为ReplicationController
metadata:
  name: nginx        #ReplicationController名字
spec:
  replicas: 3        #pod实例数目
  selector:          #pod选择器
    app: nginx
  template:          #pod模板
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx

3. 查看ReplicationController

[root@master ~]# kubectl get rc
[root@master ~]# kubectl describe rc nginx 

4. 扩缩容

扩缩容可以采用修改pod模板和直接命令方式

扩容

[root@master ~]# kubectl edit rc nginx 

缩容

[root@master ~]# kubectl scale rc nginx --replicas=4

5. 删除pod

[root@master ~]# kubectl delete po nginx-2twcf

删除pod nginx-2twcf，发现该pod被删除的同时k8s自动新增一个pod nginx-vtmt4，这也印证了之前简介中讲的"ReplicationController会持续监控正在运行的pod列表，确保pod的数量始终与其标签选择器匹配"

6. 删除ReplicationController

[root@master ~]# kubectl delete rc nginx 

删除ReplicationController会将其管理的pod一并删除，如果想保留pod，可以添加参数"--cascade = false"

7. 标签

7.1 新增标签

[root@master ~]# kubectl label po nginx-28d4k env=prod

7.2 查看标签

[root@master ~]# kubectl get po --show-labels 

7.3 更改标签

[root@master ~]# kubectl label po nginx-28d4k app=test --overwrite

更改app=nginx的标签，这将使该pod不再与ReplicationController的标签选择器匹配，只剩两个匹配的pod，ReplicationController会启动一个新的pod nginx-64w44将总数量恢复为3个。

四、ReplicaSet

1. 简介

ReplicaSet的行为与ReplicationController完全相同,但pod选择器的表达能力更强,是新一代的ReplicationController,并且将其完全替换掉(ReplicationController最终将被弃用).

2. 创建ReplicaSet

[root@master ~]# more httpd-rs.yaml 
apiVersion: apps/v1    #api版本
kind: ReplicaSet
metadata:
  name: httpd 
spec:
  replicas: 3
  selector:
    matchExpressions:
      - key: app        #标签名为app
        operator: In    #In : Label的值必须与其中一个指定的values匹配
        values:
         - httpd        #标签值为httpd
  template:             #replicaset模板
    metadata:
      labels:
        app: httpd 
    spec:
      containers:
      - name: httpd 
        image: httpd 

ReplicaSet相对于ReplicationController的主要改进是它更具表达力的标签选择器，ReplicaSet的pod选择器的表达能力更强。

3. 查看ReplicaSet

[root@master ~]# kubectl get rs
[root@master ~]# kubectl describe rs httpd 

4. 删除ReplicaSet

[root@master ~]# kubectl delete rs httpd

同理，如需保留pod可以添加参数--cascade=false

五、Deployment

1. 简介

Deployment为Pod和Replica Set(下一代 Replication Controller)提供声明式更新。你只需要在Deployment中描述你想要的目标状态是什么,Deployment controller就会帮你将Pod和Replica Set的实际状态改变到你的目标状态。你可以定义一个全新的Deployment,也可以创建一个新的替换旧的Deployment。
 
Deployment的典型应用场景 包括：

• 定义Deployment来创建Pod和ReplicaSet
• 滚动升级和回滚应用
• 扩容和缩容
• 暂停和继续Deployment

2. Deployment实践

Deployment相关操作详见：k8s实践(三)：pod常用操作

六、DaemonSet

1. 简介

与Replicationcontroller和ReplicaSet在Kubemetes集群上运行部署特定数量的pod不同,DaemonSet每个Node上最多只能运行一个副本,如果节点下线,DaemonSet不会在其他地方重新创建pod,当将一个新节点添加到集群中时,DaemonSet会立刻部署一个新的pod实例。如果有人无意删除了一个pod，它也会从配置的pod模板中创建新的pod。

 

DaemonSet保证在每个Node上都运行一个容器副本，常用来部署一些集群的日志、监控或者其他系统管理应用。典型的应用包括：

• 日志收集，比如fluentd，logstash等
• 系统监控，比如Prometheus Node Exporter，collectd，New Relic agent，Gangliagmond等
• 系统程序，比如kube-proxy, kube-dns, glusterd, ceph等

本文以日志搜集工具filebeat为例实践

2. Create DaemonSet

[root@master ~]# more filebeat-ds.yaml 
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: filebeat-ds
  labels:
    app: filebeat
spec:
  selector:
    matchLabels:
      app: filebeat
  template:
    metadata:
      labels:
        app: filebeat
      name: filebeat
    spec:
      containers:
      - name: filebeat
        image: ikubernetes/filebeat:5.6.5-alpine
        env:
        - name: REDIS_HOST
          value: db.ilinux.io:6379
        - name: LOG_LEVEL
          value: info
[root@master ~]# kubectl apply -f filebeat-ds.yaml 
daemonset.apps/filebeat-ds created

3. Check DaemonSet

[root@master ~]# kubectl get ds
[root@master ~]# kubectl describe ds filebeat-ds 
[root@master ~]# kubectl get po -o wide 

View Log

4. Update DaemonSet

[root@master ~]# kubectl set image daemonsets filebeat-ds filebeat=ikubernetes/filebeat:5.6.6-alpine

DaemonSet update image by dropping and new ways

5. rollback DaemonSet

Version 5.1 query history

[root@master ~]# kubectl rollout history ds filebeat-ds 

5.2 query a version history details

[root@master ~]# kubectl rollout history ds filebeat-ds --revision=1
[root@master ~]# kubectl rollout history ds filebeat-ds --revision=2

5.3 Rollback

[root@master ~]# kubectl rollout undo ds filebeat-ds --to-revision=1

5.4 View DaemonSet state

[root@master ~]# kubectl rollout status ds/filebeat-ds
daemon set "filebeat-ds" successfully rolled out
[root@master ~]# kubectl describe ds filebeat-ds |grep Image
    Image:      ikubernetes/filebeat:5.6.5-alpine

6. Delete DaemonSet

[root@master ~]# kubectl delete ds filebeat-ds 
daemonset.extensions "filebeat-ds" deleted

Seven, Job

1 Introduction

From the run up to distinguish between the form of the program, we can Pod divided into two categories: long-running service (http server, daemon, mysql) and one-time tasks (such as parallel data calculations, tests, batch programs, etc.). When the service is running Pod ReplicationController, ReplicaSet and DaemonSet create is long, and Pod Job creation is a one-time service.

2. Create a job

[root@master ~]# more job.yaml 
apiVersion: batch/v1    #api版本为batch/v1
kind: Job
metadata:
  name: pi
spec:
  template:
    spec:
      containers:
      - name: pi
        image: perl
        command: ["perl",  "-Mbignum=bpi", "-wle", "print bpi(2000)"]
      restartPolicy: Never    #设置容器失败后不重启，即直接新建pod
  backoffLimit: 4    #限制新建pod数目，默认为6
[root@master ~]# kubectl apply -f job.yaml 
job.batch/pi created

3. Review the job

[root@master ~]# kubectl get job
[root@master ~]# kubectl get po -o wide 

View job run results

[root@master ~]# kubectl logs pi-g2499 

The precise job is required to 2000 pi

4. Parallel job

[root@master ~]# more multi-job.yaml 
apiVersion: batch/v1
kind: Job
metadata:
  name: multi-job
spec:
  completions: 10    #设置Job成功完成Pod的总数
  parallelism: 2    #pod并行执行数
  template:
    metadata:
      labels:
        app: multi-job
    spec:
      restartPolicy: OnFailure    #设置容器失败后重启
      containers:
      - name: busybox
        image: busybox
[root@master ~]# kubectl apply -f multi-job.yaml 
job.batch/multi-job created

Every two run job, the number of pod final run was 10

5. Cronjob

New cronjob

[root@master ~]# more cronjob.yaml 
apiVersion: batch/v1beta1 
kind: CronJob
metadata:
  name: hello
spec:
  schedule: "*/1 * * * *"
  jobTemplate:
    spec:
      template:
        spec:
          containers:
          - name: hello
            image: busybox
            args:
            - /bin/sh
            - -c
            - date; echo Hello from the Kubernetes cluster
          restartPolicy: OnFailure
[root@master ~]# kubectl apply -f cronjob.yaml 
cronjob.batch/hello created

View cronjob

[root@master ~]# kubectl get cronjobs
[root@master ~]# kubectl get job --watch

Every minute job will generate a

6. Delete the job

[root@master ~]# kubectl delete job pi multi-job
[root@master ~]# kubectl delete cronjobs hello

 
 

In this paper all scripts and configuration files have been uploaded GitHub: https://github.com/loong576/k8s-Controller.git