One 、Pod Controller Introduction

stay kubernetes in , according to pod Can be divided into two categories ：
Autonomous pod：kubernetes Created directly Pod, such pod After deleting it, it's gone , It won't rebuild
Created by controller pod：kubernetes Created by the controller pod, such pod After deletion, it will be rebuilt automatically

1.Pod controller

​ Pod The controller is the manager pod The middle tier , Use Pod After the controller , Just tell Pod controller , How many and what kind of Pod That's all right. , It will create a that meets the conditions Pod And ensure that every Pod The resource is in the desired target state . If Pod The resource failed while running , It will be rearranged based on the specified policy Pod.

2.Pod Controller type

Controller type	effect
ReplicaSet	Ensure that the number of copies is maintained at the desired value , And support pod Quantity expansion and contraction capacity , Mirror version upgrade
Deployment	By controlling ReplicaSet To control Pod, And support rolling upgrade 、 Rollback version
Horizontal Pod Autoscaler	It can be adjusted automatically according to the cluster load level Pod The number of , To cut peak and fill valley
DaemonSet	Specified in the cluster Node Run on and only one copy , Generally used for tasks of daemon classes
Job	It created pod Quit as soon as you finish the task , There is no need to reboot or rebuild , Used to perform one-time tasks
Cronjob	It creates Pod Responsible for periodic task control , You don't need to keep running in the background
StatefulSet	Manage stateful applications

Two 、ReplicaSet(RS)

ReplicaSet The main function of Guarantee a certain amount of pod The normal operation , It will continue to monitor these Pod Operating state , once Pod failure , Will restart or rebuild . It also supports pod The amount of expansion and reduction and the upgrade and downgrade of the image version .

[root@t3-tkhijbs-jcsszy-app09 yaml]# cat nginx-pod.yaml 
apiVersion: apps/v1
kind: ReplicaSet   
metadata:
  name: pc-replicaset
  namespace: dev
spec:
  replicas: 3
  selector: 
    matchLabels:
      app: nginx-pod
  template:
    metadata:
      labels:
        app: nginx-pod
    spec:
      containers:
      - name: nginx
        image: nginx

In this , The configuration item that needs new understanding is spec The following options ：
（1）replicas： Specify the number of copies , In fact, it is the current rs created pod The number of , The default is 1
（2）selector： Selectors , What it does is it establishes pod Controller and pod The relationship between , Adopted Label Selector Mechanism in pod Define... On the template label, Define a selector on the controller （selector）, It can indicate what the current controller can manage pod 了
（3）template： Templates , Is the current controller creation pod Template used , It's actually what I explained earlier pod The definition of

1. expand shrink pod Number

[root@t3-tkhijbs-jcsszy-app09 ~]# kubectl get ReplicaSet -n dev
NAME            DESIRED   CURRENT   READY   AGE
pc-replicaset   3         3         3       27m

[root@t3-tkhijbs-jcsszy-app09 ~]# kubectl edit rs pc-replicaset -n dev
# edit rs Number of copies of , modify spec:replicas: 5 that will do  . This quantity is modified according to your requirements 

2. Mirror elevation

[root@t3-tkhijbs-jcsszy-app09 ~]# kubectl edit rs pc-replicaset -n dev
# Directly modify the image version 

3. Delete RS

[root@t3-tkhijbs-jcsszy-app09 ~]# kubectl delete rs pc-replicaset -n dev
 perhaps 
[root@t3-tkhijbs-jcsszy-app09 yaml]# kubectl delete -f nginx-pod.yaml 

3、 ... and 、deployment(deploy)

In order to better solve the problem of service orchestration ,kubernetes stay V1.2 Version start , Introduced Deployment controller . It is worth mentioning that , This kind of controller doesn't directly manage pod, It's through management ReplicaSet To introduce management Pod, namely ：Deployment management ReplicaSet,ReplicaSet management Pod. therefore Deployment Than ReplicaSet More powerful .
Support ReplicaSet All functions of
Support the stop of Publishing 、 continue
Support rolling upgrade and rollback version

[root@t3-tkhijbs-jcsszy-app09 yaml]# cat nginx-pod.yaml 
apiVersion: apps/v1
kind: Deployment      
metadata:
  name: pc-deployment
  namespace: dev
spec: 
  replicas: 3
  selector:
    matchLabels:
      app: nginx-pod
  template:
    metadata:
      labels:
        app: nginx-pod
    spec:
      containers:
      - name: nginx
        image: nginx

[root@t3-tkhijbs-jcsszy-app09 yaml]# kubectl apply -f nginx-pod.yaml 
deployment.apps/pc-deployment created

1.Pod Vessel expansion and contraction capacity

[root@t3-tkhijbs-jcsszy-app09 yaml]# kubectl get pod -n dev
NAME                             READY   STATUS    RESTARTS   AGE
pc-deployment-7d4f548fb9-mlksf   1/1     Running   0          94s
pc-deployment-7d4f548fb9-w5p2l   1/1     Running   0          94s
pc-deployment-7d4f548fb9-xlvvv   1/1     Running   0          94s

[root@t3-tkhijbs-jcsszy-app09 yaml]# kubectl edit deploy pc-deployment -n dev
# Just change the number here 
replicas: 5

[root@t3-tkhijbs-jcsszy-app09 yaml]# kubectl get pod -n dev
NAME                             READY   STATUS    RESTARTS   AGE
pc-deployment-7d4f548fb9-5z7n8   1/1     Running   0          27s
pc-deployment-7d4f548fb9-gfg7p   1/1     Running   0          27s
pc-deployment-7d4f548fb9-mlksf   1/1     Running   0          3m43s
pc-deployment-7d4f548fb9-w5p2l   1/1     Running   0          3m43s
pc-deployment-7d4f548fb9-xlvvv   1/1     Running   0          3m43s

2. Version rollback

2.1 --record

This parameter will record the update process

[root@t3-tkhijbs-jcsszy-app09 yaml]# cat nginx-pod.yaml 
apiVersion: apps/v1
kind: Deployment      
metadata:
  name: pc-deployment
  namespace: dev
spec: 
  replicas: 3
  selector:
    matchLabels:
      app: nginx-pod
  template:
    metadata:
      labels:
        app: nginx-pod
    spec:
      containers:
      - name: nginx
        image: nginx:1.17.1

[root@t3-tkhijbs-jcsszy-app09 yaml]# kubectl apply -f nginx-pod.yaml --record
deployment.apps/pc-deployment created

[root@t3-tkhijbs-jcsszy-app09 ~]# kubectl get rs -n dev
NAME                       DESIRED   CURRENT   READY   AGE
pc-deployment-858db84f89   3         3         3       9s

[root@t3-tkhijbs-jcsszy-app09 ~]# kubectl get pod -n dev -w
NAME                             READY   STATUS    RESTARTS   AGE
pc-deployment-858db84f89-8r5kg   1/1     Running   0          20s
pc-deployment-858db84f89-lc7wb   1/1     Running   0          20s
pc-deployment-858db84f89-s4f8f   1/1     Running   0          20s

Start updating mirror

kubectl set image deployment pc-deployment nginx=nginx:1.17.2 -n dev

After the update, I found , A new rs controller pc-deployment-6c78d7875b

[root@t3-tkhijbs-jcsszy-app09 ~]# kubectl get rs -n dev
NAME                       DESIRED   CURRENT   READY   AGE
pc-deployment-6c78d7875b   3         3         3       85s
pc-deployment-858db84f89   0         0         0       4m14s

new pod Is based on pc-deployment-6c78d7875b Produced

[root@t3-tkhijbs-jcsszy-app09 ~]# kubectl get pod -n dev
NAME                             READY   STATUS    RESTARTS   AGE
pc-deployment-6c78d7875b-9j27t   1/1     Running   0          3m1s
pc-deployment-6c78d7875b-c4wfl   1/1     Running   0          3m
pc-deployment-6c78d7875b-k5jsc   1/1     Running   0          2m57s

2.2 rollout

kubectl rollout： Version upgrade related functions , The following options are supported ：
status Displays the current upgrade status
history Show Upgrade history
pause Pause the version upgrade process
resume Continue the suspended version upgrade process
restart Restart the version upgrade process
undo Roll back to the previous version （ have access to –to-revision Rollback to specified version ）

example ：

[root@t3-tkhijbs-jcsszy-app09 yaml]# cat nginx-pod.yaml 
apiVersion: apps/v1
kind: Deployment      
metadata:
  name: pc-deployment
  namespace: dev
spec: 
  replicas: 3
  selector:
    matchLabels:
      app: nginx-pod
  template:
    metadata:
      labels:
        app: nginx-pod
    spec:
      containers:
      - name: nginx
        image: nginx:1.17.1

[root@t3-tkhijbs-jcsszy-app09 yaml]# kubectl apply -f nginx-pod.yaml --record
deployment.apps/pc-deployment created

[root@t3-tkhijbs-jcsszy-app09 yaml]# kubectl get rs -n dev
NAME                       DESIRED   CURRENT   READY   AGE
pc-deployment-858db84f89   3         3         3       23s

[root@t3-tkhijbs-jcsszy-app09 yaml]# kubectl get pod -n dev
NAME                             READY   STATUS    RESTARTS   AGE
pc-deployment-858db84f89-khkml   1/1     Running   0          29s
pc-deployment-858db84f89-swkkv   1/1     Running   0          29s
pc-deployment-858db84f89-tnn8z   1/1     Running   0          29s

Change the mirror version

[root@t3-tkhijbs-jcsszy-app09 yaml]# vim nginx-pod.yaml 
  image: nginx:1.17.2

Update configuration

[root@t3-tkhijbs-jcsszy-app09 yaml]# kubectl apply -f nginx-pod.yaml --record
deployment.apps/pc-deployment configured

View update history

[root@t3-tkhijbs-jcsszy-app09 ~]# kubectl rollout history deploy pc-deployment -n dev
deployment.apps/pc-deployment 
REVISION  CHANGE-CAUSE
1         kubectl apply --filename=nginx-pod.yaml --record=true
2         kubectl apply --filename=nginx-pod.yaml --record=true

rs The controller has also been updated

[root@t3-tkhijbs-jcsszy-app09 ~]# kubectl get rs -n dev
NAME                       DESIRED   CURRENT   READY   AGE
pc-deployment-6c78d7875b   3         3         3       19m
pc-deployment-858db84f89   0         0         0       33m

Start rolling back to the previous version

I'm going to use it directly here –to-revision=1 Rolled back to 1 edition , If you omit this option , Is to go back to the previous version

[root@t3-tkhijbs-jcsszy-app09 ~]# kubectl rollout undo deployment pc-deployment --to-revision=1 -n dev
deployment.apps/pc-deployment rolled back

[root@t3-tkhijbs-jcsszy-app09 ~]# kubectl get rs -n dev
NAME                       DESIRED   CURRENT   READY   AGE
pc-deployment-6c78d7875b   0         0         0       21m
pc-deployment-858db84f89   3         3         3       34m