Linux——k8s、deployment、pod

Xinan_____2024-09-28 15:41
  1. 声明式配置文件：要求集群中的某一个资源，处于指定的状态。
  2. 集群中都有哪些可以管理的资源？
  3. 控制器： 用来控制pod数量、运行参数
  4. deployment 管理灵活，而pod的创建、删除、运行、更新等均无需直接操作pod，只需要更新deployment的配置

1.如何控制pod

复制代码 
deployment ----> replica set (基于template 运行的pod的数量)---> 创建服务需要的pod
[root@control ~]# cat nginx-deployment.yml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  selector:
    matchLabels:
      app: nginx
  replicas: 3
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:latest
        imagePullPolicy: IfNotPresent
        ports:
        - containerPort: 80


[root@control ~]# source  .kube/k8s_bash_completion
[root@control ~]# kubectl create -f  nginx-deployment.yml
deployment.apps/nginx-deployment created
[root@control ~]# kubectl get deployments.apps -l app=nginx
No resources found in default namespace.
[root@control ~]# kubectl get deployments.apps
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
my-nginx           2/2     2            2           3d21h
nginx-deployment   3/3     3            3           29s
[root@control ~]# kubectl describe deployments.apps nginx-deployment
Name:                   nginx-deployment
Namespace:              default
CreationTimestamp:      Tue, 24 Sep 2024 14:27:32 +0800
Labels:                 <none>
Annotations:            deployment.kubernetes.io/revision: 1
Selector:               app=nginx
Replicas:               3 desired | 3 updated | 3 total | 3 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Pod Template:
  Labels:  app=nginx
  Containers:
   nginx:
    Image:         nginx:latest
    Port:          80/TCP
    Host Port:     0/TCP
    Environment:   <none>
    Mounts:        <none>
  Volumes:         <none>
  Node-Selectors:  <none>
  Tolerations:     <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Available      True    MinimumReplicasAvailable
  Progressing    True    NewReplicaSetAvailable
OldReplicaSets:  <none>
NewReplicaSet:   nginx-deployment-bf56f49c (3/3 replicas created)
Events:
  Type    Reason             Age   From                   Message
  ----    ------             ----  ----                   -------
  Normal  ScalingReplicaSet  85s   deployment-controller  Scaled up replica set nginx-deployment-bf56f49c to 3
[root@control ~]# kubectl get rs  nginx-deployment-bf56f49c
NAME                        DESIRED   CURRENT   READY   AGE
nginx-deployment-bf56f49c   3         3         3       2m22s
[root@control ~]# kubectl get pods -l app=nginx
NAME                              READY   STATUS    RESTARTS   AGE
nginx-deployment-bf56f49c-9c8gw   1/1     Running   0          6m48s
nginx-deployment-bf56f49c-n59hg   1/1     Running   0          6m48s
nginx-deployment-bf56f49c-v887p   1/1     Running   0          6m48s
[root@control ~]# kubectl get pods -l app=nginx --show-labels
NAME                              READY   STATUS    RESTARTS   AGE     LABELS
nginx-deployment-bf56f49c-9c8gw   1/1     Running   0          7m32s   app=nginx,pod-template-hash=bf56f49c
nginx-deployment-bf56f49c-n59hg   1/1     Running   0          7m32s   app=nginx,pod-template-hash=bf56f49c
nginx-deployment-bf56f49c-v887p   1/1     Running   0          7m32s   app=nginx,pod-template-hash=bf56f49c
//为了保证工作节点有，需要更新的镜像，手动上传镜像到工作节点
[root@control ~]# docker save -o nginx-19.1.tar nginx:1.19.1
[root@control ~]# scp nginx-19.1.tar root@node1:/root
root@node1's password:
nginx-19.1.tar                                                                                                                                           0%    0     0nginx-19.1.tar                                                                                                                                          40%   52MB  52nginx-19.1.tar                                                                                                                                         100%  130MB  47
[root@control ~]# scp nginx-19.1.tar root@node2:/root
root@node2's password:
nginx-19.1.tar                                                                                                                                         100%  130MB  51.7MB/s   00:02
[root@node1 ~]# ctr -n k8s.io image import  nginx-19.1.tar
[root@node2 ~]# ctr -n k8s.io image import  nginx-19.1.tar
// 查看工作节点保存的镜像
[root@node2 ~]# crictl -r unix:///var/run/containerd/containerd.sock images

返回控制节点，进行更新操作
// 更新镜像
[root@control ~]# kubectl set image deployments nginx-deployment nginx=nginx:1.19.1
deployment.apps/nginx-deployment image updated
[root@control ~]# kubectl get pods -l app=nginx
NAME                                READY   STATUS    RESTARTS   AGE
nginx-deployment-7f588fbd68-bjd67   1/1     Running   0          9s
nginx-deployment-7f588fbd68-n2fls   1/1     Running   0          5s
nginx-deployment-7f588fbd68-qnwdn   1/1     Running   0          8s
[root@control ~]# kubectl describe deployments.apps nginx-deployment
Name:                   nginx-deployment
Namespace:              default
CreationTimestamp:      Tue, 24 Sep 2024 14:27:32 +0800
Labels:                 <none>
Annotations:            deployment.kubernetes.io/revision: 2
Selector:               app=nginx
Replicas:               3 desired | 3 updated | 3 total | 3 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Pod Template:
  Labels:  app=nginx
  Containers:
   nginx:
    Image:         nginx:1.19.1
    Port:          80/TCP
    Host Port:     0/TCP
    Environment:   <none>
    Mounts:        <none>
  Volumes:         <none>
  Node-Selectors:  <none>
  Tolerations:     <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Available      True    MinimumReplicasAvailable
  Progressing    True    NewReplicaSetAvailable
OldReplicaSets:  nginx-deployment-bf56f49c (0/0 replicas created)
NewReplicaSet:   nginx-deployment-7f588fbd68 (3/3 replicas created)
Events:
  Type    Reason             Age   From                   Message
  ----    ------             ----  ----                   -------
  Normal  ScalingReplicaSet  15m   deployment-controller  Scaled up replica set nginx-deployment-bf56f49c to 3
  Normal  ScalingReplicaSet  49s   deployment-controller  Scaled up replica set nginx-deployment-7f588fbd68 to 1
  Normal  ScalingReplicaSet  48s   deployment-controller  Scaled down replica set nginx-deployment-bf56f49c to 2 from 3
  Normal  ScalingReplicaSet  48s   deployment-controller  Scaled up replica set nginx-deployment-7f588fbd68 to 2 from 1
  Normal  ScalingReplicaSet  45s   deployment-controller  Scaled down replica set nginx-deployment-bf56f49c to 1 from 2
  Normal  ScalingReplicaSet  45s   deployment-controller  Scaled up replica set nginx-deployment-7f588fbd68 to 3 from 2
  Normal  ScalingReplicaSet  44s   deployment-controller  Scaled down replica set nginx-deployment-bf56f49c to 0 from 1
// deployment 更新后创建新的rs来启动新的容器，并保留原本的rs
// rs 一般只保留两个，除非额外配置
[root@control ~]# kubectl get rs
NAME                          DESIRED   CURRENT   READY   AGE
my-nginx-7549dd6888           2         2         2       3d21h
nginx-deployment-7f588fbd68   3         3         3       2m18s
nginx-deployment-bf56f49c     0         0         0       16m
[root@control ~]# kubectl edit deployments.apps nginx-deployment
复制代码 
deployment.apps/nginx-deployment edited
// 展示更新过程
// 失败的原因是无法拉取nginx 1.191 镜像
[root@control ~]# kubectl rollout status deployment nginx-deployment  
Waiting for deployment "nginx-deployment" rollout to finish: 1 out of 3 new replicas have been updated...
^C
[root@control ~]# kubectl get pods -l app=nginx

// 一个pod 状态错误 三个pod状态正常
NAME                                READY   STATUS             RESTARTS   AGE
nginx-deployment-6dc44567c6-85glr   0/1     ImagePullBackOff   0          54s
nginx-deployment-7f588fbd68-bjd67   1/1     Running            0          8m58s
nginx-deployment-7f588fbd68-n2fls   1/1     Running            0          8m54s
nginx-deployment-7f588fbd68-qnwdn   1/1     Running            0          8m57s
[root@control ~]# kubectl get deployments.apps nginx-deployment
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment   3/3     1            3           23m
// 查看更新历史
[root@control ~]# kubectl rollout history deployment nginx-deployment
deployment.apps/nginx-deployment
REVISION  CHANGE-CAUSE
1         <none>
2         <none>
3         <none>

// 查看第二次更新的参数
[root@control ~]# kubectl rollout history deployment nginx-deployment --revision=2
deployment.apps/nginx-deployment with revision #2
Pod Template:
  Labels:       app=nginx
        pod-template-hash=7f588fbd68
  Containers:
   nginx:
    Image:      nginx:1.19.1
    Port:       80/TCP
    Host Port:  0/TCP
    Environment:        <none>
    Mounts:     <none>
  Volumes:      <none>
  Node-Selectors:       <none>
  Tolerations:  <none>


// 回滚失败的更新
[root@control ~]# kubectl rollout undo deployment nginx-deployment
deployment.apps/nginx-deployment rolled back
[root@control ~]# kubectl get deployments.apps nginx-deployment
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment   3/3     3            3           27m

deployment 是最常见的无状态服务部署方式，常见的用例包括：

  1. 使用 Deployment 来创建 ReplicaSet。ReplicaSet 在后台创建 pod。检查启动状态，看它是成功还是失败。
  2. 然后，通过更新 Deployment 的 PodTemplateSpec 字段来声明 Pod 的新状态。这会创建一个新的 ReplicaSet，Deployment 会按照控制的速率将 pod 从旧的 ReplicaSet 移动到新的 ReplicaSet 中。
  3. 如果当前状态不稳定，回滚到之前的 Deployment revision。每次回滚都会更新 Deployment 的 revision。
  4. 扩容 Deployment 以满足更高的负载。
  5. 暂停 Deployment 来应用 PodTemplateSpec 的多个修复，然后恢复上线。
  6. 根据 Deployment 的状态判断上线是否 hang 住了。
  7. 清除旧的不必要的 ReplicaSet。

无状态服务和有状态服务最直接的区别就是：

  1. pod是否需要分配固定的存储
  2. pod是否需要固定的网络参数
  3. pod 启动顺序是否有序

对于有状态服务，一般使用statefulSet来实现，常见用例：

  1. 稳定的持久化存储，即 Pod 重新调度后还是能访问到相同的持久化数据，基于 PVC 来实现，eg: 关系型数据库
  2. 稳定的网络标志，即 Pod 重新调度后其 PodName 和 HostName 不变，基于 Headless Service（即没有 Cluster IP 的 Service）来实现
  3. 有序部署，有序扩展，即 Pod 是有顺序的，在部署或者扩展的时候要依据定义的顺序依次依次进行（即从 0 到 N-1，在下一个 Pod 运行之前所有之前的 Pod 必须都是 Running 和 Ready 状态），基于 init containers 来实现
  4. 有序收缩，有序删除（即从 N-1 到 0）

使用nginx 作为反向代理 // 无状态服务 不涉及任何真实应用数据

使用lnmp架构运行web应用 // 有状态服务 与应用代码，且数据库保存应用数据，因此数据一定需要进行持久化

使用nginx 作为statefulset的练习：

复制代码 
[root@control ~]# cat nginx-stateful.yml
apiVersion: v1
kind: Service
metadata:
  name: nginx
  labels:
    app: nginx
spec:
  ports:
  - port: 80
    name: web
  clusterIP: None
  selector:
    app: nginx
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: web
spec:
  serviceName: "nginx"
  replicas: 2
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.19.1
        imagePullPolicy: IfNotPresent
        ports:
        - containerPort: 80
          name: web
        volumeMounts:
        - name: www
          mountPath: /usr/share/nginx/html
  volumeClaimTemplates:
  - metadata:
      name: www
    spec:
      storageClassName: local-storage
      accessModes: [ "ReadWriteOnce" ]
      resources:
        requests:
          storage: 4Gi

[root@control ~]# cat pv-1.yml
apiVersion: v1
kind: PersistentVolume
metadata:
  name: example-pv
spec:
  capacity:
    storage: 4Gi
  volumeMode: Filesystem
  accessModes:
  - ReadWriteOnce
  persistentVolumeReclaimPolicy: Delete
  storageClassName: local-storage
  local:
    path: /mnt/lv/swap
  nodeAffinity:
    required:
      nodeSelectorTerms:
      - matchExpressions:
        - key: kubernetes.io/hostname
          operator: In
          values:
          - node1
[root@control ~]# cat pv-2.yml
apiVersion: v1
kind: PersistentVolume
metadata:
  name: example-pv2
spec:
  capacity:
    storage: 4Gi
  volumeMode: Filesystem
  accessModes:
  - ReadWriteOnce
  persistentVolumeReclaimPolicy: Delete
  storageClassName: local-storage
  local:
    path: /mnt/lv/swap
  nodeAffinity:
    required:
      nodeSelectorTerms:
      - matchExpressions:
        - key: kubernetes.io/hostname
          operator: In
          values:
          - node2
[root@control ~]# cat local_storage.yml
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: local-storage
provisioner: kubernetes.io/no-provisioner
volumeBindingMode: WaitForFirstConsumer
[root@control ~]# kubectl create -f local_storage.yml
storageclass.storage.k8s.io/local-storage created
[root@control ~]# kubectl get storageclasses.storage.k8s.io
NAME            PROVISIONER                    RECLAIMPOLICY   VOLUMEBINDINGMODE      ALLOWVOLUMEEXPANSION   AGE
local-storage   kubernetes.io/no-provisioner   Delete          WaitForFirstConsumer   false                  2s

node1 he node2
[root@node1 ~]# mkfs.xfs -f /dev/cs_bogon/swap
meta-data=/dev/cs_bogon/swap     isize=512    agcount=4, agsize=256768 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=1, sparse=1, rmapbt=0
         =                       reflink=1    bigtime=1 inobtcount=1 nrext64=0
data     =                       bsize=4096   blocks=1027072, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
log      =internal log           bsize=4096   blocks=16384, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
[root@node1 ~]# mkdir /mnt/lv/swap -p
[root@node1 ~]# mount /dev/cs_bogon/swap /mnt/lv/swap/

返回控制节点：
创建持久卷
[root@control ~]# kubectl create -f pv-1.yml
persistentvolume/example-pv created
[root@control ~]# kubectl create -f pv-2.yml
Error from server (AlreadyExists): error when creating "pv-2.yml": persistentvolumes "example-pv" already exists
[root@control ~]# vim pv-2.yml
[root@control ~]# kubectl create -f pv-2.yml
persistentvolume/example-pv2 created
[root@control ~]# kubectl get pv
NAME          CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM   STORAGECLASS    VOLUMEATTRIBUTESCLASS   REASON   AGE
example-pv    4Gi        RWO            Delete           Available           local-storage   <unset>                          25s
example-pv2   4Gi        RWO            Delete           Available           local-storage   <unset>                          6s
[root@control ~]# kubectl apply -f nginx-stateful.yml
service/nginx created
statefulset.apps/web created
[root@control ~]# kubectl get statefulsets.apps
NAME   READY   AGE
web    2/2     7s
[root@control ~]# kubectl get pvc
NAME        STATUS   VOLUME        CAPACITY   ACCESS MODES   STORAGECLASS    VOLUMEATTRIBUTESCLASS   AGE
www-web-0   Bound    example-pv    4Gi        RWO            local-storage   <unset>                 16s
www-web-1   Bound    example-pv2   4Gi        RWO            local-storage   <unset>                 14s
[root@control ~]# kubectl describe statefulsets.apps web
Name:               web
Namespace:          default
CreationTimestamp:  Tue, 24 Sep 2024 17:18:48 +0800
Selector:           app=nginx
Labels:             <none>
Annotations:        <none>
Replicas:           2 desired | 2 total
Update Strategy:    RollingUpdate
  Partition:        0
Pods Status:        2 Running / 0 Waiting / 0 Succeeded / 0 Failed
Pod Template:
  Labels:  app=nginx
  Containers:
   nginx:
    Image:        nginx:1.19.1
    Port:         80/TCP
    Host Port:    0/TCP
    Environment:  <none>
    Mounts:
      /usr/share/nginx/html from www (rw)
  Volumes:         <none>
  Node-Selectors:  <none>
  Tolerations:     <none>
Volume Claims:
  Name:          www
  StorageClass:  local-storage
  Labels:        <none>
  Annotations:   <none>
  Capacity:      4Gi
  Access Modes:  [ReadWriteOnce]
Events:
  Type    Reason            Age   From                    Message
  ----    ------            ----  ----                    -------
  Normal  SuccessfulCreate  55s   statefulset-controller  create Claim www-web-0 Pod web-0 in StatefulSet web success
  Normal  SuccessfulCreate  55s   statefulset-controller  create Pod web-0 in StatefulSet web successful
  Normal  SuccessfulCreate  53s   statefulset-controller  create Claim www-web-1 Pod web-1 in StatefulSet web success
  Normal  SuccessfulCreate  53s   statefulset-controller  create Pod web-1 in StatefulSet web successful
[root@control ~]# kubectl get pods --watch -l app=nginx
NAME                                READY   STATUS    RESTARTS   AGE
nginx-deployment-7f588fbd68-bjd67   1/1     Running   0          160m
nginx-deployment-7f588fbd68-n2fls   1/1     Running   0          160m
nginx-deployment-7f588fbd68-qnwdn   1/1     Running   0          160m
web-0                               1/1     Running   0          3m15s
web-1                               1/1     Running   0          3m13s
^C[root@control ~]# kubectl delete pod -l app=nginx
pod "nginx-deployment-7f588fbd68-bjd67" deleted
pod "nginx-deployment-7f588fbd68-n2fls" deleted
pod "nginx-deployment-7f588fbd68-qnwdn" deleted
pod "web-0" deleted
pod "web-1" deleted

[root@control ~]#
[root@control ~]# kubectl get statefulsets.apps
NAME   READY   AGE
web    2/2     4m43s
[root@control ~]# kubectl get pods  -l app=nginx
NAME                                READY   STATUS    RESTARTS   AGE
nginx-deployment-7f588fbd68-4lrb5   1/1     Running   0          36s
nginx-deployment-7f588fbd68-8jnm5   1/1     Running   0          36s
nginx-deployment-7f588fbd68-mvgzg   1/1     Running   0          36s
web-0                               1/1     Running   0          35s
web-1                               1/1     Running   0          33s
[root@control ~]# kubectl describe statefulsets.apps web
Name:               web
Namespace:          default
CreationTimestamp:  Tue, 24 Sep 2024 17:18:48 +0800
Selector:           app=nginx
Labels:             <none>
Annotations:        <none>
Replicas:           2 desired | 2 total
Update Strategy:    RollingUpdate
  Partition:        0
Pods Status:        2 Running / 0 Waiting / 0 Succeeded / 0 Failed
Pod Template:
  Labels:  app=nginx
  Containers:
   nginx:
    Image:        nginx:1.19.1
    Port:         80/TCP
    Host Port:    0/TCP
    Environment:  <none>
    Mounts:
      /usr/share/nginx/html from www (rw)
  Volumes:         <none>
  Node-Selectors:  <none>
  Tolerations:     <none>
Volume Claims:
  Name:          www
  StorageClass:  local-storage
  Labels:        <none>
  Annotations:   <none>
  Capacity:      4Gi
  Access Modes:  [ReadWriteOnce]
Events:
  Type    Reason            Age                  From                    Message
  ----    ------            ----                 ----                    -------
  Normal  SuccessfulCreate  5m16s                statefulset-controller  create Claim www-web-0 Pod web-0 in StatefulSet web success
  Normal  SuccessfulCreate  5m14s                statefulset-controller  create Claim www-web-1 Pod web-1 in StatefulSet web success
  Normal  SuccessfulCreate  48s (x2 over 5m16s)  statefulset-controller  create Pod web-0 in StatefulSet web successful
  Normal  SuccessfulCreate  46s (x2 over 5m14s)  statefulset-controller  create Pod web-1 in StatefulSet web successful
[root@control ~]# for i in 0 1; do kubectl exec web-$i -- sh -c 'hostname'; done
web-0
web-1

结论：pod名称和持久卷的绑定都不会发生改变，因此可以实现数据和通信（无论pod如何变更，可以基于pod的名称进行通信）的固定。

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