Kubernetes K8S之固定节点nodeName和nodeSelector调度详解与示例
主机配置规划
| 服务器名称(hostname) | 系统版本 | 配置 | 内网IP | 外网IP(模拟) |
|---|---|---|---|---|
| k8s-master | CentOS7.7 | 2C/4G/20G | 172.16.1.110 | 10.0.0.110 |
| k8s-node01 | CentOS7.7 | 2C/4G/20G | 172.16.1.111 | 10.0.0.111 |
| k8s-node02 | CentOS7.7 | 2C/4G/20G | 172.16.1.112 | 10.0.0.112 |
nodeName调度
nodeName是节点选择约束的最简单形式，但是由于其限制，通常很少使用它。nodeName是PodSpec的领域。
pod.spec.nodeName将Pod直接调度到指定的Node节点上，会【跳过Scheduler的调度策略】，该匹配规则是【强制】匹配。可以越过Taints污点进行调度。
nodeName用于选择节点的一些限制是：
- 如果指定的节点不存在，则容器将不会运行，并且在某些情况下可能会自动删除。
- 如果指定的节点没有足够的资源来容纳该Pod，则该Pod将会失败，并且其原因将被指出，例如OutOfmemory或OutOfcpu。
- 云环境中的节点名称并非总是可预测或稳定的。
nodeName示例
获取当前的节点信息
1 [root@k8s-master scheduler]# kubectl get nodes -o wide 2 NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME 3 k8s-master Ready master 42d v1.17.4 172.16.1.110 <none> CentOS Linux 7 (Core) 3.10.0-1062.el7.x86_64 docker://19.3.8 4 k8s-node01 Ready <none> 42d v1.17.4 172.16.1.111 <none> CentOS Linux 7 (Core) 3.10.0-1062.el7.x86_64 docker://19.3.8 5 k8s-node02 Ready <none> 42d v1.17.4 172.16.1.112 <none> CentOS Linux 7 (Core) 3.10.0-1062.el7.x86_64 docker://19.3.8
当nodeName指定节点存在
要运行的yaml文件
1 [root@k8s-master scheduler]# pwd 2 /root/k8s_practice/scheduler 3 [root@k8s-master scheduler]# cat scheduler_nodeName.yaml 4 apiVersion: apps/v1 5 kind: Deployment 6 metadata: 7 name: scheduler-nodename-deploy 8 labels: 9 app: nodename-deploy 10 spec: 11 replicas: 5 12 selector: 13 matchLabels: 14 app: myapp 15 template: 16 metadata: 17 labels: 18 app: myapp 19 spec: 20 containers: 21 - name: myapp-pod 22 image: registry.cn-beijing.aliyuncs.com/google_registry/myapp:v1 23 imagePullPolicy: IfNotPresent 24 ports: 25 - containerPort: 80 26 # 指定节点运行 27 nodeName: k8s-master
运行yaml文件并查看信息
1 [root@k8s-master scheduler]# kubectl apply -f scheduler_nodeName.yaml 2 deployment.apps/scheduler-nodename-deploy created 3 [root@k8s-master scheduler]# 4 [root@k8s-master scheduler]# kubectl get deploy -o wide 5 NAME READY UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR 6 scheduler-nodename-deploy 0/5 5 0 6s myapp-pod registry.cn-beijing.aliyuncs.com/google_registry/myapp:v1 app=myapp 7 [root@k8s-master scheduler]# 8 [root@k8s-master scheduler]# kubectl get rs -o wide 9 NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR 10 scheduler-nodename-deploy-d5c9574bd 5 5 5 15s myapp-pod registry.cn-beijing.aliyuncs.com/google_registry/myapp:v1 app=myapp,pod-template-hash=d5c9574bd 11 [root@k8s-master scheduler]# 12 [root@k8s-master scheduler]# kubectl get pod -o wide 13 NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES 14 scheduler-nodename-deploy-d5c9574bd-6l9d8 1/1 Running 0 23s 10.244.0.123 k8s-master <none> <none> 15 scheduler-nodename-deploy-d5c9574bd-c82cc 1/1 Running 0 23s 10.244.0.119 k8s-master <none> <none> 16 scheduler-nodename-deploy-d5c9574bd-dkkjg 1/1 Running 0 23s 10.244.0.122 k8s-master <none> <none> 17 scheduler-nodename-deploy-d5c9574bd-hcn77 1/1 Running 0 23s 10.244.0.121 k8s-master <none> <none> 18 scheduler-nodename-deploy-d5c9574bd-zstjx 1/1 Running 0 23s 10.244.0.120 k8s-master <none> <none>
由上可见，yaml文件中nodeName: k8s-master生效，所有pod被调度到了k8s-master节点。如果这里是nodeName: k8s-node02，那么就会直接调度到k8s-node02节点。
当nodeName指定节点不存在
要运行的yaml文件
1 [root@k8s-master scheduler]# pwd 2 /root/k8s_practice/scheduler 3 [root@k8s-master scheduler]# cat scheduler_nodeName_02.yaml 4 apiVersion: apps/v1 5 kind: Deployment 6 metadata: 7 name: scheduler-nodename-deploy 8 labels: 9 app: nodename-deploy 10 spec: 11 replicas: 5 12 selector: 13 matchLabels: 14 app: myapp 15 template: 16 metadata: 17 labels: 18 app: myapp 19 spec: 20 containers: 21 - name: myapp-pod 22 image: registry.cn-beijing.aliyuncs.com/google_registry/myapp:v1 23 imagePullPolicy: IfNotPresent 24 ports: 25 - containerPort: 80 26 # 指定节点运行，该节点不存在 27 nodeName: k8s-node08
运行yaml文件并查看信息
1 [root@k8s-master scheduler]# kubectl apply -f scheduler_nodeName_02.yaml 2 deployment.apps/scheduler-nodename-deploy created 3 [root@k8s-master scheduler]# 4 [root@k8s-master scheduler]# kubectl get deploy -o wide 5 NAME READY UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR 6 scheduler-nodename-deploy 0/5 5 0 4s myapp-pod registry.cn-beijing.aliyuncs.com/google_registry/myapp:v1 app=myapp 7 [root@k8s-master scheduler]# 8 [root@k8s-master scheduler]# kubectl get rs -o wide 9 NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR 10 scheduler-nodename-deploy-75944bdc5d 5 5 0 9s myapp-pod registry.cn-beijing.aliyuncs.com/google_registry/myapp:v1 app=myapp,pod-template-hash=75944bdc5d 11 [root@k8s-master scheduler]# 12 [root@k8s-master scheduler]# kubectl get pod -o wide 13 NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES 14 scheduler-nodename-deploy-75944bdc5d-c8f5d 0/1 Pending 0 13s <none> k8s-node08 <none> <none> 15 scheduler-nodename-deploy-75944bdc5d-hfdlv 0/1 Pending 0 13s <none> k8s-node08 <none> <none> 16 scheduler-nodename-deploy-75944bdc5d-q9qgt 0/1 Pending 0 13s <none> k8s-node08 <none> <none> 17 scheduler-nodename-deploy-75944bdc5d-q9zl7 0/1 Pending 0 13s <none> k8s-node08 <none> <none> 18 scheduler-nodename-deploy-75944bdc5d-wxsnv 0/1 Pending 0 13s <none> k8s-node08 <none> <none>
由上可见，如果指定的节点不存在，则容器将不会运行，一直处于Pending 状态。
nodeSelector调度
nodeSelector是节点选择约束的最简单推荐形式。nodeSelector是PodSpec的领域。它指定键值对的映射。
Pod.spec.nodeSelector是通过Kubernetes的label-selector机制选择节点，由调度器调度策略匹配label，而后调度Pod到目标节点，该匹配规则属于【强制】约束。由于是调度器调度，因此不能越过Taints污点进行调度。
nodeSelector示例
获取当前的节点信息
1 [root@k8s-master ~]# kubectl get node -o wide --show-labels 2 NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME LABELS 3 k8s-master Ready master 42d v1.17.4 172.16.1.110 <none> CentOS Linux 7 (Core) 3.10.0-1062.el7.x86_64 docker://19.3.8 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=k8s-master,kubernetes.io/os=linux,node-role.kubernetes.io/master= 4 k8s-node01 Ready <none> 42d v1.17.4 172.16.1.111 <none> CentOS Linux 7 (Core) 3.10.0-1062.el7.x86_64 docker://19.3.8 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=k8s-node01,kubernetes.io/os=linux 5 k8s-node02 Ready <none> 42d v1.17.4 172.16.1.112 <none> CentOS Linux 7 (Core) 3.10.0-1062.el7.x86_64 docker://19.3.8 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=k8s-node02,kubernetes.io/os=linux
添加label标签
运行kubectl get nodes以获取群集节点的名称。然后可以对指定节点添加标签。比如：k8s-node01的磁盘为SSD，那么添加disk-type=ssd；k8s-node02的CPU核数高，那么添加cpu-type=hight；如果为Web机器，那么添加service-type=web。怎么添加标签可以根据实际规划情况而定。
1 ### 给k8s-node01 添加指定标签 2 [root@k8s-master ~]# kubectl label nodes k8s-node01 disk-type=ssd 3 node/k8s-node01 labeled 4 #### 删除标签命令 kubectl label nodes k8s-node01 disk-type- 5 [root@k8s-master ~]# 6 [root@k8s-master ~]# kubectl get node --show-labels 7 NAME STATUS ROLES AGE VERSION LABELS 8 k8s-master Ready master 42d v1.17.4 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=k8s-master,kubernetes.io/os=linux,node-role.kubernetes.io/master= 9 k8s-node01 Ready <none> 42d v1.17.4 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,disk-type=ssd,kubernetes.io/arch=amd64,kubernetes.io/hostname=k8s-node01,kubernetes.io/os=linux 10 k8s-node02 Ready <none> 42d v1.17.4 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=k8s-node02,kubernetes.io/os=linux
由上可见，已经为k8s-node01节点添加了disk-type=ssd 标签。
当nodeSelector标签存在
要运行的yaml文件
1 [root@k8s-master scheduler]# pwd 2 /root/k8s_practice/scheduler 3 [root@k8s-master scheduler]# 4 [root@k8s-master scheduler]# cat scheduler_nodeSelector.yaml 5 apiVersion: apps/v1 6 kind: Deployment 7 metadata: 8 name: scheduler-nodeselector-deploy 9 labels: 10 app: nodeselector-deploy 11 spec: 12 replicas: 5 13 selector: 14 matchLabels: 15 app: myapp 16 template: 17 metadata: 18 labels: 19 app: myapp 20 spec: 21 containers: 22 - name: myapp-pod 23 image: registry.cn-beijing.aliyuncs.com/google_registry/myapp:v1 24 imagePullPolicy: IfNotPresent 25 ports: 26 - containerPort: 80 27 # 指定节点标签选择，且标签存在 28 nodeSelector: 29 disk-type: ssd
运行yaml文件并查看信息
1 [root@k8s-master scheduler]# kubectl apply -f scheduler_nodeSelector.yaml 2 deployment.apps/scheduler-nodeselector-deploy created 3 [root@k8s-master scheduler]# 4 [root@k8s-master scheduler]# kubectl get deploy -o wide 5 NAME READY UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR 6 scheduler-nodeselector-deploy 5/5 5 5 10s myapp-pod registry.cn-beijing.aliyuncs.com/google_registry/myapp:v1 app=myapp 7 [root@k8s-master scheduler]# 8 [root@k8s-master scheduler]# kubectl get rs -o wide 9 NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR 10 scheduler-nodeselector-deploy-79455db454 5 5 5 14s myapp-pod registry.cn-beijing.aliyuncs.com/google_registry/myapp:v1 app=myapp,pod-template-hash=79455db454 11 [root@k8s-master scheduler]# 12 [root@k8s-master scheduler]# kubectl get pod -o wide 13 NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES 14 scheduler-nodeselector-deploy-79455db454-745ph 1/1 Running 0 19s 10.244.4.154 k8s-node01 <none> <none> 15 scheduler-nodeselector-deploy-79455db454-bmjvd 1/1 Running 0 19s 10.244.4.151 k8s-node01 <none> <none> 16 scheduler-nodeselector-deploy-79455db454-g5cg2 1/1 Running 0 19s 10.244.4.153 k8s-node01 <none> <none> 17 scheduler-nodeselector-deploy-79455db454-hw8jv 1/1 Running 0 19s 10.244.4.152 k8s-node01 <none> <none> 18 scheduler-nodeselector-deploy-79455db454-zrt8d 1/1 Running 0 19s 10.244.4.155 k8s-node01 <none> <none>
由上可见，所有pod都被调度到了k8s-node01节点。当然如果其他节点也有disk-type=ssd 标签，那么pod也会调度到这些节点上。
当nodeSelector标签不存在
要运行的yaml文件
1 [root@k8s-master scheduler]# pwd 2 /root/k8s_practice/scheduler 3 [root@k8s-master scheduler]# 4 [root@k8s-master scheduler]# cat scheduler_nodeSelector_02.yaml 5 apiVersion: apps/v1 6 kind: Deployment 7 metadata: 8 name: scheduler-nodeselector-deploy 9 labels: 10 app: nodeselector-deploy 11 spec: 12 replicas: 5 13 selector: 14 matchLabels: 15 app: myapp 16 template: 17 metadata: 18 labels: 19 app: myapp 20 spec: 21 containers: 22 - name: myapp-pod 23 image: registry.cn-beijing.aliyuncs.com/google_registry/myapp:v1 24 imagePullPolicy: IfNotPresent 25 ports: 26 - containerPort: 80 27 # 指定节点标签选择，且标签不存在 28 nodeSelector: 29 service-type: web
运行yaml文件并查看信息
1 [root@k8s-master scheduler]# kubectl apply -f scheduler_nodeSelector_02.yaml 2 deployment.apps/scheduler-nodeselector-deploy created 3 [root@k8s-master scheduler]# 4 [root@k8s-master scheduler]# kubectl get deploy -o wide 5 NAME READY UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR 6 scheduler-nodeselector-deploy 0/5 5 0 26s myapp-pod registry.cn-beijing.aliyuncs.com/google_registry/myapp:v1 app=myapp 7 [root@k8s-master scheduler]# 8 [root@k8s-master scheduler]# kubectl get rs -o wide 9 NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR 10 scheduler-nodeselector-deploy-799d748db6 5 5 0 30s myapp-pod registry.cn-beijing.aliyuncs.com/google_registry/myapp:v1 app=myapp,pod-template-hash=799d748db6 11 [root@k8s-master scheduler]# 12 [root@k8s-master scheduler]# kubectl get pod -o wide 13 NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES 14 scheduler-nodeselector-deploy-799d748db6-92mqj 0/1 Pending 0 40s <none> <none> <none> <none> 15 scheduler-nodeselector-deploy-799d748db6-c2w25 0/1 Pending 0 40s <none> <none> <none> <none> 16 scheduler-nodeselector-deploy-799d748db6-c8tlx 0/1 Pending 0 40s <none> <none> <none> <none> 17 scheduler-nodeselector-deploy-799d748db6-tc5n7 0/1 Pending 0 40s <none> <none> <none> <none> 18 scheduler-nodeselector-deploy-799d748db6-z8c57 0/1 Pending 0 40s <none> <none> <none> <none>
由上可见，如果nodeSelector匹配的标签不存在，则容器将不会运行，一直处于Pending 状态。
相关阅读
2、Kubernetes K8S之调度器kube-scheduler详解
3、Kubernetes K8S之affinity亲和性与反亲和性详解与示例
4、Kubernetes K8S之Taints污点与Tolerations容忍详解
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