DevOps技术

### 一、Pod资源配额
## 1.1 资源配额配置简介
容器中的程序要运行，肯定是要占用一定资源的，比如CPU和内存等，如果不对某个容器的资源做限制，那么它就可能吃掉大量资源，导致气他容器无法运行，针对这种情况，kubernetes提供了对内存和CPU的资源进行配额的机制，这种机制主要通过resources选项类实现，它有两个子选项
* limits：用于限制运行时容器的最大占用资源，当容器占用资源超过limits时会被终止，并进行重启
* requests：用于设置容器需要的最小资源，如果环境资源不够，容器就无法启动

## 1.2 资源配额配置
如下，编辑pod_base.yaml文件，对nginx容器设置资源上限和下限设置
```yaml
apiVersion: v1
kind: Namespace
metadata:
  name: dev

---

使用如下命令删除资源
```bash
[root@master pod]# kubectl delete -f pod_resources.yaml
namespace "dev" deleted
pod "pod-resources" deleted
[root@master pod]#
```

## 1.3 配额超额配置测试
这里可以做个实验，将cpu下限修改为10，上限修改为20，然后再次尝试，因为这里虚拟机的核数是4，下限修改为10后是明显不能满足要求的
```yaml
apiVersion: v1
kind: Namespace
metadata:
  name: dev

---

apiVersion: v1
kind: Pod
metadata:
  name: pod-resources
  namespace: dev
  labels:
    user: redrose2100
spec:
  containers:
  - name: nginx
    image: nginx:1.17.1
    resources:
      requests:
        cpu: "10"
        memory: "100M"
      limits:
        cpu: "20"
        memory: "512M"
```
然后使用如下命令创建：
```bash
[root@master pod]# kubectl apply -f pod_resources.yaml
namespace/dev created
pod/pod-resources created
[root@master pod]#
```
再次重新创建后通过如下命令可以看到这里提示cpu不够用了
```bash
[root@master pod]# kubectl get pod -n dev
NAME            READY   STATUS    RESTARTS   AGE
pod-resources   0/1     Pending   0          17m
[root@master pod]# kubectl describe pod pod-resources -n dev
Name:         pod-resources
Namespace:    dev
Priority:     0
Node:         <none>
Labels:       user=redrose2100
Annotations:  <none>
Status:       Pending
IP:
IPs:          <none>
Containers:
  nginx:
    Image:      nginx:1.17.1
    Port:       <none>
    Host Port:  <none>
    Limits:
      cpu:     20
      memory:  512M
    Requests:
      cpu:        10
      memory:     100M
    Environment:  <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-8kvvb (ro)
Conditions:
  Type           Status
  PodScheduled   False
Volumes:
  kube-api-access-8kvvb:
    Type:                    Projected (a volume that contains injected data from multiple sources)
    TokenExpirationSeconds:  3607
    ConfigMapName:           kube-root-ca.crt
    ConfigMapOptional:       <nil>
    DownwardAPI:             true
QoS Class:                   Burstable
Node-Selectors:              <none>
Tolerations:                 node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                             node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
  Type     Reason            Age                 From               Message
  ----     ------            ----                ----               -------
  Warning  FailedScheduling  38s (x19 over 18m)  default-scheduler  0/3 nodes are available: 1 node(s) had taint {node-role.kubernetes.io/master: }, that the pod didn't tolerate, 2 Insufficient cpu.
[root@master pod]#
```
使用如下命令删除资源
```bash
[root@master pod]# kubectl delete -f pod_resources.yaml
namespace "dev" deleted
pod "pod-resources" deleted
[root@master pod]#
```

不积跬步，无以至千里

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