# pod内资源分配的配置格式如下：
# 默认可以只配置requests，但根据生产中的经验，建议把limits资源限制也加上，因为对K8s来说，只有这两个都配置了且配置的值都要一样，这个pod资源的优先级才是最高的，在node资源不够的情况下，首先是把没有任何资源分配配置的pod资源给干掉，其次是只配置了requests的，最后才是两个都配置的情况，仔细品品resources:limits:   # 限制单个pod最多能使用1核(1000m 毫核)cpu以及2G内存cpu: "1"memory: 2Girequests: # 保证这个pod初始就能分配这么多资源cpu: "1"memory: 2Gi

# 为deployment资源web创建hpa，pod数量上限3个，最低1个，在pod平均CPU达到50%后开始扩容
kubectl  autoscale deployment web --max=3 --min=1 --cpu-percent=50#过一会看下这个hpa资源的描述(截取这下面一部分)
# 下面提示说到，HPA缺少最小资源分配的request参数
Conditions:Type           Status  Reason                   Message----           ------  ------                   -------AbleToScale    True    SucceededGetScale        the HPA controller was able to get the target's current scaleScalingActive  False   FailedGetResourceMetric  the HPA was unable to compute the replica count: missing request for cpu
Events:Type     Reason                        Age                     From                       Message----     ------                        ----                    ----                       -------Warning  FailedComputeMetricsReplicas  3m46s (x12 over 6m33s)  horizontal-pod-autoscaler  invalid metrics (1 invalid out of 1), first error is: failed to get cpu utilization: missing request for cpuWarning  FailedGetResourceMetric       89s (x21 over 6m33s)    horizontal-pod-autoscaler  missing request for cpu

# cat web.yaml
apiVersion: apps/v1
kind: Deployment
metadata:labels:app: webname: webnamespace: default
spec:replicas: 1selector:matchLabels:app: webtemplate:metadata:labels:app: webspec:containers:- image: nginxname: nginxresources:limits:   # 因为我这里是测试环境，所以这里CPU只分配50毫核(0.05核CPU)和20M的内存cpu: "50m"memory: 20Mirequests: # 保证这个pod初始就能分配这么多资源cpu: "50m"memory: 20Mi

# kubectl  apply -f web.yaml
deployment.apps/web configured

# kubectl  autoscale deployment web --max=3 --min=1 --cpu-percent=50
horizontalpodautoscaler.autoscaling/web autoscaled# 等待一会，可以看到相关的hpa信息(K8s上metrics服务收集所有pod资源的时间间隔大概在60s的时间)
# kubectl get hpa -w
NAME   REFERENCE        TARGETS         MINPODS   MAXPODS   REPLICAS   AGE
web    Deployment/web   <unknown>/50%   1         3         1          39s
web    Deployment/web   0%/50%          1         3         1          76s

# 我们启动一个临时pod，来模拟大量请求
# kubectl run -it --rm busybox --image=busybox -- sh
/ # while :;do wget -q -O- http://web;done# 等待2 ~ 3分钟，注意k8s为了避免频繁增删pod，对副本的增加速度有限制
# kubectl get hpa web -w
NAME   REFERENCE        TARGETS   MINPODS   MAXPODS   REPLICAS   AGE
web    Deployment/web   0%/50%    1         3         1          11m
web    Deployment/web   102%/50%   1         3         1          14m
web    Deployment/web   102%/50%   1         3         3          14m# 看下hpa的描述信息下面的事件记录
# kubectl describe hpa web
Events:Type     Reason                        Age                From                       Message----     ------                        ----               ----                       -------
...Normal   SuccessfulRescale             62s                horizontal-pod-autoscaler  New size: 3; reason: cpu resource utilization (percentage of request) above target

# 可以看到，在业务流量高峰下去后，HPA并不急着马上收缩pod数量，而是等待5分钟后，再进行收敛，这是稳妥的作法，是k8s为了避免频繁增删pod的一种手段
# kubectl get hpa web -w
NAME   REFERENCE        TARGETS    MINPODS   MAXPODS   REPLICAS   AGE
web    Deployment/web   102%/50%   1         3         3          16m
web    Deployment/web   0%/50%     1         3         3          16m
web    Deployment/web   0%/50%     1         3         3          20m
web    Deployment/web   0%/50%     1         3         1          21m