前言
在kubernetes中，我们使用pod对外提供服务。这时候，我们需要以下两种情形需要关注：
-
pod因为不明原因挂掉，导致服务不可用
-
Pod在高负荷的情况下，不能支撑我们的服务
如果我们人工监控pods，人工进行调整副本那么这个工作量无疑是巨大的，但kubernetes已经有了相应的机制来应对了。
那么今天就来介绍一下在k8s 1.6中的弹性伸缩的实施
k8s是kubernetes的官方简称
HPA全称Horizontal Pod Autoscaler
HPA的原理
Kubernetes有一个HPA(Horizontal Pod Autoscaler)的资源，可以实现基于CPU使用率的Pod自动伸缩的功能。HPA基于Master Node上的kube-controller-manager服务启动参数–horizontal-pod-autoscaler-sync-period定义的时长(默认为30秒)，周期性的检测Pod的CPU使用率(需要事先安装heapster)。如果需要设置–horizontal-pod-autoscaler-sync-period可以在Master Node上的/etc/default/kube-controller-manager中修改。
安装Heapster
K8S从1.8版本开始，CPU、内存等资源的metrics信息可以通过 Metrics API来获取，用户可以直接获取这些metrics信息（例如通过执行kubect top命令），HPA使用这些metics信息来实现动态伸缩，但是在之前我们使用Heapster来收集节点的相关数据
导入相关镜像
我们在实施的时候一般会创建/data目录，把所有的deployment放在此目录下，因此在k8s master创建kube-system目录
[root@master data]# mkdir kube-system
上传相镜像，并导入
# 导入heasper
[root@master kube-system]# docker load < heapster_3.tar 38ac8d0f5bb3: Loading layer [==================================================>] 1.312MB/1.312MB 388f58c4d5b0: Loading layer [==================================================>] 99.87MB/99.87MB c6772246bc46: Loading layer [==================================================>] 281.1kB/281.1kB Loaded image: registry.cn-hangzhou.aliyuncs.com/lczean/heapster-amd64-v1.3.0-beta.1:v1.3.0-beta.1 # 导入influxdb数据库 [root@master kube-system]# docker load < influxdb13.tar 7da815924651: Loading layer [==================================================>] 10.48MB/10.48MB 2d447b9e914f: Loading layer [==================================================>] 5.12kB/5.12kB Loaded image: registry.cn-hangzhou.aliyuncs.com/golden/heapster-influxdb-amd64:latest 查看导入images
[root@master kube-system]# docker images |grep heapster
registry.cn-hangzhou.aliyuncs.com/lczean/heapster-amd64-v1.3.0-beta.1 v1.3.0-beta.1 6393b81e2220 17 months ago 101MB registry.cn-hangzhou.aliyuncs.com/golden/heapster-influxdb-amd64 latest d3fccbedd180 22 months ago 11.6MB 修改images tag以便我们可以导入到私有registry中
[root@master kube-system]# docker tag registry.cn-hangzhou.aliyuncs.com/lczean/heapster-amd64-v1.3.0-beta.1:v1.3.0-beta.1 registry.k8s.osc:5000/heapster:v1.3.0 [root@master kube-system]# docker tag registry.cn-hangzhou.aliyuncs.com/golden/heapster-influxdb-amd64 registry.k8s.osc:5000/heapster-influxdb # 查看修改后的images [root@master kube-system]# docker images |grep heapster registry.cn-hangzhou.aliyuncs.com/lczean/heapster-amd64-v1.3.0-beta.1 v1.3.0-beta.1 6393b81e2220 17 months ago 101MB registry.k8s.osc:5000/heapster v1.3.0 6393b81e2220 17 months ago 101MB registry.cn-hangzhou.aliyuncs.com/golden/heapster-influxdb-amd64 latest d3fccbedd180 22 months ago 11.6MB registry.k8s.osc:5000/heapster-influxdb latest d3fccbedd180 22 months ago 11.6MB 推送到私有仓库
[root@master kube-system]# docker push registry.k8s.osc:5000/heapster:v1.3.0
The push refers to repository [registry.k8s.osc:5000/heapster]
c6772246bc46: Pushed
388f58c4d5b0: Pushed
38ac8d0f5bb3: Pushed
v1.3.0: digest: sha256:e23b30d2e131e042eec9b5fdc30af905b63e454d140dc335246e74a4e8b4c857 size: 949
[root@master kube-system]# docker push registry.k8s.osc:5000/heapster-influxdb
The push refers to repository [registry.k8s.osc:5000/heapster-influxdb]
2d447b9e914f: Pushed
7da815924651: Pushed
38ac8d0f5bb3: Mounted from heapster
latest: digest: sha256:d2ecd285eb6585d56e8853da7b9fd8f4a57de4a3006f6720173a3f3942c0e7c9 size: 945
创建deployment
[root@master kube-system]# vim influxdb-deployment.yaml
[root@master kube-system]# vim influxdb-service.yaml
[root@master kube-system]# vim heapster-deployment.yaml
[root@master kube-system]# vim heapster-service.yaml
分别看一下yaml：
influxdb-deployment.yaml
修改image
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: monitoring-influxdb
namespace: kube-system
spec:
replicas: 1
template:
metadata:
labels:
task: monitoring
k8s-app: influxdb
spec:
volumes:
- name: influxdb-storage
emptyDir: {}
containers:
- name: influxdb
image: registry.k8s.osc:5000/heapster-influxdb
volumeMounts:
- mountPath: /data
name: influxdb-storage
influxdb-service.yaml
apiVersion: v1
kind: Service
metadata:
labels:
task: monitoring
kubernetes.io/cluster-service: 'true'
kubernetes.io/name: monitoring-influxdb
name: monitoring-influxdb
namespace: kube-system
spec:
ports:
- name: http
port: 8083
targetPort: 8083
- name: api
port: 8086
targetPort: 8086
selector:
k8s-app: influxdb
创建deployment、service
[root@master kube-system]# kubectl create -f influxdb-deployment.yaml
[root@master kube-system]# kubectl create -f influxdb-service.yaml
安装这两个后查看influxdb坐在的pod ip
[root@master kube-system]# kubectl get pods -n kube-system -o wide NAME READY STATUS RESTARTS AGE IP NODE monitoring-influxdb-3696415694-q9tds 1/1 Running 0 16m 172.99.39.6 172.16.187.158 测试安装正常，再安装flanneld的node访问以下链接，如果无报错说明安装成功
[root@node0 ~]# curl http://172.99.39.6:8086/ping
创建heapster-deployment.yaml
修改image、--source、--sink
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: heapster
namespace: kube-system
spec:
replicas: 1
template:
metadata:
labels:
task: monitoring
k8s-app: heapster
version: v6
spec:
containers:
- name: heapster
image: registry.k8s.osc:5000/heapster:v1.3.0
imagePullPolicy: Always
command:
- /heapster
- --source=kubernetes:http://172.16.187.162:8080
- --sink=influxdb:http://172.99.39.6:8086
创建heapster-service.yaml
apiVersion: v1
kind: Service
metadata:
labels:
task: monitoring
kubernetes.io/cluster-service: 'true'
kubernetes.io/name: Heapster
name: heapster
namespace: kube-system
spec:
ports:
- port: 80
targetPort: 8082
selector:
k8s-app: heapster
创建heapster的deployment、service
[root@master kube-system]# kubectl create -f heapster-deployment.yaml
deployment "heapster" created
[root@master kube-system]# kubectl create -f heapster-service.yaml
service "heapster" created
全部安装后可以查看日志是否是正常启动的
[root@master kube-system]# kubectl get pods -n kube-system -o wide NAME READY STATUS RESTARTS AGE IP NODE heapster-1258036176-sjg7s 1/1 Running 0 1m 172.99.93.13 172.16.187.160 monitoring-influxdb-3696415694-q9tds 1/1 Running 0 26m 172.99.39.6 172.16.187.158 [root@master kube-system]# kubectl logs -f monitoring-influxdb-3696415694-q9tds -n kube-system 8888888 .d888 888 8888888b. 888888b. 888 d88P" 888 888 "Y88b 888 "88b 888 888 888 888 888 888 .88P 888 88888b. 888888 888 888 888 888 888 888 888 8888888K. 888 888 "88b 888 888 888 888 Y8bd8P' 888 888 888 "Y88b 888 888 888 888 888 888 888 X88K 888 888 888 888 888 888 888 888 888 Y88b 888 .d8""8b. 888 .d88P 888 d88P 8888888 888 888 888 888 "Y88888 888 888 8888888P" 8888888P" [run] 2018/12/07 05:27:33 InfluxDB starting, version unknown, branch unknown, commit unknown [run] 2018/12/07 05:27:33 Go version go1.7.4, GOMAXPROCS set to 16 [run] 2018/12/07 05:27:33 Using configuration at: /etc/config.toml [store] 2018/12/07 05:27:33 Using data dir: /data/data [subscriber] 2018/12/07 05:27:33 opened service [monitor] 2018/12/07 05:27:33 Starting monitor system [monitor] 2018/12/07 05:27:33 'build' registered for diagnostics monitoring [monitor] 2018/12/07 05:27:33 'runtime' registered for diagnostics monitoring [monitor] 2018/12/07 05: