[k8s] minikube的使用与应用部署
minikube的使用与应用部署
0. 安装minikube
minikube是K8s的单机版本，通过minikube可以熟悉k8s的运行机理和工具。
安装十分简单，只需拉取二进制文件，然后放到可执行目录即可：
curl -LO https://storage.googleapis.com/minikube/releases/latest/minikube-linux-amd64
sudo install minikube-linux-amd64 /usr/local/bin/minikube
1. 创建和查看集群
运行minikube start命令得以启动集群，在有网环境下自动拉取所需的镜像：
(base) wildkid1024@debian:~$ minikube start
😄 Debian 11.3 (kvm/amd64) 上的 minikube v1.25.2
✨ 根据现有的配置文件使用 docker 驱动程序
👍 Starting control plane node minikube in cluster minikube
🚜 Pulling base image ...
🔄 Restarting existing docker container for "minikube" ...
🐳 正在 Docker 20.10.12 中准备 Kubernetes v1.23.3…
▪ kubelet.housekeeping-interval=5m
🔎 Verifying Kubernetes components...
▪ Using image gcr.io/k8s-minikube/storage-provisioner:v5
▪ Using image kubernetesui/dashboard:v2.3.1
▪ Using image kubernetesui/metrics-scraper:v1.0.7
🌟 Enabled addons: storage-provisioner, default-storageclass, dashboard
❗ The image 'k8s.gcr.io/kube-proxy' was not found; unable to add it to cache.
❗ The image 'k8s.gcr.io/kube-controller-manager' was not found; unable to add it to cache.
🏄 Done! kubectl is now configured to use "minikube" cluster and "default" namespace by default
使用kubectl命令查看当前集群的信息,可以看到集群控制平面的运行地址和对应的DNS接口：
(base) wildkid1024@debian:~$ kubectl cluster-info
Kubernetes control plane is running at https://192.168.49.2:8443
CoreDNS is running at https://192.168.49.2:8443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy
To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.
也可查看每个node的具体信息：
(base) wildkid1024@debian:~$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
minikube Ready control-plane,master 9d v1.23.3
2. 部署应用到集群中
通过kubectl create deloyment命令将应用部署到k8s集群当中，其对应的参数为部署名称和相应的镜像位置。比如通过一个简单的方式创建一个nodejs应用：
(base) wildkid1024@debian:~$ kubectl create deployment kubernetes-bootcamp --image=gcr.io/google-samples/kubernetes-bootcamp:v1
deployment.apps/kubernetes-bootcamp created
然后通过get deployments命令查看我们刚刚部署的应用的状态：
(base) wildkid1024@debian:~$ kubectl get deployments
NAME READY UP-TO-DATE AVAILABLE AGE
kubernetes-bootcamp 1/1 1 1 34s
如何查看里面的部署是否正常工作？通过kubectl proxy进行临时调试，首先要打开调试代理接口:
(base) wildkid1024@debian:~$ kubectl proxy
Starting to serve on 127.0.0.1:8001
确认node API可访问：
(base) wildkid1024@debian:~$ curl http://localhost:8001/version
{
"major": "1",
"minor": "23",
"gitVersion": "v1.23.3",
"gitCommit": "816c97ab8cff8a1c72eccca1026f7820e93e0d25",
"gitTreeState": "clean",
"buildDate": "2022-01-25T21:19:12Z",
"goVersion": "go1.17.6",
"compiler": "gc",
"platform": "linux/amd64"
}
确认相应的pod的API也可访问，里面有相应pod描述和信息：
(base) wildkid1024@debian:~$ curl http://localhost:8001/api/v1/namespaces/default/pods/kubernetes-bootcamp-65d5b99f84-b2d8p/
{
"kind": "Pod",
"apiVersion": "v1",
"metadata": {
"name": "kubernetes-bootcamp-65d5b99f84-b2d8p",
"generateName": "kubernetes-bootcamp-65d5b99f84-",
"namespace": "default",
"uid": "6d245d32-30c9-4c04-8bca-e49ab193b086",
"resourceVersion": "340266",
"creationTimestamp": "2022-05-13T09:10:13Z",
"labels": {
"app": "kubernetes-bootcamp",
"pod-template-hash": "65d5b99f84"
}
}
3. 查看调试应用
首先通过kubectl get命令查看集群中存在的pod：
(base) wildkid1024@debian:~$ kubectl get pods
NAME READY STATUS RESTARTS AGE
kubernetes-bootcamp-65d5b99f84-b2d8p 1/1 Running 0 19m
kubia 1/1 Running 2 (35m ago) 9d
通过decribe则查看pod的创建情况，以及容器的具体信息，比如内部IP，端口，以及完成的事件信息：
(base) wildkid1024@debian:~$ kubectl describe pods
Name: kubernetes-bootcamp-65d5b99f84-b2d8p
Namespace: default
Priority: 0
Node: minikube/192.168.49.2
Start Time: Fri, 13 May 2022 17:10:13 +0800
Labels: app=kubernetes-bootcamp
pod-template-hash=65d5b99f84
Annotations: <none>
Status: Running
IP: 172.17.0.6
IPs:
IP: 172.17.0.6
Controlled By: ReplicaSet/kubernetes-bootcamp-65d5b99f84
Containers:
kubernetes-bootcamp:
Container ID: docker://c652e3a4227816c44fc0240feb6c3b0048125967a438ffffa4a96cf523382100
Image: gcr.io/google-samples/kubernetes-bootcamp:v1
Image ID: docker-pullable://gcr.io/google-samples/kubernetes-bootcamp@sha256:0d6b8ee63bb57c5f5b6156f446b3bc3b3c143d233037f3a2f00e279c8fcc64af
Port: <none>
Host Port: <none>
State: Running
Started: Fri, 13 May 2022 17:10:41 +0800
Ready: True
Restart Count: 0
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-qdn9d (ro)
Conditions:
Type Status
Initialized True
Ready True
ContainersReady True
PodScheduled True
Volumes:
kube-api-access-qdn9d:
Type: Projected (a volume that contains injected data from multiple sources)
TokenExpirationSeconds: 3607
ConfigMapName: kube-root-ca.crt
ConfigMapOptional: <nil>
DownwardAPI: true
QoS Class: BestEffort
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
---- ------ ---- ---- -------
Normal Scheduled 21m default-scheduler Successfully assigned default/kubernetes-bootcamp-65d5b99f84-b2d8p to minikube
Normal Pulling 21m kubelet Pulling image "gcr.io/google-samples/kubernetes-bootcamp:v1"
Normal Pulled 21m kubelet Successfully pulled image "gcr.io/google-samples/kubernetes-bootcamp:v1" in 27.005193363s
Normal Created 21m kubelet Created container kubernetes-bootcamp
Normal Started 21m kubelet Started container kubernetes-bootcamp
通过kubectl logs命令则可查看容器在内部运行时打印出来的log信息：
(base) wildkid1024@debian:~$ kubectl logs kubernetes-bootcamp-65d5b99f84-b2d8p
Kubernetes Bootcamp App Started At: 2022-05-13T09:10:41.099Z | Running On: kubernetes-bootcamp-65d5b99f84-b2d8p
通过kubectl exec可以在容器中临时执行命令，比如查看容器的环境变量：
(base) wildkid1024@debian:~$ kubectl exec kubernetes-bootcamp-65d5b99f84-b2d8p -- env
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
HOSTNAME=kubernetes-bootcamp-65d5b99f84-b2d8p
KUBERNETES_PORT=tcp://10.96.0.1:443
KUBERNETES_PORT_443_TCP=tcp://10.96.0.1:443
KUBERNETES_PORT_443_TCP_PROTO=tcp
KUBERNETES_PORT_443_TCP_PORT=443
KUBERNETES_PORT_443_TCP_ADDR=10.96.0.1
KUBERNETES_SERVICE_HOST=10.96.0.1
KUBERNETES_SERVICE_PORT=443
KUBERNETES_SERVICE_PORT_HTTPS=443
NPM_CONFIG_LOGLEVEL=info
NODE_VERSION=6.3.1
HOME=/root
当然也可以执行可交互的shell命令，需要添加-it参数：
(base) wildkid1024@debian:~$ kubectl exec -it kubernetes-bootcamp-65d5b99f84-b2d8p -- bash
root@kubernetes-bootcamp-65d5b99f84-b2d8p:/# cat server.js
var http = require('http');
var requests=0;
var podname= process.env.HOSTNAME;
var startTime;
var host;
var handleRequest = function(request, response) {
response.setHeader('Content-Type', 'text/plain');
response.writeHead(200);
response.write("Hello Kubernetes bootcamp! | Running on: ");
response.write(host);
response.end(" | v=1\n");
console.log("Running On:" ,host, "| Total Requests:", ++requests,"| App Uptime:", (new Date() - startTime)/1000 , "seconds", "| Log Time:",new Date());
}
var www = http.createServer(handleRequest);
www.listen(8080,function () {
startTime = new Date();;
host = process.env.HOSTNAME;
console.log ("Kubernetes Bootcamp App Started At:",startTime, "| Running On: " ,host, "\n" );
});
root@kubernetes-bootcamp-65d5b99f84-b2d8p:/# curl localhost:8080
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-65d5b99f84-b2d8p | v=1
root@kubernetes-bootcamp-65d5b99f84-b2d8p:/#
这里在容器内执行了bash脚本，并查看了server.js的源代码，并通过curl对本地的服务进行了测试。
4. 公开应用的外部接口
前述部署的应用拥有内部的ip和端口，只能在集群内部进行访问，那么如果在外部进行访问，便需要创建service资源以映射到内部的服务。
通过kubectl expose命令为相应的部署创建一个可访问的services接口：
(base) wildkid1024@debian:~$ kubectl expose deployment/kubernetes-bootcamp --type="NodePort" --port 8080
service/kubernetes-bootcamp exposed
创建了一个暴露内部8080接口的service，可通过get services命令列出当前可使用的service列表, 通过describe services描述相应的services信息：
(base) wildkid1024@debian:~$ kubectl get services
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 9d
kubernetes-bootcamp NodePort 10.99.177.162 <none> 8080:31729/TCP 84s
(base) wildkid1024@debian:~$ curl $(minikube ip):31729
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-65d5b99f84-b2d8p | v=1
当相应的应用不需要对外提供访问接口时，可将相应创建的接口删除：
(base) wildkid1024@debian:~$ kubectl delete service kubernetes-bootcamp
service "kubernetes-bootcamp" deleted
(base) wildkid1024@debian:~$ kubectl get services
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 9d
然后通过ip访问进行验证，发现外部接口可访问，但仍可通过调试的方式在内部访问：
(base) wildkid1024@debian:~$ curl $(minikube ip):31729
curl: (7) Failed to connect to 192.168.49.2 port 31729: 拒绝连接
(base) wildkid1024@debian:~$ kubectl exec -ti kubernetes-bootcamp-65d5b99f84-b2d8p -- curl localhost:8080
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-65d5b99f84-b2d8p | v=1
(base) wildkid1024@debian:~$
5. 弹性放缩应用
在部署应用后，极大可能会对不同的应用进行放缩，比如把某个应用扩充为多个实例，传统部署方案可能要重新部署一遍运行环境，然后将对应的代码复制到新的环境，在集群中，只需要使用kubectl scale一行命令便可以实现：
(base) wildkid1024@debian:~$ kubectl scale deployments/kubernetes-bootcamp --replicas=4
deployment.apps/kubernetes-bootcamp scaled
(base) wildkid1024@debian:~$ kubectl get deployments
NAME READY UP-TO-DATE AVAILABLE AGE
kubernetes-bootcamp 4/4 4 4 70m
(base) wildkid1024@debian:~$ kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
kubernetes-bootcamp-65d5b99f84-2bvw9 1/1 Running 0 25s 172.17.0.8 minikube <none> <none>
kubernetes-bootcamp-65d5b99f84-b2d8p 1/1 Running 0 70m 172.17.0.6 minikube <none> <none>
kubernetes-bootcamp-65d5b99f84-spxb5 1/1 Running 0 25s 172.17.0.7 minikube <none> <none>
kubernetes-bootcamp-65d5b99f84-ssfjp 1/1 Running 0 25s 172.17.0.9 minikube <none> <none>
可以看到部署的实例数已经变为4个，对应的pods也变成了4个，其中1个是之前创建的，另外3个是新创建的。
当再使用外部服务接口去访问应用时，发现其已经实现了负载均衡，几次访问中每次访问的实例都不尽相同：
(base) wildkid1024@debian:~$ curl $(minikube ip):32578
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-65d5b99f84-spxb5 | v=1
(base) wildkid1024@debian:~$ curl $(minikube ip):32578
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-65d5b99f84-b2d8p | v=1
(base) wildkid1024@debian:~$ curl $(minikube ip):32578
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-65d5b99f84-2bvw9 | v=1
(base) wildkid1024@debian:~$ curl $(minikube ip):32578
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-65d5b99f84-b2d8p | v=1
有时也可以回收多余的应用实例，只需把实例的数目调节到预期的数目即可：
(base) wildkid1024@debian:~$ kubectl scale deployments/kubernetes-bootcamp --replicas=2
deployment.apps/kubernetes-bootcamp scaled
(base) wildkid1024@debian:~$ kubectl get deployments
NAME READY UP-TO-DATE AVAILABLE AGE
kubernetes-bootcamp 2/2 2 2 77m
(base) wildkid1024@debian:~$ kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
kubernetes-bootcamp-65d5b99f84-2bvw9 1/1 Running 0 7m43s 172.17.0.8 minikube <none> <none>
kubernetes-bootcamp-65d5b99f84-b2d8p 1/1 Running 0 77m 172.17.0.6 minikube <none> <none>
kubernetes-bootcamp-65d5b99f84-spxb5 1/1 Terminating 0 7m43s 172.17.0.7 minikube <none> <none>
kubernetes-bootcamp-65d5b99f84-ssfjp 1/1 Terminating 0 7m43s 172.17.0.9 minikube <none> <none>
多于预期数目的实例正在停止并进行资源回收。
6. 滚动热更新应用
应用上线后，会遇到版本更新的情况，传统办法是等半夜用户都下线时再进行离线系统维护。但随着用户在线时长越来越长，难免会影响到一小部分用户的使用体验。比较流行的做法是在线热更新，即在不下线的情况下对应用进行维护和版本升级，毫不影响用户体验。
类似与应用弹性放缩，应用的版本升级同样十分简单，只需通过kubectl set image将对应的镜像进行替换即可：
(base) wildkid1024@debian:~$ kubectl set image deployments/kubernetes-bootcamp kubernetes-bootcamp=jocatalin/kubernetes-bootcamp:v2
deployment.apps/kubernetes-bootcamp image updated
(base) wildkid1024@debian:~$ kubectl get pods
NAME READY STATUS RESTARTS AGE
kubernetes-bootcamp-65d5b99f84-2bvw9 1/1 Running 0 15m
kubernetes-bootcamp-65d5b99f84-b2d8p 1/1 Running 0 86m
kubernetes-bootcamp-684bd555bb-grwpv 0/1 ContainerCreating 0 11s
kubia 1/1 Running 2 (102m ago) 9d
(base) wildkid1024@debian:~$ curl $(minikube ip):32578
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-684bd555bb-sngxj | v=2
此时应用的版本已经变成了v2版本，也可以通过rollout检查应用更新状况：
(base) wildkid1024@debian:~$ kubectl rollout status deployments/kubernetes-bootcamp
deployment "kubernetes-bootcamp" successfully rolled out
当部署了不正确的版本时，那么就需要对版本进行回滚了，kubectl同样提供了十分便捷的回滚命令。
这里通过一个错误的版本镜像来演示回滚操作：
(base) wildkid1024@debian:~$ kubectl set image deployments/kubernetes-bootcamp kubernetes-bootcamp=gcr.io/google-samples/kubernetes-bootcamp:v10
deployment.apps/kubernetes-bootcamp image updated
(base) wildkid1024@debian:~$ kubectl get pods
NAME READY STATUS RESTARTS AGE
kubernetes-bootcamp-5bbb6c8c4-vsfq6 0/1 ErrImagePull 0 9s
kubernetes-bootcamp-684bd555bb-grwpv 1/1 Running 0 5m41s
kubernetes-bootcamp-684bd555bb-sngxj 1/1 Running 0 5m25s
这里发现应用新版本出现了ErrImagePull错误，就需要通过kubectl rollout undo命令来进行回滚：
(base) wildkid1024@debian:~$ kubectl rollout undo deployments/kubernetes-bootcamp
deployment.apps/kubernetes-bootcamp rolled back
(base) wildkid1024@debian:~$ kubectl get pods
NAME READY STATUS RESTARTS AGE
kubernetes-bootcamp-684bd555bb-grwpv 1/1 Running 0 8m34s
kubernetes-bootcamp-684bd555bb-sngxj 1/1 Running 0 8m18s
------------ 完结 ------------------
