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kubernetes

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简介

在移动互联网场景下经常要用到服务器扩容，缩容的操作。管理众多的服务器，服务器之间的连接、配置都是一项很大的工作。如果有服务器宕机了，需要启动服务器去承担其工作。这种情况下，就需要k8s来帮忙搭建一套可伸缩的服务器体系。

dashboard

环境搭建

一般都是使用minikuber来学习kubernetes知识。参考里面[2]有相关流程。我这里做一下笔记。

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## 安装Ubuntu设备为例：
curl -LO https://storage.googleapis.com/minikube/releases/latest/minikube_latest_amd64.deb
sudo dpkg -i minikube_latest_amd64.deb
## 前提条件：需要本地安装一个docker；新建一个普通用户，将普通用户设置成docker用户组。
sudo usermod -aG docker $USER && newgrp docker
## start your cluster
minikube start

## 将自己加入到docker用户组里面。正常能跑起来了。
$ minikube start
* minikube v1.25.2 on Ubuntu 20.04 (amd64)
* Automatically selected the docker driver
* Starting control plane node minikube in cluster minikube
* Pulling base image ...
* Downloading Kubernetes v1.23.3 preload ...
    > preloaded-images-k8s-v17-v1...: 505.68 MiB / 505.68 MiB  100.00% 11.90 Mi
    > index.docker.io/kicbase/sta...: 379.06 MiB / 379.06 MiB  100.00% 2.87 MiB
! minikube was unable to download gcr.io/k8s-minikube/kicbase:v0.0.30, but successfully downloaded docker.io/kicbase/stable:v0.0.30 as a fallback image
* Creating docker container (CPUs=2, Memory=2200MB) ...
! This container is having trouble accessing https://k8s.gcr.io
* To pull new external images, you may need to configure a proxy: https://minikube.sigs.k8s.io/docs/reference/networking/proxy/
* Preparing Kubernetes v1.23.3 on Docker 20.10.12 ...
  - kubelet.housekeeping-interval=5m
  - Generating certificates and keys ...
  - Booting up control plane ...
  - Configuring RBAC rules ...
* Verifying Kubernetes components...
  - Using image gcr.io/k8s-minikube/storage-provisioner:v5
* Enabled addons: default-storageclass, storage-provisioner
* kubectl not found. If you need it, try: 'minikube kubectl -- get pods -A'
* Done! kubectl is now configured to use "minikube" cluster and "default" namespace by default
## 运行dashboard程序
$ minikube dashboard
* Enabling dashboard ...
  - Using image kubernetesui/metrics-scraper:v1.0.7
  - Using image kubernetesui/dashboard:v2.3.1
* Verifying dashboard health ...
* Launching proxy ...
    > kubectl.sha256: 64 B / 64 B [--------------------------] 100.00% ? p/s 0s
    > kubectl: 44.43 MiB / 44.43 MiB [-------------] 100.00% 15.70 MiB p/s 3.0s
* Verifying proxy health ...
* Opening http://127.0.0.1:38909/api/v1/namespaces/kubernetes-dashboard/services/http:kubernetes-dashboard:/proxy/ in your default browser...
  http://127.0.0.1:38909/api/v1/namespaces/kubernetes-dashboard/services/http:kubernetes-dashboard:/proxy/

dashboard效果图

dashboard

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## 通过get po获取当前在运行的实例
$ minikube kubectl -- get po -A
NAMESPACE              NAME                                        READY   STATUS    RESTARTS      AGE
kube-system            coredns-64897985d-w6j2g                     1/1     Running   0             10m
kube-system            etcd-minikube                               1/1     Running   0             10m
kube-system            kube-apiserver-minikube                     1/1     Running   0             10m
kube-system            kube-controller-manager-minikube            1/1     Running   0             10m
kube-system            kube-proxy-5m6b8                            1/1     Running   0             10m
kube-system            kube-scheduler-minikube                     1/1     Running   0             10m
kube-system            storage-provisioner                         1/1     Running   1 (10m ago)   10m
kubernetes-dashboard   dashboard-metrics-scraper-58549894f-d8xgw   1/1     Running   0             5m29s
kubernetes-dashboard   kubernetes-dashboard-ccd587f44-xbb7v        1/1     Running   0             5m29s

## 为了方便直接创建一个简称指令

alias kubectl="minikube kubectl --"

## 通过指令创建一个应用
➜  ~  kubectl create deployment hello-minikube --image=k8s.gcr.io/echoserver:1.4
deployment.apps/hello-minikube created
➜  ~  kubectl expose deployment hello-minikube --type=NodePort --port=8080
service/hello-minikube exposed
## 通过命令一直关注这个pods的变化
watch -n 1 minikube kubectl -- get pods

## minikube 启动一个web浏览器给你，用于访问这个服务
minikube service hello-minikube

## 将地址从容器里面转出来给本机使用 7080 就能去访问这个页面
kubectl port-forward service/hello-minikube 7080:8080

## 负载均衡部署

kubectl create deployment balanced --image=k8s.gcr.io/echoserver:1.4  
kubectl expose deployment balanced --type=LoadBalancer --port=8080

## 打开另外的窗口，开启tunnel（隧道）提供给 balanced 部署做支持。
minikube tunnel

## 通过指令查询路由的外部ip
kubectl get services balanced

## 管理集群

minikube pause

minikube unpause

minikube stop

## 设置内存上限
minikube config set memory 16384

## 浏览
minikube addons list

## 在老版本的k8s里面创建第二个集群
minikube start -p aged --kubernetes-version=v1.16.1

## 删除掉全部的集群
minikube delete --all

概念

conception

Master

Node

Pod

杂项

安装过程中遇到的麻烦

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-> # minikube start
* minikube v1.25.2 on Ubuntu 20.04 (amd64)
* Automatically selected the docker driver. Other choices: none, ssh
* The "docker" driver should not be used with root privileges.
* If you are running minikube within a VM, consider using --driver=none:
*   https://minikube.sigs.k8s.io/docs/reference/drivers/none/

X Exiting due to DRV_AS_ROOT: The "docker" driver should not be used with root privileges.

## 不要使用root运行 minikube
$ minikube start
* minikube v1.25.2 on Ubuntu 20.04 (amd64)
* Unable to pick a default driver. Here is what was considered, in preference order:
  - docker: Not healthy: "docker version --format {{.Server.Os}}-{{.Server.Version}}" exit status 1: Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Get http://%2Fvar%2Frun%2Fdocker.sock/v1.24/version: dial unix /var/run/docker.sock: connect: permission denied
  - docker: Suggestion: Add your user to the 'docker' group: 'sudo usermod -aG docker $USER && newgrp docker' <https://docs.docker.com/engine/install/linux-postinstall/>
* Alternatively you could install one of these drivers:
  - kvm2: Not installed: exec: "virsh": executable file not found in $PATH
  - podman: Not installed: exec: "podman": executable file not found in $PATH
  - vmware: Not installed: exec: "docker-machine-driver-vmware": executable file not found in $PATH
  - virtualbox: Not installed: unable to find VBoxManage in $PATH

X Exiting due to DRV_NOT_HEALTHY: Found driver(s) but none were healthy. See above for suggestions how to fix installed drivers.
## docker无法获取信息，也是权限不足
sudo usermod -aG docker $USER && newgrp docker

k8s使用类似 crontab相关的东西

how-to-run-a-cronjob-every-10-seconds

要让Kubernetes中的cronjob每分钟执行一次，请按照以下步骤操作：

编辑或创建cronjob.yaml文件，通过指定cron表达式来调度job的运行时间。下面是一个简单的示例：

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apiVersion: batch/v1beta1
kind: CronJob
metadata:
  name: my-cronjob
spec:
  # 执行时间设为每分钟
  schedule: "* * * * *"
  jobTemplate:
    metadata:
      name: my-cronjob-job
    spec:
      template:
        metadata:
          name: my-cronjob-pod
        spec:
          containers:
            - name: my-container
              image: my-image
              command: ["/bin/sh"]
              args: ["-c", "echo Hello World"]

可以直接使用utools来看看这个shedule还不知道如何。

使用kubectl create命令创建cronjob：

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$ kubectl create -f ./cronjob.yaml

确保cronjob正常运行并检查job的日志：

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$ kubectl get cronjobs
$ kubectl get jobs
$ kubectl logs <job-name>

如果需要更改cronjob的执行时间，请编辑cronjob.yaml文件并重新创建cronjob：

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$ kubectl replace -f ./cronjob.yaml

k8s中域名的访问方式

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本身的域名
cluster.local

namespace shuwan
shuwan.cluster.local

service common
common.shuwan.cluster.local

pod common-0
common-0.common.shuwan.cluster.local

same namespace
somebody -> common
common

different namespace
somebody -> maas.common
common.maas

how-to-use-chatgpt-in-china

参考资料