Kubernetes：应用部署、应用了解、应用公布、应用伸缩，-image=ikubernetes/myapp:v1

k8s基础命令：https://kubernetes.io/zh/docs/reference/kubectl/kubectl-cmds/

k8s基础知识：https://kubernetes.io/zh/docs/tutorials/kubernetes-basics/

一，部署应用

kubectl create deployment my-test-ngx --image=nginx
deployment.apps/my-test-ngx created

二，了解应用

查看deployment

kubectl get deployment
NAME          READY   UP-TO-DATE   AVAILABLE   AGE
my-test-ngx   1/1     1            1           103s

get deployment -o wide
NAME          READY   UP-TO-DATE   AVAILABLE   AGE     CONTAINERS   IMAGES   SELECTOR
my-test-ngx   1/1     1            1           2m17s   nginx        nginx    app=my-test-ngx

查看pod

kubectl get pod
NAME                          READY   STATUS    RESTARTS   AGE
my-test-ngx-77d994d88-srhzm   1/1     Running   0          39s

kubectl get pod -o wide
NAME                          READY   STATUS    RESTARTS   AGE     IP           NODE                   NOMINATED NODE   READINESS GATES
my-test-ngx-77d994d88-srhzm   1/1     Running   0          2m54s   10.244.0.7   master.oopxiajun.com   <none>           <none>

利用这个IP我们访问下

curl 10.244.0.7
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>body {width: 35em;margin: 0 auto;font-family: Tahoma, Verdana, Arial, sans-serif;}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p><p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p><p><em>Thank you for using nginx.</em></p>
</body>
</html>

本机浏览器也是可以访问

三，公布应用

kubectl create service clusterip my-test-ngx --tcp=8001:80
service/my-test-ngx created

这里注意：

1：my-test-ngx 这个名字需要与svc 的名字一样。

2：--tcp=8001:80 这里8001是公布对外的端口，80是容器内部端口

我看看svc详细信息

kubectl describe svc/my-test-ngx
Name:              my-test-ngx
Namespace:         default
Labels:            app=my-test-ngx
Annotations:       <none>
Selector:          app=my-test-ngx
Type:              ClusterIP
IP:                10.105.139.80
Port:              8001-80  8001/TCP
TargetPort:        80/TCP
Endpoints:         10.244.0.7:80
Session Affinity:  None
Events:            <none>

可以看到IP: 10.105.139.80

curl 10.105.139.80:8001
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>body {width: 35em;margin: 0 auto;font-family: Tahoma, Verdana, Arial, sans-serif;}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p><p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p><p><em>Thank you for using nginx.</em></p>
</body>
</html>

可以访问到这个IP:port对应的容器信息

删掉pod，看看有什么不一样。

#看看pod名
kubectl get pod
NAME                          READY   STATUS    RESTARTS   AGE
my-test-ngx-77d994d88-srhzm   1/1     Running   0          28m
#删掉pod
[root@master xiajun]# kubectl delete pod my-test-ngx-77d994d88-srhzm
pod "my-test-ngx-77d994d88-srhzm" deleted#再次看看pod
[root@master xiajun]# kubectl get pod
NAME                          READY   STATUS              RESTARTS   AGE
my-test-ngx-77d994d88-vsrwf   0/1     ContainerCreating   0          14s#发现pod名字变了

pod删掉后，又建了一个，pod名字变了，不仅仅是pod名字变了，容器的ip也有变化

kubectl describe svc/my-test-ngx
Name:              my-test-ngx
Namespace:         default
Labels:            app=my-test-ngx
Annotations:       <none>
Selector:          app=my-test-ngx
Type:              ClusterIP
IP:                10.105.139.80
Port:              8001-80  8001/TCP
TargetPort:        80/TCP
Endpoints:         10.244.0.8:80
Session Affinity:  None
Events:            <none>

前面我们看到：Endpoints: 10.244.0.7:80

这是我们看到：Endpoints: 10.244.0.8:80

Name:              my-test-ngx
Namespace:         default
Labels:            app=my-test-ngx
Annotations:       <none>
Selector:          app=my-test-ngx
Type:              ClusterIP
IP:                10.105.139.80
Port:              8001-80  8001/TCP
TargetPort:        80/TCP
Endpoints:         10.244.0.14:80
Session Affinity:  None
Events:            <none>

但是IP：10.105.139.80 是沒变的。所以pod即使是被干掉了，或者某个node的挂掉了，甚至是关机、重启宿主机，我们也一样是可以通过这个ip:port访问的。

curl 10.105.139.80:8001
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>body {width: 35em;margin: 0 auto;font-family: Tahoma, Verdana, Arial, sans-serif;}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p><p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p><p><em>Thank you for using nginx.</em></p>
</body>
</html>

很遗憾：这个地址也只能本机访问，用域名也是无法访问的。

curl my-test-ngx
curl: (6) Could not resolve host: my-test-ngx

用k8s本地的域名也是不行的。

curl my-test-ngx.default.svc.cluster.local.
curl: (7) Failed to connect to my-test-ngx.default.svc.cluster.local port 80: Connection refused

那我们怎么才能让应用公布到外网呢？

这里有一个叫kube-dns的svc，

kubectl get svc -n kube-system
NAME       TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)                  AGE
kube-dns   ClusterIP   10.96.0.10   <none>        53/UDP,53/TCP,9153/TCP   30h

说明k8s有个dns服务器，其ip地址为10.96.0.10

那么我们是否可以将作为我们宿主机的dns服务器呢？我们来试试。

cat /etc/resolv.conf
# Generated by NetworkManager
search localdomain oopxiajun.com
nameserver 192.168.134.2

这儿我们看到了我们nameserver是192.168.134.2

我们改下这个nameserver

vim /etc/resolv.conf

# Generated by NetworkManager
search localdomain oopxiajun.com
nameserver 10.96.0.10

然后访问

curl my-test-ngx.default.svc.cluster.local.
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>body {width: 35em;margin: 0 auto;font-family: Tahoma, Verdana, Arial, sans-serif;}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p><p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p><p><em>Thank you for using nginx.</em></p>
</body>
</html>

浏览器中也可以了

这样还是不够的哦。

观察下这个域名 my-test-ngx.default.svc.cluster.local

my-test-ngx：是service的名称，

default:是命名空间

svc.cluster.local：是k8s固定的dns-domain格式

我们要将这个域名改为我们自己定义的就需要在 kubeadm init 是加入我们的参数 --service-dns-domain

如果不加这个 --service-dns-domain ，那么默认的dns-domain就是svc.cluster.local.

这个点我们后面再来详细研究。

四，伸缩引用

我们这儿举例就用 k8s 提供的一个镜像 ikubernetes/myapp

#部署
kubectl create deployment myapp-test --image=ikubernetes/myapp:v1
deployment.apps/myapp-test created#公布节点
kubectl create service clusterip  myapp-test --tcp=80:80
service/myapp-test created#访问
[root@master xiajun]# curl myapp-test.default.svc.cluster.local.
Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a>#hostname.html 中就是 pod的名称
curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-6s9xhkubectl get pod
NAME                          READY   STATUS    RESTARTS   AGE
my-test-ngx-77d994d88-f99lf   1/1     Running   0          36m
myapp-test-cc8865788-6s9xh    1/1     Running   0          2m16s

扩容

kubectl scale --replicas=3 deployment myapp-test
deployment.apps/myapp-test scaled

访问

kubectl get pod
NAME                          READY   STATUS    RESTARTS   AGE
my-test-ngx-77d994d88-f99lf   1/1     Running   0          43m
myapp-test-cc8865788-6s9xh    1/1     Running   0          9m2s
myapp-test-cc8865788-dw6nc    1/1     Running   0          33s
myapp-test-cc8865788-xw2mw    1/1     Running   0          33s
[root@master xiajun]# curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-6s9xh
[root@master xiajun]# curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-6s9xh
[root@master xiajun]# curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-6s9xh
[root@master xiajun]# curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-xw2mw
[root@master xiajun]# curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-dw6nc
[root@master xiajun]# curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-6s9xh
[root@master xiajun]# curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-dw6nc
[root@master xiajun]# curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-xw2mw
[root@master xiajun]# curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-6s9xh
[root@master xiajun]# curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-dw6nc

可以看到是随机访问了pod