Table of contents

4. Deployment

Through the simple practical operation of several basic concepts, the entry operation of kubernetes (k8s) is completed, including namespace, pod, label, deployment, and service. With these operations, you can implement simple deployment and access of a service in the kubernetes cluster, but if you want to use kubernetes better, you need to study the details and principles of these resources in depth.

1. Namespace

Namespace is a very important resource in the kubernetes system. Its main function is to realize resource isolation of multiple environments or resource isolation of multi-tenants .

By default, all Pods in a kubernetes cluster can access each other. But in practice, you may not want to allow two Pods to access each other, then you can divide the two Pods into different namespaces. Kubernetes can form logical "groups" by allocating resources within the cluster to different Namespaces, so as to facilitate the isolated use and management of resources in different groups.

Through the kubernetes authorization mechanism, different namespaces can be handed over to different tenants for management, thus realizing multi-tenant resource isolation. At this time, the resource quota mechanism of kubernetes can also be combined to limit the resources that different tenants can occupy, such as CPU usage, memory usage, etc., to realize the management of tenants' available resources.

After the cluster is started, kubernetes will create several namespaces by default

[root@master ~]# kubectl get namespace

NAME STATUS AGE

default Active 45h #All objects that do not specify a Namespace will be allocated in the default namespace

kube-node-lease Active 45h #Heartbeat maintenance between cluster nodes, introduced in v1.13

kube-public Active 45h #Resources under this namespace can be accessed by everyone (including unauthenticated users)

kube-system Active 45h #All resources created by the Kubernetes system are in this namespace

Let's look at the specific operations of namespace resources:

1. View

Shell
# 1 View all ns commands: kubectl get ns
[root@master ~]# kubectl get ns
NAME STATUS AGE
default Active 45h
kube-node-lease Active 45h
kube-public Active 45h
kube-system Active 45h

# 2 View the specified ns command: kubectl get ns ns name
[root@master ~]# kubectl get ns default
NAME STATUS AGE
default Active 45h

# 3 Specify the output format Command: kubectl get ns ns name -o format parameter
# There are many formats supported by kubernetes, compare Common ones are wide, json, and yaml
[root@master ~]# kubectl get ns default -o yaml
apiVersion: v1
kind: Namespace
metadata:
creationTimestamp: "2020-04-05T04:44:16Z"
name: default
resourceVersion: "151"
selfLink: /api/v1/namespaces/default
uid: 7405f73a-e486-43d4-9db6-145f1409f090
spec:
finalizers:
- kubernetes
status:
phase: Active

# 4 View ns details command: kubectl describe ns ns name
[root@master ~]# kubectl describe ns default
Name: default
Labels: <none>
Annotations: <none>
Status: Active # Active Namespace is in use Terminating Namespace is being deleted

# ResourceQuota Resource limit for namespace
# LimitRange is a resource limit for each component in the namespace.
No resource quota.
No LimitRange resource.

2. Create

Shell
# 创建namespace
[root@master ~]# kubectl create ns dev
namespace/dev created

3、删除

Shell
# 删除namespace
[root@master ~]# kubectl delete ns dev
namespace "dev" deleted

4、配置方式

先准备一个yaml文件：ns-dev.yaml

apiVersion: v1

kind: Namespace

metadata:

name: dev

然后就可以执行对应的创建和删除命令了：

创建：kubectl create -f ns-dev.yaml

删除：kubectl delete -f ns-dev.yaml

二、Pod

Pod是kubernetes集群进行管理的最小单元，程序要运行必须部署在容器中，而容器必须存在于Pod中。

Pod可以认为是容器的封装，一个Pod中可以存在一个或者多个容器。

kubernetes在集群启动之后，集群中的各个组件也都是以Pod方式运行的。可以通过下面命令查看：

SQL
[root@master ~]# kubectl get pod -n kube-system
NAMESPACE     NAME                             READY   STATUS    RESTARTS   AGE
kube-system   coredns-6955765f44-68g6v         1/1     Running   0          2d1h
kube-system   coredns-6955765f44-cs5r8         1/1     Running   0          2d1h
kube-system   etcd-master                      1/1     Running   0          2d1h
kube-system   kube-apiserver-master            1/1     Running   0          2d1h
kube-system   kube-controller-manager-master   1/1     Running   0          2d1h
kube-system   kube-flannel-ds-amd64-47r25      1/1     Running   0          2d1h
kube-system   kube-flannel-ds-amd64-ls5lh      1/1     Running   0          2d1h
kube-system   kube-proxy-685tk                 1/1     Running   0          2d1h
kube-system   kube-proxy-87spt                 1/1     Running   0          2d1h
kube-system   kube-scheduler-master            1/1     Running   0          2d1h

1、创建并运行

kubernetes没有提供单独运行Pod的命令，都是通过Pod控制器来实现的

Shell
# 命令格式： kubectl run (pod控制器名称) [参数]
# --image 指定Pod的镜像
# --port 指定端口
# --namespace 指定namespace
[root@master ~]# kubectl run nginx --image=nginx:1.17.1 --port=80 --namespace dev
deployment.apps/nginx created

2、查看pod信息

Shell
# 查看Pod基本信息
[root@master ~]# kubectl get pods -n dev
NAME                     READY   STATUS    RESTARTS   AGE
nginx-5ff7956ff6-fg2db   1/1     Running   0          43s

# 查看Pod的详细信息
[root@master ~]# kubectl describe pod nginx-5ff7956ff6-fg2db -n dev
Name:         nginx-5ff7956ff6-fg2db
Namespace:    dev
Priority:     0
Node:         node1/192.168.109.101
Start Time:   Wed, 08 Apr 2020 09:29:24 +0800
Labels:       pod-template-hash=5ff7956ff6
              run=nginx
Annotations: <none>
Status:       Running
IP:           10.244.1.23
IPs:
IP:           10.244.1.23
Controlled By: ReplicaSet/nginx-5ff7956ff6
Containers:
nginx:
    Container ID:   docker://4c62b8c0648d2512380f4ffa5da2c99d16e05634979973449c98e9b829f6253c
    Image:          nginx:1.17.1
    Image ID:       docker-pullable://nginx@sha256:485b610fefec7ff6c463ced9623314a04ed67e3945b9c08d7e53a47f6d108dc7
    Port:           80/TCP
    Host Port:      0/TCP
    State:          Running
      Started:      Wed, 08 Apr 2020 09:30:01 +0800
    Ready:          True
    Restart Count: 0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-hwvvw (ro)
Conditions:
Type              Status
Initialized       True
Ready             True
ContainersReady   True
PodScheduled      True
Volumes:
default-token-hwvvw:
    Type:        Secret (a volume populated by a Secret)
    SecretName: default-token-hwvvw
    Optional:    false
QoS Class:       BestEffort
Node-Selectors: <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:
Type    Reason     Age        From               Message
----    ------     ----       ----              -------
Normal Scheduled <unknown> default-scheduler Successfully assigned dev/nginx-5ff7956ff6-fg2db to node1
Normal Pulling    4m11s      kubelet, node1     Pulling image "nginx:1.17.1"
Normal Pulled     3m36s      kubelet, node1     Successfully pulled image "nginx:1.17.1"
Normal Created    3m36s      kubelet, node1     Created container nginx
Normal Started    3m36s      kubelet, node1     Started container nginx

3、访问pod信息

Shell
# 获取podIP
[root@master ~]# kubectl get pods -n dev -o wide
NAME                     READY   STATUS    RESTARTS   AGE    IP             NODE    ...
nginx-5ff7956ff6-fg2db   1/1     Running   0          190s   10.244.1.23   node1   ...

#访问POD
[root@master ~]# curl http://10.244.1.23:80
<!DOCTYPE html>
<html>
<head>
    <title>Welcome to nginx!</title>
</head>
<body>
    <p><em>Thank you for using nginx.</em></p>
</body>
</html>

4、删除指定Pod

Shell
# 删除指定Pod
[root@master ~]# kubectl delete pod nginx-5ff7956ff6-fg2db -n dev
pod "nginx-5ff7956ff6-fg2db" deleted

# 此时，显示删除Pod成功，但是再查询，发现又新产生了一个
[root@master ~]# kubectl get pods -n dev
NAME                     READY   STATUS    RESTARTS   AGE
nginx-5ff7956ff6-jj4ng   1/1     Running   0          21s

# 这是因为当前Pod是由Pod控制器创建的，控制器会监控Pod状况，一旦发现Pod死亡，会立即重建
# 此时要想删除Pod，必须删除Pod控制器

# 先来查询一下当前namespace下的Pod控制器
[root@master ~]# kubectl get deploy -n dev
NAME    READY   UP-TO-DATE   AVAILABLE   AGE
nginx   1/1     1            1           9m7s

# 接下来，删除此PodPod控制器
[root@master ~]# kubectl delete deploy nginx -n dev
deployment.apps "nginx" deleted

# 稍等片刻，再查询Pod，发现Pod被删除了
[root@master ~]# kubectl get pods -n dev
No resources found in dev namespace.

5、配置操作

创建一个pod-nginx.yaml，内容如下：

Shell
apiVersion: v1
kind: Pod
metadata:
name: nginx
namespace: dev
spec:
containers:
- image: nginx:1.17.1
    name: pod
    ports:
    - name: nginx-port
      containerPort: 80
      protocol: TCP

然后就可以执行对应的创建和删除命令了：

创建：kubectl create -f pod-nginx.yaml

删除：kubectl delete -f pod-nginx.yaml

三、Label

1、介绍

Label是kubernetes系统中的一个重要概念。它的作用就是在资源上添加标识，用来对它们进行区分和选择。

Label的特点：

一个Label会以key/value键值对的形式附加到各种对象上，如Node、Pod、Service等等

一个资源对象可以定义任意数量的Label ，同一个Label也可以被添加到任意数量的资源对象上去

Label通常在资源对象定义时确定，当然也可以在对象创建后动态添加或者删除

可以通过Label实现资源的多维度分组，以便灵活、方便地进行资源分配、调度、配置、部署等管理工作。

一些常用的Label 示例如下：

版本标签："version":"release", "version":"stable"......

环境标签："environment":"dev"，"environment":"test"，"environment":"pro"

架构标签："tier":"frontend"，"tier":"backend"

标签定义完毕之后，还要考虑到标签的选择，这就要使用到Label Selector，即：

Label用于给某个资源对象定义标识

Label Selector用于查询和筛选拥有某些标签的资源对象

当前有两种Label Selector：

基于等式的Label Selector

name = slave: 选择所有包含Label中key="name"且value="slave"的对象

env != production: 选择所有包括Label中的key="env"且value不等于"production"的对象

基于集合的Label Selector

name in (master, slave): 选择所有包含Label中的key="name"且value="master"或"slave"的对象

name not in (frontend): 选择所有包含Label中的key="name"且value不等于"frontend"的对象

标签的选择条件可以使用多个，此时将多个Label Selector进行组合，使用逗号","进行分隔即可。例如：

name=slave，env!=production

name not in (frontend)，env!=production

2、命令方式

Shell
# 为pod资源打标签
[root@master ~]# kubectl label pod nginx-pod version=1.0 -n dev
pod/nginx-pod labeled

# 为pod资源更新标签
[root@master ~]# kubectl label pod nginx-pod version=2.0 -n dev --overwrite
pod/nginx-pod labeled

# 查看标签
[root@master ~]# kubectl get pod nginx-pod -n dev --show-labels
NAME        READY   STATUS    RESTARTS   AGE   LABELS
nginx-pod   1/1    Running   0          10m   version=2.0

# 筛选标签
[root@master ~]# kubectl get pod -n dev -l version=2.0 --show-labels
NAME        READY   STATUS    RESTARTS   AGE   LABELS
nginx-pod   1/1     Running   0          17m   version=2.0
[root@master ~]# kubectl get pod -n dev -l version!=2.0 --show-labels
No resources found in dev namespace.

#删除标签
[root@master ~]# kubectl label pod nginx-pod version- -n dev
pod/nginx-pod labeled

3、配置方式

Shell
apiVersion: v1
kind: Pod
metadata:
name: nginx
namespace: dev
labels:
    version: "3.0"
    env: "test"
spec:
containers:
- image: nginx:1.17.1
    name: pod
    ports:
    - name: nginx-port
      containerPort: 80
      protocol: TCP

然后就可以执行对应的更新命令了：kubectl apply -f pod-nginx.yaml

四、Deployment

在kubernetes中，Pod是最小的控制单元，但是kubernetes很少直接控制Pod，一般都是通过Pod控制器来完成的。Pod控制器用于pod的管理，确保pod资源符合预期的状态，当pod的资源出现故障时，会尝试进行重启或重建pod。

在kubernetes中Pod控制器的种类有很多，本章节只介绍一种：Deployment。

1、命令操作

Shell
# 命令格式: kubectl run deployment名称 [参数]
# --image 指定pod的镜像
# --port   指定端口
# --replicas 指定创建pod数量
# --namespace 指定namespace
[root@master ~]# kubectl run nginx --image=nginx:1.17.1 --port=80 --replicas=3 -n dev
deployment.apps/nginx created

# 查看创建的Pod
[root@master ~]# kubectl get pods -n dev
NAME                     READY   STATUS    RESTARTS   AGE
nginx-5ff7956ff6-6k8cb   1/1     Running   0          19s
nginx-5ff7956ff6-jxfjt   1/1     Running   0          19s
nginx-5ff7956ff6-v6jqw   1/1     Running   0          19s

# 查看deployment的信息
[root@master ~]# kubectl get deploy -n dev
NAME    READY   UP-TO-DATE   AVAILABLE   AGE
nginx   3/3     3            3           2m42s

# UP-TO-DATE：成功升级的副本数量
# AVAILABLE：可用副本的数量
[root@master ~]# kubectl get deploy -n dev -o wide
NAME    READY UP-TO-DATE AVAILABLE   AGE     CONTAINERS   IMAGES              SELECTOR
nginx   3/3     3         3           2m51s   nginx        nginx:1.17.1        run=nginx

# 查看deployment的详细信息
[root@master ~]# kubectl describe deploy nginx -n dev
Name:                   nginx
Namespace:              dev
CreationTimestamp:      Wed, 08 Apr 2020 11:14:14 +0800
Labels:                 run=nginx
Annotations:            deployment.kubernetes.io/revision: 1
Selector:               run=nginx
Replicas:               3 desired | 3 updated | 3 total | 3 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy: 25% max unavailable, 25% max surge
Pod Template:
Labels: run=nginx
Containers:
nginx:
    Image:        nginx:1.17.1
    Port:         80/TCP
    Host Port:    0/TCP
    Environment: <none>
    Mounts:       <none>
Volumes:        <none>
Conditions:
Type           Status Reason
----           ------ ------
Available      True    MinimumReplicasAvailable
Progressing    True    NewReplicaSetAvailable
OldReplicaSets: <none>
NewReplicaSet:   nginx-5ff7956ff6 (3/3 replicas created)
Events:
Type    Reason             Age    From                   Message
----    ------             ----   ----                   -------
Normal ScalingReplicaSet 5m43s deployment-controller Scaled up replicaset nginx-5ff7956ff6 to 3

# 删除
[root@master ~]# kubectl delete deploy nginx -n dev
deployment.apps "nginx" deleted

2、配置操作

创建一个deploy-nginx.yaml，内容如下：

Shell
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx
namespace: dev
spec:
replicas: 3
selector:
    matchLabels:
      run: nginx
template:
    metadata:
      labels:
        run: nginx
    spec:
      containers:
      - image: nginx:1.17.1
        name: nginx
        ports:
        - containerPort: 80
          protocol: TCP

然后就可以执行对应的创建和删除命令了：

创建：kubectl create -f deploy-nginx.yaml

删除：kubectl delete -f deploy-nginx.yaml

五、service

通过上节课的学习，已经能够利用Deployment来创建一组Pod来提供具有高可用性的服务。

虽然每个Pod都会分配一个单独的Pod IP，然而却存在如下两问题：

Pod IP 会随着Pod的重建产生变化

Pod IP 仅仅是集群内可见的虚拟IP，外部无法访问

这样对于访问这个服务带来了难度。因此，kubernetes设计了Service来解决这个问题。

Service可以看作是一组同类Pod对外的访问接口。借助Service，应用可以方便地实现服务发现和负载均衡。

操作一：创建集群内部可访问的Service

Shell
# 暴露Service
[root@master ~]# kubectl expose deploy nginx --name=svc-nginx1 --type=ClusterIP --port=80 --target-port=80 -n dev
service/svc-nginx1 exposed

# 查看service
[root@master ~]# kubectl get svc svc-nginx -n dev -o wide
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
svc-nginx1 ClusterIP 10.109.179.231 <none> 80/TCP 3m51s run=nginx

# 这里产生了一个CLUSTER-IP，这就是service的IP，在Service的生命周期中，这个地址是不会变动的
# 可以通过这个IP访问当前service对应的POD
[root@master ~]# curl 10.109.179.231:80
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
</head>
<body>
<h1>Welcome to nginx!</h1>
.......
</body>
</html>

操作二：创建集群外部也可访问的Service

Shell
# 上面创建的Service的type类型为ClusterIP，这个ip地址只用集群内部可访问
# 如果需要创建外部也可以访问的Service，需要修改type为NodePort
[root@master ~]# kubectl expose deploy nginx --name=svc-nginx2 --type=NodePort --port=80 --target-port=80 -n dev
service/svc-nginx2 exposed

# 此时查看，会发现出现了NodePort类型的Service，而且有一对Port（80:31928/TC）
[root@master ~]# kubectl get svc svc-nginx-1 -n dev -o wide
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
svc-nginx2 NodePort 10.100.94.0 <none> 80:31928/TCP 9s run=nginx

# 接下来就可以通过集群外的主机访问节点IP:31928访问服务了
# 例如在的电脑主机上通过浏览器访问下面的地址
http://192.168.109.100:31928/

删除Service

Shell
[root@master ~]# kubectl delete svc svc-nginx-1 -n dev service "svc-nginx-1" deleted

配置方式

创建一个svc-nginx.yaml，内容如下：

Shell
apiVersion: v1
kind: Service
metadata:
name: svc-nginx
namespace: dev
spec:
clusterIP: 10.109.179.231
ports:
- port: 80
    protocol: TCP
    targetPort: 80
selector:
    run: nginx
type: ClusterIP

然后就可以执行对应的创建和删除命令了：

创建：kubectl create -f svc-nginx.yaml

删除：kubectl delete -f svc-nginx.yaml

Cloud Native_kubernetes(k8s)_Getting Started

1. Namespace

二、Pod

三、Label

四、Deployment

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