一、Deployment的概念
K8S本身并不提供网络的功能，所以需要借助第三方网络插件进行部署K8S中的网络，以打通各个节点中容器的互通。
POD，是K8S中的一个逻辑概念，K8S管理的是POD，一个POD中包含多个容器，容器之间通过localhost互通。而POD需要ip地址。每个POD都有一个标签
POD–>RC–>RS–>Deployment （发展历程）
Deployment，表示用户对K8S集群的一次更新操作。Deployment是一个比RS应用模式更广的API对象。用于保证Pod的副本的数量。
可以是创建一个新的服务，更新一个新的服务，也可以是滚动升级一个服务。滚动升级一个服务。实际是创建一个新的RS，然后将新的RS中副本数增加到理想状态，将旧的RS中的副本数减小到0的复合操作；
RC、RS和Deployment只是保证了支撑服务的POD数量，但是没有解决如何访问这些服务的问题。一个POD只是一个运行服务的实例，随时可以能在一个节点上停止，在另一个节点以一个新的IP启动一个新的POD，因此不能以确定的IP和端口号提供服务。
要稳定地提供服务需要服务发现和负载均衡能力。服务发现完成的工作，是针对客户端访问的服务，找到对应的后端服务实例。
在K8S的集中当中，客户端需要访问的服务就是Service对象。每个Service会对应一个集群内部有效的虚拟IP，集群内部通过虚拟IP访问一个服务。
二、创建K8S的第一个应用
[root@linux-node1 ~]# kubectl run net-test --image=alpine --replicas=2 sleep 36000 #创建名称为net-test的应用，镜像指定为alpine，副本数为2个
deployment.apps "net-test" created
[root@linux-node1 ~]# kubectl get pod -o wide #查看pod的状态信息，此时是API Server从etcd中读取这些数据
NAME READY STATUS RESTARTS AGE IP NODE
net-test-7b949fc785-2v2qz 1/1 Running 0 56s 10.2.87.2 192.168.56.120
net-test-7b949fc785-6nrhm 0/1 ContainerCreating 0 56s <none> 192.168.56.130
[root@linux-node1 ~]# kubectl get deployment net-test
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
net-test 2 2 2 2 22hkubectl get deployment命令可以查看net-test的状态，输出显示两个副本正常运行。还可以在创建的过程中，通过kubectl describe deployment net-test了解详细的信息。[root@linux-node1 ~]# kubectl describe deployment net-test
Name: net-test
Namespace: default
CreationTimestamp: Thu, 16 Aug 2018 15:41:29 +0800
Labels: run=net-test
Annotations: deployment.kubernetes.io/revision=1
Selector: run=net-test
Replicas: 2 desired | 2 updated | 2 total | 2 available | 0 unavailable
StrategyType: RollingUpdate
MinReadySeconds: 0
RollingUpdateStrategy: 1 max unavailable, 1 max surge
Pod Template:
Labels: run=net-test
Containers:
net-test:
Image: alpine
Port: <none>
Host Port: <none>
Args:
sleep
360000
Environment: <none>
Mounts: <none>
Volumes: <none>
Conditions:
Type Status Reason
---- ------ ------
Available True MinimumReplicasAvailable
Progressing True NewReplicaSetAvailable
OldReplicaSets: <none>
NewReplicaSet: net-test-5767cb94df (2/2 replicas created)
Events: <none>Events是Deployment的日志，记录整个RelicaSet的启动过程，从上面的创建过程，可以看到Deployment是通过ReplicaSet来管理Pod。
[root@linux-node1 ~]# kubectl get replicaset #获取副本集信息
NAME DESIRED CURRENT READY AGE
net-test-5767cb94df 2 2 2 23h
[root@linux-node1 ~]# kubectl describe replicaset net-test-5767cb94df #查看副本集的详细信息
Name: net-test-5767cb94df
Namespace: default
Selector: pod-template-hash=1323765089,run=net-test
Labels: pod-template-hash=1323765089
run=net-test
Annotations: deployment.kubernetes.io/desired-replicas=2
deployment.kubernetes.io/max-replicas=3
deployment.kubernetes.io/revision=1
Controlled By: Deployment/net-test #指明ReplicaSet是由Deployment net-test创建
Replicas: 2 current / 2 desired
Pods Status: 3 Running / 0 Waiting / 0 Succeeded / 0 Failed
Pod Template:
Labels: pod-template-hash=1323765089
run=net-test
Containers:
net-test:
Image: alpine
Port: <none>
Host Port: <none>
Args:
sleep
360000
Environment: <none>
Mounts: <none>
Volumes: <none>
Events: <none> #Events可以查看到两个副本Pod的创建过程
[root@linux-node1 ~]# kubectl get pod #获取Pod信息，可以看到2个副本都处于Running状态
NAME READY STATUS RESTARTS AGE
net-test-5767cb94df-djt98 1/1 Running 0 22h
net-test-5767cb94df-zb8m4 1/1 Running 0 23h
[root@linux-node1 ~]# kubectl describe pod net-test-5767cb94df-djt98 #查看pod的详细信息
Name: net-test-5767cb94df-djt98
Namespace: default
Node: 192.168.56.13/192.168.56.13
Start Time: Thu, 16 Aug 2018 15:53:00 +0800
Labels: pod-template-hash=1323765089
run=net-test
Annotations: <none>
Status: Running
IP: 10.2.73.3
Controlled By: ReplicaSet/net-test-5767cb94df
Containers:
net-test:
Container ID: docker://c8e267326ed80f3cbe8111377c74dd1f016beaef513196b941165e180a5d5733
Image: alpine
Image ID: docker-pullable://alpine@sha256:7043076348bf5040220df6ad703798fd8593a0918d06d3ce30c6c93be117e430
Port: <none>
Host Port: <none>
Args:
sleep
360000
State: Running
Started: Thu, 16 Aug 2018 15:53:06 +0800
Ready: True
Restart Count: 0
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-mnqx5 (ro)
Conditions:
Type Status
Initialized True
Ready True
PodScheduled True
Volumes:
default-token-mnqx5:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-mnqx5
Optional: false
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: <none>
Events: <none>Controlled By 指明此 Pod 是由 ReplicaSet/net-test-5767cb94df 创建。Events 记录了 Pod 的启动过程。如果操作失败（比如 image 不存在），也能在这里查看到原因。
总结创建的过程：
（1）用户通过kubectl创建Deployment
（2）Deployment创建ReplicaSet
（3）ReplicaSet创建Pod
如图：
三、K8S创建资源的两种方式
Kubernetes 支持两种方式创建资源：
（1）用kubectl命令直接创建，在命令行中通过参数指定资源的属性。此方式简单直观，比较适合临时测试或实验使用。
kubectl run net-test --image=alpine --replicas=2 sleep 36000（2）通过配置文件和kubectl create创建。在配置文件中描述了应用的信息和需要达到的预期状态。
kubectl create -f nginx-deployment.yaml四、以Deployment YAML方式创建Nginx服务
- 1、创建deployment
[root@linux-node1 ~]# vim nginx-deployment.yaml #使用yaml的方式进行创建应用
apiVersion: apps/v1 #apiVersion是当前配置格式的版本
kind: Deployment #kind是要创建的资源类型，这里是Deploymnet
metadata: #metadata是该资源的元数据，name是必须的元数据项
name: nginx-deployment
labels:
app: nginx
spec: #spec部分是该Deployment的规则说明
replicas: 3 #relicas指定副本数量，默认为1
selector:
matchLabels:
app: nginx
template: #template定义Pod的模板，这是配置的重要部分
metadata: #metadata定义Pod的元数据，至少要顶一个label，label的key和value可以任意指定
labels:
app: nginx
spec: #spec描述的是Pod的规则，此部分定义pod中每一个容器的属性，name和image是必需的
containers:
- name: nginx
image: nginx:1.13.12
ports:
- containerPort: 80
[root@linux-node1 ~]# kubectl create -f nginx-deployment.yaml #创建nginx-deployment应用
deployment.apps "nginx-deployment" created- 2、查看deployment
[root@linux-node1 ~]# kubectl get deployment
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
net-test 2 2 2 2 32m
nginx-deployment 3 3 3 0 10s
[root@linux-node1 ~]# kubectl describe deployment nginx-deployment #查看deployment详情
Name: nginx-deployment
Namespace: default
CreationTimestamp: Thu, 16 Aug 2018 16:13:37 +0800
Labels: app=nginx
Annotations: deployment.kubernetes.io/revision=1
Selector: app=nginx
Replicas: 3 desired | 3 updated | 3 total | 0 available | 3 unavailable
StrategyType: RollingUpdate
MinReadySeconds: 0
RollingUpdateStrategy: 25% max unavailable, 25% max surge
Pod Template:
Labels: app=nginx
Containers:
nginx:
Image: nginx:1.13.12
Port: 80/TCP
Host Port: 0/TCP
Environment: <none>
Mounts: <none>
Volumes: <none>
Conditions:
Type Status Reason
---- ------ ------
Available False MinimumReplicasUnavailable
Progressing True ReplicaSetUpdated
OldReplicaSets: <none>
NewReplicaSet: nginx-deployment-6c45fc49cb (3/3 replicas created)
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal ScalingReplicaSet 1m deployment-controller Scaled up replica set nginx-deployment-6c45fc49cb to 3- 3、查看Pod
[root@linux-node1 ~]# kubectl get pod #查看pod在状态，正在创建中，此时应该正在拉取镜像
NAME READY STATUS RESTARTS AGE
net-test-5767cb94df-djt98 1/1 Running 0 22m
net-test-5767cb94df-hcwv7 1/1 Unknown 0 34m
net-test-5767cb94df-zb8m4 1/1 Running 0 34m
nginx-deployment-6c45fc49cb-dmc22 0/1 ContainerCreating 0 2m
nginx-deployment-6c45fc49cb-fd8xm 0/1 ContainerCreating 0 2m
nginx-deployment-6c45fc49cb-sc8sh 0/1 ContainerCreating 0 2m
[root@linux-node1 ~]# kubectl describe pod nginx-deployment-6c45fc49cb-dmc22 #查看具体某个pod的状态信息
[root@linux-node1 ~]# kubectl get pod -o wide #创建成功，状态为Running
NAME READY STATUS RESTARTS AGE IP NODE
net-test-5767cb94df-djt98 1/1 Running 0 24m 10.2.73.3 192.168.56.13
net-test-5767cb94df-hcwv7 1/1 Unknown 0 36m 10.2.10.2 192.168.56.12
net-test-5767cb94df-zb8m4 1/1 Running 0 36m 10.2.73.2 192.168.56.13
nginx-deployment-6c45fc49cb-dmc22 1/1 Running 0 4m 10.2.73.6 192.168.56.13
nginx-deployment-6c45fc49cb-fd8xm 1/1 Running 0 4m 10.2.73.4 192.168.56.13
nginx-deployment-6c45fc49cb-sc8sh 1/1 Running 0 4m 10.2.73.5 192.168.56.13Deployment、ReplicaSet、Pod 都已经就绪。如果要删除这些资源，执行 kubectl delete deployment nginx-deployment 或者 kubectl delete -f nginx-deployment.yaml。
- 4、测试Pod访问
[root@linux-node1 ~]# curl --head http://10.2.73.6
HTTP/1.1 200 OK
Server: nginx/1.13.12
Date: Thu, 16 Aug 2018 08:18:14 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Mon, 09 Apr 2018 16:01:09 GMT
Connection: keep-alive
ETag: "5acb8e45-264"
Accept-Ranges: bytes- 5、更新Deployment
[root@linux-node1 ~]# kubectl set image deployment/nginx-deployment nginx=nginx:1.15.2 --record #nginx的版本升级，由1.13.2升级为1.15.2，记录需要加参数--record
deployment.apps "nginx-deployment" image updated
[root@linux-node1 ~]# kubectl get deployment -o wide #查看更新后的deployment，可以看到当前4个副本，说明还在滚动升级中
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
net-test 2 2 2 2 39m net-test alpine run=net-test
nginx-deployment 3 4 1 3 6m nginx nginx:1.15.2 app=nginx- 6、查看更新历史
[root@linux-node1 ~]# kubectl rollout history deployment/nginx-deployment #查看更新历史记录
deployments "nginx-deployment"
REVISION CHANGE-CAUSE
1 <none>
2 kubectl set image deployment/nginx-deployment nginx=nginx:1.15.2 --record=true- 7、查看具体某一个版本的升级历史
[root@linux-node1 ~]# kubectl rollout history deployment/nginx-deployment --revision=1
deployments "nginx-deployment" with revision #1
Pod Template:
Labels: app=nginx
pod-template-hash=2701970576
Containers:
nginx:
Image: nginx:1.13.12
Port: 80/TCP
Host Port: 0/TCP
Environment: <none>
Mounts: <none>
Volumes: <none>- 8、查看更新后的Deployment，并进行访问
[root@linux-node1 ~]# kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE
net-test-5767cb94df-djt98 1/1 Running 0 30m 10.2.73.3 192.168.56.13
net-test-5767cb94df-hcwv7 1/1 Unknown 0 42m 10.2.10.2 192.168.56.12
net-test-5767cb94df-zb8m4 1/1 Running 0 42m 10.2.73.2 192.168.56.13
nginx-deployment-64749d4b59-djttr 1/1 Running 0 37s 10.2.73.8 192.168.56.13
nginx-deployment-64749d4b59-jp7fw 1/1 Running 0 3m 10.2.73.7 192.168.56.13
nginx-deployment-64749d4b59-q4fsn 1/1 Running 0 33s 10.2.73.9 192.168.56.13
[root@linux-node1 ~]# curl --head http://10.2.73.7
HTTP/1.1 200 OK
Server: nginx/1.15.2 #版本已经升级为1.15.2
Date: Thu, 16 Aug 2018 08:24:09 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 24 Jul 2018 13:02:29 GMT
Connection: keep-alive
ETag: "5b572365-264"
Accept-Ranges: bytes- 9、快速回滚到上一个版本
[root@linux-node1 ~]# kubectl rollout undo deployment/nginx-deployment #回滚上一个版本
deployment.apps "nginx-deployment"
[root@linux-node1 ~]# kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE
net-test-5767cb94df-djt98 1/1 Running 0 32m 10.2.73.3 192.168.56.13
net-test-5767cb94df-hcwv7 1/1 Unknown 0 43m 10.2.10.2 192.168.56.12
net-test-5767cb94df-zb8m4 1/1 Running 0 43m 10.2.73.2 192.168.56.13
nginx-deployment-6c45fc49cb-b9h84 1/1 Running 0 24s 10.2.73.11 192.168.56.13
nginx-deployment-6c45fc49cb-g4mrg 1/1 Running 0 26s 10.2.73.10 192.168.56.13
nginx-deployment-6c45fc49cb-k29kq 1/1 Running 0 21s 10.2.73.12 192.168.56.13
[root@linux-node1 ~]# curl --head http://10.2.73.10
HTTP/1.1 200 OK
Server: nginx/1.13.12
Date: Thu, 16 Aug 2018 08:25:35 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Mon, 09 Apr 2018 16:01:09 GMT
Connection: keep-alive
ETag: "5acb8e45-264"
Accept-Ranges: bytes
回滚完成，每一次更新或者回滚ip都会变化，所以需要通过vip进行访问，这就引入了service- 10、使用service的vip进行访问应用
[root@linux-node1 ~]# vim nginx-service.yaml #使用yaml方式创建service
kind: Service
apiVersion: v1
metadata:
name: nginx-service
spec:
selector:
app: nginx
ports:
- protocol: TCP
port: 80
targetPort: 80
[root@linux-node1 ~]# kubectl create -f nginx-service.yaml #创建service
service "nginx-service" created
[root@linux-node1 ~]# kubectl get service
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.1.0.1 <none> 443/TCP 4h
nginx-service ClusterIP 10.1.213.126 <none> 80/TCP 15s #这个就是vip
[root@linux-node2 ~]# curl --head http://10.1.213.126 #在node2节点上进行访问vip测试，在node1上无法访问是因为没有安装kube-proxy导致无法访问
HTTP/1.1 200 OK
Server: nginx/1.13.12
Date: Thu, 16 Aug 2018 08:30:08 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Mon, 09 Apr 2018 16:01:09 GMT
Connection: keep-alive
ETag: "5acb8e45-264"
Accept-Ranges: bytes
[root@linux-node2 ~]# ipvsadm -Ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 10.1.0.1:443 rr persistent 10800
-> 192.168.56.11:6443 Masq 1 0 0
TCP 10.1.213.126:80 rr
-> 10.2.73.10:80 Masq 1 0 1
-> 10.2.73.11:80 Masq 1 0 1
-> 10.2.73.12:80 Masq 1 0 0
查看LVS状态可以看到，当访问VIP：10.1.213.126时，会进行负载均衡到各个pod- 11、扩容到5个节点
[root@linux-node1 ~]# kubectl scale deployment nginx-deployment --replicas 5 #对应用的副本数进行扩容，直接指定副本数为5
deployment.extensions "nginx-deployment" scaled
[root@linux-node1 ~]# kubectl get pod #查看pod状态，可以看到已经增加到5个副本
NAME READY STATUS RESTARTS AGE
net-test-5767cb94df-djt98 1/1 Running 0 38m
net-test-5767cb94df-hcwv7 1/1 Unknown 0 50m
net-test-5767cb94df-zb8m4 1/1 Running 0 50m
nginx-deployment-6c45fc49cb-b9h84 1/1 Running 0 6m
nginx-deployment-6c45fc49cb-g4mrg 1/1 Running 0 7m
nginx-deployment-6c45fc49cb-k29kq 1/1 Running 0 6m
nginx-deployment-6c45fc49cb-n9qkx 1/1 Running 0 24s
nginx-deployment-6c45fc49cb-xpx9s 1/1 Running 0 24s
[root@linux-node2 ~]# ipvsadm -Ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 10.1.0.1:443 rr persistent 10800
-> 192.168.56.11:6443 Masq 1 0 0
TCP 10.1.213.126:80 rr
-> 10.2.73.10:80 Masq 1 0 0
-> 10.2.73.11:80 Masq 1 0 0
-> 10.2.73.12:80 Masq 1 0 1
-> 10.2.73.13:80 Masq 1 0 0
-> 10.2.73.14:80 Masq 1 0 0
Don't forget the beginner's mind
