Quick start to kubernetes series tutorial

1.1 Clusters and Nodes

kubernetes is an open source container engine management platform, which implements automated deployment of containerized applications, task scheduling, resilience scaling, load balancing and other functions. The cluster is composed of master and node roles, in which master is responsible for managing the cluster. The master node is composed of kube-apiserver, kube-controller-manager, kube-scheduler, etcd roles, and the node node runs in practice.The application consists of Container Runtime, kubelet, and kube-proxy, where Container Runtime may be Docker, rke, containerd, and node nodes may be composed of physical or virtual machines.

1. View master component roles

[root@node-1 ~]# kubectl get componentstatuses NAME STATUS MESSAGE ERROR scheduler Healthy ok controller-manager Healthy ok etcd-0 Healthy {"health":"true"}

2. View node list

[root@node-1 ~]# kubectl get nodes NAME STATUS ROLES AGE VERSION node-1 Ready master 26h v1.14.1 node-2 Ready <none> 26h v1.14.1 node-3 Ready <none> 26h v1.14.1

3. View node details

[root@node-1 ~]# kubectl describe node node-3 Name: node-3 Roles: <none> Labels: beta.kubernetes.io/arch=amd64. #Labels and Annotations beta.kubernetes.io/os=linux kubernetes.io/arch=amd64 kubernetes.io/hostname=node-3 kubernetes.io/os=linux Annotations: flannel.alpha.coreos.com/backend-data: {"VtepMAC":"22:f8:75:bb:da:4e"} flannel.alpha.coreos.com/backend-type: vxlan flannel.alpha.coreos.com/kube-subnet-manager: true flannel.alpha.coreos.com/public-ip: 10.254.100.103 kubeadm.alpha.kubernetes.io/cri-socket: /var/run/dockershim.sock node.alpha.kubernetes.io/ttl: 0 volumes.kubernetes.io/controller-managed-attach-detach: true CreationTimestamp: Sat, 10 Aug 2019 17:50:00 +0800 Taints: <none> Unschedulable: false. #Whether scheduling is disabled, the identity bit controlled by the cordon command. Conditions: #Resource scheduling capability, memory Pressure memory pressure (i.e., insufficient memory) #DiskPressure Disk Pressure #PIDPressure Disk Pressure #Ready, Ready, indicating whether the node is working properly, indicating that resources are available + the related process is working properly Type Status LastHeartbeatTime LastTransitionTime Reason Message ---- ------ ----------------- ------------------ ------ ------- MemoryPressure False Sun, 11 Aug 2019 20:32:07 +0800 Sat, 10 Aug 2019 17:50:00 +0800 KubeletHasSufficientMemory kubelet has sufficient memory available DiskPressure False Sun, 11 Aug 2019 20:32:07 +0800 Sat, 10 Aug 2019 17:50:00 +0800 KubeletHasNoDiskPressure kubelet has no disk pressure PIDPressure False Sun, 11 Aug 2019 20:32:07 +0800 Sat, 10 Aug 2019 17:50:00 +0800 KubeletHasSufficientPID kubelet has sufficient PID available Ready True Sun, 11 Aug 2019 20:32:07 +0800 Sat, 10 Aug 2019 18:04:20 +0800 KubeletReady kubelet is posting ready status Addresses: #Address and hostname InternalIP: 10.254.100.103 Hostname: node-3 Capacity: #Resource capacity of containers cpu: 2 ephemeral-storage: 51473868Ki hugepages-2Mi: 0 memory: 3880524Ki pods: 110 Allocatable: #Allocated resources cpu: 2 ephemeral-storage: 47438316671 hugepages-2Mi: 0 memory: 3778124Ki pods: 110 System Info: #System information, such as kernel version, operating system version, cpu architecture, node node software version Machine ID: 0ea734564f9a4e2881b866b82d679dfc System UUID: D98ECAB1-2D9E-41CC-9A5E-51A44DC5BB97 Boot ID: 6ec81f5b-cb05-4322-b47a-a8e046d9bf79 Kernel Version: 3.10.0-957.el7.x86_64 OS Image: CentOS Linux 7 (Core) Operating System: linux Architecture: amd64 Container Runtime Version: docker://18.3.1. #Container Runtime is docker, version 18.3.1 Kubelet Version: v1.14.1 #kubelet version Kube-Proxy Version: v1.14.1 #kube-proxy version PodCIDR: 10.244.2.0/24 #Network used by pod Non-terminated Pods: (4 in total). #Here are the resource usage per pod Namespace Name CPU Requests CPU Limits Memory Requests Memory Limits AGE --------- ---- ------------ ---------- --------------- ------------- --- kube-system coredns-fb8b8dccf-hrqm8 100m (5%) 0 (0%) 70Mi (1%) 170Mi (4%) 26h kube-system coredns-fb8b8dccf-qwwks 100m (5%) 0 (0%) 70Mi (1%) 170Mi (4%) 26h kube-system kube-flannel-ds-amd64-zzm2g 100m (5%) 100m (5%) 50Mi (1%) 50Mi (1%) 26h kube-system kube-proxy-x8zqh 0 (0%) 0 (0%) 0 (0%) 0 (0%) 26h Allocated resources: #Allocated resources (Total limits may be over 100 percent, i.e., overcommitted.) Resource Requests Limits -------- -------- ------ cpu 300m (15%) 100m (5%) memory 190Mi (5%) 390Mi (10%) ephemeral-storage 0 (0%) 0 (0%) Events: <none>

1.2 Containers and Applications

Kubernetes is the container orchestration engine, which is responsible for container scheduling, management and container operation. However, the smallest unit of kubernetes scheduling is not container, but pod. A pod can contain multiple containers. Usually, pod is not run directly in the cluster, but through various controllers such as Deployments, ReplicaSets, DaemonSets. What?Because the controller ensures the consistency of the pod state, as officially described,'make sure the current state match to the desire state', ensures that the current state is consistent with the expected state. Simply put, the pod is abnormal, and the controller rebuilds at other nodes to ensure that the pod currently running in the cluster is consistent with the expected settings.

• Container, a lightweight virtualization technology, enables easy deployment and distribution of applications by encapsulating them in a mirror.
• Pod, the smallest dispatching unit in kubernetes, encapsulates containers that contain a pause container and an application container, sharing the same namespace, network, storage, and sharing processes between containers.
• Deployments, also known as deployment groups, are strictly stateless applications. Another stateless application is StatefulSets. Deployments is a controller that controls the replicas of an application and controls the status of the replicas through Deployments Controller in kube-controller-manager.

1.3 Service Access

The pod in kubernetes is the carrier that actually runs. The pod is attached to the node. The node may fail. The controller of kubernetes, such as replicasets, will pull up a pod on other nodes, and the new pod will assign a new IP. Furthermore, the application deployment will contain multiple copies of replicas, just like an application deployment deployment deployments deploying three copies of pod, which is equivalent to the Real Server on the back end.How do you access these three applications?In this case, we usually add a load balancing Load Balancer in front of Real Server. Service is the load balancing scheduler of pod. Service abstracts dynamic pod as a service. Application can access service directly, and service automatically forwards requests to back-end pod.There are two mechanisms responsible for service forwarding rules: iptables and ipvs, iptables achieve load balancing by setting rules such as DNA T, and IPVS sets forwarding rules through ipvsadm.

Depending on how services are accessed, services are categorized into the following types: ClusterIP, NodePort, LoadBalancer, and _ExternalName, which can be set by type.

• ClusterIP, intra-cluster mutual access, and DNS are combined to achieve intra-cluster service discovery;
• NodePort, which exposes a port for each node through NAT for external access;
• LoadBalancer, an interface for external access for cloud vendors, relies on cloud service providers to implement specific technical details, such as Tencent Cloud integration with CBB.

• ExternalName, which exposes the service name through the service name, is currently implemented by ingress and forwards external requests to the cluster in the form of domain name forwarding. It depends on specific external implementations, such as nginx, traefik, and access details by major cloud computing vendors.

  Pod is dynamic, ip address may change (such as node failure), replica number may change, such as the application of extended scale up, the application of lock scale down, etc. How can service recognize the dynamic change of pod?The answer is labels, which automatically filters out the Endpoints of an application and automatically updates them when the pod changes. Different applications are made up of different labels.For labels, you can refer to the following https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/

2. Create an application

We started deploying an application called deployments. Kubernetes contains various workloads such as Deployments with stateless words, StatefulSets with statefulness, DaemonSets with daemon processes, and workloads in the United States and China correspond to different application scenarios. We started with Deployments as an example, and other workloads are similar. Generally, deploying applications in kubernetes is done as yaml filesDeployment, for beginners, writing yaml files is too lengthy for beginners to learn, let's first implement the access of API by kubectl command line.

1. Deploy nginx applications and deploy three copies

[root@node-1 ~]# kubectl run nginx-app-demo --image=nginx:1.7.9 --port=80 --replicas=3 kubectl run --generator=deployment/apps.v1 is DEPRECATED and will be removed in a future version. Use kubectl run --generator=run-pod/v1 or kubectl create instead. deployment.apps/nginx-app-demo created

2. Look at the application list, you can see that the current pod state is normal, Ready is the current state, AVAILABLE is the target state

[root@node-1 ~]# kubectl get deployments NAME READY UP-TO-DATE AVAILABLE AGE nginx-app-demo 3/3 3 3 72s

3. Look at the details of the application. As we can see below, Deployments controls the number of copies through ReplicaSets and the number of pod s through ReplicaSets

[root@node-1 ~]# kubectl describe deployments nginx-app-demo Name: nginx-app-demo #apply name Namespace: default #Namespace CreationTimestamp: Sun, 11 Aug 2019 21:52:32 +0800 Labels: run=nginx-app-demo #Labels, important, subsequent service s are accessed through labels Annotations: deployment.kubernetes.io/revision: 1 #Rolling Upgrade Version Number Selector: run=nginx-app-demo #selector for labels Replicas: 3 desired | 3 updated | 3 total | 3 available | 0 unavailable #Replica Controller StrategyType: RollingUpdate #Upgrade policy to RollingUpdate MinReadySeconds: 0 RollingUpdateStrategy: 25% max unavailable, 25% max surge #RollingUpdate upgrade policy, i.e. pod up to 25% Pod Template: #Container application template, including mirror, port, storage, etc. Labels: run=nginx-app-demo Containers: nginx-app-demo: Image: nginx:1.7.9 Port: 80/TCP Host Port: 0/TCP Environment: <none> Mounts: <none> Volumes: <none> Conditions: #current state Type Status Reason ---- ------ ------ Available True MinimumReplicasAvailable Progressing True NewReplicaSetAvailable OldReplicaSets: <none> NewReplicaSet: nginx-app-demo-7bdfd97dcd (3/3 replicas created) #ReplicaSets Controller Name Events: #Run Events Type Reason Age From Message ---- ------ ---- ---- ------- Normal ScalingReplicaSet 3m24s deployment-controller Scaled up replica set nginx-app-demo-7bdfd97dcd to 3

4. Look at replicasets and see that the replicasets replica controller generated three pod s

1. See replicasets list [root@node-1 ~]# kubectl get replicasets NAME DESIRED CURRENT READY AGE nginx-app-demo-7bdfd97dcd 3 3 3 9m9s 2. See replicasets details [root@node-1 ~]# kubectl describe replicasets nginx-app-demo-7bdfd97dcd Name: nginx-app-demo-7bdfd97dcd Namespace: default Selector: pod-template-hash=7bdfd97dcd,run=nginx-app-demo Labels: pod-template-hash=7bdfd97dcd #labels, add a hash label recognition replicasets run=nginx-app-demo Annotations: deployment.kubernetes.io/desired-replicas: 3 #Rolling Upgrade Information, Replica Tree, Maximum Number, Application Version deployment.kubernetes.io/max-replicas: 4 deployment.kubernetes.io/revision: 1 Controlled By: Deployment/nginx-app-demo #Parent control of the copy, for nginx-app-demo this Deployments Replicas: 3 current / 3 desired Pods Status: 3 Running / 0 Waiting / 0 Succeeded / 0 Failed Pod Template: #Container template, inherited from deployments Labels: pod-template-hash=7bdfd97dcd run=nginx-app-demo Containers: nginx-app-demo: Image: nginx:1.7.9 Port: 80/TCP Host Port: 0/TCP Environment: <none> Mounts: <none> Volumes: <none> Events: #Event log, generating three different pod s Type Reason Age From Message ---- ------ ---- ---- ------- Normal SuccessfulCreate 9m25s replicaset-controller Created pod: nginx-app-demo-7bdfd97dcd-hsrft Normal SuccessfulCreate 9m25s replicaset-controller Created pod: nginx-app-demo-7bdfd97dcd-qtbzd Normal SuccessfulCreate 9m25s replicaset-controller Created pod: nginx-app-demo-7bdfd97dcd-7t72x

5. View the pod and apply the deployed carrier. A nginx container is deployed in the pod and an IP is assigned to access the application directly through the ip.

1. See pod List of, and replicasets Generated names are consistent [root@node-1 ~]# kubectl get pods NAME READY STATUS RESTARTS AGE nginx-app-demo-7bdfd97dcd-7t72x 1/1 Running 0 13m nginx-app-demo-7bdfd97dcd-hsrft 1/1 Running 0 13m nginx-app-demo-7bdfd97dcd-qtbzd 1/1 Running 0 13m //View details of the pod [root@node-1 ~]# kubectl describe pods nginx-app-demo-7bdfd97dcd-7t72x Name: nginx-app-demo-7bdfd97dcd-7t72x Namespace: default Priority: 0 PriorityClassName: <none> Node: node-3/10.254.100.103 Start Time: Sun, 11 Aug 2019 21:52:32 +0800 Labels: pod-template-hash=7bdfd97dcd #labels name run=nginx-app-demo Annotations: <none> Status: Running IP: 10.244.2.4 #ip address of pod Controlled By: ReplicaSet/nginx-app-demo-7bdfd97dcd #Replica controller is replicasets Containers: #Container information, including container id, mirror, drop button, state, environment variable, etc. nginx-app-demo: Container ID: docker://5a0e5560583c5929e9768487cef43b045af4c6d3b7b927d9daf181cb28867766 Image: nginx:1.7.9 Image ID: docker-pullable://nginx@sha256:e3456c851a152494c3e4ff5fcc26f240206abac0c9d794affb40e0714846c451 Port: 80/TCP Host Port: 0/TCP State: Running Started: Sun, 11 Aug 2019 21:52:40 +0800 Ready: True Restart Count: 0 Environment: <none> Mounts: /var/run/secrets/kubernetes.io/serviceaccount from default-token-txhkc (ro) Conditions: #Status conditions of containers Type Status Initialized True Ready True ContainersReady True PodScheduled True Volumes: #Container Volume default-token-txhkc: Type: Secret (a volume populated by a Secret) SecretName: default-token-txhkc Optional: false QoS Class: BestEffort #QOS Type Node-Selectors: <none> #Stain type Tolerations: node.kubernetes.io/not-ready:NoExecute for 300s node.kubernetes.io/unreachable:NoExecute for 300s Events: #Event state, mirror pull, launch container Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 14m default-scheduler Successfully assigned default/nginx-app-demo-7bdfd97dcd-7t72x to node-3 Normal Pulling 14m kubelet, node-3 Pulling image "nginx:1.7.9" Normal Pulled 14m kubelet, node-3 Successfully pulled image "nginx:1.7.9" Normal Created 14m kubelet, node-3 Created container nginx-app-demo Normal Started 14m kubelet, node-3 Started container nginx-app-demo

3. Accessing applications

kubernetes assigns an ip address to each pod, through which an application can be accessed directly, which is equivalent to accessing RS, but an application is a whole, consists of multiple copies, and relies on services to achieve load balancing of the application. service explores how ClusterIP and NodePort are accessed.

3.1 Access to Pod IP

1. Set up the content of the pod. For easy distinction, we set the nginx site content of the three pods to be different to see the effect of load balancing

See pod list [root@node-1 ~]# kubectl get pods NAME READY STATUS RESTARTS AGE nginx-app-demo-7bdfd97dcd-7t72x 1/1 Running 0 28m nginx-app-demo-7bdfd97dcd-hsrft 1/1 Running 0 28m nginx-app-demo-7bdfd97dcd-qtbzd 1/1 Running 0 28m //Enter the pod container [root@node-1 ~]# kubectl exec -it nginx-app-demo-7bdfd97dcd-7t72x /bin/bash //Set up site content [root@nginx-app-demo-7bdfd97dcd-7t72x:/# echo "web1" >/usr/share/nginx/html/index.html //By analogy, set the contents of the other two pod s to web2 and web3 [root@nginx-app-demo-7bdfd97dcd-hsrft:/# echo web2 >/usr/share/nginx/html/index.html [root@nginx-app-demo-7bdfd97dcd-qtbzd:/# echo web3 >/usr/share/nginx/html/index.html

2. Get the ip address of the pod, how to get the ip address of the pod quickly? You can display more content through the -o wide parameter, which will include the node and ip to which the pod belongs.

[root@node-1 ~]# kubectl get pods -o wide NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES nginx-app-demo-7bdfd97dcd-7t72x 1/1 Running 0 34m 10.244.2.4 node-3 <none> <none> nginx-app-demo-7bdfd97dcd-hsrft 1/1 Running 0 34m 10.244.1.2 node-2 <none> <none> nginx-app-demo-7bdfd97dcd-qtbzd 1/1 Running 0 34m 10.244.1.3 node-2 <none> <none>

3. Visit the ip of the pod to see the content of the site, different pod site content is consistent with the above steps.

[root@node-1 ~]# curl http://10.244.2.4 web1 [root@node-1 ~]# curl http://10.244.1.2 web2 [root@node-1 ~]# curl http://10.244.1.3 web3

3.2 ClusterIP Access

Direct ip access applications through pods can be implemented for single pod applications, but applications with multiple replicas do not meet the requirements. Load balancing needs to be achieved through services, which need to set different type s, defaulting to ClusterIP, which means internal cluster access. Services are exposed to services through the expose subcommand as follows.

1. Expose the service, where port represents the proxy listening port, target-port represents the port of the container, type sets the type of service

[root@node-1 ~]# kubectl expose deployment nginx-app-demo --name nginx-service-demo \ --port=80 \ --protocol=TCP \ --target-port=80 \ --type ClusterIP service/nginx-service-demo exposed

2. Check the details of the service to see that the service automatically generates endpoints for the pod's ip via the labels selector

See service List, showing two, kubernetes Created for the default cluster service [root@node-1 ~]# kubectl get services NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 29h nginx-service-demo ClusterIP 10.102.1.1 <none> 80/TCP 2m54s //Looking at the service details, you can see that Labels'eletor matches the previous Deployments settings, and Endpoints makes up a list of pod s [root@node-1 ~]# kubectl describe services nginx-service-demo Name: nginx-service-demo #Name Namespace: default #Namespace Labels: run=nginx-app-demo #Label Name Annotations: <none> Selector: run=nginx-app-demo #tag chooser Type: ClusterIP #service type is ClusterIP IP: 10.102.1.1 #The ip of the service, vip, is automatically assigned within the cluster Port: <unset> 80/TCP #Service Port, which is the port ClusterIP accesses outdoors TargetPort: 80/TCP #Container Port Endpoints: 10.244.1.2:80,10.244.1.3:80,10.244.2.4:80 #Access Address List Session Affinity: None #Load Balance Scheduling Algorithm Events: <none>

3. By accessing the address of the service, you can see that the service automatically balances the load of the pods. The scheduling strategy is polling. Why?Because the service's default dispatch policy, Session Affinity, is None, which is a round-robin training, can be set to ClientIP to maintain session, and requests from the same client IP are dispatched to the same pod.

[root@node-1 ~]# curl http://10.102.1.1 web3 [root@node-1 ~]# curl http://10.102.1.1 web1 [root@node-1 ~]# curl http://10.102.1.1 web2 [root@node-1 ~]# curl http://10.102.1.1

4. In-depth analysis of ClusterIP principle, there are two mechanisms to implement service backend: iptables and ipvs. Environment installation uses iptables, iptables generate access rules through nat chain, KUBE-SVC-R5Y5DZHD7Q6DDTFZ is inbound DNA T forwarding rule, KUBE-MARK-MASQ is outbound forwarding rule.

[root@node-1 ~]# iptables -t nat -L -n Chain KUBE-SERVICES (2 references) target prot opt source destination KUBE-MARK-MASQ tcp -- !10.244.0.0/16 10.102.1.1 /* default/nginx-service-demo: cluster IP */ tcp dpt:80 KUBE-SVC-R5Y5DZHD7Q6DDTFZ tcp -- 0.0.0.0/0 10.102.1.1 /* default/nginx-service-demo: cluster IP */ tcp dpt:80 Outbound: When the KUBE-MARK-MASQ source address segment is not 10.244.0.0/16 accessing target port 80 of 10.102.1.1, forward the request to the KUBE-MARK-MASQ chain Inbound: Forward request to KUBE-SVC-R5Y5DZHD7Q6DDTFZ chain when any original address accesses target port 80 of target 10.102.1.1

5. View the inbound request rules. The inbound request rules will be mapped to different chains, and different chains will be forwarded to different pod ip s.

1. View Inbound Rules KUBE-SVC-R5Y5DZHD7Q6DDTFZ，Request will be forwarded to three chains [root@node-1 ~]# iptables -t nat -L KUBE-SVC-R5Y5DZHD7Q6DDTFZ -n Chain KUBE-SVC-R5Y5DZHD7Q6DDTFZ (1 references) target prot opt source destination KUBE-SEP-DSWLUQNR4UPH24AX all -- 0.0.0.0/0 0.0.0.0/0 statistic mode random probability 0.33332999982 KUBE-SEP-56SLMGHHOILJT36K all -- 0.0.0.0/0 0.0.0.0/0 statistic mode random probability 0.50000000000 KUBE-SEP-K6G4Z74HQYF6X7SI all -- 0.0.0.0/0 0.0.0.0/0 2. View the rules for the three chains actually forwarded,Actually map to different pod Of ip Address [root@node-1 ~]# iptables -t nat -L KUBE-SEP-DSWLUQNR4UPH24AX -n Chain KUBE-SEP-DSWLUQNR4UPH24AX (1 references) target prot opt source destination KUBE-MARK-MASQ all -- 10.244.1.2 0.0.0.0/0 DNAT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp to:10.244.1.2:80 [root@node-1 ~]# iptables -t nat -L KUBE-SEP-56SLMGHHOILJT36K -n Chain KUBE-SEP-56SLMGHHOILJT36K (1 references) target prot opt source destination KUBE-MARK-MASQ all -- 10.244.1.3 0.0.0.0/0 DNAT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp to:10.244.1.3:80 [root@node-1 ~]# iptables -t nat -L KUBE-SEP-K6G4Z74HQYF6X7SI -n Chain KUBE-SEP-K6G4Z74HQYF6X7SI (1 references) target prot opt source destination KUBE-MARK-MASQ all -- 10.244.2.4 0.0.0.0/0 DNAT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp to:10.244.2.4:80

3.3 NodePort Access

Services can only provide access to applications within a cluster through ClusterIP, but can not access applications directly from outside. If external access is required, there are several ways: NodePort, LoadBalancer and Ingress, where LoadBalancer needs to be implemented by a cloud Service provider, Ingress needs to install a separate Ingress Controller, daily testing can be done through NodePort, and NodePort canExpose a port of the node to external network access.

1. Modify the type of the type from ClusterIP to NodePort (or recreate it, specifying that the type is NodePort)

1. adopt patch modify type Type of [root@node-1 ~]# kubectl patch services nginx-service-demo -p '{"spec":{"type": "NodePort"}}' service/nginx-service-demo patched 2. confirm yaml File configuration, assigned a NodePort Ports, that is, each node Will listen on this port [root@node-1 ~]# kubectl get services nginx-service-demo -o yaml apiVersion: v1 kind: Service metadata: creationTimestamp: "2019-08-11T14:35:59Z" labels: run: nginx-app-demo name: nginx-service-demo namespace: default resourceVersion: "157676" selfLink: /api/v1/namespaces/default/services/nginx-service-demo uid: 55e29b78-bc45-11e9-b073-525400490421 spec: clusterIP: 10.102.1.1 externalTrafficPolicy: Cluster ports: - nodePort: 32416 #A NodePort port is automatically assigned port: 80 protocol: TCP targetPort: 80 selector: run: nginx-app-demo sessionAffinity: None type: NodePort #Modify type to NodePort status: loadBalancer: {} 3. See service List, you know service Of type Has been modified to NodePort,Also retained ClusterIP Access to IP [root@node-1 ~]# kubectl get services NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 30h nginx-service-demo NodePort 10.102.1.1 <none> 80:32416/TCP 68m

2. Accessing applications through NodePort, where each node's address corresponds to vip, achieves the same load balancing effect and CluserIP functionality is available

1. NodePort Load balancing [root@node-1 ~]# curl http://node-1:32416 web1 [root@node-1 ~]# curl http://node-2:32416 web1 [root@node-1 ~]# curl http://node-3:32416 web1 [root@node-1 ~]# curl http://node-3:32416 web3 [root@node-1 ~]# curl http://node-3:32416 web2 2. ClusterIP Load balancing [root@node-1 ~]# curl http://10.102.1.1 web2 [root@node-1 ~]# curl http://10.102.1.1 web1 [root@node-1 ~]# curl http://10.102.1.1 web1 [root@node-1 ~]# curl http://10.102.1.1 web3

3. NodePort forwarding principle, each node listens on the port of NodePort through kube-proxy, and the port is forwarded by iptables on the back end

1. NodePort Listening Port [root@node-1 ~]# netstat -antupl |grep 32416 tcp6 0 0 :::32416 :::* LISTEN 32052/kube-proxy 2. See nat Table forwarding rules, there are two rules KUBE-MARK-MASQ Export and KUBE-SVC-R5Y5DZHD7Q6DDTFZ Inbound direction. Chain KUBE-NODEPORTS (1 references) target prot opt source destination KUBE-MARK-MASQ tcp -- 0.0.0.0/0 0.0.0.0/0 /* default/nginx-service-demo: */ tcp dpt:32416 KUBE-SVC-R5Y5DZHD7Q6DDTFZ tcp -- 0.0.0.0/0 0.0.0.0/0 /* default/nginx-service-demo: */ tcp dpt:32416 3. View inbound request rule chain KUBE-SVC-R5Y5DZHD7Q6DDTFZ [root@node-1 ~]# iptables -t nat -L KUBE-SVC-R5Y5DZHD7Q6DDTFZ -n Chain KUBE-SVC-R5Y5DZHD7Q6DDTFZ (2 references) target prot opt source destination KUBE-SEP-DSWLUQNR4UPH24AX all -- 0.0.0.0/0 0.0.0.0/0 statistic mode random probability 0.33332999982 KUBE-SEP-56SLMGHHOILJT36K all -- 0.0.0.0/0 0.0.0.0/0 statistic mode random probability 0.50000000000 KUBE-SEP-K6G4Z74HQYF6X7SI all -- 0.0.0.0/0 0.0.0.0/0 4. Continue to view forwarding chains containing DNAT Forwarding and KUBE-MARK-MASQ And rules for outbound returns [root@node-1 ~]# iptables -t nat -L KUBE-SEP-DSWLUQNR4UPH24AX -n Chain KUBE-SEP-DSWLUQNR4UPH24AX (1 references) target prot opt source destination KUBE-MARK-MASQ all -- 10.244.1.2 0.0.0.0/0 DNAT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp to:10.244.1.2:80 [root@node-1 ~]# iptables -t nat -L KUBE-SEP-56SLMGHHOILJT36K -n Chain KUBE-SEP-56SLMGHHOILJT36K (1 references) target prot opt source destination KUBE-MARK-MASQ all -- 10.244.1.3 0.0.0.0/0 DNAT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp to:10.244.1.3:80 [root@node-1 ~]# iptables -t nat -L KUBE-SEP-K6G4Z74HQYF6X7SI -n Chain KUBE-SEP-K6G4Z74HQYF6X7SI (1 references) target prot opt source destination KUBE-MARK-MASQ all -- 10.244.2.4 0.0.0.0/0 DNAT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp to:10.244.2.4:80

4. Extend applications

When the application load is too high to satisfy the application request, we usually expand the number of RS. In kubernetes, expanding RS is actually done by expanding the number of replicas, which makes expanding RS very convenient and fast to achieve flexible scaling.kubernets can provide two scaling capabilities: 1. manual scaling capabilities scale up and scale down, 2. dynamic elastic scaling horizontalpodautoscalers, based on the utilization rate of CPU to achieve automatic elastic scaling, need to rely on and monitor components such as metrics server, which is not currently implemented, and will be further explored later. This paper expands the number of copies of applications by manual scaling.

1. Manually expand the number of copies

[root@node-1 ~]# kubectl scale --replicas=4 deployment nginx-app-demo deployment.extensions/nginx-app-demo scaled

2. View replica extensions and deployments automatically deploy an application

[root@node-1 ~]# kubectl get deployments NAME READY UP-TO-DATE AVAILABLE AGE nginx-app-demo 4/4 4 4 133m

3. What happens to the service at this time?View service details, new extended pod s will be automatically updated to service endpoints, automatic service discovery

See service details [root@node-1 ~]# kubectl describe services nginx-service-demo Name: nginx-service-demo Namespace: default Labels: run=nginx-app-demo Annotations: <none> Selector: run=nginx-app-demo Type: NodePort IP: 10.102.1.1 Port: <unset> 80/TCP TargetPort: 80/TCP NodePort: <unset> 32416/TCP Endpoints: 10.244.1.2:80,10.244.1.3:80,10.244.2.4:80 + 1 more...#Address has been added automatically Session Affinity: None External Traffic Policy: Cluster Events: <none> //View endpioints details [root@node-1 ~]# kubectl describe endpoints nginx-service-demo Name: nginx-service-demo Namespace: default Labels: run=nginx-app-demo Annotations: endpoints.kubernetes.io/last-change-trigger-time: 2019-08-11T16:04:56Z Subsets: Addresses: 10.244.1.2,10.244.1.3,10.244.2.4,10.244.2.5 NotReadyAddresses: <none> Ports: Name Port Protocol ---- ---- -------- <unset> 80 TCP Events: <none>

4. Test, set the new pod site content to web4, refer to the previous setup method, test the ip of service to see the load balancing effect

[root@node-1 ~]# curl http://10.102.1.1 web4 [root@node-1 ~]# curl http://10.102.1.1 web4 [root@node-1 ~]# curl http://10.102.1.1 web2 [root@node-1 ~]# curl http://10.102.1.1 web3 [root@node-1 ~]# curl http://10.102.1.1 web1 [root@node-1 ~]# curl http://10.102.1.1 web2 [root@node-1 ~]# curl http://10.102.1.1 web1

Thus, elastic scaling is automatically added to the service to achieve service auto-discovery and load balancing, and the application scaling is much faster than traditional applications.

5. Rolling Upgrade

When updating an application in kubernetes, you can package the application in a mirror and then update the application's mirror to upgrade.The default Deployments upgrade strategy is RollingUpdate, which updates 25% of the pods in the application each time, creating new pods to replace one by one, preventing the application from becoming unavailable during the upgrade process.At the same time, if the application upgrade process fails, the application can also be rolled back to its previous state by rollback, which is achieved by replicasets.

1. Replace the mirror of nginx, upgrade the application to the latest version, open another window and use kubectl get pods -w to watch the upgrade process

[root@node-1 ~]# kubectl set image deployments/nginx-app-demo nginx-app-demo=nginx:latest deployment.extensions/nginx-app-demo image updated

2. Watch the upgrade process and see that the upgrade process is a new + delete way to replace the pod one by one

[root@node-1 ~]# kubectl get pods -w NAME READY STATUS RESTARTS AGE nginx-app-demo-7bdfd97dcd-7t72x 1/1 Running 0 145m nginx-app-demo-7bdfd97dcd-hsrft 1/1 Running 0 145m nginx-app-demo-7bdfd97dcd-j6lgd 1/1 Running 0 12m nginx-app-demo-7bdfd97dcd-qtbzd 1/1 Running 0 145m nginx-app-demo-5cc8746f96-xsxz4 0/1 Pending 0 0s #Create a new pod nginx-app-demo-5cc8746f96-xsxz4 0/1 Pending 0 0s nginx-app-demo-7bdfd97dcd-j6lgd 1/1 Terminating 0 14m #Delete old pod, replace nginx-app-demo-5cc8746f96-xsxz4 0/1 ContainerCreating 0 0s nginx-app-demo-5cc8746f96-s49nv 0/1 Pending 0 0s #New Second pod nginx-app-demo-5cc8746f96-s49nv 0/1 Pending 0 0s nginx-app-demo-5cc8746f96-s49nv 0/1 ContainerCreating 0 0s nginx-app-demo-7bdfd97dcd-j6lgd 0/1 Terminating 0 14m #Replace the second pod nginx-app-demo-5cc8746f96-s49nv 1/1 Running 0 7s nginx-app-demo-7bdfd97dcd-qtbzd 1/1 Terminating 0 146m nginx-app-demo-5cc8746f96-txjqh 0/1 Pending 0 0s nginx-app-demo-5cc8746f96-txjqh 0/1 Pending 0 0s nginx-app-demo-5cc8746f96-txjqh 0/1 ContainerCreating 0 0s nginx-app-demo-7bdfd97dcd-j6lgd 0/1 Terminating 0 14m nginx-app-demo-7bdfd97dcd-j6lgd 0/1 Terminating 0 14m nginx-app-demo-5cc8746f96-xsxz4 1/1 Running 0 9s nginx-app-demo-5cc8746f96-txjqh 1/1 Running 0 1s nginx-app-demo-7bdfd97dcd-hsrft 1/1 Terminating 0 146m nginx-app-demo-7bdfd97dcd-qtbzd 0/1 Terminating 0 146m nginx-app-demo-5cc8746f96-rcpmw 0/1 Pending 0 0s nginx-app-demo-5cc8746f96-rcpmw 0/1 Pending 0 0s nginx-app-demo-5cc8746f96-rcpmw 0/1 ContainerCreating 0 0s nginx-app-demo-7bdfd97dcd-7t72x 1/1 Terminating 0 146m nginx-app-demo-7bdfd97dcd-7t72x 0/1 Terminating 0 147m nginx-app-demo-7bdfd97dcd-hsrft 0/1 Terminating 0 147m nginx-app-demo-7bdfd97dcd-hsrft 0/1 Terminating 0 147m nginx-app-demo-5cc8746f96-rcpmw 1/1 Running 0 2s nginx-app-demo-7bdfd97dcd-7t72x 0/1 Terminating 0 147m nginx-app-demo-7bdfd97dcd-7t72x 0/1 Terminating 0 147m nginx-app-demo-7bdfd97dcd-hsrft 0/1 Terminating 0 147m nginx-app-demo-7bdfd97dcd-hsrft 0/1 Terminating 0 147m nginx-app-demo-7bdfd97dcd-qtbzd 0/1 Terminating 0 147m nginx-app-demo-7bdfd97dcd-qtbzd 0/1 Terminating 0 147m

3. Check the details of the deployments again to see that the deployments have replaced the new replicasets. The original replicasets version is 1 and can be used for rollback.

[root@node-1 ~]# kubectl describe deployments nginx-app-demo Name: nginx-app-demo Namespace: default CreationTimestamp: Sun, 11 Aug 2019 21:52:32 +0800 Labels: run=nginx-app-demo Annotations: deployment.kubernetes.io/revision: 2 #New version number for rollback Selector: run=nginx-app-demo Replicas: 4 desired | 4 updated | 4 total | 4 available | 0 unavailable StrategyType: RollingUpdate MinReadySeconds: 0 RollingUpdateStrategy: 25% max unavailable, 25% max surge Pod Template: Labels: run=nginx-app-demo Containers: nginx-app-demo: Image: nginx:latest 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-app-demo-5cc8746f96 (4/4 replicas created) #A new replicaset, actually replacing the new replicasets Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal ScalingReplicaSet 19m deployment-controller Scaled up replica set nginx-app-demo-7bdfd97dcd to 4 Normal ScalingReplicaSet 4m51s deployment-controller Scaled up replica set nginx-app-demo-5cc8746f96 to 1 Normal ScalingReplicaSet 4m51s deployment-controller Scaled down replica set nginx-app-demo-7bdfd97dcd to 3 Normal ScalingReplicaSet 4m51s deployment-controller Scaled up replica set nginx-app-demo-5cc8746f96 to 2 Normal ScalingReplicaSet 4m43s deployment-controller Scaled down replica set nginx-app-demo-7bdfd97dcd to 2 Normal ScalingReplicaSet 4m43s deployment-controller Scaled up replica set nginx-app-demo-5cc8746f96 to 3 Normal ScalingReplicaSet 4m42s deployment-controller Scaled down replica set nginx-app-demo-7bdfd97dcd to 1 Normal ScalingReplicaSet 4m42s deployment-controller Scaled up replica set nginx-app-demo-5cc8746f96 to 4 Normal ScalingReplicaSet 4m42s deployment-controller Scaled down replica set nginx-app-demo-7bdfd97dcd to 0

4. Looking at the version of the rolling upgrade, you can see two versions corresponding to two different replicasets

[root@node-1 ~]# kubectl rollout history deployment nginx-app-demo deployment.extensions/nginx-app-demo REVISION CHANGE-CAUSE 1 <none> 2 <none> //View the replicasets list, old containing pod 0 [root@node-1 ~]# kubectl get replicasets NAME DESIRED CURRENT READY AGE nginx-app-demo-5cc8746f96 4 4 4 9m2s nginx-app-demo-7bdfd97dcd 0 0 0 155m

5. Test the upgrade of the application and find that nginx has been upgraded to the latest nginx/1.17.2 version

[root@node-1 ~]# curl -I http://10.102.1.1 HTTP/1.1 200 OK Server: nginx/1.17.2 #nginx version information Date: Sun, 11 Aug 2019 16:30:03 GMT Content-Type: text/html Content-Length: 612 Last-Modified: Tue, 23 Jul 2019 11:45:37 GMT Connection: keep-alive ETag: "5d36f361-264" Accept-Ranges: bytes

6. Roll back to the old version

[root@node-1 ~]# kubectl rollout undo deployment nginx-app-demo --to-revision=1 deployment.extensions/nginx-app-demo rolled back //Test the application again and roll back to the old version. [root@node-1 ~]# curl -I http://10.102.1.1 HTTP/1.1 200 OK Server: nginx/1.7.9 Date: Sun, 11 Aug 2019 16:34:33 GMT Content-Type: text/html Content-Length: 612 Last-Modified: Tue, 23 Dec 2014 16:25:09 GMT Connection: keep-alive ETag: "54999765-264" Accept-Ranges: bytes

Write at the end: This article explores the most important concepts involved in kubernetes in command line practice: application deployment, load balancing, resilient scaling and roll-up, and acts as a command line. Readers can quickly get started by referencing the document, which will be mostly deployed as a yaml file and interact with kubernets.

Reference Documents

Basic concepts: https://kubernetes.io/docs/tutorials/kubernetes-basics/

Deploy applications: https://kubernetes.io/docs/tutorials/kubernetes-basics/deploy-app/deploy-intro/

Access applications: https://kubernetes.io/docs/tutorials/kubernetes-basics/explore/explore-intro/

External access: https://kubernetes.io/docs/tutorials/kubernetes-basics/expose/expose-intro/

Access applications: https://kubernetes.io/docs/tutorials/kubernetes-basics/scale/scale-intro/

Rolling Upgrade: https://kubernetes.io/docs/tutorials/kubernetes-basics/update/update-intro/

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