研发工程师玩转Kubernetes |
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研发工程师玩转Kubernetes
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多副本维护是指，对一组在任何时候都处于运行状态的 Pod 副本的稳定集合进行维护。说的直白点，就是保证某种的Pod数量会被自动维持——增加了该类Pod会自动删除多余的，减少了该类Pod会自动新增以弥补，以保证Pod数量不变。 Kubernetes是一个一直在迭代更新的系统，其多副本维护方案也经历了几个版本大的改动。本文将采用最新的Deployment方案，而不是老版本的ReplicaSet和ReplicationController。 编写清单文件在《研发工程师玩转Kubernetes——通过文件创建Service》一文中，我们通过两个不同的pod清单文件创建了两个Pod。  在这里插入图片描述可以看到，它们只是name不同。 如果我们对name没有特别的要求，这样做起来就比较繁琐。比如我们要创建1000个Pod，难道要创建1000个清单文件才可以吗？而且它们的区别只有很小。 Deployment则帮我们解决了这个问题。如下面内容 代码语言：javascript复制apiVersion: apps/v1 kind: Deployment metadata: name: simple-http-deployment spec: replicas: 2 selector: matchLabels: app: simple_http template: metadata: labels: app: simple_http spec: containers: - name: simple-http-container image: localhost:32000/simple_http:v1 ports: - containerPort: 8888kind: Deployment表示该清单文件是用来描述Deployment组件的。它和Pod之间的关系如下图，即Deployment通过ReplicaSet来管理Pods。 metadata.name: simple-http-deployment用于描述该Deployment组件名。它还有一个重要作用，就是Pod的名字也是基于它生成的。  在这里插入图片描述spec.replicas: 2表示我们将维持两个Pod的副本。 spec.selector.matchLabels.app: simple_http用于描述维持的Pod副本的匹配规则，即该Pod的app是simple_http。 template字段则是描述Pod的清单内容。它和《研发工程师玩转Kubernetes——通过文件创建Pod》的区别在于，前者不提供template.metadata.name字段。因为动态创建的Pod的名称如果需要指定，则需要在清单文件中写明。而在需要多副本维护的情况下，准确的Pod名没有太多意义。 template.metadata.labels.app和spec.selector.matchLabels.app相呼应，即Deployment维持的副本模板要强匹配app这个label。当然这个app不是必须的，我们可以改成其他的字段，因为它只是一个label。 提交部署将上述yaml文件保存为simple_http_deployment.yaml ，并执行 代码语言：javascript复制kubectl apply -f simple_http_deployment.yamldeployment.apps/simple-http-deployment created 查看Pod代码语言：javascript复制kubectl describe pods代码语言：javascript复制Name: simple-http-deployment-5995f574dc-jrm8z Namespace: default Priority: 0 Service Account: default Node: fangliang-virtual-machine/172.30.45.36 Start Time: Mon, 22 May 2023 17:07:36 +0800 Labels: app=simple_http pod-template-hash=5995f574dc Annotations: cni.projectcalico.org/containerID: 89f704ef7c1e19ee9e18e3d80c60fbf00e7c66690ea4bcd3f8bb18f7faa495bb cni.projectcalico.org/podIP: 10.1.62.161/32 cni.projectcalico.org/podIPs: 10.1.62.161/32 Status: Pending IP: IPs: Controlled By: ReplicaSet/simple-http-deployment-5995f574dc Containers: simple-http-container: Container ID: Image: localhost:32000/simple_http:v1 Image ID: Port: 8888/TCP Host Port: 0/TCP State: Waiting Reason: ContainerCreating Ready: False Restart Count: 0 Environment: Mounts: /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-l4f4q (ro) Conditions: Type Status Initialized True Ready False ContainersReady False PodScheduled True Volumes: kube-api-access-l4f4q: Type: Projected (a volume that contains injected data from multiple sources) TokenExpirationSeconds: 3607 ConfigMapName: kube-root-ca.crt ConfigMapOptional: DownwardAPI: true QoS Class: BestEffort Node-Selectors: Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s node.kubernetes.io/unreachable:NoExecute op=Exists for 300s Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 2s default-scheduler Successfully assigned default/simple-http-deployment-5995f574dc-jrm8z to fangliang-virtual-machine Normal Pulled 1s kubelet Container image "localhost:32000/simple_http:v1" already present on machine Normal Created 1s kubelet Created container simple-http-container Normal Started 0s kubelet Started container simple-http-container Name: simple-http-deployment-5995f574dc-zmczp Namespace: default Priority: 0 Service Account: default Node: fangliang-virtual-machine/172.30.45.36 Start Time: Mon, 22 May 2023 17:07:36 +0800 Labels: app=simple_http pod-template-hash=5995f574dc Annotations: cni.projectcalico.org/containerID: 37d38e3883308d283e1f21bbd2d66cecdc0b1b52342b0fc31d833c692f2c5a85 cni.projectcalico.org/podIP: 10.1.62.153/32 cni.projectcalico.org/podIPs: 10.1.62.153/32 Status: Pending IP: IPs: Controlled By: ReplicaSet/simple-http-deployment-5995f574dc Containers: simple-http-container: Container ID: Image: localhost:32000/simple_http:v1 Image ID: Port: 8888/TCP Host Port: 0/TCP State: Waiting Reason: ContainerCreating Ready: False Restart Count: 0 Environment: Mounts: /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-82c7h (ro) Conditions: Type Status Initialized True Ready False ContainersReady False PodScheduled True Volumes: kube-api-access-82c7h: Type: Projected (a volume that contains injected data from multiple sources) TokenExpirationSeconds: 3607 ConfigMapName: kube-root-ca.crt ConfigMapOptional: DownwardAPI: true QoS Class: BestEffort Node-Selectors: Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s node.kubernetes.io/unreachable:NoExecute op=Exists for 300s Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 2s default-scheduler Successfully assigned default/simple-http-deployment-5995f574dc-zmczp to fangliang-virtual-machine Normal Pulled 1s kubelet Container image "localhost:32000/simple_http:v1" already present on machine Normal Created 1s kubelet Created container simple-http-container Normal Started 0s kubelet Started container simple-http-container我们观察Name字段，可以看到Deployment生成了名字叫simple-http-deployment-5995f574dc-jrm8z和simple-http-deployment-5995f574dc-zmczp的Pod。他们都是基于Deployment的name：simple-http-deployment自动生成的。 维护实验手动删除Pod，Deployment自动增加我们删除simple-http-deployment-5995f574dc-jrm8z 代码语言：javascript复制kubectl delete pod simple-http-deployment-5995f574dc-jrm8zpod “simple-http-deployment-5995f574dc-jrm8z” deleted 然后查看Pod的状态 代码语言：javascript复制kubectl describe pods代码语言：javascript复制Name: simple-http-deployment-5995f574dc-zmczp Namespace: default Priority: 0 Service Account: default Node: fangliang-virtual-machine/172.30.45.36 Start Time: Mon, 22 May 2023 17:07:36 +0800 Labels: app=simple_http pod-template-hash=5995f574dc Annotations: cni.projectcalico.org/containerID: 37d38e3883308d283e1f21bbd2d66cecdc0b1b52342b0fc31d833c692f2c5a85 cni.projectcalico.org/podIP: 10.1.62.153/32 cni.projectcalico.org/podIPs: 10.1.62.153/32 Status: Running IP: 10.1.62.153 IPs: IP: 10.1.62.153 Controlled By: ReplicaSet/simple-http-deployment-5995f574dc Containers: simple-http-container: Container ID: containerd://9e4b29af865933cf876b8af1c9cc10a86b5ccbcc4fca2c184a56317b6a7ea097 Image: localhost:32000/simple_http:v1 Image ID: localhost:32000/simple_http@sha256:cbee584f83426593efb95a9e2213bb40143a1c86c3d217e65d30430033f846d4 Port: 8888/TCP Host Port: 0/TCP State: Running Started: Mon, 22 May 2023 17:07:38 +0800 Ready: True Restart Count: 0 Environment: Mounts: /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-82c7h (ro) Conditions: Type Status Initialized True Ready True ContainersReady True PodScheduled True Volumes: kube-api-access-82c7h: Type: Projected (a volume that contains injected data from multiple sources) TokenExpirationSeconds: 3607 ConfigMapName: kube-root-ca.crt ConfigMapOptional: DownwardAPI: true QoS Class: BestEffort Node-Selectors: Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s node.kubernetes.io/unreachable:NoExecute op=Exists for 300s Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 100s default-scheduler Successfully assigned default/simple-http-deployment-5995f574dc-zmczp to fangliang-virtual-machine Normal Pulled 100s kubelet Container image "localhost:32000/simple_http:v1" already present on machine Normal Created 100s kubelet Created container simple-http-container Normal Started 99s kubelet Started container simple-http-container Name: simple-http-deployment-5995f574dc-46kk5 Namespace: default Priority: 0 Service Account: default Node: fangliang-virtual-machine/172.30.45.36 Start Time: Mon, 22 May 2023 17:08:57 +0800 Labels: app=simple_http pod-template-hash=5995f574dc Annotations: cni.projectcalico.org/containerID: b755b01f8ead112314377158b6a9520bec9a02f4be97edfdf906f715b6fd4a94 cni.projectcalico.org/podIP: 10.1.62.157/32 cni.projectcalico.org/podIPs: 10.1.62.157/32 Status: Running IP: 10.1.62.157 IPs: IP: 10.1.62.157 Controlled By: ReplicaSet/simple-http-deployment-5995f574dc Containers: simple-http-container: Container ID: containerd://c0354e53cf916d8d826f5e8a2bf0a475c038b47bddb947b0fb7233be612f139f Image: localhost:32000/simple_http:v1 Image ID: localhost:32000/simple_http@sha256:cbee584f83426593efb95a9e2213bb40143a1c86c3d217e65d30430033f846d4 Port: 8888/TCP Host Port: 0/TCP State: Running Started: Mon, 22 May 2023 17:08:57 +0800 Ready: True Restart Count: 0 Environment: Mounts: /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-wvsx8 (ro) Conditions: Type Status Initialized True Ready True ContainersReady True PodScheduled True Volumes: kube-api-access-wvsx8: Type: Projected (a volume that contains injected data from multiple sources) TokenExpirationSeconds: 3607 ConfigMapName: kube-root-ca.crt ConfigMapOptional: DownwardAPI: true QoS Class: BestEffort Node-Selectors: Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s node.kubernetes.io/unreachable:NoExecute op=Exists for 300s Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 20s default-scheduler Successfully assigned default/simple-http-deployment-5995f574dc-46kk5 to fangliang-virtual-machine Normal Pulled 20s kubelet Container image "localhost:32000/simple_http:v1" already present on machine Normal Created 20s kubelet Created container simple-http-container Normal Started 20s kubelet Started container simple-http-container可以看到simple-http-deployment-5995f574dc-zmczp没有变动，simple-http-deployment-5995f574dc-jrm8z被删除了（可能会处在Terminating中间状态），simple-http-deployment-5995f574dc-46kk5被新建出来。 手动调整副本我们可以通过kubectl scale指令调整的大小，比如下面指令将副本数调整为1。 代码语言：javascript复制kubectl scale deployment simple-http-deployment --replicas=1deployment.apps/simple-http-deployment scaled 查看现存的Pod 代码语言：javascript复制 kubectl describe pod代码语言：javascript复制Name: simple-http-deployment-5995f574dc-zmczp Namespace: default Priority: 0 Service Account: default Node: fangliang-virtual-machine/172.30.45.36 Start Time: Mon, 22 May 2023 17:07:36 +0800 Labels: app=simple_http pod-template-hash=5995f574dc Annotations: cni.projectcalico.org/containerID: 37d38e3883308d283e1f21bbd2d66cecdc0b1b52342b0fc31d833c692f2c5a85 cni.projectcalico.org/podIP: 10.1.62.153/32 cni.projectcalico.org/podIPs: 10.1.62.153/32 Status: Running IP: 10.1.62.153 IPs: IP: 10.1.62.153 Controlled By: ReplicaSet/simple-http-deployment-5995f574dc Containers: simple-http-container: Container ID: containerd://9e4b29af865933cf876b8af1c9cc10a86b5ccbcc4fca2c184a56317b6a7ea097 Image: localhost:32000/simple_http:v1 Image ID: localhost:32000/simple_http@sha256:cbee584f83426593efb95a9e2213bb40143a1c86c3d217e65d30430033f846d4 Port: 8888/TCP Host Port: 0/TCP State: Running Started: Mon, 22 May 2023 17:07:38 +0800 Ready: True Restart Count: 0 Environment: Mounts: /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-82c7h (ro) Conditions: Type Status Initialized True Ready True ContainersReady True PodScheduled True Volumes: kube-api-access-82c7h: Type: Projected (a volume that contains injected data from multiple sources) TokenExpirationSeconds: 3607 ConfigMapName: kube-root-ca.crt ConfigMapOptional: DownwardAPI: true QoS Class: BestEffort Node-Selectors: Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s node.kubernetes.io/unreachable:NoExecute op=Exists for 300s Events:可以看到只有simple-http-deployment-5995f574dc-zmczp存在了。 查看Deployment代码语言：javascript复制kubectl describe deployments.apps simple-http-deployment 代码语言：javascript复制Name: simple-http-deployment Namespace: default CreationTimestamp: Mon, 22 May 2023 17:07:36 +0800 Labels: Annotations: deployment.kubernetes.io/revision: 1 Selector: app=simple_http Replicas: 1 desired | 1 updated | 1 total | 1 available | 0 unavailable StrategyType: RollingUpdate MinReadySeconds: 0 RollingUpdateStrategy: 25% max unavailable, 25% max surge Pod Template: Labels: app=simple_http Containers: simple-http-container: Image: localhost:32000/simple_http:v1 Port: 8888/TCP Host Port: 0/TCP Environment: Mounts: Volumes: Conditions: Type Status Reason ---- ------ ------ Progressing True NewReplicaSetAvailable Available True MinimumReplicasAvailable OldReplicaSets: NewReplicaSet: simple-http-deployment-5995f574dc (1/1 replicas created) Events:我们看到Deployment下有个字段NewReplicaSet，它是其管理的ReplicaSet的名字。 查看ReplicaSetDeployment底层是通过ReplicaSet来实现的，我们可以通过下面指令看下rc 代码语言：javascript复制kubectl describe replicasets.apps代码语言：javascript复制Name: simple-http-deployment-5995f574dc Namespace: default Selector: app=simple_http,pod-template-hash=5995f574dc Labels: app=simple_http pod-template-hash=5995f574dc Annotations: deployment.kubernetes.io/desired-replicas: 1 deployment.kubernetes.io/max-replicas: 2 deployment.kubernetes.io/revision: 1 Controlled By: Deployment/simple-http-deployment Replicas: 1 current / 1 desired Pods Status: 1 Running / 0 Waiting / 0 Succeeded / 0 Failed Pod Template: Labels: app=simple_http pod-template-hash=5995f574dc Containers: simple-http-container: Image: localhost:32000/simple_http:v1 Port: 8888/TCP Host Port: 0/TCP Environment: Mounts: Volumes: Events:可以看到这个RC的Name是simple-http-deployment-5995f574dc，而之前通过Deployment创建的Pod的名字是simple-http-deployment-5995f574dc-zmczp、simple-http-deployment-5995f574dc-jrm8z和simple-http-deployment-5995f574dc-46kk5——它们的名气都是RC的名字拼接上几个字符。即： ReplicaSet Name = Deployment Name + “-” +“some hash”Pod Name = ReplicaSet Name+ “-” +“some hash”而且新创建的Pod都会带上label： pod-template-hash=5995f574dc。RC通过Selector中的指定pod-template-hash=5995f574dc来聚合这些Pod。 手动新增Pod，Deployment自动删除我们已经洞悉上述Deployment使用RC simple-http-deployment-5995f574dc来维护副本，而RC使用了app=simple_http,pod-template-hash=5995f574dc来筛选Pod。如果我们手工创建一个符合这些label的Pod，看看什么效果。 代码语言：javascript复制apiVersion: v1 kind: Pod metadata: name: simple-http-c labels: name: simple-http-c app: simple_http pod-template-hash: 5995f574dc spec: containers: - name: simple-http-container image: localhost:32000/simple_http:v1 ports: - containerPort: 8888保存为simple_http_c.yaml，然后执行 代码语言：javascript复制kubectl create -f simple_http_c.yamlpod/simple-http-c created 我们再查看rc 代码语言：javascript复制kubectl describe replicasets.apps代码语言：javascript复制Name: simple-http-deployment-5995f574dc Namespace: default Selector: app=simple_http,pod-template-hash=5995f574dc Labels: app=simple_http pod-template-hash=5995f574dc Annotations: deployment.kubernetes.io/desired-replicas: 1 deployment.kubernetes.io/max-replicas: 2 deployment.kubernetes.io/revision: 1 Controlled By: Deployment/simple-http-deployment Replicas: 1 current / 1 desired Pods Status: 2 Running / 0 Waiting / 0 Succeeded / 0 Failed Pod Template: Labels: app=simple_http pod-template-hash=5995f574dc Containers: simple-http-container: Image: localhost:32000/simple_http:v1 Port: 8888/TCP Host Port: 0/TCP Environment: Mounts: Volumes: Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal SuccessfulDelete 19s replicaset-controller Deleted pod: simple-http-c可以看到刚刚创建的Pod被删除了。此时simple-http-c处于Terminating状态。 该RC还是维持着动态调整后的副本数。 删除代码语言：javascript复制kubectl delete deployments.apps simple-http-deploymentdeployment.apps “simple-http-deployment” deleted 此时我们看到这个Deployment创建的Pod也会被删除 代码语言：javascript复制kubectl describe pod代码语言：javascript复制Name: simple-http-deployment-5995f574dc-zmczp Namespace: default Priority: 0 Service Account: default Node: fangliang-virtual-machine/172.30.45.36 Start Time: Mon, 22 May 2023 17:07:36 +0800 Labels: app=simple_http pod-template-hash=5995f574dc Annotations: cni.projectcalico.org/containerID: 37d38e3883308d283e1f21bbd2d66cecdc0b1b52342b0fc31d833c692f2c5a85 cni.projectcalico.org/podIP: 10.1.62.153/32 cni.projectcalico.org/podIPs: 10.1.62.153/32 Status: Terminating (lasts ) Termination Grace Period: 30s IP: 10.1.62.153 IPs: IP: 10.1.62.153 Controlled By: ReplicaSet/simple-http-deployment-5995f574dc Containers: simple-http-container: Container ID: containerd://9e4b29af865933cf876b8af1c9cc10a86b5ccbcc4fca2c184a56317b6a7ea097 Image: localhost:32000/simple_http:v1 Image ID: localhost:32000/simple_http@sha256:cbee584f83426593efb95a9e2213bb40143a1c86c3d217e65d30430033f846d4 Port: 8888/TCP Host Port: 0/TCP State: Running Started: Mon, 22 May 2023 17:07:38 +0800 Ready: True Restart Count: 0 Environment: Mounts: /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-82c7h (ro) Conditions: Type Status Initialized True Ready True ContainersReady True PodScheduled True Volumes: kube-api-access-82c7h: Type: Projected (a volume that contains injected data from multiple sources) TokenExpirationSeconds: 3607 ConfigMapName: kube-root-ca.crt ConfigMapOptional: DownwardAPI: true QoS Class: BestEffort Node-Selectors: Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s node.kubernetes.io/unreachable:NoExecute op=Exists for 300s Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Killing 27s kubelet Stopping container simple-http-container参考资料https://kubernetes.io/zh-cn/docs/concepts/workloads/controllers/deployment/https://kubernetes.io/zh-cn/docs/concepts/workloads/controllers/replicaset/https://kubernetes.io/zh-cn/docs/concepts/workloads/controllers/replicationcontroller/ |
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