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k8s(Kubernetes) 中 Pod,Deployment,ReplicaSet,Service 之间关系分析

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发布于: 2021 年 03 月 24 日
k8s(Kubernetes)中Pod,Deployment,ReplicaSet,Service之间关系分析

看完 k8s 文档,好多概念似乎明白了,又似乎不明白,多个概念之间的关系也很混乱,不是很明白,不要紧,接下来,好好分析一下。


结论


您有可能在急着找答案搜到我这篇文章,不费话,结论就在开头,请看下图。

deploy 控制 RS,RS 控制 Pod,这一整套,向外提供稳定可靠的 Service。

分析

以下是分析的过程

  • 首先,我们先从最小的调度单位 pod 开始。

我的 k8s 集群中目前有一个 pod,它的 name 为 mq-svc-5b96bf78d9-brpjw

[root@VM_0_17_centos ~]# kubectl get podsNAME                      READY     STATUS    RESTARTS   AGEmq-svc-5b96bf78d9-brpjw   1/1       Running   0          51m
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来看一下它的详情

[root@VM_0_17_centos ~]# kubectl describe pod mq-svc-5b96bf78d9-brpjwName:           mq-svc-5b96bf78d9-brpjwNamespace:      defaultNode:           10.0.0.17/10.0.0.17Start Time:     Fri, 17 Aug 2018 17:24:44 +0800Labels:         pod-template-hash=1652693485                qcloud-app=mq-svcAnnotations:    <none>Status:         RunningIP:             172.16.0.39Controlled By:  ReplicaSet/mq-svc-5b96bf78d9Containers:  queue-mq:    Container ID:   docker://700cdc55c111a413faaa8cabb8680009d2663701ccbe84b8a50ea6e6fe1d538c    Image:          rabbitmq:management    Image ID:       docker-pullable://rabbitmq@sha256:0b36ea1a8df9e53228aaeee277680de2cc97c7d675bc2d5dbe1cc9e3836a9d9f    Port:           <none>    Host Port:      <none>    State:          Running      Started:      Fri, 17 Aug 2018 17:24:49 +0800    Ready:          True    Restart Count:  0    Limits:      cpu:     500m      memory:  1Gi    Requests:      cpu:        250m      memory:     256Mi    Environment:  <none>    Mounts:      /var/run/secrets/kubernetes.io/serviceaccount from default-token-vzhz4 (ro)Conditions:  Type           Status  Initialized    True   Ready          True   PodScheduled   True Volumes:  default-token-vzhz4:    Type:        Secret (a volume populated by a Secret)    SecretName:  default-token-vzhz4    Optional:    falseQoS Class:       BurstableNode-Selectors:  <none>Tolerations:     <none>Events:  Type    Reason                 Age   From                Message  ----    ------                 ----  ----                -------  Normal  Scheduled              51m   default-scheduler   Successfully assigned mq-svc-5b96bf78d9-brpjw to 10.0.0.17  Normal  SuccessfulMountVolume  51m   kubelet, 10.0.0.17  MountVolume.SetUp succeeded for volume "default-token-vzhz4"  Normal  Pulling                51m   kubelet, 10.0.0.17  pulling image "rabbitmq:management"  Normal  Pulled                 51m   kubelet, 10.0.0.17  Successfully pulled image "rabbitmq:management"  Normal  Created                51m   kubelet, 10.0.0.17  Created container  Normal  Started                51m   kubelet, 10.0.0.17  Started container
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其实有一个敏感的信息,pod 是被一个名字为 mq-svc-5b96bf78d9 的 ReplicaSet 管理的,所以我们认为,RS 是比 Pod 高一级别的专门用来管理 pod 的组件。一个 RS 会管理一批 pod。

Controlled By:  ReplicaSet/mq-svc-5b96bf78d9
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而且在 pod 里面发生的实践也都是对容器的操作,比如拉取镜像、启动容器等等

Events:  Type    Reason                 Age   From                Message  ----    ------                 ----  ----                -------  Normal  Scheduled              51m   default-scheduler   Successfully assigned mq-svc-5b96bf78d9-brpjw to 10.0.0.17  Normal  SuccessfulMountVolume  51m   kubelet, 10.0.0.17  MountVolume.SetUp succeeded for volume "default-token-vzhz4"  Normal  Pulling                51m   kubelet, 10.0.0.17  pulling image "rabbitmq:management"  Normal  Pulled                 51m   kubelet, 10.0.0.17  Successfully pulled image "rabbitmq:management"  Normal  Created                51m   kubelet, 10.0.0.17  Created container  Normal  Started                51m   kubelet, 10.0.0.17  Started container
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  • 接下来,我们就看看这个 RS 的详细情况

[root@VM_0_17_centos ~]# kubectl describe rs mq-svc-5b96bf78d9Name:           mq-svc-5b96bf78d9Namespace:      defaultSelector:       pod-template-hash=1652693485,qcloud-app=mq-svcLabels:         pod-template-hash=1652693485                qcloud-app=mq-svcAnnotations:    deployment.changecourse=Updating                deployment.kubernetes.io/desired-replicas=1                deployment.kubernetes.io/max-replicas=2                deployment.kubernetes.io/revision=2                description=Service based on rabbitmq.Controlled By:  Deployment/mq-svcReplicas:       1 current / 1 desiredPods Status:    1 Running / 0 Waiting / 0 Succeeded / 0 FailedPod Template:  Labels:  pod-template-hash=1652693485           qcloud-app=mq-svc  Containers:   queue-mq:    Image:      rabbitmq:management    Port:       <none>    Host Port:  <none>    Limits:      cpu:     500m      memory:  1Gi    Requests:      cpu:        250m      memory:     256Mi    Environment:  <none>    Mounts:       <none>  Volumes:        <none>Events:  Type    Reason            Age   From                   Message  ----    ------            ----  ----                   -------  Normal  SuccessfulCreate  50m   replicaset-controller  Created pod: mq-svc-5b96bf78d9-r8n8t  Normal  SuccessfulCreate  49m   replicaset-controller  Created pod: mq-svc-5b96bf78d9-l4zj2  Normal  SuccessfulCreate  49m   replicaset-controller  Created pod: mq-svc-5b96bf78d9-m8tmv  Normal  SuccessfulDelete  49m   replicaset-controller  Deleted pod: mq-svc-5b96bf78d9-m8tmv  Normal  SuccessfulCreate  49m   replicaset-controller  Created pod: mq-svc-5b96bf78d9-r9wkj  Normal  SuccessfulCreate  49m   replicaset-controller  Created pod: mq-svc-5b96bf78d9-8wzpq  Normal  SuccessfulCreate  49m   replicaset-controller  Created pod: mq-svc-5b96bf78d9-d8gwc  Normal  SuccessfulDelete  49m   replicaset-controller  Deleted pod: mq-svc-5b96bf78d9-d8gwc  Normal  SuccessfulDelete  49m   replicaset-controller  Deleted pod: mq-svc-5b96bf78d9-8wzpq  Normal  SuccessfulDelete  49m   replicaset-controller  Deleted pod: mq-svc-5b96bf78d9-l4zj2  Normal  SuccessfulDelete  49m   replicaset-controller  Deleted pod: mq-svc-5b96bf78d9-r9wkj  Normal  SuccessfulDelete  45m   replicaset-controller  Deleted pod: mq-svc-5b96bf78d9-r8n8t
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关键信息

Controlled By:  Deployment/mq-svc
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这个 RS 被名字为 mq-svc 的 Deployment 控制,这样看,Deployment 是比 RS 高一级别用于管理 RS 的组件。

在 RS 级别上发生的事件,均是对 pod 的操作,创建 pod,删除 pod

Events:  Type    Reason            Age   From                   Message  ----    ------            ----  ----                   -------  Normal  SuccessfulCreate  50m   replicaset-controller  Created pod: mq-svc-5b96bf78d9-r8n8t  Normal  SuccessfulCreate  49m   replicaset-controller  Created pod: mq-svc-5b96bf78d9-l4zj2  Normal  SuccessfulCreate  49m   replicaset-controller  Created pod: mq-svc-5b96bf78d9-m8tmv  Normal  SuccessfulDelete  49m   replicaset-controller  Deleted pod: mq-svc-5b96bf78d9-m8tmv  Normal  SuccessfulCreate  49m   replicaset-controller  Created pod: mq-svc-5b96bf78d9-r9wkj  Normal  SuccessfulCreate  49m   replicaset-controller  Created pod: mq-svc-5b96bf78d9-8wzpq  Normal  SuccessfulCreate  49m   replicaset-controller  Created pod: mq-svc-5b96bf78d9-d8gwc  Normal  SuccessfulDelete  49m   replicaset-controller  Deleted pod: mq-svc-5b96bf78d9-d8gwc  Normal  SuccessfulDelete  49m   replicaset-controller  Deleted pod: mq-svc-5b96bf78d9-8wzpq  Normal  SuccessfulDelete  49m   replicaset-controller  Deleted pod: mq-svc-5b96bf78d9-l4zj2  Normal  SuccessfulDelete  49m   replicaset-controller  Deleted pod: mq-svc-5b96bf78d9-r9wkj  Normal  SuccessfulDelete  45m   replicaset-controller  Deleted pod: mq-svc-5b96bf78d9-r8n8t
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  • 接下来,我们来看看 Delpoyment

[root@VM_0_17_centos ~]# kubectl describe deploy  mq-svcName:                   mq-svcNamespace:              defaultCreationTimestamp:      Fri, 17 Aug 2018 17:21:13 +0800Labels:                 qcloud-app=mq-svcAnnotations:            deployment.changecourse=Updating                        deployment.kubernetes.io/revision=2                        description=Service based on rabbitmq.Selector:               qcloud-app=mq-svcReplicas:               1 desired | 1 updated | 1 total | 1 available | 0 unavailableStrategyType:           RollingUpdateMinReadySeconds:        10RollingUpdateStrategy:  0 max unavailable, 1 max surgePod Template:  Labels:  qcloud-app=mq-svc  Containers:   queue-mq:    Image:      rabbitmq:management    Port:       <none>    Host Port:  <none>    Limits:      cpu:     500m      memory:  1Gi    Requests:      cpu:        250m      memory:     256Mi    Environment:  <none>    Mounts:       <none>  Volumes:        <none>Conditions:  Type           Status  Reason  ----           ------  ------  Progressing    True    NewReplicaSetAvailable  Available      True    MinimumReplicasAvailableOldReplicaSets:  <none>NewReplicaSet:   mq-svc-5b96bf78d9 (1/1 replicas created)Events:  Type    Reason             Age   From                   Message  ----    ------             ----  ----                   -------  Normal  ScalingReplicaSet  58m   deployment-controller  Scaled up replica set mq-svc-5b96bf78d9 to 2  Normal  ScalingReplicaSet  57m   deployment-controller  Scaled up replica set mq-svc-5b96bf78d9 to 3  Normal  ScalingReplicaSet  57m   deployment-controller  Scaled up replica set mq-svc-5b96bf78d9 to 4  Normal  ScalingReplicaSet  57m   deployment-controller  Scaled down replica set mq-svc-5b96bf78d9 to 3  Normal  ScalingReplicaSet  57m   deployment-controller  Scaled up replica set mq-svc-5b96bf78d9 to 6  Normal  ScalingReplicaSet  57m   deployment-controller  Scaled down replica set mq-svc-5b96bf78d9 to 4  Normal  ScalingReplicaSet  56m   deployment-controller  Scaled down replica set mq-svc-5b96bf78d9 to 2  Normal  ScalingReplicaSet  53m   deployment-controller  Scaled down replica set mq-svc-5b96bf78d9 to 1
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可以看出,在 deployment 级别上,不再受其他组件的控制,而他的状态的转变是作为 API 被调用而产生的。我们看到,在 deployment 级别上发生的事件一般是创建服务、滚动升级一个服务,或者是操作 RS 伸缩 Pod 集群。

最后,到这里也很明白了,service 其实是在这一整套基础之上提供给外部的稳定的服务。


发布于: 2021 年 03 月 24 日阅读数: 11
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k8s(Kubernetes)中Pod,Deployment,ReplicaSet,Service之间关系分析