关于etcd:EtcdKubernetes集群的大脑

Etcd 是 Kubernetes 的要害组件，因为它存储了集群的整个状态：其配置，规格以及运行中的工作负载的状态。在本文中，咱们将会揭开其神秘的面纱，理解 etcd 如何存储所有这些信息。

Etcd 被定义为分布式，牢靠的键值存储，用于分布式系统中最要害的数据。

在 Kubernetes 世界中，etcd 用作服务发现的后端，并存储集群的状态及其配置。

Etcd 被部署为一个集群，几个节点的通信由 Raft 算法解决。在生产环境中，集群蕴含奇数个节点，并且至多须要三个。在 http://thesecretlivesofdata.com/ 中，您能够找到一个很好的动画，阐明该算法的运行形式，它阐明了集群生命周期的几个阶段，其中包含：

选主
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在 Kubernetes 集群的上下文中，etcd 实例能够作为 Pod 部署在 master 节点上（这是咱们将在本文中应用的示例）。

为了减少安全性和弹性，还能够将其部署为内部集群。

以下来自 Heptio 博客的序列图显示了在简略的 Pod 创立过程中波及的组件。它很好地阐明了 API 服务器和 etcd 的交互作用。

在本篇文章中，咱们应用的 Kubernetes 集群，由 kubeadm 创立的三个节点组成，其中一个 master 节点运行了 Etcd。所选的网络附加组件是 weavenet。这种配置不适宜理论的 HA 集群，但足以浏览 etcd 中存储的数据。

$ kubectl get nodes
NAME    STATUS ROLES  AGE   VERSION
node-01 Ready  master 56m   v1.15.2
node-02 Ready  <none> 2m17  v1.15.2
node-03 Ready  <none> 2m17  v1.15.2

首先，让咱们列出集群中运行的所有 Pod：

$ kubectl get pods --all-namespaces
NAMESPACE   NAME                           READY STATUS  RESTART AGE
kube-system coredns-5c98db65d4–5kjjv       1/1   Running 0       57m
kube-system coredns-5c98db65d4–88hkq       1/1   Running 0       57m
kube-system etcd-node-01                   1/1   Running 0       56m
kube-system kube-apiserver-node-01         1/1   Running 0       56m
kube-system kube-controller-manager-node-01 1/1  Running 0       56m
kube-system kube-proxy-7642v               1/1   Running 0       3m
kube-system kube-proxy-jsp4r               1/1   Running 0       3m
kube-system kube-proxy-xj8qm               1/1   Running 0       57m
kube-system kube-scheduler-node-01         1/1   Running 0       56m
kube-system weave-net-2hvbx                2/2   Running 0       87s
kube-system weave-net-5mrjl                2/2   Running 0       87s
kube-system weave-net-c76fx                2/2   Running 0       87s

因为集群刚刚被初始化，因而只有 kube-system 名称空间中的 Pod 正在运行。这些 Pod 负责集群的治理工作。咱们感兴趣的 Pod 是etcd-node-01，它运行 etcd 的实例来负责存储集群的状态。

首先，在 etcd Pod 中运行一个 shell，并查看其中运行的 etcd 容器的配置：

应用 --advertise-client-urls 标记的值，咱们能够应用 etcdctl 实用程序获取所有现有的键 / 值对，并将其保留在 etcd-kv.json 中。

$ ADVERTISE_URL="https://134.209.178.162:2379"
$ kubectl exec etcd-node-01 -n kube-system -- sh -c 
"ETCDCTL_API=3 etcdctl 
--endpoints $ADVERTISE_URL 
--cacert /etc/kubernetes/pki/etcd/ca.crt 
--key /etc/kubernetes/pki/etcd/server.key 
--cert /etc/kubernetes/pki/etcd/server.crt 
get ""--prefix=true -w json" > etcd-kv.json

疾速查看此文件将显示健列表及其对应的值，它们均以 base64 编码（此处仅显示文件的摘录）。

首先让咱们以纯文本格式获取所有键，以查看其内容。我把所有键输入：

$ for k in $(cat etcd-kv.json | jq '.kvs[].key' | cut -d '"' -f2); do echo $k | base64 --decode; echo; done

/registry/apiregistration.k8s.io/apiservices/v1.
/registry/apiregistration.k8s.io/apiservices/v1.apps
/registry/apiregistration.k8s.io/apiservices/v1.authentication.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1.authorization.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1.autoscaling
/registry/apiregistration.k8s.io/apiservices/v1.batch
/registry/apiregistration.k8s.io/apiservices/v1.coordination.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1.networking.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1.rbac.authorization.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1.scheduling.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1.storage.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1beta1.admissionregistration.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1beta1.apiextensions.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1beta1.apps
/registry/apiregistration.k8s.io/apiservices/v1beta1.authentication.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1beta1.authorization.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1beta1.batch
/registry/apiregistration.k8s.io/apiservices/v1beta1.certificates.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1beta1.coordination.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1beta1.events.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1beta1.extensions
/registry/apiregistration.k8s.io/apiservices/v1beta1.networking.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1beta1.node.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1beta1.policy
/registry/apiregistration.k8s.io/apiservices/v1beta1.rbac.authorization.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1beta1.scheduling.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1beta1.storage.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1beta2.apps
/registry/apiregistration.k8s.io/apiservices/v2beta1.autoscaling
/registry/apiregistration.k8s.io/apiservices/v2beta2.autoscaling
/registry/certificatesigningrequests/csr-h9mcg
/registry/certificatesigningrequests/csr-qwnxf
/registry/certificatesigningrequests/csr-xklls
/registry/clusterrolebindings/cluster-admin
/registry/clusterrolebindings/kubeadm:kubelet-bootstrap
/registry/clusterrolebindings/kubeadm:node-autoapprove-bootstrap
/registry/clusterrolebindings/kubeadm:node-autoapprove-certificate-rotation
/registry/clusterrolebindings/kubeadm:node-proxier
/registry/clusterrolebindings/system:basic-user
/registry/clusterrolebindings/system:controller:attachdetach-controller
/registry/clusterrolebindings/system:controller:certificate-controller
/registry/clusterrolebindings/system:controller:clusterrole-aggregation-controller
/registry/clusterrolebindings/system:controller:cronjob-controller
/registry/clusterrolebindings/system:controller:daemon-set-controller
/registry/clusterrolebindings/system:controller:deployment-controller
/registry/clusterrolebindings/system:controller:disruption-controller
/registry/clusterrolebindings/system:controller:endpoint-controller
/registry/clusterrolebindings/system:controller:expand-controller
/registry/clusterrolebindings/system:controller:generic-garbage-collector
/registry/clusterrolebindings/system:controller:horizontal-pod-autoscaler
/registry/clusterrolebindings/system:controller:job-controller
/registry/clusterrolebindings/system:controller:namespace-controller
/registry/clusterrolebindings/system:controller:node-controller
/registry/clusterrolebindings/system:controller:persistent-volume-binder
/registry/clusterrolebindings/system:controller:pod-garbage-collector
/registry/clusterrolebindings/system:controller:pv-protection-controller
/registry/clusterrolebindings/system:controller:pvc-protection-controller
/registry/clusterrolebindings/system:controller:replicaset-controller
/registry/clusterrolebindings/system:controller:replication-controller
/registry/clusterrolebindings/system:controller:resourcequota-controller
/registry/clusterrolebindings/system:controller:route-controller
/registry/clusterrolebindings/system:controller:service-account-controller
/registry/clusterrolebindings/system:controller:service-controller
/registry/clusterrolebindings/system:controller:statefulset-controller
/registry/clusterrolebindings/system:controller:ttl-controller
/registry/clusterrolebindings/system:coredns
/registry/clusterrolebindings/system:discovery
/registry/clusterrolebindings/system:kube-controller-manager
/registry/clusterrolebindings/system:kube-dns
/registry/clusterrolebindings/system:kube-scheduler
/registry/clusterrolebindings/system:node
/registry/clusterrolebindings/system:node-proxier
/registry/clusterrolebindings/system:public-info-viewer
/registry/clusterrolebindings/system:volume-scheduler
/registry/clusterrolebindings/weave-net
/registry/clusterroles/admin
/registry/clusterroles/cluster-admin
/registry/clusterroles/edit
/registry/clusterroles/system:aggregate-to-admin
/registry/clusterroles/system:aggregate-to-edit
/registry/clusterroles/system:aggregate-to-view
/registry/clusterroles/system:auth-delegator
/registry/clusterroles/system:basic-user
/registry/clusterroles/system:certificates.k8s.io:certificatesigningrequests:nodeclient
/registry/clusterroles/system:certificates.k8s.io:certificatesigningrequests:selfnodeclient
/registry/clusterroles/system:controller:attachdetach-controller
/registry/clusterroles/system:controller:certificate-controller
/registry/clusterroles/system:controller:clusterrole-aggregation-controller
/registry/clusterroles/system:controller:cronjob-controller
/registry/clusterroles/system:controller:daemon-set-controller
/registry/clusterroles/system:controller:deployment-controller
/registry/clusterroles/system:controller:disruption-controller
/registry/clusterroles/system:controller:endpoint-controller
/registry/clusterroles/system:controller:expand-controller
/registry/clusterroles/system:controller:generic-garbage-collector
/registry/clusterroles/system:controller:horizontal-pod-autoscaler
/registry/clusterroles/system:controller:job-controller
/registry/clusterroles/system:controller:namespace-controller
/registry/clusterroles/system:controller:node-controller
/registry/clusterroles/system:controller:persistent-volume-binder
/registry/clusterroles/system:controller:pod-garbage-collector
/registry/clusterroles/system:controller:pv-protection-controller
/registry/clusterroles/system:controller:pvc-protection-controller
/registry/clusterroles/system:controller:replicaset-controller
/registry/clusterroles/system:controller:replication-controller
/registry/clusterroles/system:controller:resourcequota-controller
/registry/clusterroles/system:controller:route-controller
/registry/clusterroles/system:controller:service-account-controller
/registry/clusterroles/system:controller:service-controller
/registry/clusterroles/system:controller:statefulset-controller
/registry/clusterroles/system:controller:ttl-controller
/registry/clusterroles/system:coredns
/registry/clusterroles/system:csi-external-attacher
/registry/clusterroles/system:csi-external-provisioner
/registry/clusterroles/system:discovery
/registry/clusterroles/system:heapster
/registry/clusterroles/system:kube-aggregator
/registry/clusterroles/system:kube-controller-manager
/registry/clusterroles/system:kube-dns
/registry/clusterroles/system:kube-scheduler
/registry/clusterroles/system:kubelet-api-admin
/registry/clusterroles/system:node
/registry/clusterroles/system:node-bootstrapper
/registry/clusterroles/system:node-problem-detector
/registry/clusterroles/system:node-proxier
/registry/clusterroles/system:persistent-volume-provisioner
/registry/clusterroles/system:public-info-viewer
/registry/clusterroles/system:volume-scheduler
/registry/clusterroles/view
/registry/clusterroles/weave-net
/registry/configmaps/kube-public/cluster-info
/registry/configmaps/kube-system/coredns
/registry/configmaps/kube-system/extension-apiserver-authentication
/registry/configmaps/kube-system/kube-proxy
/registry/configmaps/kube-system/kubeadm-config
/registry/configmaps/kube-system/kubelet-config-1.15
/registry/configmaps/kube-system/weave-net
/registry/controllerrevisions/kube-system/kube-proxy-84c6b844cd
/registry/controllerrevisions/kube-system/weave-net-7db89b6d4
/registry/daemonsets/kube-system/kube-proxy
/registry/daemonsets/kube-system/weave-net
/registry/deployments/kube-system/coredns
/registry/events/default/node-01.15b9e0cd75ea6932
/registry/events/default/node-02.15b9e0ae0342c323
/registry/events/default/node-02.15b9e0ae0f9c2ae3
/registry/events/default/node-02.15b9e0ae0f9c5fa9
/registry/events/default/node-02.15b9e0ae0f9c7206
/registry/events/default/node-02.15b9e0ae1575182e
/registry/events/default/node-02.15b9e0aea1c4eeaf
/registry/events/default/node-02.15b9e0af99ba73a2
/registry/events/default/node-02.15b9e0ca43c5e760
/registry/events/default/node-03.15b9e0ae9bdae96c
/registry/events/default/node-03.15b9e0aea880813c
/registry/events/default/node-03.15b9e0aea880ae05
/registry/events/default/node-03.15b9e0aea880c0de
/registry/events/default/node-03.15b9e0aeb13cfeef
/registry/events/default/node-03.15b9e0afcbcf299b
/registry/events/default/node-03.15b9e0b02f28fa3c
/registry/events/default/node-03.15b9e0cadf7dce89
/registry/events/kube-system/coredns-5c98db65d4-5kjjv.15b9ddb67e6ab700
/registry/events/kube-system/coredns-5c98db65d4-5kjjv.15b9e0af3bdb47fe
/registry/events/kube-system/coredns-5c98db65d4-5kjjv.15b9e0cbbbb7579d
/registry/events/kube-system/coredns-5c98db65d4-5kjjv.15b9e0cc279fbd33
/registry/events/kube-system/coredns-5c98db65d4-5kjjv.15b9e0cc34fb8de2
/registry/events/kube-system/coredns-5c98db65d4-5kjjv.15b9e0cc4994ad54
/registry/events/kube-system/coredns-5c98db65d4-88hkq.15b9ddb6850e5ff1
/registry/events/kube-system/coredns-5c98db65d4-88hkq.15b9e0aea988964f
/registry/events/kube-system/coredns-5c98db65d4-88hkq.15b9e0cbbb3af928
/registry/events/kube-system/coredns-5c98db65d4-88hkq.15b9e0cc2ffb9d11
/registry/events/kube-system/coredns-5c98db65d4-88hkq.15b9e0cc3a4def6c
/registry/events/kube-system/coredns-5c98db65d4-88hkq.15b9e0cc4bd20265
/registry/events/kube-system/coredns-5c98db65d4-88hkq.15b9e0cc6e488534
/registry/events/kube-system/kube-proxy-7642v.15b9e0ae1444b38c
/registry/events/kube-system/kube-proxy-7642v.15b9e0ae7ff6f434
/registry/events/kube-system/kube-proxy-7642v.15b9e0af631fa3d0
/registry/events/kube-system/kube-proxy-7642v.15b9e0af7632698a
/registry/events/kube-system/kube-proxy-7642v.15b9e0af85356aad
/registry/events/kube-system/kube-proxy-jsp4r.15b9e0aeadc2ce3a
/registry/events/kube-system/kube-proxy-jsp4r.15b9e0af27535c1b
/registry/events/kube-system/kube-proxy-jsp4r.15b9e0affc7fc79e
/registry/events/kube-system/kube-proxy-jsp4r.15b9e0b00a290340
/registry/events/kube-system/kube-proxy-jsp4r.15b9e0b01b0a4eef
/registry/events/kube-system/kube-proxy.15b9e0ae1333a730
/registry/events/kube-system/kube-proxy.15b9e0aeaad76df0
/registry/events/kube-system/weave-net-2hvbx.15b9e0c6e9b6c1de
/registry/events/kube-system/weave-net-2hvbx.15b9e0c71a365ad4
/registry/events/kube-system/weave-net-2hvbx.15b9e0c88a5af203
/registry/events/kube-system/weave-net-2hvbx.15b9e0c8a5998774
/registry/events/kube-system/weave-net-2hvbx.15b9e0c8b54252cb
/registry/events/kube-system/weave-net-2hvbx.15b9e0c8b5543df6
/registry/events/kube-system/weave-net-2hvbx.15b9e0c98384d3e1
/registry/events/kube-system/weave-net-2hvbx.15b9e0c9916478ce
/registry/events/kube-system/weave-net-2hvbx.15b9e0c9a090c521
/registry/events/kube-system/weave-net-5mrjl.15b9e0c6e9523ad2
/registry/events/kube-system/weave-net-5mrjl.15b9e0c7194191cb
/registry/events/kube-system/weave-net-5mrjl.15b9e0c89c46497c
/registry/events/kube-system/weave-net-5mrjl.15b9e0c8b335c817
/registry/events/kube-system/weave-net-5mrjl.15b9e0c8c714f12d
/registry/events/kube-system/weave-net-5mrjl.15b9e0c8c770ebdd
/registry/events/kube-system/weave-net-5mrjl.15b9e0c995196184
/registry/events/kube-system/weave-net-5mrjl.15b9e0c9a24d099d
/registry/events/kube-system/weave-net-5mrjl.15b9e0c9b2e0cdef
/registry/events/kube-system/weave-net-c76fx.15b9e0c6ec0133eb
/registry/events/kube-system/weave-net-c76fx.15b9e0c7255593bb
/registry/events/kube-system/weave-net-c76fx.15b9e0c8d4f52821
/registry/events/kube-system/weave-net-c76fx.15b9e0c90ebfeb95
/registry/events/kube-system/weave-net-c76fx.15b9e0c922410c3a
/registry/events/kube-system/weave-net-c76fx.15b9e0c922580ded
/registry/events/kube-system/weave-net-c76fx.15b9e0c9f7834364
/registry/events/kube-system/weave-net-c76fx.15b9e0ca15411664
/registry/events/kube-system/weave-net-c76fx.15b9e0ca2d254f2c
/registry/events/kube-system/weave-net.15b9e0c6e7edf622
/registry/events/kube-system/weave-net.15b9e0c6e9c8d2c1
/registry/events/kube-system/weave-net.15b9e0c6ea880cd2
/registry/leases/kube-node-lease/node-01
/registry/leases/kube-node-lease/node-02
/registry/leases/kube-node-lease/node-03
/registry/masterleases/134.209.178.162
/registry/minions/node-01
/registry/minions/node-02
/registry/minions/node-03
/registry/namespaces/default
/registry/namespaces/kube-node-lease
/registry/namespaces/kube-public
/registry/namespaces/kube-system
/registry/pods/kube-system/coredns-5c98db65d4-5kjjv
/registry/pods/kube-system/coredns-5c98db65d4-88hkq
/registry/pods/kube-system/etcd-node-01
/registry/pods/kube-system/kube-apiserver-node-01
/registry/pods/kube-system/kube-controller-manager-node-01
/registry/pods/kube-system/kube-proxy-7642v
/registry/pods/kube-system/kube-proxy-jsp4r
/registry/pods/kube-system/kube-proxy-xj8qm
/registry/pods/kube-system/kube-scheduler-node-01
/registry/pods/kube-system/weave-net-2hvbx
/registry/pods/kube-system/weave-net-5mrjl
/registry/pods/kube-system/weave-net-c76fx
/registry/priorityclasses/system-cluster-critical
/registry/priorityclasses/system-node-critical
/registry/ranges/serviceips
/registry/ranges/servicenodeports
/registry/replicasets/kube-system/coredns-5c98db65d4
/registry/rolebindings/kube-public/kubeadm:bootstrap-signer-clusterinfo
/registry/rolebindings/kube-public/system:controller:bootstrap-signer
/registry/rolebindings/kube-system/kube-proxy
/registry/rolebindings/kube-system/kubeadm:kubelet-config-1.15
/registry/rolebindings/kube-system/kubeadm:nodes-kubeadm-config
/registry/rolebindings/kube-system/system::extension-apiserver-authentication-reader
/registry/rolebindings/kube-system/system::leader-locking-kube-controller-manager
/registry/rolebindings/kube-system/system::leader-locking-kube-scheduler
/registry/rolebindings/kube-system/system:controller:bootstrap-signer
/registry/rolebindings/kube-system/system:controller:cloud-provider
/registry/rolebindings/kube-system/system:controller:token-cleaner
/registry/rolebindings/kube-system/weave-net
/registry/roles/kube-public/kubeadm:bootstrap-signer-clusterinfo
/registry/roles/kube-public/system:controller:bootstrap-signer
/registry/roles/kube-system/extension-apiserver-authentication-reader
/registry/roles/kube-system/kube-proxy
/registry/roles/kube-system/kubeadm:kubelet-config-1.15
/registry/roles/kube-system/kubeadm:nodes-kubeadm-config
/registry/roles/kube-system/system::leader-locking-kube-controller-manager
/registry/roles/kube-system/system::leader-locking-kube-scheduler
/registry/roles/kube-system/system:controller:bootstrap-signer
/registry/roles/kube-system/system:controller:cloud-provider
/registry/roles/kube-system/system:controller:token-cleaner
/registry/roles/kube-system/weave-net
/registry/secrets/default/default-token-nz988
/registry/secrets/kube-node-lease/default-token-4w7tf
/registry/secrets/kube-public/default-token-pzhnr
/registry/secrets/kube-system/attachdetach-controller-token-69mzv
/registry/secrets/kube-system/bootstrap-signer-token-584pq
/registry/secrets/kube-system/bootstrap-token-w1d2kx
/registry/secrets/kube-system/certificate-controller-token-rff4s
/registry/secrets/kube-system/clusterrole-aggregation-controller-token-6hks4
/registry/secrets/kube-system/coredns-token-b2874
/registry/secrets/kube-system/cronjob-controller-token-55pgx
/registry/secrets/kube-system/daemon-set-controller-token-nhcdf
/registry/secrets/kube-system/default-token-f5kl4
/registry/secrets/kube-system/deployment-controller-token-lm58l
/registry/secrets/kube-system/disruption-controller-token-4tw6s
/registry/secrets/kube-system/endpoint-controller-token-qdh8q
/registry/secrets/kube-system/expand-controller-token-6stw5
/registry/secrets/kube-system/generic-garbage-collector-token-hqfqx
/registry/secrets/kube-system/horizontal-pod-autoscaler-token-h6czj
/registry/secrets/kube-system/job-controller-token-nmw8f
/registry/secrets/kube-system/kube-proxy-token-zcrj8
/registry/secrets/kube-system/namespace-controller-token-trhl9
/registry/secrets/kube-system/node-controller-token-mmf4d
/registry/secrets/kube-system/persistent-volume-binder-token-wnh9s
/registry/secrets/kube-system/pod-garbage-collector-token-h7vvp
/registry/secrets/kube-system/pv-protection-controller-token-lcqb6
/registry/secrets/kube-system/pvc-protection-controller-token-k2kf8
/registry/secrets/kube-system/replicaset-controller-token-zhc7k
/registry/secrets/kube-system/replication-controller-token-l8hr6
/registry/secrets/kube-system/resourcequota-controller-token-bglb2
/registry/secrets/kube-system/service-account-controller-token-5dhxz
/registry/secrets/kube-system/service-controller-token-l98rk
/registry/secrets/kube-system/statefulset-controller-token-dj85r
/registry/secrets/kube-system/token-cleaner-token-qz8hs
/registry/secrets/kube-system/ttl-controller-token-6vbv6
/registry/secrets/kube-system/weave-net-token-87h6x
/registry/serviceaccounts/default/default
/registry/serviceaccounts/kube-node-lease/default
/registry/serviceaccounts/kube-public/default
/registry/serviceaccounts/kube-system/attachdetach-controller
/registry/serviceaccounts/kube-system/bootstrap-signer
/registry/serviceaccounts/kube-system/certificate-controller
/registry/serviceaccounts/kube-system/clusterrole-aggregation-controller
/registry/serviceaccounts/kube-system/coredns
/registry/serviceaccounts/kube-system/cronjob-controller
/registry/serviceaccounts/kube-system/daemon-set-controller
/registry/serviceaccounts/kube-system/default
/registry/serviceaccounts/kube-system/deployment-controller
/registry/serviceaccounts/kube-system/disruption-controller
/registry/serviceaccounts/kube-system/endpoint-controller
/registry/serviceaccounts/kube-system/expand-controller
/registry/serviceaccounts/kube-system/generic-garbage-collector
/registry/serviceaccounts/kube-system/horizontal-pod-autoscaler
/registry/serviceaccounts/kube-system/job-controller
/registry/serviceaccounts/kube-system/kube-proxy
/registry/serviceaccounts/kube-system/namespace-controller
/registry/serviceaccounts/kube-system/node-controller
/registry/serviceaccounts/kube-system/persistent-volume-binder
/registry/serviceaccounts/kube-system/pod-garbage-collector
/registry/serviceaccounts/kube-system/pv-protection-controller
/registry/serviceaccounts/kube-system/pvc-protection-controller
/registry/serviceaccounts/kube-system/replicaset-controller
/registry/serviceaccounts/kube-system/replication-controller
/registry/serviceaccounts/kube-system/resourcequota-controller
/registry/serviceaccounts/kube-system/service-account-controller
/registry/serviceaccounts/kube-system/service-controller
/registry/serviceaccounts/kube-system/statefulset-controller
/registry/serviceaccounts/kube-system/token-cleaner
/registry/serviceaccounts/kube-system/ttl-controller
/registry/serviceaccounts/kube-system/weave-net
/registry/services/endpoints/default/kubernetes
/registry/services/endpoints/kube-system/kube-controller-manager
/registry/services/endpoints/kube-system/kube-dns
/registry/services/endpoints/kube-system/kube-scheduler
/registry/services/specs/default/kubernetes
/registry/services/specs/kube-system/kube-dns
compact_rev_key

下面的结果显示了 342 个键，这些键定义了集群中所有资源的配置和状态：

Nodes
Namespaces
ServiceAccounts
Roles and RoleBindings, ClusterRoles / ClusterRoleBindings
ConfigMaps
Secrets
Workloads: Deployments, DaemonSets, Pods, …
Cluster’s certificates
The resources within each apiVersion
The events that bring the cluster in the current state

抉择这些键之一后，咱们能够应用以下命令获取关联的值：

$ kubectl exec etcd-node-01 -n kube-system —- sh -c 
"ETCDCTL_API=3 etcdctl 
--endpoints $ADVERTISE_URL 
--cacert /etc/kubernetes/pki/etcd/ca.crt 
--key /etc/kubernetes/pki/etcd/server.key 
--cert /etc/kubernetes/pki/etcd/server.crt 
get "KEY" -w json"

例如，让咱们获取与 /registry/deployments/kube-system/coredns 键相关联的值：

如果咱们解码与此键关联的值，则返回值将很难读，因为无法解释某些字符，然而，当然，Kubernetes 晓得如何正确处理它们。

依据此后果，咱们能够推断出此 key 用于存储管理 coredns Pods 的部署的标准和状态。

让咱们创立一个 Pod，并查看如何批改集群的状态以及增加哪些新 Key。

$ cat <<EoF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
  name: www
spec:
  containers:
  - name: nginx
    image: nginx:1.16-alpine
EoF

应用与之前雷同的命令，咱们获取所有 key 并将此列表保留在 etcd-kv-after-nginx-pod.json 中。疾速比拟这两个键列表，一个是在创立集群后立刻检索的键（etcd-kv.json），另一个是在咱们部署了 www Pod 之后检索的键（etcd-kv-after-nginx-pod.json），显示以下内容：

> /registry/events/default/www.15b9e3051648764f
> /registry/events/default/www.15b9e3056b8ce3f0
> /registry/events/default/www.15b9e306918312ea
> /registry/events/default/www.15b9e306a32beb6d
> /registry/events/default/www.15b9e306b5892b60
> /registry/pods/default/www

产生了五个事件和一个 Pod，这很有意义。让咱们认真看看，首先解码与事件键关联的值。依照工夫程序，咱们能够看到它们与以下操作关联：

调度 default/www 到 node-02
拉取镜像“nginx:1.16-alpine
胜利拉取镜像“nginx:1.16-alpine
创立容器 nginx
启动 ”Started container nginx

这些事件在形容 Pod 的命令开端列出：

$ kubectl describe pod www

最初一个键_/registry/pods/default/www_，提供与新创建的 Pod 相干的所有信息：

最近的配置
相干的 token
I 状态
…

本文的目标不是深入研究 etcd，而是略微解释一下其中蕴含的内容以及信息的组织形式。这样做是心愿它看起来不像黑盒子。

PS: 本文属于翻译，原文

关于etcd:EtcdKubernetes集群的大脑

Etcd 简介

Kubernetes 中的 Etcd

Kubernetes 测试集群

The Etcd Pod

Pod 的创立

总结