is there any documentation about kubernetes data structure on etcd? - database

Question

Kubernetes stores all its data on etcd but I can not find any documentation regarding the hierarchy in which those data are stored.
I have been looking around with no success at all so any help will be appreciated.
Thanks in advance.

Answer 1

Kubernetes store the data in the following format:
/registry/<object-type>/<name-space>/<object-name>
Eg:
/registry/pods/default/mypod
To get the details of a particular object:
Syntax:
export ETCDCTL_API=3
sudo etcdctl --endpoints <etcd-server-endpoint-ip> --cert=<client-certificate> --key=<client-key> --cacert=<ca-certificate> get /registry/<object-type>/<name-space>/<object-name>
Example:
sudo etcdctl --cert=/etc/ssl/etcd/ssl/node-kube-master.pem --key=/etc/ssl/etcd/ssl/node-kube-master-key.pem --cacert=/etc/ssl/etcd/ssl/ca.pem get /registry/pods/default/foo
Output:
/registry/pods/default/foo
k8s
v1Pod▒
▒
foodefault"*$2b95568a-d1e8-4c50-9770-fe0a9ba6cbf02▒ˮ▒Z
runfooz▒▒
kubectl-runUpdatev▒ˮ▒FieldsV1:▒
▒{"f:metadata":{"f:labels":{".":{},"f:run":{}}},"f:spec":{"f:containers":{"k:{\"name\":\"foo\"}":{".":{},"f:image":{},"f:imagePullPolicy":{},"f:name":{},"f:resources":{},"f:terminationMessagePath":{},"f:terminationMessagePolicy":{}}},"f:dnsPolicy":{},"f:enableServiceLinks":{},"f:restartPolicy":{},"f:schedulerName":{},"f:securityContext":{},"f:terminationGracePeriodSeconds":{}}}B▒▒
Go-http-clientUpdatev▒ˮ▒FieldsV1:▒
▒{"f:status":{"f:conditions":{"k:{\"type\":\"ContainersReady\"}":{".":{},"f:lastProbeTime":{},"f:lastTransitionTime":{},"f:status":{},"f:type":{}},"k:{\"type\":\"Initialized\"}":{".":{},"f:lastProbeTime":{},"f:lastTransitionTime":{},"f:status":{},"f:type":{}},"k:{\"type\":\"Ready\"}":{".":{},"f:lastProbeTime":{},"f:lastTransitionTime":{},"f:status":{},"f:type":{}}},"f:containerStatuses":{},"f:hostIP":{},"f:phase":{},"f:podIP":{},"f:podIPs":{".":{},"k:{\"ip\":\"10.233.120.2\"}":{".":{},"f:ip":{}}},"f:startTime":{}}}Bstatus▒
▒.....redacting more info for clean output
Getting the structure:
Now, if you want to check the structure of the data stored in the etcd use --prefix --keys-only.
sudo etcdctl --cert=<client-certificate> --key=<client-key> --cacert=<ca-certificate> get /registry --prefix --keys-only
Example:
sudo etcdctl --cert=/etc/ssl/etcd/ssl/node-kube-master.pem --key=/etc/ssl/etcd/ssl/node-kube-master-key.pem --cacert=/etc/ssl/etcd/ssl/ca.pem get /registry --prefix --keys-only
/registry/apiregistration.k8s.io/apiservices/v1.
/registry/apiregistration.k8s.io/apiservices/v1.admissionregistration.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1.apiextensions.k8s.io
/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.certificates.k8s.io
.....