kubernetes-handbook/guide/using-etcdctl-to-access-kubernetes-data.md

# 使用etcdctl访问kubernetes数据

Kubenretes1.6中使用etcd V3版本的API，使用`etcdctl`直接`ls`的话只能看到`/kube-centos`一个路径。需要在命令前加上`ETCDCTL_API=3`这个环境变量才能看到kuberentes在etcd中保存的数据。

```bash
ETCDCTL_API=3 etcdctl get /registry/namespaces/default -w=json|python -m json.tool
```

- `-w`指定输出格式

将得到这样的json的结果：

```json
{
    "count": 1,
    "header": {
        "cluster_id": 12091028579527406772,
        "member_id": 16557816780141026208,
        "raft_term": 36,
        "revision": 29253467
    },
    "kvs": [
        {
            "create_revision": 5,
            "key": "L3JlZ2lzdHJ5L25hbWVzcGFjZXMvZGVmYXVsdA==",
            "mod_revision": 5,
            "value": "azhzAAoPCgJ2MRIJTmFtZXNwYWNlEmIKSAoHZGVmYXVsdBIAGgAiACokZTU2YzMzMDgtMWVhOC0xMWU3LThjZDctZjRlOWQ0OWY4ZWQwMgA4AEILCIn4sscFEKOg9xd6ABIMCgprdWJlcm5ldGVzGggKBkFjdGl2ZRoAIgA=",
            "version": 1
        }
    ]
}
```

使用`--prefix`可以看到所有的子目录，如查看集群中的namespace：

```bash
ETCDCTL_API=3 etcdctl get /registry/namespaces --prefix -w=json|python -m json.tool
```

输出结果中可以看到所有的namespace。

```bash
{
    "count": 8,
    "header": {
        "cluster_id": 12091028579527406772,
        "member_id": 16557816780141026208,
        "raft_term": 36,
        "revision": 29253722
    },
    "kvs": [
        {
            "create_revision": 24310883,
            "key": "L3JlZ2lzdHJ5L25hbWVzcGFjZXMvYXV0b21vZGVs",
            "mod_revision": 24310883,
            "value": "azhzAAoPCgJ2MRIJTmFtZXNwYWNlEmQKSgoJYXV0b21vZGVsEgAaACIAKiQ1MjczOTU1ZC1iMzEyLTExZTctOTcwYy1mNGU5ZDQ5ZjhlZDAyADgAQgsI7fSWzwUQ6Jv1Z3oAEgwKCmt1YmVybmV0ZXMaCAoGQWN0aXZlGgAiAA==",
            "version": 1
        },
        {
            "create_revision": 21387676,
            "key": "L3JlZ2lzdHJ5L25hbWVzcGFjZXMvYnJhbmQ=",
            "mod_revision": 21387676,
            "value": "azhzAAoPCgJ2MRIJTmFtZXNwYWNlEmEKRwoFYnJhbmQSABoAIgAqJGNkZmQ1Y2NmLWExYzktMTFlNy05NzBjLWY0ZTlkNDlmOGVkMDIAOABCDAjR9qLOBRDYn83XAXoAEgwKCmt1YmVybmV0ZXMaCAoGQWN0aXZlGgAiAA==",
            "version": 1
        },
        {
            "create_revision": 5,
            "key": "L3JlZ2lzdHJ5L25hbWVzcGFjZXMvZGVmYXVsdA==",
            "mod_revision": 5,
            "value": "azhzAAoPCgJ2MRIJTmFtZXNwYWNlEmIKSAoHZGVmYXVsdBIAGgAiACokZTU2YzMzMDgtMWVhOC0xMWU3LThjZDctZjRlOWQ0OWY4ZWQwMgA4AEILCIn4sscFEKOg9xd6ABIMCgprdWJlcm5ldGVzGggKBkFjdGl2ZRoAIgA=",
            "version": 1
        },
        {
            "create_revision": 18504694,
            "key": "L3JlZ2lzdHJ5L25hbWVzcGFjZXMvZGV2",
            "mod_revision": 24310213,
            "value": "azhzAAoPCgJ2MRIJTmFtZXNwYWNlEmwKUgoDZGV2EgAaACIAKiQyOGRlMGVjNS04ZTEzLTExZTctOTcwYy1mNGU5ZDQ5ZjhlZDAyADgAQgwI89CezQUQ0v2fuQNaCwoEbmFtZRIDZGV2egASDAoKa3ViZXJuZXRlcxoICgZBY3RpdmUaACIA",
            "version": 4
        },
        {
            "create_revision": 10,
            "key": "L3JlZ2lzdHJ5L25hbWVzcGFjZXMva3ViZS1wdWJsaWM=",
            "mod_revision": 10,
            "value": "azhzAAoPCgJ2MRIJTmFtZXNwYWNlEmcKTQoLa3ViZS1wdWJsaWMSABoAIgAqJGU1ZjhkY2I1LTFlYTgtMTFlNy04Y2Q3LWY0ZTlkNDlmOGVkMDIAOABCDAiJ+LLHBRDdrsDPA3oAEgwKCmt1YmVybmV0ZXMaCAoGQWN0aXZlGgAiAA==",
            "version": 1
        },
        {
            "create_revision": 2,
            "key": "L3JlZ2lzdHJ5L25hbWVzcGFjZXMva3ViZS1zeXN0ZW0=",
            "mod_revision": 2,
            "value": "azhzAAoPCgJ2MRIJTmFtZXNwYWNlEmYKTAoLa3ViZS1zeXN0ZW0SABoAIgAqJGU1NmFhMDVkLTFlYTgtMTFlNy04Y2Q3LWY0ZTlkNDlmOGVkMDIAOABCCwiJ+LLHBRDoq9ASegASDAoKa3ViZXJuZXRlcxoICgZBY3RpdmUaACIA",
            "version": 1
        },
        {
            "create_revision": 3774247,
            "key": "L3JlZ2lzdHJ5L25hbWVzcGFjZXMvc3BhcmstY2x1c3Rlcg==",
            "mod_revision": 3774247,
            "value": "azhzAAoPCgJ2MRIJTmFtZXNwYWNlEoABCmYKDXNwYXJrLWNsdXN0ZXISABoAIgAqJDMyNjY3ZDVjLTM0YWMtMTFlNy1iZmJkLThhZjFlM2E3YzViZDIAOABCDAiA1cbIBRDU3YuAAVoVCgRuYW1lEg1zcGFyay1jbHVzdGVyegASDAoKa3ViZXJuZXRlcxoICgZBY3RpdmUaACIA",
            "version": 1
        },
        {
            "create_revision": 15212191,
            "key": "L3JlZ2lzdHJ5L25hbWVzcGFjZXMveWFybi1jbHVzdGVy",
            "mod_revision": 15212191,
            "value": "azhzAAoPCgJ2MRIJTmFtZXNwYWNlEn0KYwoMeWFybi1jbHVzdGVyEgAaACIAKiQ2YWNhNjk1Yi03N2Y5LTExZTctYmZiZC04YWYxZTNhN2M1YmQyADgAQgsI1qiKzAUQkoqxDloUCgRuYW1lEgx5YXJuLWNsdXN0ZXJ6ABIMCgprdWJlcm5ldGVzGggKBkFjdGl2ZRoAIgA=",
            "version": 1
        }
    ]
}
```

key的值是经过base64编码，需要解码后才能看到实际值，如：

```bash
$ echo L3JlZ2lzdHJ5L25hbWVzcGFjZXMvYXV0b21vZGVs|base64 -d
/registry/namespaces/automodel
```

## etcd中kubernetes的元数据

我们使用kubectl命令获取的kubernetes的对象状态实际上是保存在etcd中的，使用下面的脚本可以获取etcd中的所有kubernetes对象的key：

> 注意，我们使用了ETCD v3版本的客户端命令来访问etcd。

```bash
#!/bin/bash
# Get kubernetes keys from etcd
export ETCDCTL_API=3
keys=`etcdctl get /registry --prefix -w json|python -m json.tool|grep key|cut -d ":" -f2|tr -d '"'|tr -d ","`
for x in $keys;do
  echo $x|base64 -d|sort
done
```

通过输出的结果我们可以看到kubernetes的原数据是按何种结构包括在kuberentes中的，输出结果如下所示：

```ini
/registry/ThirdPartyResourceData/istio.io/istioconfigs/default/route-rule-details-default
/registry/ThirdPartyResourceData/istio.io/istioconfigs/default/route-rule-productpage-default
/registry/ThirdPartyResourceData/istio.io/istioconfigs/default/route-rule-ratings-default
...
/registry/configmaps/default/namerctl-script
/registry/configmaps/default/namerd-config
/registry/configmaps/default/nginx-config
...
/registry/deployments/default/sdmk-page-sdmk
/registry/deployments/default/sdmk-payment-web
/registry/deployments/default/sdmk-report
...
```

我们可以看到所有的Kuberentes的所有元数据都保存在`/registry`目录下，下一层就是API对象类型（复数形式），再下一层是`namespace`，最后一层是对象的名字。

以下是etcd中存储的kubernetes所有的元数据类型：

```ini
ThirdPartyResourceData
apiextensions.k8s.io
apiregistration.k8s.io
certificatesigningrequests
clusterrolebindings
clusterroles
configmaps
controllerrevisions
controllers
daemonsets
deployments
events
horizontalpodautoscalers
ingress
limitranges
minions
monitoring.coreos.com
namespaces
persistentvolumeclaims
persistentvolumes
poddisruptionbudgets
pods
ranges
replicasets
resourcequotas
rolebindings
roles
secrets
serviceaccounts
services
statefulsets
storageclasses
thirdpartyresources
```

## 参考

- [etcd中文文档](https://github.com/doczhcn/etcd)
- [etcd官方文档](https://coreos.com/etcd/docs/latest/)