API Server
kube-apiserver 是 Kubernetes 最重要的核心组件之一，主要提供以下的功能
- 提供集群管理的 REST API 接口，包括认证授权、数据校验以及集群状态变更等
- 提供其他模块之间的数据交互和通信的枢纽（其他模块通过 API Server 查询或修改数据，只有 API Server 才直接操作 etcd）
工作原理
kube-apiserver 提供了 Kubernetes 的 REST API，实现了认证、授权、准入控制等安全校验功能，同时也负责集群状态的存储操作（通过 etcd）。
API 访问
有多种方式可以访问 Kubernetes 提供的 REST API：
代码语言：javascript复制1、kubectl 命令行工具
2、SDK，支持多种语言
Go
Python
Javascript
Java
CSharp
3、其他 OpenAPI 支持的语言，可以通过 gen 工具生成相应的 client
kubectl
代码语言：javascript复制kubectl get --raw /api/v1/namespaces
kubectl get --raw /apis/metrics.k8s.io/v1beta1/nodes
kubectl get --raw /apis/metrics.k8s.io/v1beta1/pods
kubectl proxy
代码语言：javascript复制$ kubectl proxy --port=8080 &
$ curl http://localhost:8080/api/
{
"versions": [
"v1"
]
}
curl
代码语言：javascript复制# In Pods with service account.
$ TOKEN=$(cat /run/secrets/kubernetes.io/serviceaccount/token)
$ CACERT=/run/secrets/kubernetes.io/serviceaccount/ca.crt
$ curl --cacert $CACERT --header "Authorization: Bearer $TOKEN" https://$KUBERNETES_SERVICE_HOST:$KUBERNETES_SERVICE_PORT/api
{
"kind": "APIVersions",
"versions": [
"v1"
],
"serverAddressByClientCIDRs": [
{
"clientCIDR": "0.0.0.0/0",
"serverAddress": "10.0.1.149:443"
}
]
}
# Outside of Pods.
$ APISERVER=$(kubectl config view | grep server | cut -f 2- -d ":" | tr -d " ")
$ TOKEN=$(kubectl describe secret $(kubectl get secrets | grep default | cut -f1 -d ' ') | grep -E '^token'| cut -f2 -d':'| tr -d 't')
$ curl $APISERVER/api --header "Authorization: Bearer $TOKEN" --insecure
{
"kind": "APIVersions",
"versions": [
"v1"
],
"serverAddressByClientCIDRs": [
{
"clientCIDR": "0.0.0.0/0",
"serverAddress": "10.0.1.149:443"
}
]
}
API 资源使用
API Resources
我们可以通过下面的命令来获取Kubernetes集群支持的所有 API 资源：（1.11以上版本才可以有此命令）
kubectl api-resources -o wide
NAME SHORTNAMES APIGROUP NAMESPACED KIND VERBS
bindings true Binding [create]
componentstatuses cs false ComponentStatus [get list]
configmaps cm true ConfigMap [create delete deletecollection get list patch update watch]
endpoints ep true Endpoints [create delete deletecollection get list patch update watch]
events ev true Event [create delete deletecollection get list patch update watch]
limitranges limits true LimitRange [create delete deletecollection get list patch update watch]
namespaces ns false Namespace [create delete get list patch update watch]
nodes no false Node [create delete deletecollection get list patch proxy update watch]
persistentvolumeclaims pvc true PersistentVolumeClaim [create delete deletecollection get list patch update watch]
persistentvolumes pv false PersistentVolume [create delete deletecollection get list patch update watch]
pods po true Pod [create delete deletecollection get list patch proxy update watch]
podtemplates true PodTemplate [create delete deletecollection get list patch update watch]
replicationcontrollers rc true ReplicationController [create delete deletecollection get list patch update watch]
resourcequotas quota true ResourceQuota [create delete deletecollection get list patch update watch]
secrets true Secret [create delete deletecollection get list patch update watch]
serviceaccounts sa true ServiceAccount [create delete deletecollection get list patch update watch]
services svc true Service [create delete get list patch proxy update watch]
mutatingwebhookconfigurations admissionregistration.k8s.io false MutatingWebhookConfiguration [create delete deletecollection get list patch update watch]
validatingwebhookconfigurations admissionregistration.k8s.io false ValidatingWebhookConfiguration [create delete deletecollection get list patch update watch]
customresourcedefinitions crd apiextensions.k8s.io false CustomResourceDefinition [create delete deletecollection get list patch update watch]
apiservices apiregistration.k8s.io false APIService [create delete deletecollection get list patch update watch]
controllerrevisions apps true ControllerRevision [create delete deletecollection get list patch update watch]
daemonsets ds apps true DaemonSet [create delete deletecollection get list patch update watch]
deployments deploy apps true Deployment [create delete deletecollection get list patch update watch]
replicasets rs apps true ReplicaSet [create delete deletecollection get list patch update watch]
statefulsets sts apps true StatefulSet [create delete deletecollection get list patch update watch]
...
上面的命令输出了很多有用的信息：
SHORTNAMES- 资源名称的简写，比如 deployments 简写就是 deploy，我们可以将这些快捷方式与kubectl一起使用APIGROUP- 我们可以查看官方文档以了解更多信息，但简而言之，您将在yaml文件中使用它像apiVersion：<APIGROUP>/v1KIND- 资源名称VERBS- 可用的方法，在您想要定义ClusterRole RBAC规则时也很有用，您还可以选择获取特定 API 组的 API 资源，例如：
kubectl api-resources --api-group apps -o wide
NAME SHORTNAMES APIGROUP NAMESPACED KIND VERBS
controllerrevisions apps true ControllerRevision [create delete deletecollection get list patch update watch]
daemonsets ds apps true DaemonSet [create delete deletecollection get list patch update watch]
deployments deploy apps true Deployment [create delete deletecollection get list patch update watch]
replicasets rs apps true ReplicaSet [create delete deletecollection get list patch update watch]
statefulsets sts apps true StatefulSet
对于上面的每种资源类型，我们都可以使用kubectl explain命令来获取有关的资源详细信息：
kubectl explain configmap
DESCRIPTION:
ConfigMap holds configuration data for pods to consume.
FIELDS:
apiVersion <string>
APIVersion defines the versioned schema of this representation of an
object. Servers should convert recognized schemas to the latest internal
value, and may reject unrecognized values. More info:
https://git.k8s.io/community/contributors/devel/api-conventions.md#resources
data <object>
Data contains the configuration data. Each key must consist of alphanumeric
characters, '-', '_' or '.'.
kind <string>
Kind is a string value representing the REST resource this object
represents. Servers may infer this from the endpoint the client submits
requests to. Cannot be updated. In CamelCase. More info:
https://git.k8s.io/community/contributors/devel/api-conventions.md#types-kinds
metadata <Object>
Standard object's metadata. More info:
https://git.k8s.io/community/contributors/devel/api-conventions.md#metadata
kubectl explain命令非常有用，特别是在我们不知道该如何编写YAML文件的时候，就可以使用改命令来帮助我们获得更多提示信息。
需要注意的是explain命令可能会显示旧的group/version，我们可以通过--api-version参数显示设置它，比如：请注意，explain可能会显示旧组/版本，但您可以使用–api-version显式设置它，例如：
kubectl explain replicaset --api-version apps/v1
API Versions
我们也可以使用下面的命令来获取集群支持的所有 API 版本：
代码语言：javascript复制kubectl api-versions
admissionregistration.k8s.io/v1beta1
apiextensions.k8s.io/v1beta1
apiregistration.k8s.io/v1beta1
apps/v1
apps/v1beta1
apps/v1beta2
authentication.k8s.io/v1
authentication.k8s.io/v1beta1
authorization.k8s.io/v1
authorization.k8s.io/v1beta1
autoscaling/v1
autoscaling/v2beta1
batch/v1
batch/v1beta1
certificates.k8s.io/v1beta1
certmanager.k8s.io/v1alpha1
enterprises.upmc.com/v1
events.k8s.io/v1beta1
extensions/v1beta1
metrics.k8s.io/v1beta1
monitoring.coreos.com/v1
networking.k8s.io/v1
policy/v1beta1
rbac.authorization.k8s.io/v1
rbac.authorization.k8s.io/v1beta1
storage.k8s.io/v1
storage.k8s.io/v1beta1
v
