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Kubernetes

基于 Kubernetes 的服务发现#

Kubernetes 服务发现以 List-Watch 方式监听 Kubernetes 集群 Endpoints 资源的实时变化,并将其值存储到 ngx.shared.DICT 中。

同时遵循 APISIX Discovery 规范 提供了节点查询接口。

Kubernetes 服务发现的使用#

目前 Kubernetes 服务发现支持单集群和多集群模式,分别适用于待发现的服务分布在单个或多个 Kubernetes 的场景。

单集群模式 Kubernetes 服务发现的配置格式#

单集群模式 Kubernetes 服务发现的完整配置如下:

discovery:
kubernetes:
service:
# apiserver schema, options [http, https]
schema: https #default https

# apiserver host, options [ipv4, ipv6, domain, environment variable]
host: ${KUBERNETES_SERVICE_HOST} #default ${KUBERNETES_SERVICE_HOST}

# apiserver port, options [port number, environment variable]
port: ${KUBERNETES_SERVICE_PORT} #default ${KUBERNETES_SERVICE_PORT}

client:
# serviceaccount token or token_file
token_file: /var/run/secrets/kubernetes.io/serviceaccount/token

#token: |-
# eyJhbGciOiJSUzI1NiIsImtpZCI6Ikx5ME1DNWdnbmhQNkZCNlZYMXBsT3pYU3BBS2swYzBPSkN3ZnBESGpkUEEif
# 6Ikx5ME1DNWdnbmhQNkZCNlZYMXBsT3pYU3BBS2swYzBPSkN3ZnBESGpkUEEifeyJhbGciOiJSUzI1NiIsImtpZCI

default_weight: 50 # weight assigned to each discovered endpoint. default 50, minimum 0

# kubernetes discovery support namespace_selector
# you can use one of [equal, not_equal, match, not_match] filter namespace
namespace_selector:
# only save endpoints with namespace equal default
equal: default

# only save endpoints with namespace not equal default
#not_equal: default

# only save endpoints with namespace match one of [default, ^my-[a-z]+$]
#match:
#- default
#- ^my-[a-z]+$

# only save endpoints with namespace not match one of [default, ^my-[a-z]+$]
#not_match:
#- default
#- ^my-[a-z]+$

# kubernetes discovery support label_selector
# for the expression of label_selector, please refer to https://kubernetes.io/docs/concepts/overview/working-with-objects/labels
label_selector: |-
first="a",second="b"

# reserved lua shared memory size, 1m memory can store about 1000 pieces of endpoint
shared_size: 1m #default 1m

# if watch_endpoint_slices setting true, watch apiserver with endpointslices instead of endpoints
watch_endpoint_slices: false #default false

如果 Kubernetes 服务发现运行在 Pod 内,你可以使用如下最简配置:

discovery:
kubernetes: { }

如果 Kubernetes 服务发现运行在 Pod 外,你需要新建或选取指定的 ServiceAccount, 获取其 Token 值,然后使用如下配置:

discovery:
kubernetes:
service:
schema: https
host: # enter apiserver host value here
port: # enter apiServer port value here
client:
token: # enter serviceaccount token value here
#token_file: # enter token file path here

单集群模式 Kubernetes 服务发现的查询接口#

单集群模式 Kubernetes 服务发现遵循 APISIX Discovery 规范 提供节点查询接口。

函数: nodes(service_name)

说明: service_name 必须满足格式:[namespace]/[name]:[portName]

  • namespace: Endpoints 所在的命名空间

  • name: Endpoints 的资源名

  • portName: Endpoints 定义包含的 ports.name 值,如果 Endpoints 没有定义 ports.name,请依次使用 targetPort, port 代替。设置了 ports.name 的情况下,不能使用后两者。

返回值: 以如下 Endpoints 为例:

apiVersion: v1
kind: Endpoints
metadata:
name: plat-dev
namespace: default
subsets:
- addresses:
- ip: "10.5.10.109"
- ip: "10.5.10.110"
ports:
- port: 3306
name: port

nodes("default/plat-dev:port") 调用会得到如下的返回值:

 {
{
host="10.5.10.109",
port= 3306,
weight= 50,
},
{
host="10.5.10.110",
port= 3306,
weight= 50,
},
}

多集群模式 Kubernetes 服务发现的配置格式#

多集群模式 Kubernetes 服务发现的完整配置如下:

discovery:
kubernetes:
- id: release # a custom name refer to the cluster, pattern ^[a-z0-9]{1,8}
service:
# apiserver schema, options [http, https]
schema: https #default https

# apiserver host, options [ipv4, ipv6, domain, environment variable]
host: "1.cluster.com"

# apiserver port, options [port number, environment variable]
port: "6443"

client:
# serviceaccount token or token_file
token_file: /var/run/secrets/kubernetes.io/serviceaccount/token

#token: |-
# eyJhbGciOiJSUzI1NiIsImtpZCI6Ikx5ME1DNWdnbmhQNkZCNlZYMXBsT3pYU3BBS2swYzBPSkN3ZnBESGpkUEEif
# 6Ikx5ME1DNWdnbmhQNkZCNlZYMXBsT3pYU3BBS2swYzBPSkN3ZnBESGpkUEEifeyJhbGciOiJSUzI1NiIsImtpZCI

default_weight: 50 # weight assigned to each discovered endpoint. default 50, minimum 0

# kubernetes discovery support namespace_selector
# you can use one of [equal, not_equal, match, not_match] filter namespace
namespace_selector:
# only save endpoints with namespace equal default
equal: default

# only save endpoints with namespace not equal default
#not_equal: default

# only save endpoints with namespace match one of [default, ^my-[a-z]+$]
#match:
#- default
#- ^my-[a-z]+$

# only save endpoints with namespace not match one of [default, ^my-[a-z]+$]
#not_match:
#- default
#- ^my-[a-z]+$

# kubernetes discovery support label_selector
# for the expression of label_selector, please refer to https://kubernetes.io/docs/concepts/overview/working-with-objects/labels
label_selector: |-
first="a",second="b"

# reserved lua shared memory size,1m memory can store about 1000 pieces of endpoint
shared_size: 1m #default 1m

# if watch_endpoint_slices setting true, watch apiserver with endpointslices instead of endpoints
watch_endpoint_slices: false #default false

多集群模式 Kubernetes 服务发现没有为 serviceclient 域填充默认值,你需要根据集群配置情况自行填充。

多集群模式 Kubernetes 服务发现的查询接口#

多集群模式 Kubernetes 服务发现遵循 APISIX Discovery 规范 提供节点查询接口。

函数: nodes(service_name)

说明: service_name 必须满足格式:[id]/[namespace]/[name]:[portName]

  • id: Kubernetes 服务发现配置中定义的集群 id 值

  • namespace: Endpoints 所在的命名空间

  • name: Endpoints 的资源名

  • portName: Endpoints 定义包含的 ports.name 值,如果 Endpoints 没有定义 ports.name,请依次使用 targetPort, port 代替。设置了 ports.name 的情况下,不能使用后两者。

返回值: 以如下 Endpoints 为例:

apiVersion: v1
kind: Endpoints
metadata:
name: plat-dev
namespace: default
subsets:
- addresses:
- ip: "10.5.10.109"
- ip: "10.5.10.110"
ports:
- port: 3306
name: port

nodes("release/default/plat-dev:port") 调用会得到如下的返回值:

 {
{
host="10.5.10.109",
port= 3306,
weight= 50,
},
{
host="10.5.10.110",
port= 3306,
weight= 50,
},
}

Q&A#

Q: 为什么只支持配置 token 来访问 Kubernetes APIServer?

A: 一般情况下,我们有三种方式可以完成与 Kubernetes APIServer 的认证:

  • mTLS
  • Token
  • Basic authentication

因为 lua-resty-http 目前不支持 mTLS, Basic authentication 不被推荐使用,所以当前只实现了 Token 认证方式。

Q: APISIX 继承了 NGINX 的多进程模型,是否意味着每个 APISIX 工作进程都会监听 Kubernetes Endpoints?

A: Kubernetes 服务发现只使用特权进程监听 Kubernetes Endpoints,然后将其值存储到 ngx.shared.DICT 中,工作进程通过查询 ngx.shared.DICT 来获取结果。

Q: ServiceAccount 需要的权限有哪些?

A: ServiceAccount 需要集群级 [ get,list,watch ] endpoints 资源的的权限,其声明式定义如下:

kind: ServiceAccount
apiVersion: v1
metadata:
name: apisix-test
namespace: default
---

kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
name: apisix-test
rules:
- apiGroups: [ "" ]
resources: [ endpoints,endpointslices ]
verbs: [ get,list,watch ]
---

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
name: apisix-test
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: ClusterRole
name: apisix-test
subjects:
- kind: ServiceAccount
name: apisix-test
namespace: default

Q: 怎样获取指定 ServiceAccount 的 Token 值?

A: 假定你指定的 ServiceAccount 资源名为“kubernetes-discovery“, 命名空间为“apisix”, 请按如下步骤获取其 Token 值。

  1. 获取 Secret 资源名。执行以下命令,输出的第一列内容就是目标 Secret 资源名:

    kubectl -n apisix get secrets | grep kubernetes-discovery
  2. 获取 Token 值。假定你获取到的 Secret 资源名为 "kubernetes-discovery-token-c64cv", 执行以下命令,输出内容就是目标 Token 值:

    kubectl -n apisix get secret kubernetes-discovery-token-c64cv -o jsonpath={.data.token} | base64 -d

调试 API#

它还提供了用于调试的控制 api。

内存 Dump API#

GET /v1/discovery/kubernetes/dump

例子

# curl http://127.0.0.1:9090/v1/discovery/kubernetes/dump | jq
{
"endpoints": [
{
"endpoints": [
{
"value": "{\"https\":[{\"host\":\"172.18.164.170\",\"port\":6443,\"weight\":50},{\"host\":\"172.18.164.171\",\"port\":6443,\"weight\":50},{\"host\":\"172.18.164.172\",\"port\":6443,\"weight\":50}]}",
"name": "default/kubernetes"
},
{
"value": "{\"metrics\":[{\"host\":\"172.18.164.170\",\"port\":2379,\"weight\":50},{\"host\":\"172.18.164.171\",\"port\":2379,\"weight\":50},{\"host\":\"172.18.164.172\",\"port\":2379,\"weight\":50}]}",
"name": "kube-system/etcd"
},
{
"value": "{\"http-85\":[{\"host\":\"172.64.89.2\",\"port\":85,\"weight\":50}]}",
"name": "test-ws/testing"
}
],
"id": "first"
}
],
"config": [
{
"default_weight": 50,
"id": "first",
"client": {
"token": "xxx"
},
"service": {
"host": "172.18.164.170",
"port": "6443",
"schema": "https"
},
"shared_size": "1m"
}
]
}