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Kubernetes

Summary#

The Kubernetes service discovery List-Watch real-time changes of Endpoints resources, then store theirs value into ngx.shared.kubernetes \ Discovery also provides a query interface in accordance with the APISIX Discovery Specification

Configuration#

A detailed configuration for the kubernetes service discovery is as follows:

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 ${KUBERNETES_SERVICE_PORT}
    client:      # serviceaccount token or token_file      token_file: /var/run/secrets/kubernetes.io/serviceaccount/token
      #token: |-       # eyJhbGciOiJSUzI1NiIsImtpZCI6Ikx5ME1DNWdnbmhQNkZCNlZYMXBsT3pYU3BBS2swYzBPSkN3ZnBESGpkUEEif       # 6Ikx5ME1DNWdnbmhQNkZCNlZYMXBsT3pYU3BBS2swYzBPSkN3ZnBESGpkUEEifeyJhbGciOiJSUzI1NiIsImtpZCI
    # kubernetes discovery plugin support use namespace_selector    # you can use one of [equal, not_equal, match, not_match] filter namespace    namespace_selector:      # only save endpoints with namespace equal default      equal: default
      # only save endpoints with namespace not equal default      #not_equal: default
      # only save endpoints with namespace match one of [default, ^my-[a-z]+$]      #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 plugin support use 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"

If the kubernetes service discovery runs inside a pod, you can use minimal configuration:

discovery:  kubernetes: { }

If the kubernetes service discovery runs outside a pod, you need to create or select a specified ServiceAccount, then get its token value, and use following configuration:

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 file path here

Interface#

the kubernetes service discovery provides a query interface in accordance with the APISIX Discovery Specification

function: \ nodes(service_name)

description: \ nodes() function attempts to look up the ngx.shared.kubernetes for nodes corresponding to servicename, \ service_name should match pattern: [namespace]/[name]:[portName]_

  • namespace: The namespace where the kubernetes endpoints is located

  • name: The name of the kubernetes endpoints

  • portName: The portName of the kubernetes endpoints, if there is no portName, use targetPort, port instead

return value: \ if the kubernetes endpoints value is as follows:

apiVersion: v1kind: Endpointsmetadata:  name: plat-dev  namespace: defaultsubsets:  - addresses:      - ip: "10.5.10.109"      - ip: "10.5.10.110"    ports:      - port: 3306

a nodes("default/plat-dev:3306") call will get follow result:

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

Q&A#

Q: Why only support configuration token to access Kubernetes APIServer \ A: Usually, we will use three ways to complete the authentication of Kubernetes APIServer:

  • mTLS
  • token
  • basic authentication

Because lua-resty-http does not currently support mTLS, and basic authentication is not recommended,\ So currently only the token authentication method is implemented

Q: APISIX inherits Nginx's multiple process model, does it mean that each nginx worker process will List-Watch kubernetes endpoints resources \ A: The kubernetes service discovery only uses privileged processes to List-Watch kubernetes endpoints resources, then store theirs value \ into ngx.shared.kubernetes, worker processes get results by querying ngx.shared.kubernetes

Q: How to get ServiceAccount token value \ A: Assume your ServiceAccount located in namespace apisix and name is kubernetes-discovery, you can use the following steps to get token value

  1. Get secret name: \ you can execute the following command, the output of the first column is the secret name we want
kubectl -n apisix get secrets | grep kubernetes-discovery
  1. Get token value: \ assume secret resources name is kubernetes-discovery-token-c64cv, you can execute the following command, the output is the service account token value we want
kubectl -n apisix get secret kubernetes-discovery-token-c64cv -o jsonpath={.data.token} | base64 -d