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: v1
kind: Endpoints
metadata:
  name: plat-dev
  namespace: default
subsets:
  - 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

2. 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