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Version: 2.15

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
  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