Kubernetes

Summary

The Kubernetes service discovery List-Watch real-time changes of Endpoints resources, then store theirs value into ngx.shared.DICT.

Discovery also provides a node query interface in accordance with the APISIX Discovery Specification.

How To Use

Kubernetes service discovery both support single-cluster and multi-cluster mode, applicable to the case where the service is distributed in a single or multiple Kubernetes clusters.

Single-Cluster Mode Configuration

A detailed configuration for single-cluster mode Kubernetes service discovery is as follows:

  1. discovery:
  2. kubernetes:
  3. service:
  4. # apiserver schema, options [http, https]
  5. schema: https #default https
  6. # apiserver host, options [ipv4, ipv6, domain, environment variable]
  7. host: ${KUBERNETES_SERVICE_HOST} #default ${KUBERNETES_SERVICE_HOST}
  8. # apiserver port, options [port number, environment variable]
  9. port: ${KUBERNETES_SERVICE_PORT} #default ${KUBERNETES_SERVICE_PORT}
  10. client:
  11. # serviceaccount token or token_file
  12. token_file: /var/run/secrets/kubernetes.io/serviceaccount/token
  13. #token: |-
  14. # eyJhbGciOiJSUzI1NiIsImtpZCI6Ikx5ME1DNWdnbmhQNkZCNlZYMXBsT3pYU3BBS2swYzBPSkN3ZnBESGpkUEEif
  15. # 6Ikx5ME1DNWdnbmhQNkZCNlZYMXBsT3pYU3BBS2swYzBPSkN3ZnBESGpkUEEifeyJhbGciOiJSUzI1NiIsImtpZCI
  16. default_weight: 50 # weight assigned to each discovered endpoint. default 50, minimum 0
  17. # kubernetes discovery support namespace_selector
  18. # you can use one of [equal, not_equal, match, not_match] filter namespace
  19. namespace_selector:
  20. # only save endpoints with namespace equal default
  21. equal: default
  22. # only save endpoints with namespace not equal default
  23. #not_equal: default
  24. # only save endpoints with namespace match one of [default, ^my-[a-z]+$]
  25. #match:
  26. #- default
  27. #- ^my-[a-z]+$
  28. # only save endpoints with namespace not match one of [default, ^my-[a-z]+$ ]
  29. #not_match:
  30. #- default
  31. #- ^my-[a-z]+$
  32. # kubernetes discovery support label_selector
  33. # for the expression of label_selector, please refer to https://kubernetes.io/docs/concepts/overview/working-with-objects/labels
  34. label_selector: |-
  35. first="a",second="b"
  36. # reserved lua shared memory size,1m memory can store about 1000 pieces of endpoint
  37. shared_size: 1m #default 1m

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

  1. discovery:
  2. 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:

  1. discovery:
  2. kubernetes:
  3. service:
  4. schema: https
  5. host: # enter apiserver host value here
  6. port: # enter apiserver port value here
  7. client:
  8. token: # enter serviceaccount token value here
  9. #token_file: # enter file path here

Single-Cluster Mode Query 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.DICT 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 ports.name value in the Kubernetes endpoints, if there is no ports.name, use targetPort, port instead

return value: if the Kubernetes endpoints value is as follows:

  1. apiVersion: v1
  2. kind: Endpoints
  3. metadata:
  4. name: plat-dev
  5. namespace: default
  6. subsets:
  7. - addresses:
  8. - ip: "10.5.10.109"
  9. - ip: "10.5.10.110"
  10. ports:
  11. - port: 3306
  12. name: port

a nodes(“default/plat-dev:port”) call will get follow result:

  1. {
  2. {
  3. host="10.5.10.109",
  4. port= 3306,
  5. weight= 50,
  6. },
  7. {
  8. host="10.5.10.110",
  9. port= 3306,
  10. weight= 50,
  11. },
  12. }

Multi-Cluster Mode Configuration

A detailed configuration for multi-cluster mode Kubernetes service discovery is as follows:

  1. discovery:
  2. kubernetes:
  3. - id: release # a custom name refer to the cluster, pattern ^[a-z0-9]{1,8}
  4. service:
  5. # apiserver schema, options [http, https]
  6. schema: https #default https
  7. # apiserver host, options [ipv4, ipv6, domain, environment variable]
  8. host: "1.cluster.com"
  9. # apiserver port, options [port number, environment variable]
  10. port: "6443"
  11. client:
  12. # serviceaccount token or token_file
  13. token_file: /var/run/secrets/kubernetes.io/serviceaccount/token
  14. #token: |-
  15. # eyJhbGciOiJSUzI1NiIsImtpZCI6Ikx5ME1DNWdnbmhQNkZCNlZYMXBsT3pYU3BBS2swYzBPSkN3ZnBESGpkUEEif
  16. # 6Ikx5ME1DNWdnbmhQNkZCNlZYMXBsT3pYU3BBS2swYzBPSkN3ZnBESGpkUEEifeyJhbGciOiJSUzI1NiIsImtpZCI
  17. default_weight: 50 # weight assigned to each discovered endpoint. default 50, minimum 0
  18. # kubernetes discovery support namespace_selector
  19. # you can use one of [equal, not_equal, match, not_match] filter namespace
  20. namespace_selector:
  21. # only save endpoints with namespace equal default
  22. equal: default
  23. # only save endpoints with namespace not equal default
  24. #not_equal: default
  25. # only save endpoints with namespace match one of [default, ^my-[a-z]+$]
  26. #match:
  27. #- default
  28. #- ^my-[a-z]+$
  29. # only save endpoints with namespace not match one of [default, ^my-[a-z]+$]
  30. #not_match:
  31. #- default
  32. #- ^my-[a-z]+$
  33. # kubernetes discovery support label_selector
  34. # for the expression of label_selector, please refer to https://kubernetes.io/docs/concepts/overview/working-with-objects/labels
  35. label_selector: |-
  36. first="a",second="b"
  37. # reserved lua shared memory size,1m memory can store about 1000 pieces of endpoint
  38. shared_size: 1m #default 1m

Multi-Kubernetes service discovery does not fill default values for service and client fields, you need to fill them according to the cluster configuration.

Multi-Cluster Mode Query 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.DICT for nodes corresponding to servicename, \ service_name should match pattern: [id]/[namespace]/[name]:[portName]_

  • id: value defined in service discovery configuration

  • namespace: The namespace where the Kubernetes endpoints is located

  • name: The name of the Kubernetes endpoints

  • portName: The ports.name value in the Kubernetes endpoints, if there is no ports.name, use targetPort, port instead

return value: if the Kubernetes endpoints value is as follows:

  1. apiVersion: v1
  2. kind: Endpoints
  3. metadata:
  4. name: plat-dev
  5. namespace: default
  6. subsets:
  7. - addresses:
  8. - ip: "10.5.10.109"
  9. - ip: "10.5.10.110"
  10. ports:
  11. - port: 3306
  12. name: port

a nodes(“release/default/plat-dev:port”) call will get follow result:

  1. {
  2. {
  3. host="10.5.10.109",
  4. port= 3306,
  5. weight= 50,
  6. },
  7. {
  8. host="10.5.10.110",
  9. port= 3306,
  10. weight= 50,
  11. },
  12. }

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.DICT, worker processes get results by querying ngx.shared.DICT.

Q: What permissions do ServiceAccount require?

A: ServiceAccount requires the permissions of cluster-level [ get, list, watch ] endpoints resources, the declarative definition is as follows:

  1. kind: ServiceAccount
  2. apiVersion: v1
  3. metadata:
  4. name: apisix-test
  5. namespace: default
  6. ---
  7. kind: ClusterRole
  8. apiVersion: rbac.authorization.k8s.io/v1
  9. metadata:
  10. name: apisix-test
  11. rules:
  12. - apiGroups: [ "" ]
  13. resources: [ endpoints ]
  14. verbs: [ get,list,watch ]
  15. ---
  16. apiVersion: rbac.authorization.k8s.io/v1
  17. kind: ClusterRoleBinding
  18. metadata:
  19. name: apisix-test
  20. roleRef:
  21. apiGroup: rbac.authorization.k8s.io
  22. kind: ClusterRole
  23. name: apisix-test
  24. subjects:
  25. - kind: ServiceAccount
  26. name: apisix-test
  27. namespace: default

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:

    1. 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:

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