LoadBalancer internals

LBaaS resources

For a given Kubernetes Service of type LoadBalancer, we need to manage numerous Anexia LBaaS resources

  1. one Frontend and Backend per port in the Service

  2. one FrontendBind per Frontend + external IP address

  3. one BackendServer per Backend + Kubernetes node

These resources have a name suffix of .$serviceName.$serviceNamespace.$clusterName, with resource-specific data before:

  1. Frontend and Backend use the name of the port (http.test-service.default.some-cluster)

  2. FrontendBinds use the address family (v4/v6) and name of the port (v4.http.test-service.default.some-cluster)

  3. BackendServers use the name of the node and name of the port (machine-deploy-a-2345413453-0843q.test-service.default.some-cluster)

LBaaS resources are tagged with anxccm-svc-uid=$service-uid ($service-uid is .metadata.uid) to find them later.

Reconcilation

  1. retrieve resources tagged with the service UID

    1. filter resources by the LoadBalancer they belong to as a given Service can be provisioned onto many LBaaS LoadBalancers and still have the same tag

    2. Frontends and Backends are directly attached to their LoadBalancer

    3. FrontendBinds and BackendServers are checked after all resources are retrieved and kept in the working set if their Frontend/Backend is in the working set

  2. in a loop over the resource types (in the order Backend, Frontend, FrontendBind, BackendServer), until something needs to be created:

    1. determine the target set of resources

    2. compare with existing resources, creating a list of resources to create and a list of resources to destroy

  3. destroy any resources that are not needed anymore

  4. create new resources

  5. if something was destroyed or created: go to step 1