openstack-helm/doc/source/devref/endpoints.rst

Endpoints

The project's goal is to provide a consistent mechanism for endpoints. OpenStack is a highly interconnected application, with various components requiring connectivity details to numerous services, including other OpenStack components and infrastructure elements such as databases, queues, and memcached infrastructure. The project's goal is to ensure that it can provide a consistent mechanism for defining these "endpoints" across all charts and provide the macros necessary to convert those definitions into usable endpoints. The charts should consistently default to building endpoints that assume the operator is leveraging all charts to build their OpenStack cloud. Endpoints should be configurable if an operator would like a chart to work with their existing infrastructure or run elements in different namespaces.

For instance, in the Neutron chart values.yaml the following endpoints are defined:

# typically overridden by environmental
# values, but should include all endpoints
# required by this chart
endpoints:
  image:
    hosts:
      default: glance-api
    type: image
    path: null
    scheme: 'http'
    port:
      api: 9292
      registry: 9191
  compute:
    hosts:
      default: nova-api
    path: "/v2/%(tenant_id)s"
    type: compute
    scheme: 'http'
    port:
      api: 8774
      metadata: 8775
      novncproxy: 6080
  identity:
    hosts:
      default: keystone-api
    path: /v3
    type: identity
    scheme: 'http'
    port:
      admin: 35357
      public: 5000
  network:
    hosts:
      default: neutron-server
    path: null
    type: network
    scheme: 'http'
    port:
      api: 9696

These values define all the endpoints that the Neutron chart may need in order to build full URL compatible endpoints to various services. Long-term, these will also include database, memcached, and rabbitmq elements in one place. Essentially, all external connectivity can be defined centrally.

The macros that help translate these into the actual URLs necessary are defined in the helm-toolkit chart. For instance, the cinder chart defines a glance_api_servers definition in the cinder.conf template:

{{- if empty .Values.conf.cinder.DEFAULT.glance_api_servers -}}
{{- $_ := tuple "image" "internal" "api" . | include "helm-toolkit.endpoints.keystone_endpoint_uri_lookup"| set .Values.conf.cinder.DEFAULT "glance_api_servers" -}}
{{- end -}}

As an example, this line uses the endpoints.keystone_endpoint_uri_lookup macro in the helm-toolkit chart (since it is used by all charts). Note that there is a second convention here. All {{ define }} macros in charts should be pre-fixed with the chart that is defining them. This allows developers to easily identify the source of a Helm macro and also avoid namespace collisions. In the example above, the macro endpoints.keystone_endpoint_uri_lookup is defined in the helm-toolkit chart. This macro is passing three parameters (aided by the tuple method built into the go/sprig templating library used by Helm):

• image: This is the OpenStack service that the endpoint is being built for. This will be mapped to glance which is the image service for OpenStack.
• internal: This is the OpenStack endpoint type we are looking for -valid values would be internal, admin, and public
• api: This is the port to map to for the service. Some components, such as glance, provide an api port and a registry port, for example.

Charts should not use hard coded values such as http://keystone-api:5000 because these are not compatible with operator overrides and do not support spreading components out over various namespaces.

By default, each endpoint is located in the same namespace as the current service's helm chart. To connect to a service which is running in a different Kubernetes namespace, a namespace can be provided for each individual endpoint.