sunbeam-charms/ops-sunbeam/doc/writing-OS-API-charm.rst

New API Charm

The example below will walk through the creation of a basic API charm for the OpenStack Ironic service designed to run on kubernetes.

Create the skeleton charm

Prerequisite

Build a base geneeric charm with the charmcraft tool.

mkdir charm-ironic-k8s
cd charm-ironic-k8s
charmcraft init --author $USER --name ironic-k8s

Add ASO common files to new charm. The script will ask a few basic questions:

git clone https://opendev.org/openstack/charm-ops-sunbeam
cd charm-ops-sunbeam
./sunbeam-charm-init.sh ~/charm-ironic-k8s

This tool is designed to be used after 'charmcraft init' was initially run
service_name [ironic]: ironic
charm_name [ironic-k8s]: ironic-k8s
ingress_port []: 6385
db_sync_command [] ironic-dbsync --config-file /etc/ironic/ironic.conf create_schema: 

Fetch interface libs corresponding to the requires interfaces:

cd charm-ironic-k8s
charmcraft login --export ~/secrets.auth
export CHARMCRAFT_AUTH=$(cat ~/secrets.auth)
charmcraft fetch-lib charms.nginx_ingress_integrator.v0.ingress
charmcraft fetch-lib charms.data_platform_libs.v0.database_requires
charmcraft fetch-lib charms.keystone_k8s.v1.identity_service
charmcraft fetch-lib charms.rabbitmq_k8s.v0.rabbitmq
charmcraft fetch-lib charms.traefik_k8s.v1.ingress

Templates

Much of the service configuration is covered by common templates which were copied into the charm in the previous step. The only additional template for this charm is for ironic.conf. Add the following into ./src/templates/ironic.conf.j2

[DEFAULT]
debug = {{ options.debug }}
auth_strategy=keystone
transport_url = {{ amqp.transport_url }}

[keystone_authtoken]
{% include "parts/identity-data" %}

[database]
{% include "parts/database-connection" %}

[neutron]
{% include "parts/identity-data" %}

[glance]
{% include "parts/identity-data" %}

[cinder]
{% include "parts/identity-data" %}

[service_catalog]
{% include "parts/identity-data" %}

Make charm deployable

The next step is to pack the charm into a deployable format

cd charm-ironic-k8s
charmcraft pack

Deploy Charm

The charm can now be deployed. The Kolla project has images that can be used to run the service. Juju can pull the image directly from dockerhub.

juju deploy ./ironic-k8s_ubuntu-20.04-amd64.charm --resource ironic-api-image=kolla/ubuntu-binary-ironic-api:yoga ironic
juju relate ironic mysql
juju relate ironic keystone
juju relate ironic rabbitmq
juju relate ironic:ingress-internal traefik:ingress
juju relate ironic:ingress-public traefik:ingress

Test Service

Check that the juju status shows the charms is active and no error messages are preset. Then check the ironic api service is responding.

$ juju status ironic
Model  Controller  Cloud/Region        Version  SLA          Timestamp
ks     micro       microk8s/localhost  2.9.22   unsupported  13:31:41Z

App     Version  Status  Scale  Charm                    Store  Channel  Rev  OS          Address        Message
ironic           active      1  ironic-k8s  local             0  kubernetes  10.152.183.73

Unit       Workload  Agent  Address       Ports  Message
ironic/0*  active    idle   10.1.155.106

$ curl http://10.1.155.106:6385 | jq '.'
{
  "name": "OpenStack Ironic API",
  "description": "Ironic is an OpenStack project which aims to provision baremetal machines.",
  "default_version": {
    "id": "v1",
    "links": [
      {
        "href": "http://10.1.155.106:6385/v1/",
        "rel": "self"
      }
     ],
    "status": "CURRENT",
    "min_version": "1.1",
    "version": "1.72"
  },
  "versions": [
    {
      "id": "v1",
      "links": [
        {
          "href": "http://10.1.155.106:6385/v1/",
          "rel": "self"
        }
       ],
      "status": "CURRENT",
      "min_version": "1.1",
      "version": "1.72"
    }
  ]
}