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# Lightweight service orchestrator
This page describes the inner workings of the Lightweight Service Orchestrator
(LSO), that handles the interaction between GSO and Ansible.
## Motivation
For the deployment of new services in the GÉANT network, Ansible playbooks are
used to deploy configuration statements onto remote devices. To make this
interaction possible, LSO exposes an API that allows for the remote execution
of playbooks.
The need to externalise this interaction comes from the fact that the Python
library used to execute playbooks, introduces a potential situation where
dependency versions could be conflicting. To prevent this from happening, GSO
and LSO each are their own Python package, with each their own, independent
library dependencies.
## Inner workings
LSO uses <a href="https://ansible.readthedocs.io/projects/runner/en/latest/"
target="_blank">`ansible-runner`</a> for the execution of Ansible playbooks.
This package fully dictates the way in which GAP interacts with Ansible itself.
LSO only introduces an API with a single REST endpoint that exposes its
functionality.
In the case of GAP, all Ansible playbooks operate without an inventory that
contains all relevant `group_vars` and `host_vars`. The inventory is passed to
the API endpoint for executing a playbook, which contains all required
`host_vars`. For the other information relevant to the playbook, this is passed
through the API by making use of `extra_vars`. In virtually all cases, the
`extra_vars` will at least consist of the subscription object that is being
deployed, and assisting variables, such as 'verb' used to express an operation.
As an example, the following object is passed to the Ansible playbook for the
deployment of a new router in the network.
``` json
extra_vars = {
"subscription": {
"product": {
"product_id": "27c9dc35-f0fa-4901-bda4-65df5bb7499d",
"name": "Router",
"description": "A Router",
"product_type": "Router",
"tag": "RTR",
"status": "active",
"created_at": "2024-01-24T15:47:13+00:00",
"end_date": None,
},
"customer_id": "8f0df561-ce9d-4d9c-89a8-7953d3ffc961",
"subscription_id": "b57cbbc8-e8d1-47f8-add6-7923ecd7e3d5",
"description": "Router SrzptDtKBIFGijnHrglQ.flores.bb.geant.net",
"status": "provisioning",
"insync": False,
"start_date": None,
"end_date": None,
"note": None,
"router": {
"name": "RouterBlock",
"subscription_instance_id": "09d6bea9-8c79-4e75-9a69-ef249bb9de5e",
"owner_subscription_id": "b57cbbc8-e8d1-47f8-add6-7923ecd7e3d5",
"label": None,
"router_fqdn": "SrzptDtKBIFGijnHrglQ.flores.bb.geant.net",
"router_ts_port": 4223,
"router_access_via_ts": True,
"router_lo_ipv4_address": "74.95.57.63",
"router_lo_ipv6_address": "ac6f:7008:40d3:d431:bcc4:2eac:b443:f6b8",
"router_lo_iso_address": "49.51e5.0001.0740.9505.7063.00",
"router_role": "amt",
"router_site": {
"name": "SiteBlock",
"subscription_instance_id": "874ffb0b-cf55-49ea-810f-7268c02891fa",
"owner_subscription_id": "324239ea-555b-464d-bfde-54666470d71d",
"label": None,
"site_name": "flores",
"site_city": "Whitemouth",
"site_country": "Zimbabwe",
"site_country_code": "BB",
"site_latitude": "45.39258",
"site_longitude": "137.727838",
"site_internal_id": 9881,
"site_bgp_community_id": 8738,
"site_tier": "1",
"site_ts_address": "137.105.143.190",
},
"vendor": "nokia",
},
},
"dry_run": True,
"verb": "deploy",
"commit_comment": "GSO_PROCESS_ID: 549aae60-0574-4c5a-a736-00c83fdb446a -
TT_NUMBER: TT#1987043028032905 - Deploy base config"
}
```
In this example, four top-level keys are included: `subscription`, `dry_run`,
`verb`, and `commit_comment`. In order, these are used for the following.
The `subscription` key includes a dictionary representation of the subscription
that is being provisioned. In the case of a router, `router` contains
information about the subscription object, with its child key `router_site` that
contains information about the site at which this router is deployed.
Information about this router site comes from the related site subscription
which is already 'deployed' in GSO.
For the distinction between practice runs, and actual deployments, the variable
`dry_run` is included. The difference between an execution which is a dry run
and one that is not, is the commitment of configuration. With a dry run,
configuration is only checked, and not committed to the remote machine. When
`dry_run` is set to `False`, the configuration is checked and then committed.
To distinguish between different actions that can be taken with service
deployments, 'verbs' are introduced. In the example, the verb is set to 'deploy'
to provision a new service. Other examples of verbs can include 'deactivate',
'modify', or 'terminate'.
The `commit_comment` is used for bookkeeping purposes on the remote machines.
This can be used for debugging or accounting purposes, among others. It always
includes the process ID of the workflow that is related to an operation, and the
associated trouble ticket number.
### The full API request
From the previous section, `extra_vars` is only one piece of the puzzle. For a
full-fledged API request to LSO, an example call is given.
``` json
{
"playbook_name": "deploy_a_service.yaml",
"callback": "https://orchestrator.gap.geant.org/api/processes/(…)/callback/(…)",
"inventory": {
"all": {
"hosts": {
"edge1-host": {
"example-var": "A value",
"another-var": "Totally optional, and can differ per host"
},
"edge2-host": null // Note that the `null` is a mandatory YAML-restriction
}
},
"extra_vars": {
…as shown above
}
}
}
```
## Code documentation
Code documentation for LSO can be found
<a href="https://workfloworchestrator.org/lso" target="_blank">here</a>.
## Deployment within GÉANT
For the deployment in GÉANT, LSO runs inside a Docker container. The Dockerfile
used to build this container is available <a href=
"https://gitlab.software.geant.org/goat/gap/lso/-/blob/develop/Dockerfile"
target="_blank">here</a>.
When building the Docker image, some Ansible roles and collections are installed
that are required for interacting with Juniper and Nokia equipment. For another
organisation that would want to use LSO in their deployment, it is highly
recommended to use this Dockerfile as a starting point. From this another Docker
image can be built with custom Ansible requirements pre-installed.
It also opens up the possibility to include an Ansible inventory, if so desired.
Do note however, that this introduces a requirement to re-build LSO every time
the inventory is updated, or to have it included as a volume mount inside the
running container. Including a dynamic inventory with every API call is
therefore the recommended way to go.