ansible.netcommon.restconf_get: Option to allow not existing instances

[netgab]

SUMMARY

When ansible.netcommon.restconf_get is used to retrieve not existing data, the RESTCONF server sends an HTTP 404 error and the corresponding Ansible task fails. As a consequence processing of subsequent task for the given host stops.

Especially when performing queries (GET requests), it may be sane that a resource does not exists. Imagine there is a playbook with multiple tasks querying different RESTCONF resources, to report the precense (or absence) or certain configuration.

ISSUE TYPE

• Feature Idea

COMPONENT NAME

ansible.netcommon.restconf_get

ADDITIONAL INFORMATION

The RESTCONF RFC states the following regarding not-existing resources:

   If a retrieval request for a data resource represents an instance
   that does not exist, then an error response containing a "404 Not
   Found" status-line MUST be returned by the server.  The error-tag
   value "invalid-value" is used in this case.

It is proposed, that a new attribute is added to ansible.netcommon.restconf_get:

• Parameter: ignore_not_exist_resource (boolean) / Default: false

When the parameter is set to true, Ansible does not consider the task failed, when:
code==404 and error-tag == 'invalid-value'

This is an example for a verbose task output:

TASK [RESTCONF: Get interface (1)] *************************************************************************************************************************************************************************************************************************************************
ok: [device1] => {"changed": false, "failed_when_result": false, "response": {"Cisco-IOS-XE-native:Loopback": [{"logging": {"event": {"link-status-enable": false}}, "name": 900}]}}
ok: [device2] => {"changed": false, "code": 404, "failed_when_result": false, "msg": "{'ietf-restconf:errors': {'error': [{'error-type': 'application', 'error-tag': 'invalid-value', 'error-message': 'uri keypath not found'}]}}"}

The task for device2 succeeds, although the resource has not been found.

I simulated this with the following failed_when statement:

  tasks:
    - name: "RESTCONF: Get interface (1)"
      ansible.netcommon.restconf_get:
        path: "/Cisco-IOS-XE-native:native/interface/Loopback=900"
      register: restconf_result
      failed_when:
        - restconf_result.response is not defined
        - restconf_result.code != 404