add an option for tower_host to merge variables instead of replacing

[orgito]

SUMMARY

I want to use the tower_host module to add/replace one specific variable of an existing host in tower. Currently the module will remove all existing variables from the host leaving only the variable specified in the task.

ISSUE TYPE

• Feature Idea

COMPONENT NAME

tower_host

ANSIBLE VERSION

ansible 2.5.5

CONFIGURATION

ANSIBLE_PIPELINING(/home/renato/.ansible.cfg) = True
ANSIBLE_SSH_ARGS(/home/renato/.ansible.cfg) = -C -o ControlMaster=auto -o ControlPersist=60s -o ForwardAgent=yes
ANSIBLE_SSH_CONTROL_PATH(/home/renato/.ansible.cfg) = %(directory)s/ansible-ssh-%%C
CACHE_PLUGIN(/home/renato/.ansible.cfg) = redis
CACHE_PLUGIN_TIMEOUT(/home/renato/.ansible.cfg) = 86100
DEFAULT_FILTER_PLUGIN_PATH(/home/renato/.ansible.cfg) = [u'/home/renato/ansible/plugins/filter_plugins']
DEFAULT_FORKS(/home/renato/.ansible.cfg) = 15
DEFAULT_GATHERING(/home/renato/.ansible.cfg) = smart
DEFAULT_HOST_LIST(/home/renato/.ansible.cfg) = [u'/home/renato/ansible/hosts']
DEFAULT_REMOTE_USER(/home/renato/.ansible.cfg) = root
DEFAULT_ROLES_PATH(/home/renato/.ansible.cfg) = [u'/home/renato/ansible/roles']
DEFAULT_VAULT_PASSWORD_FILE(/home/renato/.ansible.cfg) = /home/renato/ansible/.vault-passwd.sh
HOST_KEY_CHECKING(/home/renato/.ansible.cfg) = False

OS / ENVIRONMENT

Ansible Host: Fedora 28 with ansible-tower-cli (3.3.0)
Tower Test Host: Centos 7.5.1804 / AWX 1.0.6.16

STEPS TO REPRODUCE

Task to add/replace a variable to an existing tower host.

  - name: Update host in Tower
    tower_host:
      name: "{{ inventory_hostname }}"
      inventory: "Telecom Hosts - Production"
      variables:
        vm_uuid: "{{facts.instance.hw_product_uuid}}"
      tower_verify_ssl: no
    connection: local

In order not to change the current behavior, which potentially breaks existing playbooks, maybe there should be a new parameter, like merge_variable, to specify that the variable(s) should be added and not completely replace existing variables:

  - name: Update host in Tower
    tower_host:
      name: "{{ inventory_hostname }}"
      inventory: "Telecom Hosts - Production"
      merge_variables: yes     
      variables:
        vm_uuid: "{{facts.instance.hw_product_uuid}}"
      tower_verify_ssl: no
    connection: local

EXPECTED RESULTS

The vm_uuid variable should be added to the existing list of variables if it is not already there or changed if already there and different. Any other variables should not be touched

ACTUAL RESULTS

The module delete all the existing variables and keep only the variables specified in the task.

[ansibot]

Files identified in the description:

• lib/ansible/modules/web_infrastructure/ansible_tower/tower_host.py

If these files are inaccurate, please update the component name section of the description or use the !component bot command.

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[ansibot]

cc @AlanCoding @ghjm @jlaska @matburt @rooftopcellist @ryanpetrello @simfarm @wwitzel3
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[AlanCoding]

I would consider this first as a feature in tower-cli, and then update the tower modules to use that call pattern (which possibly some version detection). The approach should be the same as:

ansible/tower-cli#552

That was done to solve a slightly different problem, but it handles the variable merging behavior at the correct point. The tower-cli library already does a preliminary request to get the object, and you need to modify data here to have the changed status remain accurate.

[orgito]

So, the idea would be something like:

tower-cli host modify --name="myhost" --subinput vm_uuid xxxxxxxxxx

Possibly with multiple --subinput if there are multiple variables. Then we could change the ansible module to have a parameter to toggle subinput use.

Any idea when will that land in tower-cli?

[AlanCoding]

This is such a high-impact detail across all the resources in AWX that I want to get it right. I would probably call it something different in this case, it might look like:

tower-cli host modify --name="myhost" --variable vm_uuid xxxxxxxxxx --variable vm_user xxxxxxxxxx

Then if we do it like this, the call pattern from python would look like:

import tower_cli
res = tower_cli.get_resource('host')
res.modify(name="myhost", variable=(('vm_uuid', 'xxxx'), ('vm_user', 'xxxx')))

We might be able to have --variable as a CLI alias but have variables as the function keyword argument. That would probably be ideal, and it would be good to do the same thing with subinput / subinputs.

My first interest here is credentials, but there are already bugs related to sub-fields of JSON/YAML fields in notification templates. Then, the same feature request would apply to all inventory things, job templates, etc.

I'm not sure what the timeline will be, but the related credentials fix is somewhat of a priority.

[ansibot]

cc @jladdjr @kdelee
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[ansibot]

cc @chrismeyersfsu
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[AlanCoding]

Right now @ryanpetrello is working on the new AWX CLI. Until a CLI starts to support variable merges, I would rather not put it into consideration for the modules. As I've been saying in other issues here, we are migrating these modules out of core into an independent collection at https://github.com/ansible/awx/tree/devel/awx_collection. You can re-open another request in that issue queue, but I don't personally find this issue compelling enough right now to migrate over.

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