How to add when or if condition on Ansible Variable - jenkins

Question

It is possible to add when or if condition on Ansible variable?
For example we have 2 jenkins server (server A and server B), we want to apply different plugins version for both of them.
Example:
jenkins_plugins:
- name: plugin-x
version: "1.1" {"if server == A"}
- name: plugin-x
version: "1.5" {"if server == B"}
Thanks.
I want to apply different plugins version to different servers.

Answer 1

Create the dictionary
jenkins_plugins:
A:
- name: plugin-x
version: 1.1
B:
- name: plugin-x
version: 1.5
Use it
- debug:
var: jenkins_plugins[inventory_hostname]
Notes
Given the inventory
shell> cat hosts
A
B
Example of a complete playbook for testing
- hosts: all
vars:
jenkins_plugins:
A:
- name: plugin-x
version: 1.1
B:
- name: plugin-x
version: 1.5
tasks:
- debug:
var: jenkins_plugins[inventory_hostname]
gives
PLAY [all] ***********************************************************************************
TASK [debug] *********************************************************************************
ok: [A] =>
jenkins_plugins[inventory_hostname]:
- name: plugin-x
version: 1.1
ok: [B] =>
jenkins_plugins[inventory_hostname]:
- name: plugin-x
version: 1.5
PLAY RECAP ***********************************************************************************
A: ok=1 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
B: ok=1 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
Elegant and clean option is putting the variables into the group_vars. For example,
shell> cat group_vars/all/jenkins_plugins.yml
jenkins_plugins_dict:
default:
- name: plugin-x
version: 1.0
A:
- name: plugin-x
version: 1.1
B:
- name: plugin-x
version: 1.5
jenkins_plugins: "{{ jenkins_plugins_dict[inventory_hostname]|
default(jenkins_plugins_dict.default) }}"
Then, given the inventory
shell> cat hosts
A
B
X
The playbook
- hosts: all
tasks:
- debug:
var: jenkins_plugins
gives
PLAY [all] ***********************************************************************************
TASK [debug] *********************************************************************************
ok: [B] =>
jenkins_plugins:
- name: plugin-x
version: 1.5
ok: [A] =>
jenkins_plugins:
- name: plugin-x
version: 1.1
ok: [X] =>
jenkins_plugins:
- name: plugin-x
version: 1.0
PLAY RECAP ***********************************************************************************
A: ok=1 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
B: ok=1 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
X: ok=1 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0

Answer 2

Ansible can hold different variables for each of your servers/groups in your inventory out of the box and this can actually be much more powerfull and maintainable than your above condition.
As an illustration of How to build your inventory, and to go a bit beyond your actual example let's imagine you have a default list of plugins for all jenkins servers and you want to override the version for some of them or add additional ones on specific server.
(Note: this example will not address removing specific plugins from the default but that is also possible...)
Here's my example global file structure:
.
├── check_plugins_versions.yml
└── inventories
└── demo
├── group_vars
│   └── jenkins
│   └── plugins.yml
├── hosts.yml
└── host_vars
└── server2.jenkins.local
└── specific_jenkins_plugins.yml
The hosts are declared in inventories/demo/hosts.yml
---
jenkins:
hosts:
server1.jenkins.local:
server2.jenkins.local:
As you can see, I declared two host as in your question and placed them in a jenkins group. So we can now declare variables for that group inside the inventories/demo/group_vars/jenkins directory where I placed the plugins.yml file
---
# List of plugins to install by default
_default_jenkins_plugins:
- name: plugin-a
version: "1.1"
- name: plugin-b
version: "2.2"
- name: plugin-x
version: "1.1"
# Customize plugin list with specific plugins for host if they exist. For this we
# transform the above default list and the specific one to dicts
# combine them and turn them back into a result list
_d_plug_dict: "{{ _default_jenkins_plugins
| items2dict(key_name='name', value_name='version') }}"
_s_plug_dict: "{{ _specific_jenkins_plugins | d([])
| items2dict(key_name='name', value_name='version') }}"
jenkins_plugins: "{{ _d_plug_dict | combine(_s_plug_dict)
| dict2items(key_name='name', value_name='version') }}"
Now we can give a list of specific plugins/versions for server2.jenkins.local. I placed those values in inventories/demo/host_vars/server2.jenkins.local/specific_jenkins_plugins.yml
---
_specific_jenkins_plugins:
# Override version for plugin-x
- name: plugin-x
version: "1.5"
# Install an additional plugin-z
- name: plugin-z
version: "9.9"
Then we have a simple check_plugins_versions.yml test playbook to verify that the above is doing the job as expected:
---
- hosts: jenkins
gather_facts: false
tasks:
- name: show computed plugins for each server
debug:
var: jenkins_plugins
Which gives when called with the relevant inventory
$ ansible-playbook -i inventories/demo/ check_plugins_versions.yml
PLAY [jenkins] *************************************************************************************************************************************************************************************************************************
TASK [show computed plugins for each server] *******************************************************************************************************************************************************************************************
ok: [server1.jenkins.local] => {
"jenkins_plugins": [
{
"name": "plugin-a",
"version": "1.1"
},
{
"name": "plugin-b",
"version": "2.2"
},
{
"name": "plugin-x",
"version": "1.1"
}
]
}
ok: [server2.jenkins.local] => {
"jenkins_plugins": [
{
"name": "plugin-a",
"version": "1.1"
},
{
"name": "plugin-b",
"version": "2.2"
},
{
"name": "plugin-x",
"version": "1.5"
},
{
"name": "plugin-z",
"version": "9.9"
}
]
}
PLAY RECAP *****************************************************************************************************************************************************************************************************************************
server1.jenkins.local : ok=1 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
server2.jenkins.local : ok=1 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0