# Looking for a more elegant way to declare complex variables **URL:** \ **Category:** Ansible Project\ **Created:** [November 20, 2017, 4:49am UTC](https://forum.ansible.com/t/looking-for-a-more-elegant-way-to-declare-complex-variables/26076 "2017-11-20T04:49:20Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Behrang](https://avatars.discourse-cdn.com/v4/letter/b/ed655f/32.png) [@Behrang](https://forum.ansible.com/u/Behrang)\ **Post date:** [November 20, 2017, 4:49am UTC](https://forum.ansible.com/t/looking-for-a-more-elegant-way-to-declare-complex-variables/26076/1 "2017-11-20T04:49:20Z")
Sensu is monitoring services like Nagios and the things it should monitor can be configured with [JSON check definition files](https://sensuapp.org/docs/1.1/guides/getting-started/intro-to-checks.html). A JSON check definition file can have one or more check definitions. Here is a simplified example: ```auto { "checks": { "cron": { "command": "check-process.rb -p cron", "interval": 60 } } } ``` Let’s say I have defined the following template for generating check files: ```auto { "checks": { {% for check_def in item.check_defs %} "{{ check_def.name }}": { "command": "{{ check_def.command }}", "interval": {{ check_def.check_interval }} }{{ ',' if not loop.last else '' }} {% endfor %} } } ``` I apply this template a task like this: ```auto - copy: content: "{{ lookup('template', 'check_def.json.j2') | to_nice_json }}" dest: "{{ somewhere }}" with_items: "{{ check_sets }}" notify: Restart Sensu ``` The `check_sets` variable is defined similar to: ```auto vars: services: - foo - bar - baz tasks: set_fact: check_defs: > {{ check_defs|default([]) + [ { 'name' : 'my-check-def-for' + item.name, 'command' : 'check-process.rb', 'command_args' : '-p ' + item } ] }} with_items: "{{ services }}" ``` I find this approach to defining `check_defs` to be ugly for several reasons: 1- It is not declarative (e.g. `check_defs|default([])` as well as appending items to the list are not declarative). 2- I don’t like the string concat logic using `+` and using quotes around hardcoded strings 3- For newcomers, it is not easy to understand what is going on If I use a static list, I have to repeat some variables/values. For example: ```auto check_defs: - name: my-check-def-for-foo command: check-process.rb command_args: -p foo ``` Here `foo` is repeated twice. Also users might diverge from the naming convention. For example by providing: ```auto check_defs: - name: foo-check command: check-process.rb command_args: -p foo ``` Is there a more elegant way to declare the `check_defs` variable that doesn’t have any of these drawbacks? Thanks in advance. ---
**Author:** ![shankerbalan](https://avatars.discourse-cdn.com/v4/letter/s/c68b51/32.png) [@shankerbalan](https://forum.ansible.com/u/shankerbalan)\ **Post date:** [November 20, 2017, 10:28am UTC](https://forum.ansible.com/t/looking-for-a-more-elegant-way-to-declare-complex-variables/26076/2 "2017-11-20T10:28:11Z")
Hi Behrang, Comments inline... > Sensu is monitoring services like Nagios and the things it should monitor can be configured with JSON check definition files. > > A JSON check definition file can have one or more check definitions. Here is a simplified example: > > { >   "checks": { >     "cron": { >       "command": "check-process.rb -p cron", >       "interval": 60 >     } >   } > } > > Let's say I have defined the following template for generating check files: > > { >   "checks": { >     {% for check\_def in item.check\_defs %} >         "{{ check\_def.name }}": { >         "command": "{{ check\_def.command }}", >           "interval": {{ check\_def.check\_interval }} >         }{{ ',' if not loop.last else '' }} >     {% endfor %} >   } > } \ I am using Ansible to manage checks.json myself but am doing so with the Sensu module from [http://docs.ansible.com/ansible/latest/sensu\_check\_module.html](http://docs.ansible.com/ansible/latest/sensu_check_module.html) as below: name: Updating checks in - /etc/sensu/conf.d/{{sensu\_check\_filename|default(check\_filename)}}   sensu\_check:     #path: "{{ sensu\_check\_filename|default(check\_filename) }}"     path: /etc/sensu/conf.d/checks.json     name: "{{ item.name }}"     command: "{{ item.command }}"     interval: "{{ item.interval|default(check\_interval) }}"     metric: "{{ item.metric | default('no') }}"     handle: "{{ item.handle | default('yes') }}"     occurrences: "{{ item.occurrences | default(check\_occurrences) }}"     timeout: "{{ item.timeout | default(check\_timeout) }}"     dependencies: "{{ item.dependencies | default(omit) }}"     subscribers: "{{ item.subscribers|default(default\_subscribers) }}"     handlers: "{{ item.handlers | default(omit) }}"     refresh: "{{ item.refresh | default(check\_refresh) }}"     state: "{{ item.state | default('present') }}"     standalone: "{{ item.standalone | default('no') }}"     ttl: "{{ item.ttl | default(900) }}"     aggregate: "{{ item.aggregate | default('no') }}"     subdue\_begin: "{{ item.subdue\_begin | default(omit) }}"     subdue\_end: "{{ item.subdue\_end | default(omit) }}"     source: "{{ item.source | default(omit) }}"     low\_flap\_threshold: "{{ item.low\_flap\_threshold | default(omit) }}"     high\_flap\_threshold: "{{ item.high\_flap\_threshold | default(omit) }}"   notify:     - restart\_sensu\_server     - restart\_sensu\_client     - restart\_sensu\_api   with\_items: "{{ \_sensu\_check\_list|sort }}" Is there any particular reason why you chose to use a template? Regards. @shankerbalan ---
**Author:** ![system](https://us1.discourse-cdn.com/ansible/original/1X/1882d9a01da5d8996a862359b0913cc568a39b84.svg) [@system](https://forum.ansible.com/u/system)\ **Post date:** [November 20, 2017, 2:51pm UTC](https://forum.ansible.com/t/looking-for-a-more-elegant-way-to-declare-complex-variables/26076/3 "2017-11-20T14:51:21Z")
Just a note, this task does x2 transformations it does not need to, if you use template directly you avoid many problems. so instead of: - copy:     content: "{{ lookup('template', 'check\_def.json.j2') | to\_nice\_json }}"     dest: "{{ somewhere }}"   with\_items: "{{ check\_sets }}"   notify: Restart Sensu use: - template: src=check\_def.json.j2 dest={{somewhere}}   with\_items: "{{ check\_sets }}"   notify: Restart Sensu ---
**Author:** ![Behrang](https://avatars.discourse-cdn.com/v4/letter/b/ed655f/32.png) [@Behrang](https://forum.ansible.com/u/Behrang)\ **Post date:** [November 20, 2017, 10:37pm UTC](https://forum.ansible.com/t/looking-for-a-more-elegant-way-to-declare-complex-variables/26076/4 "2017-11-20T22:37:15Z")
I want to pretty print the generated JSON file. Otherwise I would have used the template module. ---
**Author:** ![Behrang](https://avatars.discourse-cdn.com/v4/letter/b/ed655f/32.png) [@Behrang](https://forum.ansible.com/u/Behrang)\ **Post date:** [November 20, 2017, 10:38pm UTC](https://forum.ansible.com/t/looking-for-a-more-elegant-way-to-declare-complex-variables/26076/5 "2017-11-20T22:38:06Z")
Oops. I didn’t know this module existed. I am maintaining a set of scripts that was written before 2.0 and this module were released.