var values in the same line

[Nicolas G]

Hi all,

We have a role var defined for every role like bellow :

# roles/db/vars/main.yml :

role : db

# roles/web/vars/main.yml :

role : web

# roles/app/vars/main.yml :

role : app

We need to have this var a specific "config :" line in a configuration file in a way that will be the same if we run 1 single role on a host or all roles :

if we only run the db role the file should be :

# /etc/file.conf :

config: role : db

if we run all roles on the host the file should look like :

# /etc/file.conf :

config: role : db, role: web, role:app

This might look simple but I'm having a hard time to code the logic in Ansible.. any ideas ?

Thanks in advance.

[Philippe Eveque]

Hi Nicolas,

thinking about a regexp that check and add the string below if not present (e.g: with lineinfile)
role: <name>

it will use the negative look ahead pattern of regexp

I will pass it to you tomorrow if someone else do not beat me

Stay tuned

Phil

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[Nicolas G.]

Thank you Phil that will be great.

Looking forward to see your solution.

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[Philippe Eveque]

Nicolas,

for clarity I made a small modification to you specification so the config file contains something like below

role: common,web,app,db

then you can use this regexp to check that rolename is not already part of the list

(^role\s*[:]\s*(?!rolename)[\w]+)((,(?!rolename)[\w]+)*)$

for the explanations you can use: https://regex101.com/
to see what's happening

copy the regexp above in the "Regular Expression" field

for the test use the string below:
role: rolenam1,common,app,web,rolenam2,db,rolenam3

look at the "MATCH INFORMATION" window and you will get it I think

change rolenam1 to rolename => no match

that will be the same for rolenam2 or rolename3

to show the position of the decl does not matter.

then from an Ansible perspective

each role can have a task like below, that will append the rolename to the list if not already done

  vars:
    - therole: "rolename"
    - string: "role: common"
   
  tasks:

  - name: check if config exist
    stat: path="/tmp/config"
    register: stat_result
   
   
  - name: start with a basis /tmp/config file
    shell: echo "{{ string }}" > /tmp/config
    when: stat_result.stat.exists  == False

  - name: Append rolename string to the list if not present already
    lineinfile:
      dest=/tmp/config
      backrefs=True
      state=present
      regexp='(^role\s*[:]\s*(?!rolename)[\w]+)((,(?!rolename)[\w]+)*)$'
      line='\1\2,rolename'

it will be easy to :

- parameterize the rolename string with an ansible variable

  relace it with {{therole}} in the lineifile task

- adapt back to you original spec (config: role:app, role:web)

- deal with any number of white spaces

there is one limitation: the need to have a firt role being declared in the config.

It is possible to address this but then the regex will be, say, harder to read

HTH

Phil

[Philippe Eveque]

sorry to answer my own post

I should have put a ref to  https://regex101.com/r/xQ6tI0/1

Phil