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ansible_hostworks

  • Purpose

    • generate an Ansible inventory using a list of hosts and a parsing template
    • inventory is in INI

  • Definitions

    • host file: file that is a list of hosts to be parsed
    • template: a YAML template that uses regexp to parse a list of hosts

  • Usage

    • define a list of hosts in a file, as in test_hosts
    • define a template, as in test_template.yml
    • run:

      python inventory_generator.yml --hosts='<host file>' --template='<YAML template file>'

    • test resulting inventory:

      ansible -m ping -i <resulting inventory as file> all

  • Description

    • the template YAML file is parsed into a template dict
    • one template dict becomes one group in the resulting inventory

    • template dict == group (in inventory)

    • the dict has a structure similar to (almost identical to) an Ansible YAML inventory
    • the parser is defined in GroupWorks.py
    • parsing
      • the "children" key
        • in Ansible inventory, a group YAML object has a key named "children", which is a set of groups
        • similarly, a template dict has a key named "children" that is a set (dict) of templates
      • the "hosts" key
        • defines which hosts are present in a group
        • a child templates hosts are a subset of its parent's hosts
        • i.e. the hosts key narrows the entire set of hosts when parsing recurses
    • when the parser finishes defining a group, it will recurse on the template's children to create child groups
    • the parser handles the INI parent child relation (e.g. creates [all:children] using children defined in "all" template)

  • Technicalities

    • Group objects
      • defined in Group.py
      • will not copy hosts, rather they point to a list of hosts
      • therefore, if a list of hosts is defined, then passed to a Group object, changing that list will change the list for the Group object
      • this is desireable for now, because if multiple groups rely on a host in one list, then changing that host will change it in each Group that references it
    • Capture groups
      • only the first match in a regex pattern is used as the name for the (child) groups generated by regex by the parser
      • to work around this limitation, nest child group regexp in a group defined by literal name
      • (TODO) other workarounds are under work

  • testing: