Review Dictionary Merging in Ansible Projects

Projects: c2platform/rws/ansible-gis, c2platform.wincore, c2platform.core

Configuring hash_behaviour

Ensure the hash_behaviour in ansible.cfg is set to merge to enable dictionary merging in your Ansible inventory project.

Review variables

Variables in C2 Platform Ansible Roles like win_resources and linux_resources can be complex dictionaries. Use this command to locate win_resources in your project:

grep -HnA1 '^win_resources:' $(find group_vars -name "*.yml")

Example Output:

 ~/git/azure/rws/ansible-gis$ grep -HnA1 '^win_resources:' $(find group_vars -name "*.yml")
group_vars/fme/win.yml:2:win_resources:
group_vars/fme/win.yml-3-  2-fme:
--
group_vars/windows/main.yml:20:win_resources:
group_vars/windows/main.yml-21-  0-bootstrap:
--
group_vars/fme_engine/main.yml:12:win_resources:
group_vars/fme_engine/main.yml-13-  fme_arcpy_path:
rws →
 ~/git/azure/rws/ansible-gis$

It shows three occurrences in three Ansible groups:

If a node is part of all three groups, Ansible will merge these lists, for example to a dictionary similar to:

win_resources:
  2-fme:
    - <list item>
    - <list item>
  0-bootstrap:
    - <list item>
    - <list item>
  fme_arcpy_path:
    - <list item>

C2 Ansible Roles will then typically first process these dictionaries using the filter c2platform.core.groups2items for simplified handling. This filter will flatten and also sort alphabetically the list on the group name. The Ansible role c2platform.wincore.win also uses this filter. The result is shown below:

win_resources:
  - group: 0-bootstrap
    <list item>
  - group: 0-bootstrap
    <list item>
  - group: 2-fme
    <list item>
  - group: fme_arcpy_path
    <list item>

Review other “merging” dictionaries

Review all other variables that are dictionaries and that are or can be merged. For example, C2 Platform product roles can include the c2platform.wincore.win role and define their own “resources” variables. Search for _win_resources. The result might look like below.

ostraaten@localhost:~/git/azure/ansible-gis$ grep -HnA1 '_win_resources:' $(find group_vars -name "*.yml")
group_vars/fme_core/main.yml:11:fme_flow_win_resources:
group_vars/fme_core/main.yml-12-  core:
--
group_vars/fme_core/tomcat.yml:26:tomcat_win_resources:
group_vars/fme_core/tomcat.yml-27-  tomcat:
ostraaten@localhost:~/git/azure/ansible-gis$

From this we can derive that the tomcat role and fme_flow include the c2platform.wincore.win role. Respectively the roles utilize this role though the fme_flow_win_resources and tomcat_win_resources variables.

Additional Information

• See the guideline Managing Dictionary Merging in C2 Platform Ansible Projects.