Managing Dictionary Merging

Best practices for utilizing dictionary merging in Ansible inventory projects.

Projects: c2platform/ansible, c2platform/rws/ansbile-gis


Make sure you understand dictionary merging and variable precedence in C2 Platform Ansible projects.


Problem

In C2 Platform Ansible inventory projects , hash_behaviour = merge is the default setting. See for examples the ansible.cfg files in c2platform/ansible and c2platform/rws/ansbile-gis

However, users may encounter issues or confusion when merging dictionaries, because this is a more advanced Ansible feature. Clear guidance is needed to navigate this configuration effectively.

Context

C2 Platform Ansible inventory projects are commonly configured with hash_behaviour = merge, allowing for flexible data structuring. Users often leverage roles like c2platform.wincore.win for Windows systems management but may need assistance in merging dictionaries seamlessly within this context.

Solution

Review and Document Inventory Structure

  • Examine your Ansible inventory projects and identify where hash_behaviour = merge is being applied.
  • Ensure your inventory structure is well-documented, and any use of merged dictionaries is clearly explained in comments.

Use Merging Sparingly

  • Only employ merging where necessary, typically for host or group variables requiring merging.
  • Avoid unnecessary merging, as it can lead to complexity and unintended consequences.

Define Default Values Thoughtfully

  • When merging dictionaries, define default values that are meaningful and compatible with specific data.
  • Consider how defaults will interact with specific values during merging.

Test Playbooks Rigorously

  • Thoroughly test playbooks to ensure merged dictionaries behave as expected.
  • Verify that merged data produces the desired results and doesn’t introduce unexpected issues.

Understand Variable Precedence

  • Familiarize yourself with Ansible’s variable precedence rules.
  • Be aware of how variables defined at different levels (e.g., host, group, playbook) interact when merged.

Monitor and Document Changes

  • Periodically review your inventory and configurations, documenting any changes.
  • Communicate changes to your team members to maintain transparency and consistency.

Handle Key Conflicts

  • Be prepared to address conflicts when the same key exists in multiple dictionaries being merged.
  • Document your approach to resolving such conflicts.

Respect Data Security

  • If you’re merging dictionaries containing sensitive data, exercise extreme caution.
  • Use Ansible Vault or other encryption methods to protect sensitive information and use only simple string variables in a vault.

Example and implementation

See the Ansible role c2platform.wincore.win  Ansible role. in the c2platform.wincore Ansible collection for examples on how merging is used.