Automation Assumes a Consistency We Did Not Have

Description and use

Automation assumes consistency that may not exist. The author demonstrates how defining a single desired state and documenting exceptions enabled reliable automation across a heterogeneous server fleet.

Problem

Twelve servers behind a single application had undocumented, divergent configurations, making automation impossible.

Outcome

Standardizing the desired state reduced manual drift to three documented exceptions, enabling reliable automation and daily drift reporting.

Workflow

• 1. Inventory all servers and document current state.
• 2. Identify undocumented differences and classify them as exceptions.
• 3. Create a single desired state configuration file for the application servers.
• 4. Rebuild each server to match the desired state, applying exceptions where necessary.
• 5. Set up daily drift detection and reporting.
• 6. Enforce that any future changes must be made through the desired state file.

Evidence

The automation worked immediately on seven of them. The other five each failed differently.

Source