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Atmos Now Detects Circular Dependencies in YAML Functions

· 2 min read
Atmos Team
Atmos Team
Atmos Team

Atmos now detects circular dependencies in YAML function calls and provides a clear call stack showing exactly where the cycle occurs.

What Changed​

Previously, circular dependencies in YAML functions like !terraform.state and !terraform.output would cause stack overflow panics with cryptic error messages. Now Atmos detects these cycles before they cause problems and shows you exactly where the circular dependency exists.

Why This Matters​

Circular dependencies can easily occur when components reference each other:

# Component A references Component B
vars:
  vpc_id: !terraform.state vpc core vpc_id

# Component B references Component A
vars:
  transit_gateway_id: !terraform.state transit-gateway core tgw_id

How It Works​

When Atmos encounters a circular dependency, it now provides a detailed error message with the full dependency chain:

circular dependency detected

Dependency chain:
  1. Component 'vpc' in stack 'core'
     → !terraform.state transit-gateway core transit_gateway_id
  2. Component 'transit-gateway' in stack 'core'
     → !terraform.state vpc core vpc_id
  3. Component 'vpc' in stack 'core' (cycle detected)
     → !terraform.state transit-gateway core transit_gateway_id

To fix this issue:
  - Review your component dependencies and break the circular reference
  - Consider using Terraform data sources or direct remote state instead
  - Ensure dependencies flow in one direction only

Performance Impact​

The cycle detection adds negligible overhead (less than 0.001% of execution time) and uses goroutine-local storage to ensure thread safety.

Get Involved​