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New !random YAML Function: Generate Random Values in Your Configurations

· One min read
Erik Osterman
Erik Osterman
Founder @ Cloud Posse

Need to generate random port numbers, worker IDs, or other numeric values in your Atmos configurations? The new !random YAML function makes it easy.

What's New​

We've added a new !random YAML function that generates cryptographically secure random integers. Use it anywhere in your Atmos stack manifests:

vars:
  app_port: !random 49152 65535  # Random ephemeral port
  worker_id: !random 1000 9999   # Random worker ID

The function accepts 0, 1, or 2 arguments:

  • !random - Random number 0-65535
  • !random 100 - Random number 0-100
  • !random 1024 65535 - Random number 1024-65535

Common Use Cases​

DevContainer Port Forwarding​

Avoid port conflicts when running multiple devcontainer instances:

components:
  devcontainer:
    backend-api:
      spec:
        image: mcr.microsoft.com/devcontainers/go:1.24
        forwardPorts:
          - !random 8000 9000
          - !random 5432 5442

Dynamic Configuration​

Generate unique identifiers and random values for testing:

vars:
  worker_id: !random 1000 9999
  test_port: !random 20000 29999
  backend_ports:
    api: !random 10000 10999
    metrics: !random 11000 11999

Resources​