Scalr Serverless Agent Pool

Terraform/OpenTofu configurations for running Scalr agent pools as serverless workloads on AWS or Azure.

Each webhook from Scalr spins up an ephemeral container that executes a single Terraform run and exits. Containers scale to zero when idle — you only pay for actual compute time.

Architecture

Scalr.io ── webhook ──> API Gateway ── auth ──> Ephemeral Container (scalr/agent)
                                                       |
                                                 Persistent Cache (providers & modules)

1. Scalr needs to execute a Terraform run and sends a webhook to the configured endpoint
2. The API gateway authenticates the request via API key
3. An ephemeral container starts with the Scalr agent (SCALR_SINGLE=true)
4. The agent connects to Scalr, executes the run, and exits
5. Persistent storage caches Terraform providers and modules across runs

Platforms

	AWS	Azure
Webhook gateway	API Gateway (REST API) + Lambda	API Management (Consumption)
Compute	ECS Fargate	Container Apps Job
Cache storage	EFS	Azure Files
Cold start	~10-20s	~5-15s
Docs	aws/README.md	azure/README.md

Prerequisites

• Terraform >= 1.0 or OpenTofu
• Scalr account with API access (SCALR_HOSTNAME and SCALR_TOKEN environment variables)
• Cloud provider CLI authenticated (AWS CLI or Azure CLI)

Quick Start

cd aws    # or: cd azure
cp terraform.tfvars.example terraform.tfvars
# Edit terraform.tfvars
tofu init && tofu apply

See the platform-specific README for detailed configuration, cost estimates, and troubleshooting.

Custom Container Image

Build your own image with pre-cached providers:

FROM scalr/agent:latest
COPY providers/ /terraform-cache/

Contributing

1. Fork the repository
2. Create a feature branch
3. Test your changes
4. Submit a pull request

License

MIT License - see LICENSE file for details