Overview

This PR implements a comprehensive GitHub Actions workflow that automates the lifecycle management of self-hosted runners on lab hosts, addressing the need to dynamically provision runners, execute build/test matrices, and clean up resources afterwards.

Problem Statement

Previously, there was no automated way to:

• Provision self-hosted runners on specific lab hosts on-demand
• Run build/test matrices using those runners
• Automatically remove/cleanup runners after job completion

Solution

Added a complete self-hosted runner management system (self-hosted-runner.yml) that:

1. Dynamic Runner Provisioning

• Generates setup scripts to configure GitHub Actions runners on specified lab hosts
• Supports configurable number of parallel runners (default: 2)
• Creates unique runner labels per workflow run (runner-<run_id>) to prevent conflicts
• Downloads and configures runner binaries automatically

2. Build Matrix Execution

• Dynamically generates device test matrix from labnet.yaml based on selected host
• Integrates seamlessly with existing labgrid infrastructure
• Executes pytest tests with firmware download and device management
• Uploads test results as workflow artifacts

3. Automatic Cleanup

• Configures runners as ephemeral - they automatically self-remove after completing one job
• Generates cleanup scripts for manual intervention if needed
• Ensures clean state for each workflow run

Key Features

• Flexible Triggering: Manual trigger with host selection dropdown + weekly scheduled execution (Monday 2 AM UTC)
• Script-Based Approach: Generates portable bash scripts that work with SSH, Ansible, or manual execution
• Security: Uses short-lived tokens (1 hour validity), no credentials stored in workflow
• Comprehensive Documentation: Includes architecture diagram, usage guide, troubleshooting, and security considerations

Usage Example

# 1. Trigger workflow via GitHub UI (Actions → Self-Hosted Runner Matrix Tests)
# 2. Download setup script from artifacts
# 3. Execute on lab host:
bash setup-runners.sh "12345678" "2" "$RUNNER_TOKEN" "https://github.com/aparcar/openwrt-tests"

Integration with Existing Infrastructure

• Uses same labnet.yaml configuration structure
• Compatible with labgrid-client device management
• Follows patterns from existing workflows (daily.yml, pull_requests.yml)
• Can coexist with the global-coordinator runner

Implementation Details

The workflow consists of 4 jobs:

1. generate-matrix: Parses labnet.yaml to create device test matrix for selected host
2. setup-runners: Obtains registration token and generates setup scripts (uploaded as artifacts)
3. test-matrix: Executes tests on self-hosted runners (disabled by default, if: false)
4. cleanup-runners: Generates cleanup scripts and obtains removal tokens (uploaded as artifacts)

Note on Test Matrix Job

The test-matrix job is intentionally disabled by default (if: false) because it requires runners to be physically deployed on lab hosts. This allows the workflow to be merged and tested incrementally. To enable full functionality:

1. Deploy runners on a lab host using the generated setup script
2. Verify runners appear in GitHub Settings → Actions → Runners
3. Change if: false to if: true in the test-matrix job configuration

Files Added

• .github/workflows/self-hosted-runner.yml - Main workflow (368 lines)
• docs/self-hosted-runners.md - User documentation with architecture diagram (262 lines)
• docs/IMPLEMENTATION_SUMMARY.md - Technical implementation details (298 lines)
• README.md - Added self-hosted runner management section (20 lines)

Benefits

• ✅ Automated: No manual runner setup required for each test run
• ✅ Scalable: Support multiple parallel runners for faster test execution
• ✅ Secure: Ephemeral runners prevent persistence, short-lived tokens
• ✅ Flexible: Works with various deployment methods (SSH, Ansible, manual)
• ✅ Maintainable: Well-documented with clear usage examples

Future Enhancements

Potential improvements documented in implementation summary:

• Automated SSH execution of setup/cleanup scripts
• Runner health monitoring and auto-restart
• Dynamic scaling based on matrix size
• Integration with Ansible playbooks
• Webhook-based triggers for upstream OpenWrt commits

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