cbbkrd-tech/ln-783-container-launcher

Paths: File paths (shared/, references/, ../ln-*) are relative to skills repo root. If not found at CWD, locate this SKILL.md directory and go up one level for repo root.

ln-783-container-launcher

Type: L3 Worker Category: 7XX Project Bootstrap Parent: ln-780-bootstrap-verifier

---

Purpose

Builds Docker images, launches containers, and performs comprehensive health verification using Docker native health checks and retry strategies.

Scope:

• Detect and validate docker-compose.yml configuration
• Build Docker images
• Launch containers with proper startup order
• Verify container health using native health checks
• Provide access URLs and cleanup instructions

Out of Scope:

• Building application code (handled by ln-781)
• Running tests (handled by ln-782)
• Container orchestration beyond single host (Kubernetes, Swarm)

---

When to Use

| Scenario | Use This Skill | |----------|---------------| | Called by ln-780 orchestrator | Yes | | Standalone container launch | Yes | | Development environment setup | Yes | | Production deployment | No, use proper CI/CD |

---

Workflow

Step 1: Pre-flight Checks

Verify Docker environment readiness.

| Check | Failure Action | |-------|---------------| | Docker daemon running | Report error with installation instructions | | Docker Compose available | Report error, suggest installation | | Compose file exists | Report error, list expected locations | | Required ports free | Report conflict, suggest alternatives | | Sufficient disk space | Warn if low space (<2GB free) |

Step 2: Parse Compose Configuration

Extract service information from docker-compose.yml.

| Information | Purpose | |-------------|---------| | Service names | Track which containers to monitor | | Exposed ports | Know which ports to check | | Health check definitions | Use native health checks if defined | | Dependencies (depends_on) | Understand startup order | | Volume mounts | Verify paths exist |

Step 3: Build Images

Build all images defined in compose file.

| Aspect | Strategy | |--------|----------| | Build context | Use paths from compose file | | Build args | Pass through from compose configuration | | Cache | Use Docker layer cache for speed | | Failure | Report build errors with full log |

Step 4: Launch Containers

Start containers with proper orchestration.

| Aspect | Strategy | |--------|----------| | Startup order | Respect depends_on and healthcheck conditions | | Detached mode | Run in background | | Network | Use compose-defined networks | | Volumes | Mount all defined volumes |

Step 5: Health Verification

Verify all containers are healthy using appropriate strategy.

Strategy Selection:

| Condition | Strategy | |-----------|----------| | Service has healthcheck: in compose | Use native Docker health status | | Service has depends_on: condition: service_healthy | Wait for Docker health status | | No healthcheck defined | Use external HTTP probe with retry |

Retry Configuration:

| Parameter | Value | Rationale | |-----------|-------|-----------| | Max attempts | 10 | Allow slow-starting services | | Initial delay | 5s | Give containers time to start | | Backoff | Exponential (5, 10, 20, 40s) | Avoid overwhelming services | | Max total wait | 120s | Reasonable upper limit |

Health Check Methods:

| Method | When to Use | |--------|------------| | Docker health status | When container has healthcheck defined | | HTTP GET to exposed port | For web services without healthcheck | | Container exec | For services without exposed ports | | TCP port check | For databases and message queues |

Step 6: Report Results

Return structured results to orchestrator.

Result Structure:

| Field | Description | |-------|-------------| | containers | Array of container status objects | | healthChecks | Array of health check results | | accessUrls | Map of service name to access URL | | overallStatus | healthy / unhealthy / partial | | startupDuration | Time from launch to all healthy |

Container Status Object:

| Field | Description | |-------|-------------| | name | Container name | | service | Service name from compose | | status | running / exited / restarting | | health | healthy / unhealthy / starting / none | | port | Exposed port (if any) | | startedAt | Container start timestamp |

Health Check Result:

| Field | Description | |-------|-------------| | url | Checked URL or endpoint | | status | HTTP status code or check result | | responseTime | Time to respond in ms | | healthy | Boolean health status |

---

Error Handling

| Error Type | Action | |------------|--------| | Docker daemon not running | Report with start instructions | | Port already in use | Report conflict, suggest docker compose down first | | Image build failed | Report with build logs | | Container exited | Report with container logs | | Health check timeout | Report with last known status and logs | | Network unreachable | Check Docker network configuration |

---

Options

| Option | Default | Description | |--------|---------|-------------| | keepRunning | true | Leave containers running after verification | | stopAfter | false | Stop containers after successful verification | | healthTimeout | 120 | Max seconds to wait for healthy status | | showLogs | true | Show container logs on failure | | buildFirst | true | Build images before starting | | pullLatest | false | Pull base images before build |

---

Cleanup Instructions

Provide user with cleanup commands in report.

| Action | Description | |--------|-------------| | Stop containers | Stop running containers, preserve data | | Remove containers and networks | Clean up containers but keep volumes | | Remove everything | Full cleanup including volumes and images |

---

Critical Rules

1. Use native health checks when available - more reliable than external probes
2. Implement retry with backoff - services need time to initialize
3. Always collect logs on failure - essential for debugging
4. Parse compose file for ports - do not hardcode port numbers
5. Respect depends_on order - critical for database-dependent services

---

Definition of Done

• [ ] Docker environment verified
• [ ] All images built successfully
• [ ] All containers running
• [ ] All health checks passing
• [ ] Access URLs provided
• [ ] Results returned to orchestrator

---

Reference Files

• Parent: ../ln-780-bootstrap-verifier/SKILL.md

---

Version: 2.0.0 Last Updated: 2026-01-10