ln-783-container-launcher

Paths: File paths (references/, ../ln-*) are relative to this skill directory.

ln-783-container-launcher

Type: L3 Worker Category: 7XX Project Bootstrap

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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)

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When to Use

Scenario	Use This Skill
Standalone-capable	Yes
Standalone container launch	Yes
Development environment setup	Yes
Production deployment	No, use proper CI/CD

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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

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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

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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

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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

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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

Monitor Integration (Claude Code 2.1.98+)

MANDATORY READ: Load references/monitor_integration_pattern.md

For container health verification, use Monitor to stream container logs:

Pattern	Command	timeout_ms
Readiness signal	docker compose logs -f 2>&1 | grep --line-buffered -iE 'ready|listening|healthy|started'	healthTimeout * 1000
Error watch	docker compose logs -f 2>&1 | grep --line-buffered -iE 'error|fatal|panic|exit'	healthTimeout * 1000

Use persistent: true if keepRunning is true and ongoing log monitoring is needed. Fallback: if Monitor is unavailable, use retry loop with sleep + curl health check.

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Definition of Done

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

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Reference Files

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

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Version: 2.0.0 Last Updated: 2026-01-10