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ln-783-container-launcher

Type: L3 Worker Category: 7XX Project Bootstrap

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

Standalone-capable 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

• Use native health checks when available - more reliable than external probes

• Implement retry with backoff - services need time to initialize

• Always collect logs on failure - essential for debugging

• Parse compose file for ports - do not hardcode port numbers

• Respect depends_on order - critical for database-dependent services

Monitor Integration (Claude Code 2.1.98+)

MANDATORY READ: Load shared/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.

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