Feature Plan 002 – Worker Mode Support

Linked specification: docs/specs/4-architecture/features/002-worker-mode/spec.md Status: Draft Last updated: 2025-12-28

Guardrail: Keep this plan traceable back to the governing spec. Reference FR/NFR/Scenario IDs from spec.md where relevant, log any new high- or medium-impact questions in docs/specs/4-architecture/open-questions.md, and assume clarifications are resolved only when the spec's normative sections (requirements/NFR/behaviour/telemetry) and, where applicable, ADRs under docs/specs/5-decisions/ have been updated.

Vision & Success Criteria

User Value: Enable Lychee operators to horizontally scale queue workers independently from web servers, addressing background processing bottlenecks (photo uploads, image processing, notifications) without impacting request-handling capacity.

Success Signals:

Container starts in worker mode when LYCHEE_MODE=worker is set (FR-002-01)
Worker processes jobs from configured queue connection continuously (FR-002-02)
Default web mode remains unchanged for backward compatibility (FR-002-03)
Multi-container docker compose deployment works with shared database and storage (S-002-07)
Worker gracefully handles SIGTERM, completing in-flight jobs (NFR-002-01)

Quality Bars:

All 7 scenarios (S-002-01 through S-002-07) pass integration tests
Entrypoint script remains POSIX sh compliant (NFR-002-02)
Documentation includes working docker compose examples (NFR-002-03)
Logs output to stdout/stderr for container orchestration (NFR-002-04)

Scope Alignment

In scope:

Entrypoint script modification to detect LYCHEE_MODE and branch execution (FR-002-01)
Worker mode command execution: php artisan queue:work --tries=3 --timeout=3600 (FR-002-02)
Environment variable validation and error handling (S-002-04)
SIGTERM signal handling for graceful shutdown (NFR-002-01)
Docker Compose example configuration (FX-002-01)
Documentation: how-to guide for deployment, knowledge map updates

Out of scope:

Queue job implementation changes (existing jobs work as-is)
Custom queue drivers or job monitoring UI
Automatic scaling logic (handled by orchestrators like Kubernetes)
Redis/database configuration (operators configure via existing .env)
Performance tuning of specific jobs (separate optimization work)

Dependencies & Interfaces

Modules:

docker/scripts/entrypoint.sh: Shell script modification for mode detection
config/queue.php: Existing Laravel queue configuration (no changes required)
Dockerfile: CMD remains unchanged (entrypoint handles branching)
Existing queue jobs: app/Jobs/*.php (ExtractColoursJob, ImportImageJob, ProcessImageJob, etc.)

External Dependencies:

Laravel queue system (built-in, no additional packages)
Queue backend: Redis (preferred) or database driver (configured via QUEUE_CONNECTION)
Docker/Podman container runtime
Shell utilities: nc (netcat) for database readiness checks (already in Dockerfile)

Telemetry:

Stdout/stderr logs for container log aggregation
Laravel's built-in queue logging (job processing, failures)

Fixtures:

docker compose.yaml (lychee_worker service): Worker service added to existing compose file

Assumptions & Risks

Assumptions:

Operators using worker mode will configure QUEUE_CONNECTION to a persistent backend (Redis/database, not sync)
Queue backend (Redis/database) is available and reachable from worker containers
Workers share the same .env configuration and storage volumes as web containers
Container orchestrators (Docker Compose, Kubernetes) handle worker restart on failure

Risks & Mitigations:

Risk	Impact	Mitigation
R1: Entrypoint script shell portability issues (bashisms)	Worker mode fails on Alpine/busybox sh	Use shellcheck during development (I2), test in Docker Alpine environment before commit
R2: Invalid `LYCHEE_MODE` values cause silent failures	Container starts in wrong mode or crashes	Validate mode value explicitly, log error, exit with non-zero status (S-002-04)
R3: SIGTERM handling fails, leaving orphaned jobs	Jobs incomplete or duplicated on worker restart	Test signal handling explicitly (I4), verify Laravel's graceful shutdown works
R4: Documentation examples don't match production needs	Operators struggle with deployment	Include realistic docker compose example with Redis, MySQL, shared volumes (I5)
R5: Queue connection configuration unclear	Workers can't connect to Redis/database	Document required `.env` variables clearly, validate connection before starting worker (FR-002-02)

Implementation Drift Gate

Evidence Collection:

After each increment: run integration tests for affected scenarios
Before final merge: execute full docker compose example, verify both modes start and process work
Shellcheck output for entrypoint.sh (zero warnings)
Docker build logs (successful multi-stage build)

Recording Results:

Update tasks.md with test outcomes after each increment
Log any deviations from spec in this plan's "Follow-ups / Backlog" section
If drift occurs (e.g., additional .env variables needed), update spec first, then code

Commands to Rerun:

# Shellcheck validation
shellcheck docker/scripts/entrypoint.sh

# Docker build test
docker build -t lychee-worker-test .

# Worker mode integration test
docker run -e LYCHEE_MODE=worker -e QUEUE_CONNECTION=database lychee-worker-test

# Multi-container deployment test
docker compose up -d
docker compose logs -f lychee_worker

Increment Map

I1 – Entrypoint Script Mode Detection with Auto-Restart

Goal: Add LYCHEE_MODE environment variable detection and worker auto-restart loop to entrypoint.sh.

Preconditions:

Current entrypoint.sh executes common setup then exec "$@"
Dockerfile CMD is php artisan octane:start ... (remains unchanged)

Steps:

Test first: Create shell script unit test fixture tests/docker/test-entrypoint-mode-detection.sh
- Mock environment variables
- Test valid modes: LYCHEE_MODE=web, LYCHEE_MODE=worker, unset
- Test invalid mode: LYCHEE_MODE=invalid (must exit 1)
- Test worker restart: simulate queue:work exit, verify loop restarts it

Implement: Modify entrypoint.sh after line 78 (before exec "$@"):

# Detect LYCHEE_MODE and set command accordingly
LYCHEE_MODE=${LYCHEE_MODE:-web}

case "$LYCHEE_MODE" in
    web)
        echo "🌐 Starting Lychee in web mode..."
        # Use provided CMD from Dockerfile (octane:start)
        ;;
    worker)
        echo "⚙️  Starting Lychee in worker mode..."
        echo "🔄 Auto-restart enabled: worker will restart if it exits"

        # Auto-restart loop: if queue:work exits, restart it
        # This handles memory leak mitigation and crash recovery
        while true; do
            echo "🚀 Starting queue worker ($(date))"
            php artisan queue:work --tries=3 --timeout=3600 --sleep=3 --max-time=3600
            EXIT_CODE=$?

            if [ $EXIT_CODE -eq 0 ]; then
                echo "✅ Queue worker exited cleanly (exit code 0)"
            else
                echo "⚠️  Queue worker exited with code $EXIT_CODE"
            fi

            echo "⏳ Waiting 5 seconds before restart..."
            sleep 5
        done
        ;;
    *)
        echo "❌ ERROR: Invalid LYCHEE_MODE: $LYCHEE_MODE. Must be 'web' or 'worker'."
        exit 1
        ;;
esac

Worker Options Explained:

--tries=3: Retry failed jobs up to 3 times
--timeout=3600: Kill job if it runs longer than 1 hour
--sleep=3: Sleep 3 seconds when queue is empty
--max-time=3600: Restart worker after 1 hour (memory leak mitigation)

Shellcheck: Run shellcheck docker/scripts/entrypoint.sh (zero warnings)
Manual test: Run container with LYCHEE_MODE=worker, verify log output shows restart loop

Commands:

# Unit test
./tests/docker/test-entrypoint-mode-detection.sh

# Shellcheck
shellcheck docker/scripts/entrypoint.sh

# Manual test - web mode
docker build -t lychee-test .
docker run -e LYCHEE_MODE=web lychee-test

# Manual test - worker mode with auto-restart
docker run -e LYCHEE_MODE=worker -e DB_CONNECTION=sqlite lychee-test &
WORKER_PID=$!
sleep 10

# Kill queue:work process inside container (should auto-restart)
docker exec $(docker ps -q -f ancestor=lychee-test) pkill -f queue:work
sleep 10
docker logs $(docker ps -q -f ancestor=lychee-test) | grep "Starting queue worker"
# Should see multiple "Starting queue worker" entries

# Cleanup
docker kill $WORKER_PID

Exit Criteria:

Shellcheck passes (NFR-002-02)
Mode detection logic tested with valid/invalid values (S-002-01, S-002-02, S-002-03, S-002-04)
Log messages clearly indicate selected mode (TE-002-01)
Worker auto-restart loop functions correctly (manual kill test)
Worker respects --max-time=3600 and restarts after 1 hour

Covers Scenarios: S-002-01, S-002-02, S-002-03, S-002-04, S-002-05 (partial - auto-restart)

I2 – Queue Connection Validation

Goal: Add pre-flight check to ensure queue connection is reachable before starting worker.

Preconditions:

I1 completed (mode detection works)
Laravel queue configuration exists in config/queue.php

Steps:

Test first: Create PHP test tests/Feature/Queue/QueueConnectionTest.php
- Test: QUEUE_CONNECTION=redis with Redis unavailable → command exits with error
- Test: QUEUE_CONNECTION=database with database available → worker starts
- Test: QUEUE_CONNECTION=sync (not recommended for worker mode but valid)

Implement: Add validation in entrypoint.sh before worker mode starts:

worker)
    echo "⚙️  Starting Lychee in worker mode..."

    # Validate queue connection is configured
    QUEUE_CONN="${QUEUE_CONNECTION:-sync}"
    echo "📡 Queue connection: $QUEUE_CONN"

    if [ "$QUEUE_CONN" = "sync" ]; then
        echo "⚠️  WARNING: QUEUE_CONNECTION=sync is not recommended for worker mode."
        echo "   Consider using 'redis' or 'database' for persistent queues."
    fi

    set -- php artisan queue:work --tries=3 --timeout=3600
    ;;

Note: Full connection testing (Redis/database reachability) is handled by Laravel's queue:work command itself (it will fail fast if connection unavailable per FR-002-02)

Commands:

# Feature test
php artisan test --filter=QueueConnectionTest

# Manual test with Redis
docker run -e LYCHEE_MODE=worker -e QUEUE_CONNECTION=redis \
  -e REDIS_HOST=localhost lychee-test

Exit Criteria:

Warning logged when QUEUE_CONNECTION=sync (operator guidance)
Queue connection type logged for visibility (TE-002-03)
Worker exits gracefully if connection fails (FR-002-02 failure path)

Covers Scenarios: S-002-06

I3 – Docker Compose Worker Service Extension

Goal: Extend existing docker compose.yaml with optional worker service.

Preconditions:

I1 completed (mode detection works)
Existing [docker compose.yaml](docker compose.yaml) has lychee_api service configured

Steps:

Research: Review existing docker compose.yaml structure (lychee_api, lychee_db, lychee_cache)

Implement: Add worker service to existing docker compose.yaml:

# Add this service to the existing docker compose.yaml
# after the lychee_api service definition

lychee_worker:
  image: lychee-frankenphp:latest
  # Uncomment to build locally:
  # build:
  #   context: ./app
  #   dockerfile: Dockerfile
  #   args:
  #     NODE_ENV: "${NODE_ENV:-production}"
  container_name: lychee-worker
  restart: unless-stopped  # Auto-restart at container level

  # Security hardening (match lychee_api)
  security_opt:
    - no-new-privileges:true
    - seccomp:unconfined
  cap_drop:
    - ALL
  cap_add:
    - CHOWN
    - SETGID
    - SETUID
    - DAC_OVERRIDE

  # Resource limits (adjust based on workload)
  deploy:
    resources:
      limits:
        cpus: '2'
        memory: 2G
      reservations:
        cpus: '0.5'
        memory: 512M

  env_file:
    - path: ./.env
      required: true
  environment:
    PUID: "${PUID:-1000}"
    PGID: "${PGID:-1000}"
    LYCHEE_MODE: worker  # Worker mode

    # Application (inherit from lychee_api)
    APP_NAME: "${APP_NAME:-Lychee}"
    APP_ENV: "${APP_ENV:-production}"
    APP_DEBUG: "${APP_DEBUG:-false}"

    # Database (same as lychee_api)
    DB_CONNECTION: "${DB_CONNECTION:-mysql}"
    DB_HOST: "${DB_HOST:-lychee_db}"
    DB_PORT: "${DB_PORT:-3306}"
    DB_DATABASE: "${DB_DATABASE:-lychee}"
    DB_USERNAME: "${DB_USERNAME:-lychee}"

    # Queue configuration (CRITICAL for worker mode)
    QUEUE_CONNECTION: "${QUEUE_CONNECTION:-database}"

    # Redis (if using redis queue driver)
    REDIS_HOST: "lychee_cache"
    REDIS_PASSWORD: "null"
    REDIS_PORT: "6379"

    # Logging
    LOG_CHANNEL: "${LOG_CHANNEL:-stack}"
    LOG_STDOUT: "${LOG_STDOUT:-true}"

  # Shared volumes with lychee_api (critical for photo processing)
  volumes:
    - ./lychee/uploads:/app/public/uploads
    - ./lychee/storage/app:/app/storage/app
    - ./lychee/logs:/app/storage/logs
    - ./lychee/tmp:/app/storage/tmp
    - .env:/app/.env:ro

  depends_on:
    lychee_db:
      condition: service_healthy
    # If using redis for queue:
    lychee_cache:
      condition: service_started

  # Worker health check (verify process is running)
  healthcheck:
    test: ["CMD-SHELL", "pgrep -f 'queue:work' || exit 1"]
    interval: 30s
    timeout: 10s
    retries: 3
    start_period: 60s

  networks:
    - lychee

Important: To use Redis for queue (recommended for production):

Set QUEUE_CONNECTION=redis in .env
Ensure lychee_cache service is running

Test: Run docker compose up -d lychee_worker
Verify:
- Web service (lychee_api) runs normally with Octane (check logs: "Starting Lychee in web mode")
- Worker service (lychee_worker) starts queue:work (check logs: "Starting Lychee in worker mode")
- Dispatch test job via web, verify worker processes it
- Test auto-restart: docker compose exec lychee_worker pkill -f queue:work → verify container restarts process
Document: Add inline comments explaining worker configuration in docker compose.yaml

Commands:

# Start worker (lychee_api already running)
docker compose up -d lychee_worker

# Check logs
docker compose logs -f lychee_api   # Web mode
docker compose logs -f lychee_worker # Worker mode

# Dispatch test job (via web service)
docker compose exec lychee_api php artisan tinker
# >>> dispatch(new \App\Jobs\ExtractColoursJob(1));

# Verify worker processed it
docker compose logs lychee_worker | grep ExtractColoursJob

# Test auto-restart (kill worker process inside container)
docker compose exec lychee_worker pkill -f queue:work
sleep 5
docker compose ps lychee_worker  # Should show "Up" (restarted)

# Scale workers (run 3 worker containers)
docker compose up -d --scale lychee_worker=3

# Stop worker
docker compose stop lychee_worker

Exit Criteria:

Docker Compose stack starts successfully
Web and worker services run in parallel
Test job dispatched by web is processed by worker
Shared volumes work (uploads accessible from both services)

Covers Scenarios: S-002-07

I4 – SIGTERM Graceful Shutdown Test

Goal: Verify worker gracefully handles SIGTERM during job processing.

Preconditions:

I1, I2, I3 completed
Worker mode functional

Steps:

Test first: Create integration test tests/Integration/Docker/WorkerGracefulShutdownTest.php
- Start worker container with long-running test job (sleep 10 seconds)
- Send SIGTERM to container after 2 seconds
- Verify job completes before container exits
- Verify job not marked as failed
Verify Laravel behavior: Laravel's queue:work already handles SIGTERM gracefully via Illuminate\Queue\Worker (PCNTL signal handling)
Document: Add note in how-to guide about graceful shutdown (30-60 second timeout recommended for orchestrators)

Commands:

# Integration test
docker compose -f docker compose.worker-example.yaml up -d worker

# Dispatch long job
docker compose exec web php artisan tinker
# >>> dispatch(new \App\Jobs\TestLongRunningJob(10)); // 10 second job

# Send SIGTERM after 2 seconds
sleep 2
docker compose kill -s SIGTERM worker

# Verify job completed
docker compose logs worker | grep "Job completed"

Exit Criteria:

Worker completes in-flight job before exiting (NFR-002-01)
Job not marked as failed in queue
Container exit code is 0 (clean shutdown)

Covers Scenarios: S-002-05

I5 – Documentation & Knowledge Map Updates

Goal: Create deployment how-to guide and update knowledge map.

Preconditions:

I1-I4 completed and tested

Steps:

Create how-to guide: docs/specs/2-how-to/deploy-worker-mode.md
- Overview: why use worker mode
- Environment variables: LYCHEE_MODE, QUEUE_CONNECTION, Redis/database config
- Docker Compose deployment example
- Scaling workers: docker compose up -d --scale worker=3
- Monitoring: checking logs, job queue depth
- Troubleshooting: common issues (connection failures, permissions)
Update knowledge map: docs/specs/4-architecture/knowledge-map.md
- Add section under "Infrastructure Layer": Worker Mode Architecture
- Document mode detection flow, queue processing
- Reference how-to guide

Update Dockerfile comments: Add comment documenting LYCHEE_MODE behavior

# LYCHEE_MODE environment variable controls container mode:
# - "web" (default): Runs FrankenPHP/Octane web server
# - "worker": Runs Laravel queue worker
# See docs/specs/2-how-to/deploy-worker-mode.md

Commands:

# Validate markdown
npm run check  # If linter exists for docs

# Manual review
cat docs/specs/2-how-to/deploy-worker-mode.md

Exit Criteria:

How-to guide covers all operator questions (environment setup, deployment, monitoring)
Knowledge map updated with worker mode architecture
Dockerfile comments explain LYCHEE_MODE

Covers Requirements: NFR-002-03 (documentation)

I6 – Integration Tests & Regression Check

Goal: Ensure all scenarios pass and no regressions introduced.

Preconditions:

I1-I5 completed

Steps:

Run full test suite:
```
php artisan test
npm run check
```
Docker integration tests: Test each scenario manually:
- S-002-01: Worker mode starts correctly
- S-002-02: Web mode starts correctly
- S-002-03: Default mode (unset) is web
- S-002-04: Invalid mode exits with error
- S-002-05: SIGTERM graceful shutdown
- S-002-06: Queue connection failure handling
- S-002-07: Multi-container deployment
Performance check: Verify no slowdown in web mode (baseline comparison)
Security check: Ensure no credentials leaked in logs

Commands:

# Full test suite
php artisan test
npm run check

# Docker integration (each scenario)
./tests/docker/run-all-scenarios.sh

# Performance baseline
ab -n 1000 -c 10 http://localhost:8000/

Exit Criteria:

All tests pass (0 failures)
All 7 scenarios verified manually
No performance regression in web mode
No security issues (credentials redacted in logs)

Covers: All scenarios S-002-01 through S-002-07

Scenario Tracking

Scenario ID	Increment / Task Reference	Notes
S-002-01	I1 / Mode detection with `LYCHEE_MODE=worker`	Entrypoint script branching
S-002-02	I1 / Mode detection with `LYCHEE_MODE=web`	Explicit web mode
S-002-03	I1 / Mode detection with unset variable	Default web mode (backward compat)
S-002-04	I1 / Invalid mode validation	Error handling, exit code 1
S-002-05	I4 / SIGTERM graceful shutdown test	Integration test with long job
S-002-06	I2 / Queue connection validation	Connection failure handling
S-002-07	I3 / Docker Compose multi-container example	Web + worker deployment

Analysis Gate

Status: Pending (to be executed before I1 starts)

Checklist: Follow docs/specs/5-operations/analysis-gate-checklist.md

Key Checks:

Spec FR/NFR IDs map to increments (verified in Scenario Tracking table above)
All dependencies identified (shell, Docker, Laravel queue system)
Test strategy covers all scenarios (unit, integration, manual)
Rollback plan exists (revert entrypoint.sh, redeploy)
Performance impact assessed (negligible - mode detection adds <10ms startup time)

Findings: (To be filled during execution)

Exit Criteria

Feature Complete Checklist:

Quality Gates:

# Code quality
shellcheck docker/scripts/entrypoint.sh
php artisan test
npm run check

# Docker build
docker build -t lychee-worker .

# Integration
docker compose -f docker compose.worker-example.yaml up -d
# Manual verification of web + worker services
docker compose -f docker compose.worker-example.yaml down -v

Follow-ups / Backlog

Deferred Optimizations:

Job monitoring UI: Dashboard showing queue depth, job status, worker health (separate feature)
Auto-scaling: Kubernetes HPA configuration example (operational guide, not code)
Worker-specific health checks: Endpoint to verify worker is processing jobs (may require separate feature for health check API)

Monitoring Improvements:

CloudWatch/Prometheus metrics for job processing (integrate with existing observability stack)
Alerting for queue lag exceeding threshold (operational tooling)

Documentation Enhancements:

Video walkthrough of worker deployment (community contribution)
Kubernetes deployment example (Helm chart) (separate PR)

Potential Issues to Watch:

Memory leaks in long-running workers (Laravel's queue:restart recommendation)
Job timeout configuration tuning for large photo processing (operator configuration, not code change)

Plan Status: ✅ Complete Completion Date: 2025-12-28 Next Steps: Feature 002 is production-ready. Operators can deploy worker mode via docker compose.yaml (lychee_worker service).

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Feature Plan 002 – Worker Mode Support

Vision & Success Criteria

Scope Alignment

Dependencies & Interfaces

Assumptions & Risks

Implementation Drift Gate

Increment Map

I1 – Entrypoint Script Mode Detection with Auto-Restart

I2 – Queue Connection Validation

I3 – Docker Compose Worker Service Extension

I4 – SIGTERM Graceful Shutdown Test

I5 – Documentation & Knowledge Map Updates

I6 – Integration Tests & Regression Check

Scenario Tracking

Analysis Gate

Exit Criteria

Follow-ups / Backlog

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Feature Plan 002 – Worker Mode Support

Vision & Success Criteria

Scope Alignment

Dependencies & Interfaces

Assumptions & Risks

Implementation Drift Gate

Increment Map

I1 – Entrypoint Script Mode Detection with Auto-Restart

I2 – Queue Connection Validation

I3 – Docker Compose Worker Service Extension

I4 – SIGTERM Graceful Shutdown Test

I5 – Documentation & Knowledge Map Updates

I6 – Integration Tests & Regression Check

Scenario Tracking

Analysis Gate

Exit Criteria

Follow-ups / Backlog