docs: add implementation plan

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# Docker Watcher — Implementation Plan
## Overview
A self-hosted tool that automates Docker container deployment with Nginx Proxy Manager integration. Detects new images from Gitea/GitHub registries, deploys containers, and configures reverse proxy routing — all from a web dashboard.
## Architecture
```
Gitea CI → pushes image → Registry
Docker Watcher (Go)
├── Webhook listener (instant)
└── Registry poller (fallback)
Match tag → project + stage
┌── auto_deploy? ──┐
↓ ↓
Deploy now Notify, wait for
manual trigger (UI)
↓ ↓
Pull image
Stop old container
Start new container on shared network
NPM API: create/update proxy host
→ stage-dev-project.example.com
Health check
→ success: done, notify
→ failure: rollback, alert
```
## Decisions
| Decision | Choice | Rationale |
|----------|--------|-----------|
| Language | Go | Single binary, excellent Docker SDK, low resource usage |
| Web UI | SvelteKit (embedded in Go binary) | User's existing stack, lightweight |
| Reverse proxy | Nginx Proxy Manager | Already deployed, API available |
| Routing | Subdomain-based | No sub-path issues with SPAs |
| Image detection | Webhook + polling | Webhook for speed, polling as fallback |
| Config | YAML | Version-controlled, easy to edit |
| Deployment target | Same TrueNAS host | Docker socket mounted |
## Subdomain Convention
| Stage | Pattern | Example |
|-------|---------|---------|
| Dev | `stage-dev-{project}.{domain}` | `stage-dev-web-app-launcher.dolgolyov-family.by` |
| Release | `stage-rel-{project}.{domain}` | `stage-rel-web-app-launcher.dolgolyov-family.by` |
| Production | `{custom}.{domain}` | `launcher.dolgolyov-family.by` |
## Config Format
```yaml
global:
domain: dolgolyov-family.by
network: staging-net
npm:
url: http://npm:81
email: docker-watcher@dolgolyov-family.by
password_env: NPM_PASSWORD
subdomain_pattern: "stage-{stage}-{project}"
notification_url: https://notify.dolgolyov-family.by/webhook
registries:
gitea:
url: https://git.dolgolyov-family.by
type: gitea
token_env: GITEA_TOKEN
# github:
# url: https://ghcr.io
# type: github
# token_env: GITHUB_TOKEN
projects:
web-app-launcher:
registry: gitea
image: gitea.dolgolyov-family.by/alexei/web-app-launcher
port: 3000
healthcheck: /api/health
env_file: ./envs/web-app-launcher.env
volumes: []
stages:
dev:
tag_pattern: "dev-*"
auto_deploy: true
rel:
tag_pattern: "v*"
auto_deploy: false
prod:
tag_pattern: "v*"
auto_deploy: false
confirm: true
promote_from: rel
subdomain: launcher # overrides pattern → launcher.dolgolyov-family.by
```
## Project Structure
```
docker-watcher/
├── cmd/
│ └── server/
│ └── main.go # Entry point
├── internal/
│ ├── config/
│ │ ├── config.go # YAML parsing, validation
│ │ └── config_test.go
│ ├── docker/
│ │ ├── client.go # Docker Engine API wrapper
│ │ ├── container.go # Create, start, stop, remove
│ │ └── client_test.go
│ ├── npm/
│ │ ├── client.go # NPM API client (auth, CRUD proxy hosts)
│ │ └── client_test.go
│ ├── registry/
│ │ ├── registry.go # Interface
│ │ ├── gitea.go # Gitea registry implementation
│ │ ├── github.go # GitHub Container Registry (future)
│ │ ├── poller.go # Periodic tag polling
│ │ └── registry_test.go
│ ├── deployer/
│ │ ├── deployer.go # Orchestrates full deploy flow
│ │ ├── rollback.go # Rollback on failure
│ │ └── deployer_test.go
│ ├── health/
│ │ ├── checker.go # HTTP health checks with retries
│ │ └── checker_test.go
│ ├── notify/
│ │ ├── notifier.go # Webhook notifications
│ │ └── notifier_test.go
│ ├── webhook/
│ │ ├── handler.go # Receive push events from Gitea/GitHub
│ │ └── handler_test.go
│ ├── api/
│ │ ├── router.go # HTTP API for web UI
│ │ ├── projects.go # Project endpoints
│ │ ├── deploys.go # Deploy endpoints
│ │ └── middleware.go # Auth, logging, CORS
│ └── store/
│ ├── store.go # Deploy history, state (SQLite)
│ └── store_test.go
├── web/ # SvelteKit frontend
│ ├── src/
│ │ ├── routes/
│ │ │ ├── +page.svelte # Dashboard
│ │ │ ├── projects/
│ │ │ │ └── [id]/
│ │ │ │ └── +page.svelte # Project detail + deploy controls
│ │ │ └── settings/
│ │ │ └── +page.svelte # Config view
│ │ ├── lib/
│ │ │ ├── api.ts # API client
│ │ │ └── types.ts # Shared types
│ │ └── app.html
│ ├── package.json
│ ├── svelte.config.js
│ └── vite.config.ts
├── docker-watcher.example.yaml
├── Dockerfile
├── docker-compose.yml
├── go.mod
└── go.sum
```
## Implementation Phases
### Phase 1: Foundation
Core infrastructure — config, Docker client, NPM client.
1. **Go project init** — go.mod, directory structure, dependencies
2. **Config loader** — parse YAML, validate, resolve env vars
3. **Docker client** — connect to socket, pull image, list/start/stop/remove containers, manage networks
4. **NPM client** — authenticate (JWT), create/update/delete proxy hosts, list existing hosts
5. **Store** — SQLite for deploy history and state tracking
### Phase 2: Detection & Deployment
The core loop — detecting new images and deploying them.
6. **Registry client** — Gitea registry API: list tags, compare with last known
7. **Poller** — periodic check for new tags matching configured patterns
8. **Webhook handler** — HTTP endpoint receiving push events from Gitea CI
9. **Deployer** — orchestrate: pull → stop old → start new → NPM update → health check
10. **Health checker** — HTTP GET with retries and timeout
11. **Rollback** — on health check failure: stop new, restart old, revert NPM
12. **Notifications** — send webhook on deploy success/failure
### Phase 3: Web UI
Dashboard for visibility and manual control.
13. **API layer** — REST endpoints for projects, stages, deploys, manual trigger
14. **SvelteKit app** — dashboard, project detail, deploy log, manual deploy button
15. **Embed in Go** — build SvelteKit to static, embed with `go:embed`, serve from Go
16. **Real-time updates** — SSE or WebSocket for deploy progress
### Phase 4: Hardening
17. **Blue-green deploys** — start new, health check, swap, stop old (zero downtime)
18. **Promote flow** — enforce `promote_from` for production deploys
19. **Auth on dashboard** — basic auth or token-based
20. **Graceful shutdown** — drain in-progress deploys on SIGTERM
21. **Structured logging** — JSON logs with deploy context
## Key Dependencies (Go)
- `github.com/docker/docker` — Docker Engine API
- `github.com/go-chi/chi` or `net/http` — HTTP routing
- `gopkg.in/yaml.v3` — YAML config
- `github.com/mattn/go-sqlite3` or `modernc.org/sqlite` — SQLite (CGo-free)
- `github.com/robfig/cron` — Polling scheduler
## Docker Compose (self-deployment)
```yaml
services:
docker-watcher:
image: docker-watcher:latest
container_name: docker-watcher
restart: unless-stopped
ports:
- "8080:8080"
volumes:
- /var/run/docker.sock:/var/run/docker.sock
- ./docker-watcher.yaml:/app/config.yaml:ro
- ./envs:/app/envs:ro
- ./data:/app/data # SQLite DB
environment:
- NPM_PASSWORD=${NPM_PASSWORD}
- GITEA_TOKEN=${GITEA_TOKEN}
networks:
- staging-net
networks:
staging-net:
external: true
```
## API Endpoints (Phase 3)
```
GET /api/projects — list all projects with current status
GET /api/projects/:id — project detail + stage statuses
GET /api/projects/:id/stages/:stage — stage detail + deploy history
POST /api/projects/:id/stages/:stage/deploy — trigger manual deploy
POST /api/projects/:id/stages/:stage/rollback — rollback to previous
GET /api/deploys — recent deploys across all projects
GET /api/deploys/:id/logs — deploy log stream (SSE)
POST /api/webhook/gitea — Gitea push event receiver
POST /api/webhook/github — GitHub push event receiver (future)
```