# SAAC Deployment — How Your App Gets Built

> **READ THIS FIRST.** This file explains exactly how SAAC deploys your app.
> Understanding this will save you hours of debugging.

## The Build Process

When you run `saac deploy`, the daemon executes these exact commands in your repo:

```bash
docker compose -f docker-compose.yml -f docker-compose.saac.yml build
docker compose -p saac-{uuid} -f docker-compose.yml -f docker-compose.saac.yml up -d
```

**Your `docker-compose.yml` and `Dockerfile` ARE used.** The auto-generated `docker-compose.saac.yml` overlay ADDS labels, networks, and restart policy — it never replaces your config.

## Required Files

Your repo MUST have:
1. `docker-compose.yml` — defines services (app, postgres, redis)
2. `Dockerfile` — referenced by the build directive in compose

## CRITICAL: Two Containers Per App

Every app gets TWO containers. Understanding this prevents the #1 debugging confusion:

| Container | Domain | How it runs your code | When it updates |
|-----------|--------|----------------------|-----------------|
| **Production** | `yourapp.startanaicompany.com` | Built from your `Dockerfile` (immutable image) | Only on `saac deploy` |
| **Hot-reload** | `yourapp-hot.startanaicompany.com` | Volume-mounts your git repo, runs `npm run dev` | Instantly on `git push` |

**Key facts:**
- **Production** runs the Docker image you built. Your Dockerfile, CMD, and build steps all apply.
- **Hot-reload** does NOT use your Dockerfile. It mounts your source code directly and runs nodemon/npm run dev.
- **Your main domain routes to PRODUCTION, not hot-reload.** If production works but hot-reload doesn't, your app is fine.
- **TypeScript projects**: Production container compiles TS in the Dockerfile (`RUN npm run build`). Hot-reload needs a `dev` script in package.json that compiles and runs (e.g., `"dev": "tsc && node dist/server.js"` or `"dev": "tsx watch src/server.ts"`).

**Common confusion:** "My Docker build works but the app serves old code!" — You're probably looking at the hot-reload container. Check the PRODUCTION domain (without `-hot`).

## The 5 Rules

### Rule 1: Use `expose`, NEVER `ports`

Traefik reverse proxy handles all external routing. Host port bindings conflict with other apps.

```yaml
# WRONG — will conflict with other apps on the server
ports:
  - "3000:3000"

# CORRECT — Traefik routes traffic to this port
expose:
  - "3000"
```

### Rule 2: Database host = service name, NOT localhost

In Docker Compose, services talk to each other by service name.

```yaml
# WRONG — localhost means "inside this container" in Docker
DATABASE_URL: postgresql://postgres:postgres@localhost:5432/mydb

# CORRECT — "postgres" is the service name in docker-compose.yml
DATABASE_URL: postgresql://postgres:postgres@postgres:5432/mydb
```

### Rule 3: Database name must match between app and postgres service

The `POSTGRES_DB` in your postgres service creates the database. Your app must connect to the SAME name.

```yaml
services:
  app:
    environment:
      # Must match POSTGRES_DB below!
      - DATABASE_URL=postgresql://postgres:postgres@postgres:5432/postgres
  postgres:
    environment:
      - POSTGRES_DB=postgres  # This creates the database
```

**WARNING:** If you change `POSTGRES_DB` after first deploy, the old name persists in the Docker volume. The new name won't exist. Either keep the original name or destroy and recreate the postgres volume.

### Rule 4: Keep it simple — iterate incrementally

**Start with the working template, then add features one at a time.**

DO NOT:
- Replace Express with TypeScript + Prisma + monorepo in one commit
- Create complex multi-stage Dockerfiles before the basic app works
- Have multiple agents push changes simultaneously (causes deploy loops)

DO:
- Get the template deploying first (`saac deploy`, verify with `saac logs`)
- Add one feature, deploy, verify
- Add the next feature, deploy, verify
- **Coordinate deploys** — only ONE agent should push/deploy at a time

### Rule 5: Dockerfile must produce a running container

```dockerfile
FROM node:20-alpine
WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .
# If TypeScript: RUN npm run build
CMD ["node", "server.js"]
```

For TypeScript projects:
```dockerfile
FROM node:20-alpine
WORKDIR /app
COPY package*.json ./
RUN npm install          # Install ALL deps (including devDependencies for tsc)
COPY . .
RUN npm run build        # Compile TypeScript
RUN npm prune --production  # Remove devDeps from final image
CMD ["node", "dist/server.js"]
```

## Environment Variables

Env vars set via `saac env set KEY=VALUE` are written to `.env` in your repo directory before build.

## Debugging Commands

```bash
saac logs                              # Runtime logs (production container)
saac logs --type build                 # Build/deploy logs
saac exec "ls -la"                     # Run command in production container
saac exec "cat package.json"           # Check what's in the container
saac db sql "SELECT * FROM users LIMIT 5"  # Query database
```

## Common Mistakes and Fixes

| Mistake | Fix |
|---------|-----|
| `ports: "3000:3000"` | Change to `expose: ["3000"]` |
| `DB_HOST=localhost` | Change to `DB_HOST=postgres` (service name) |
| Changed `POSTGRES_DB` name after first deploy | Keep original name or delete postgres volume |
| `tsc: not found` in Dockerfile | Install ALL deps first: `RUN npm install` (not `--production`) |
| `.dockerignore` has `dist/` | Remove it — dist is built inside container |
| Multiple agents deploying simultaneously | Coordinate — one agent deploys at a time |
| "App serves old code" | Check production domain (not hot-reload). Run `saac deploy` to rebuild. |
| Hot-reload container crashes | This is separate from production. Fix `package.json` `dev` script. |

## Do NOT Add Traefik Labels

The SAAC daemon handles Traefik routing automatically via file provider. Traefik Docker labels in your docker-compose.yml are **ignored**. You can remove them.