https://chatgpt.com/c/68ca7564-3e44-8326-b12e-64ca3029fe59

date : September 17, 2025
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Nice — below is a clear, step-by-step end-to-end workflow for your app (what runs, in what order, how a request travels, and where to look when something fails). I’ll show both the startup sequence and the runtime request flow for common actions (GET /users, POST /users, POST /users/:id/delete), plus debugging checks. Follow these steps in order.

1) Project startup (what runs first)

You run: npm run dev

package.json script executes: nodemon --watch ./ --ext ts,json --exec ts-node server.ts.

server.ts loads first:

dotenv.config() runs → .env values populate process.env.

import app from './app' loads Express app (see step 3).

app.listen(PORT) starts HTTP server on process.env.PORT (or fallback).

Note: PORT is your web port (3000/3001). Not MySQL port.

2) App initialization (what app does)

app.ts (or app/index) runs next:

Sets view engine: app.set('view engine', 'ejs').

Sets views folder: app.set('views', path.join(__dirname, 'views')).

Middleware: app.use(express.urlencoded(...)), app.use(express.json()), static files, etc.

Mounts routes: app.use('/', userRoutes) (your routes/user.routes.ts).

Routes file is simple mapping between URLs and controller methods.

3) Database pool initialization (what config/database.ts does)

config/database.ts (imported by models) runs when first required:

Calls dotenv.config() (if not already) and reads DB_HOST/DB_PORT/DB_USER/DB_PASSWORD/DB_NAME.

Creates mysql2 pool: mysql.createPool(...).promise().

Optionally runs a test query (SELECT 1) and logs Database connected successfully or exits on failure.

This pool (export default pool) is reused by all model queries.

4) Request flow: GET /users (full path, what happens step by step)

Browser requests http://localhost:3001/users.

Express router matches the route and calls UserController.getAll.

File: core/controllers/UserController.ts.

UserController.getAll calls UserService.getAllUsers().

File: core/services/UserService.ts.

UserService.getAllUsers calls UserModel.findAll().

File: core/models/User.ts (your DB queries live here).

UserModel.findAll() executes a SQL query using the pool:

Example: SELECT * FROM users WHERE status = 1 ORDER BY id DESC.

Returns rows (array of objects).

Rows bubble back up: model → service → controller.

UserController.getAll does res.render('users/index', { users }).

Express renders views/users/index.ejs with users data.

Browser receives rendered HTML and displays users table.

5) Request flow: POST /users (create new user)

Form on users/create.ejs submits to /users (method POST).

Router calls UserController.create.

Controller extracts form data from req.body and validates basic fields.

Calls UserService.createUser(userData) which:

Optionally validates, checks duplicate email (via UserModel.findByEmail()), etc.

Calls UserModel.create(userData) to run INSERT SQL.

Returns inserted id.

Controller redirects: res.redirect('/users').

Browser loads GET /users again and sees updated list.

6) Request flow: POST /users/:id/delete (soft delete)

User clicks delete; form posts to /users/:id/delete.

Router → UserController.delete.

Controller calls UserService.deleteUser(id):

UserModel.delete(id) runs UPDATE users SET status = 0 WHERE id = ?.

Redirect back to /users. Deleted row no longer appears (because findAll() filters status = 1).

7) Important files & their responsibilities

.env — configuration (DB credentials, PORT). Must exist in project root.

server.ts — program entry point, starts HTTP server.

app.ts — initializes Express app (middleware, view engine, routes).

config/database.ts — creates & exports MySQL pool.

core/models/User.ts — raw SQL queries, data shape (IUser).

core/services/UserService.ts — business rules, validation, calling model functions.

core/controllers/UserController.ts — HTTP layer: gets req, calls service, sends view/redirect.

routes/user.routes.ts — route → controller mapping.

views/users/*.ejs — templates rendered to the browser.

8) Common pitfalls & how to debug them (step-by-step checks)

Server not starting / EADDRINUSE

Check process.env.PORT. If port in use: netstat -ano | findstr :3001 → taskkill /PID <pid> /F or change PORT.

Env variables not loaded

Ensure .env exists (not .env.example) and dotenv.config() is executed before using process.env.

DB connection fails

Check config/database.ts logs. Verify DB credentials with MySQL client:

mysql -u root -p -h localhost -P 3306
USE node_project_db;
SELECT 1;


SQL errors like Unknown column 'status' in 'where clause'

Either add status column to users table or change model query to remove status filter.

To add status column run (MySQL):

ALTER TABLE users ADD COLUMN status TINYINT(1) NOT NULL DEFAULT 1;
ALTER TABLE users ADD COLUMN created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP;
ALTER TABLE users ADD COLUMN updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP;


View not found / EJS errors

Ensure app.set('views', path.join(__dirname, 'views')) points to compiled TS output folder (dist or build) or run with ts-node (so __dirname is project src path). Check file exists: views/users/index.ejs.

No rows returned

Run query directly in MySQL to verify data: SELECT * FROM users LIMIT 5;

Silent failures

Add console.error in catch blocks (controller/service/model) and add logging in UserService.getAllUsers() to print rows length.

9) Quick test commands you can run now

Start server:

npm run dev


Test DB from terminal (MySQL CLI):

mysql -u root -p -h localhost -P 3306
USE node_project_db;
SELECT * FROM users LIMIT 5;


Quick HTTP tests:

Open http://localhost:3001/users in browser.

Or curl:

curl -i http://localhost:3001/users


Check server logs (where npm run dev is running) for error stacks.

10) Minimal troubleshooting checklist (do these in order)

.env exists and has correct DB credentials & PORT.

npm run dev shows Server is running on port XXXX and Database connected successfully.

Run SQL DESCRIBE users; → confirm status/email columns exist.

Check views/users/index.ejs is at views/users/index.ejs relative to app view folder.

Access http://localhost:PORT/users. If error, read server terminal log and paste it here if you need help.

If you want, I can:

provide a single-page sequence diagram text (arrow style) or

create a migration script (scripts/add_status_column.ts) that auto-adds status and timestamps, or

generate the route file and a minimal app.ts / server.ts ready-to-run copy you can paste.

Which of those would help you most next?