contoh_2_koneksi.ts

import { createConnection, Connection } from 'typeorm'
import User from 'some-folder'
import { Request, Response, NextFunction } from 'express'

// Infrastructure Codes

let readConn: Connection
let writeConn: Connection

// Contoh misal user repo

export async function dbRead() {
  if (!readConn) {
    readConn = await createConnection({
      type: 'mysql',
      host: 'some-read-only-db-ip', // Target to Read-only database. It's always different IP
      port: 3306,
      username: 'test',
      password: 'test',
      database: 'test',
    })
  }
  return readConn.getRepository(User)
}

export async function dbWrite() {
  if (!writeConn) {
    writeConn = await createConnection({
      type: 'mysql',
      host: 'some-write-only-db-ip', // Target to database with write access. It's always different IP from Read-Only
      port: 3306,
      username: 'test',
      password: 'test',
      database: 'test',
    })
  }
  return writeConn.getRepository(User)
}

// Endpoint Express JS (contoh)

app.post('/user', postUser)
app.get('/user', getUser)

// Controllers

async function getUser(req: Request, res: Response, next: NextFunction) {
  const id = req.params.id
  try {
    const user = await getUser(Number(id))
    res.send(user)
  } catch (err) {
    res.send(err)
  }
}

async function postUser(req: Request, res: Response, next: NextFunction) {
  const { id, username } = req.body
  try {
    const user = await updateUsername(id, username)
    res.send(user)
  } catch (err) {
    res.send(err)
  }
}

// Repository Code

async function getUser(id: number): Promise<User> {
  const db = await dbRead()
  return await db.findOne(id)
}

async function updateUsername(id: number, username: string): Promise<User> {
  const db = await dbWrite()
  const user = new User()
  user.name = username
  await db.update(id, user)
  // Don't use Read DB here. Most likely Master db has not sync yet to read db
  const updatedUser = await db.findOne(id)
  return updatedUser
}