router-transaction.js

const router = require('express').Router()
const kue = require('kue')
const queue = kue.createQueue()

queue.process('order', async (job, done) => {
  try {
    let outOfStock = {
      bool: false,
      data: [],
    }
    let allProduct = (await Product.findAll({
      where: {
        id: {
          in: job.data.items.map((el) => el.id),
        },
      },
      attributes: ['id', 'stock'],
    })).map((el) => {
      if (el.stock < job.data.items.find((inner) => inner.id === el.id).item) {
        outOfStock.bool = true
        outOfStock.data.push(el)
      }
      return {
        id: el.id,
        stock: el.stock,
      }
    })

    if (outOfStock.bool) {
      return done(
        JSON.stringify({
          errorMsg: 'Stuff out of Stock',
          data: outOfStock.data,
        })
      )
    }
    await Promise.all(
      allProduct.map((el) => {
        return Product.update(
          {
            stock:
              el.stock -
              job.data.items.find((inner) => inner.id === el.id).item,
          },
          {
            where: {
              id: el.id,
            },
            transaction,
          }
        )
      })
    )
    done(null, 'ok') //parameter pertama berisi null untuk menandakan tidak ada error. Parameter kedua berisi nilai kembalian
  } catch (err) {
    done(err) //mengembalikan nilai error
  }
})

router.post('order', (req, res) => {
  const job = queue.create('order', {
    items: req.body.items,
    /**
     * items berisi:
     * {
     *    id, //id produk
     *    count //jumlah produk yang diinginkan
     * }
     */
  })
  job.on('failed', (err) => {
    console.log(err) //nilai kembalian error akan dipassing disini.
  })
  job.on('complete', (result) => {
    console.log(result) //nilai kembalian jika sukses akan dipassing disini.
  })
  job.save()
  return res.json('Wait the queue please :)')
})

module.exports = router