Using Transaction in Mongoose

Transactions let you execute multiple operations in isolation and potentially undo all the operations if one of them fails.

Use case: Creating a new document in a collection.

• import models you defined, as well as startSessionas an object from mongoose. session is an instance of the MongoDB Node.js driver's ClientSession class.

const food = require('../models/food')
const drink = require('../models/drink')

const { startSession } = require('mongoose')

• startSession() returns a promise that resolves to a classcleintSession , hence use async to get it.

router.get("/food", async (req, res) => {
    const session = await startSession()

• In your try statement, wrap the codes you want to be excueted as a group between startTransaction() and commitTransaction(), then endSession() to end the session, once it is done.

    try {
        session.startTransaction()

        await food.create([{name:'Tacos'}], {session})
        await drink.create([{name:'Coke'}], {session})

        await session.commitTransaction()
        session.endSession()
        res.send('Success')

• In your catch statement, instead of commit, use abortTransaction() to undo all the operations.

    } catch (err) {
        await session.abortTransaction()
        session.endSession()
        console.log(err)
        res.send('Error')
    }
})

Note

• commitTransaction and abortTransaction are both promise objects. Therefore, use await.
• Any validation tests must be done before the transaction starts to prevent having unfinished transactions due to error.
• when you use it with create query, wrap your object in an array