Migrate MongoDB Collections using Mongoose.js

migrate-mongodb-collections-mongoose.js

const fs = require('fs')
const mongoose = require('mongoose')
const ModelOne = require('./models/ModelOne')
const ModelTwo = require('./models/ModelTwo')

let source = "mongodb://source.database.com:27017/srcdb"
let destination = "mongodb://dest.database.com:27017/dstdb"

let models = [
    ModelOne,
    ModelTwo
]

migrateDbs (sourceConnectionString, destinationConnectionString, dataMap)

async function migrateDbs (source, destination, dataMap) {
    await exportDbToJson(source, dataMap)
    await importJsonIntoDestination(destination, dataMap)
}

async function exportDbToJson (source, models) {
    let sourceConnection = await mongoose.connect(source, { useNewUrlParser: true})
    for(let i = 0; i < models.length; i++) {
        let data = await models[i].find({})
        await writeDataToFile(models[i].modelName, data)
    }
    sourceConnection.connection.close()
}

async function importJsonIntoDestination (destination, models) {
    let destinationConnection = await mongoose.connect(destination, { useNewUrlParser: true })
    for(let i = 0; i < models.length; i++) {
        let data = await getDataFromFile(models[i].modelName)
        await models[i].create(data)
    }
    destinationConnection.connection.close()
}

function getDataFromFile (modelName) {
    return new Promise((resolve, reject) => {
        let filename = `./data/${modelName}.json`
        fs.readFile(filename, 'utf8', function (err, data) {
            if (err) reject(err)
            resolve(JSON.parse(data))
        })
    })
}

function writeDataToFile (modelName, data) {
    return new Promise((resolve, reject) => {
        if (!fs.existsSync('./data')) {
            fs.mkdirSync('./data');
        }
        let filename = `./data/${modelName}.json`
        fs.writeFile(filename, JSON.stringify(data), 'utf8', err => {
            if(err) reject(err)
            resolve()
        })
    })
}