Versioning Module MongoDB

Module for versioning in MongoDB, inspired by Vermongo (https://www.npmjs.com/package/mongoose-vermongo, https://github.com/codela/mongoose-vermongo and https://github.com/thiloplanz/v7files/wiki/Vermongo).

It includes support for transactions to avoid inconsistency when performing an update or deletion since this operations involve the main and the shadow collection (see instructions below).

This module allows to keep the change history of every document and the deleted documents. The idea is to have a "main collection" storing the current document versions and a different collection called "shadow collection" to keep all the past versions and deleted documents.

See Basic Usage.

Use

In order to use the package just install it as a dependency

npm install mongoose-versioned

Basic usage

This package requires mongoose and it is added as a plugin to each individual model that will be versioned. Get familiar with mongoose before using this package (https://mongoosejs.com/docs/index.html).

// import versioning and mongoose related dependencies
const versioning = require('mongoose-versioned')
const constants = require('mongoose-versioned/source/constants')

const mongoose = require('mongoose')
mongoose.Promise = require('bluebird')
let Schema = mongoose.Schema

// connect to the database following mongoose instructions, for example:
let mongodb_uri = 'mongodb://localhost/test'

const versionItems = async(mongodb_uri) => {
  try {
      await mongoose.connect(mongodb_uri, { useUnifiedTopology: true, useNewUrlParser: true, useFindAndModify: false })
      console.log("Database.connect: DB connected ")
  } catch (err) {
      console.error(`Database.connect: MongoDB connection error. Please make sure MongoDB is running:` + err.message)
      throw new Error(err)
  }

  const db = mongoose.connection

  // create the model
  let itemSchema = new Schema({
    code: { type: Number, required: true, unique: true },
    name: { type: String, required: true, unique: false }
  })

  // add the versioning plugin to the schema and specify
  // the name of the shadow collection
  const name = 'item'
  itemSchema.plugin(versioning, {collection: name + "s.versioning", mongoose})

  // instantiate the model
  let Item = mongoose.model(name, itemSchema)
  // at this point a collection named 'tests'

  // add a new document
  const newItem = {
    code: 1,
    name: "first item"
  }

  let savedItem = await new Item(newItem).save()
  console.log(`saved item with id: ${savedItem._id}, version: ${savedItem._version}`)

  let id = savedItem._id

  // update document info
  savedItem.name = "modified item"

  // add edition information
  savedItem[constants.EDITOR] = "editing user"
  
  // perform the update
  let updatedItem = await savedItem.save()
  console.log(`updated item with name: ${updatedItem.name}, version: ${updatedItem._version}`)

  // find current version
  let foundCurrent = await Item.findVersion(id, 2, Item)
  console.log(`found current version ${foundCurrent._version}, name = ${foundCurrent.name}`)

  // find old version
  let foundOld = await Item.findVersion(id, 1, Item)
  console.log(`found current version ${foundOld._version}, name = ${foundOld.name}`)

  await db.close()
}

versionItems(mongodb_uri)

Using transactions

Transactions

Transactions can be used to ensure the database remains in a consistent state even if the operation fails. Update and delete operations involve changes in both main and shadow collections and therefore need to be wrapped in a transaction to ensure serialization.

The transaction should be stated before calling the update/delete operation and in addition the session should be stored in a reserved "_session" inside the document and passed as an option to save/delete method.

const versioning = require('mongoose-versioned')
const constants = require('mongoose-versioned/source/constants')

const mongoose = require('mongoose')
mongoose.Promise = require('bluebird')

[...]

try {
  // start transaction
  session = await mongoose.startSession()
  session.startTransaction()

  // store session in the document
  document[constants.SESSION] = session

  // save sending the session as option
  await document.save({session})

  // commit transaction
  await session.commitTransaction()
  session.endSession()

} catch(error) {
  if (session) session.endSession()
  const message = `Error updating document ${id} in the collection ${collection}.`
  processError(res, error, message)
}